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An encyclopedia of detailed information from anchoring and foundations to sagging support beams…

Anchoring new concrete to old existing foundations

I am about to start constructing an addition to increase the size of our kitchen. The new foundation will extend 15 feet into our back yard. The addition will be a two-storey structure. Can I cast 6-inch cement walls? Should I tie the new walls into the old basement cement walls with steel dowels? If the foundation walls are laterally supported at the top you can cast 6 inch walls provided they are no higher than 2.5 metres (8’-4”). The concrete must be at least 20 MPA strength and the maximum height of the finished ground on the outside of the wall should be no more than 1.8 metres (6’-00”) high. “Laterally supported” means that the floor joist system and sill plates are mechanically anchored to the top of each of the concrete walls. Anchoring is accomplished by inserting threaded bolts into the new concrete at about 2.5 metre (7’-00”) spaces.

In other words you can’t build a “pony wall” and then install your floor joists on top of that wall because the concrete wall under the “pony wall” will not be laterally braced by the floor system. If you choose to build a 6 inch concrete wall your footing size should be at least double the wall thickness and at least 100 mm (4inches) thick. These specifications apply only to conventional wood frame construction. If you are supporting masonry block or brick these specifications do not apply.

There are different schools of thought about anchoring new concrete to old existing foundations. Personally, I prefer not to tie old and new together. I have seen enough new cracked concrete addition walls to question the practice. Old buildings have finished settling years ago. New additions will continue to settle for years to come. That settlement stresses the tied joint between the two structures and it is the newer concrete that will crack first. As well, the floor system provides horizontal bracing (lateral support) against the inward pressure of the backfill at the joint between the old and new walls. So anchoring to the old walls is redundant. I think it is more important to compact the soil thoroughly under the new foundation walls to reduce settlement. Then consider saw cutting a deep vertical groove in the old foundation walls where the new walls will tie in. Insert rubber “waterbar” split half-and-half between the old and new wall. If you can’t locate “waterbar” at your building supply store you can improvise with any soft rubber membrane like heavy tire inner tubing. Cut strips at least six inches wide and insert the rubber into the old wall so that three inches will project into the new concrete walls. Pour the new concrete carefully around this “waterbar”. This membrane will prevent water from seeping through the “construction joint” between the old and new concrete but it will not create a stress point between the two vertical surfaces.

Deck flooring and structure rotting

The plywood on my deck is rotting and some of the floor joists under it have also started to rot. I sealed the deck with paint–on deck sealer when I built it four years ago. Why is it rotting already?One of the most common problems with decks is rot in the flooring and structure. Subsequently re-building a sundeck has become a national summer pastime. Unfortunately, it is not the way most of us would prefer to spend a summer vacation.

The most common reason for deck failures is a lack of maintenance for these types of paint–on deck coatings. They will fail and allow water to seep through to the plywood, joists, ledgers and beams if the coating is not re-installed to the manufacturer’s specifications. This is usually specified at least every second year, an easily overlooked maintenance issue when you are enjoying your weekend deck hammock. Remember that the deck is out in the weather every day of the year not just during the times we are enjoying it. This constant exposure to the elements means maintenance.

Although they are significantly more money, vinyl decking, plastic wood, pressure treated 5 quarter lumber or stained cedar decking are good long term, low maintenance solutions to paint-on deck sealers. If you are going to switch to an open spaced decking material that allows water into the structural components you do run the risk of structural rot in the future. If you are constructing a new deck with open spaced decking, consider using all pressure treated structural materials or well stained cedar throughout.

Metal stringers vs. wooden stairs

The wooden stairs from our back deck and front porch are both in need of repair. So I have been thinking about replacing them with the pre-fabricated metal stair stringers that building supply stores carry. Is this a better way to go than re-building these stairs from lumber?One advantage of metal stair stringers is that metal is a lot more weather resistant than wood products, which makes them an attractive alternative. However, there are several problems that can make metal stringers a poor choice for your application.

First, these pre-fabricated stringers come in very limited lengths; often the maximum number of treads they will carry is as few as seven. So if your existing stairs have more treads than the metal stringers can provide, the metal stringers will not work for you.

Here is another problem you will likely encounter with pre-fabricated metal stringers. When they are constructed in the factory an arbitrary rise is selected for the stringer. This arbitrary or generic rise will likely not match your deck / stair landing exactly. So you’ll wind up with at least one stair riser of a different height than the other risers. This usually occurs at the top riser next to the stair landing or deck surface. This may not seem like a big concern, but our feet memorize the rises in a flight of stairs. Even a 6mm difference in a rise can cause you to trip and fall. Because the unequal rise usually occurs at the top of the flight of stairs, it also presents the worst risk of a serious accident.

In my opinion you would be better served by building new wooden sets of stairs in both locations. But before you take the old stairs apart, make sure that it’s not just the treads that need replacing. Often the stair stringers are quite sound and you can simply replace a few treads and get years more service from them.

If the stringers and treads are rotting, I recommend that you hire a carpenter with experience in stair construction. Cutting an accurate set of stair stringers takes a good deal of training, skill and practice. So select your trades person carefully. Consider using pressure treated wood materials for the treads and stringers. Set the bottom edges of the stringers on a concrete pad with an asphalt roof shingle between the stringer and the concrete. This is where the stringers will rot first if they are in contact with lawns or garden soil.

Deck flooring and structure rotting

The plywood on my deck is rotting and some of the floor joists under it have also started to rot. I sealed the deck with paint–on deck sealer when I built it four years ago. Why is it rotting already?One of the most common problems with decks is rot in the flooring and structure. Subsequently re-building a sundeck has become a national summer pastime. Unfortunately, it is not the way most of us would prefer to spend a summer vacation.

The most common reason for deck failures is a lack of maintenance for these types of paint–on deck coatings. They will fail and allow water to seep through to the plywood, joists, ledgers and beams if the coating is not re-installed to the manufacturer’s specifications. This is usually specified at least every second year, an easily overlooked maintenance issue when you are enjoying your weekend deck hammock. Remember that the deck is out in the weather every day of the year not just during the times we are enjoying it. This constant exposure to the elements means maintenance.

Although they are significantly more money, vinyl decking, plastic wood, pressure treated 5 quarter lumber or stained cedar decking are good long term, low maintenance solutions to paint-on deck sealers. If you are going to switch to an open spaced decking material that allows water into the structural components you do run the risk of structural rot in the future. If you are constructing a new deck with open spaced decking, consider using all pressure treated structural materials or well stained cedar throughout.

Repairing vs. replacing rotting deck

I just noticed that some of the posts, beams and floor joists on my deck are weathered and starting to rot. Water has been getting into the 3-ply beam through the spaces between the 2”x6” decking and the water is also causing rot around the bottoms of some of the posts. I’m inclined to tear the deck down and re-build, but is it worth saving?Without seeing the extent of the water damage it’s difficult to say, but here are a few ideas that I hope help you with your decision. Tearing your deck down and replacing it at about $25 – $30 a square foot is an expensive proposition, when you may be able to repair it for half the cost. Often the rot you see has not affected the structural integrity of the deck. In other words, the structure is still strong enough to support the load. You may want to get the advice of a qualified carpenter or building inspector on this if you don’t feel knowledgeable enough to “make the call”. If the structural damage is affecting the integrity of the deck, it is usually worth repairing the rot by replacing floor joists or a beam member or posts.

We should address the source of the problem in the repair, which is the open spaced 2”x6” decking that has allowed the water to come through to the deck structure. There is no point in completing these structural repairs to be faced with the same problem five years from now. So once the structural repairs are complete, consider budgeting for a new fully sheathed deck surface.

You can do this by installing ½” exterior grade plywood directly over your existing 2”x6” decking. If you intend to do this, make sure when you’re replacing posts that you cut them a little short to give the deck a slope away from your home’s exterior walls so the water that used to flow through the decking will flow over the far edges of the deck. Once the plywood is installed you can cover it with a paintable water sealant like “Deck Tuff,” but I prefer vinyl because it is a durable, long-life material that is virtually maintenance free. The bonus for all your efforts is that you will have saved considerable money by restoring your existing deck, and you will gain dry storage under the deck for bikes, garden tools and seasonal recreational gear.

Dry rot explained

A neighbour was looking at the bottom edges of my wood walls in the basement and said they were damaged by “dry rot”. Could one of you fellows explain how rot can be dry and whether I can or should do anything about it?I can certainly understand your confusion. The difficulty in understanding the term “dry rot” is simply that the term itself is misleading because the term combines two stages of a problem. During the first stage the wood is exposed to a continuous source of moisture. Usually, when it is the bottom plate of a wood wall in the basement, the moisture comes from garden or flowerbed soil on the outside of the wall that has been built up against the wall for years. To be termed “dry rot” the second stage must also occur. That is, the soil has been removed at some point and the wood that was exposed to the moisture has completely dried. Once the source of moisture is removed, the wood and the rotting sections dry out and the wood stops rotting. Now that the rot has stopped and is in fact dry, it is accurate to call it “dry rot”.

However, there are a couple of additional concerns that should be considered. First, is the rot in your basement dry? In other words, has the source of moisture been removed permanently? For obvious reasons this is an important point to determine. Second, has the rot caused sufficient structural damage in the wood to warrant repairs? Sometimes, the rot or “dry rot” has not damaged the wood sufficiently to effect the structural integrity of the wood. However, this is best determined by an experienced trade’s person or qualified inspector because the judgement call can seriously affect the long-term health of your home. Conversely, if the judgment call is wrong, you could spend substantial time and money repairing damaged wood that is actually still structurally sound.

Mobile home foundations

I own a mobile home located in a park near Castlegar. I want to build a combination workshop and deck along the length of one side of the trailer. The dimensions will be about 24 feet long by 12 feet wide. I’ve heard several different opinions about the type of footings and foundations that I should use. What would you suggest?It is true that there are a lot of different ideas about foundations for mobile home additions. I like to start with a few basic premises. For instance, the original mobile home foundations, which are usually wood cribbings, often sit directly on top of the ground. When the ground freezes each winter the cribbings move up with the frost and back down again in the spring when the ground thaws. So the mobile home is constantly rising and falling with the seasons. This is why you should regularly check the contact points between the home’s metal frame and the wood cribbings.

When you build an addition that is attached to your mobile home, I think it is reasonable to remove the topsoil (overburden) and install the foundations directly on the sub-soil without going below the frost line. This approach allows both the old and new structures to move together seasonally. Conversely, imagine the stress on the connection points between the old and new structures if one structure moves up and down and the other remains stationary because its foundations are below frost.

Another consideration is the size of the footings / foundations you install under the addition. This depends on the amount of live and dead loads on the foundations. It is a good idea to discuss this detail with your municipal or regional district building department.

Salvaging an old garage

I have an old single car garage on the back of our lot adjacent to the alley. I use it for car parking and a bit of storage but it’s leaning and starting to look like another winter snow load will take it down. Is it salvageable?Check around the sole plates at the bottoms of the exterior walls. If these walls have had garden soil up against them for years there may be extensive rot damage, which makes the project marginal. However, if there is little or no rot (or you’re prepared to do a lot of serious structural rot repair) then I think the building is probably worth saving.

Here’s another point to consider. Many of these old garages in back lanes could not be built in the same locations today because zoning bylaws usually require at least five feet (1.5 metre) setbacks to rear lot lines and these garages often sit on rear lot lines or into public lanes. So it is worth restoring an old garage especially if you use it regularly. The best part is that as long as you do not tear it down you can repair and maintain it indefinitely even though the zoning bylaw may not permit you garage in that location today.

Often, old garages start to lean because they lack enough diagonal sway bracing. So you should push the building back to “plumb” (vertical) using leverage from adjacent structures, trees or temporary diagonal braces staked to the ground. Once the building is “plumb” and re-leveled install diagonal sway bracing on the inside of at least three walls. The longer the bracing is the more effective it will be. So on a typical wall the most effective braces will run from the top right and top left corners of each wall corner and meet at the middle of the bottom plates. Your roof may also need additional support. Fortunately, the same principles of diagonal bracing apply only this time the bracing is called ceiling joists and collar ties. You can install ceiling joists at the points where the rafters meet the top plates of the walls. Nail the ceiling joists to the rafters and the tops of the walls. If your garage already has ceiling joists and the roof is still sagging, install second horizontal members (collar ties) half way between the ceiling joists and the peak of the roof. This will definitely increase the strength and stability of your roof by “splitting” the rafter span.

Rotting floor joists

My house is supported on a concrete foundation with a crawlspace. When I went down into the crawlspace to turn on the baseboard heater, I noticed to my horror that all the ends of the floor joists, rim joists and sill plates the floor sits on are rotting. The whole floor system sits on a 4-inch deep shelf that has been cast into the top of the foundation wall. I went outside and looked at the garden soil because I thought it might be in contact with the rotting wood. But the dirt is up against the vertical part of the concrete shelf so it is protecting the floor joists, sills and rim joists. So why is all this wood rotting?The way you describe the construction I imagine that the whole floor joist assembly is resting on an “L” shaped concrete ledge at the top of the foundation wall. Fortunately, this design detail for supporting the floor is uncommon. The most conventional design detail has the floor joists, rim joists and sill plate sitting on top of the foundation wall, not recessed into it. Another variation on this detail is floor joists cast directly into the top 10 inches of the poured concrete foundation wall. These were older construction designs that have been abandoned in recent years for good reason.

Here a few of the potential problems with this type of construction detail. Concrete, for all its rigidity, density and permanence, is a very porous material. It is, in fact, like a sponge. When wood comes in contact with concrete, it wicks moisture from the “sponge,” and if there is a continuous and sufficient supply of moisture, the wood in contact with the concrete will rot. Even though the garden soil on the outside of your foundation wall is not in direct contact with your floor joist system, it might as well be because the concrete is simply a porous sponge between your wood floor joist system and the garden soil.

This wood, concrete, soil contact can be mitigated by installing a tar paper gasket between all the wood surfaces in contact with the concrete foundation wall. However, “back in the day” there was little or no awareness of a need for a capillary break between concrete and wood. Unfortunately, you have inherited the result of this lack of understanding.

Another drawback of this construction detail is that the vertical portion of the cast concrete ledge usually forms a “shoulder” or lip on the exterior wall at the base of the wood frame wall. Inevitably, the builders didn’t install a flashing at these “shoulders”. So the concrete lip often wicks rainwater into the wall and floor joist system which aggravates the problem. As well, if your roof has no gutters, all your roof water saturates the garden soil laying against the vertical part of the concrete ledge and a significant portion of that water soaks through the concrete and into the wood behind the foundation wall.

After removing and replacing all the rotting wood, consider implementing these preventative measures. Lower all the soil grades below the floor joist system. Install dampproofing tar on the exterior, above grade, exposed concrete foundation wall. Flash the concrete “shoulder” to wall joint and install a tar paper dampproof membrane between all the new wood floor components and the cast concrete shelf.

Affordable, expandable building designs

I’ve just purchased a 5-acre parcel of land in the Slocan Valley. I don’t have the money to build a full size house, so I’m thinking of constructing something around 400 square feet just to get started. Are there any codes or bylaws that could prevent my idea?Some regional districts and municipalities do have building and planning bylaw regulations that specify the minimum width, height or footprint of newly constructed single-family dwellings. Those same bylaws often specify where you can locate the building on your property (the building envelope). So you should discuss this project with the regional district planning and building departments before proceeding with a set of plans.

Because you are working with a modest budget, you may want to consider a few building designs that readily accommodate future additions. For instance, if you begin with a post and beam crawlspace, you can easily continue this type of foundation for future additions. As well, post and beam wall assemblies allow flexibility when you expand the building footprint. For contrast, let’s compare traditional stick framed walls with post and beam wall flexibility. If you decide to expand by adding on to one side of a stick framed wall structure, you will have to replace the framing with posts and beams when you remove portions or all of the exterior wall(s). The beauty and versatility of post and beam wall construction is that the structural support is already in place, and the infill stick framed walls can be easily removed without having to re-support the original structure.

You will also benefit from planning your possible future additions before you begin constructing the original 400 square foot building. This advance planning will allow you to locate critical structural posts in locations that best suit a future expansion. As well, you should consider how the original roofline and future rooflines would tie in. Try to avoid bottlenecks where roof water will get trapped and also avoid low pitch shed roofs that hold snow against original higher pitched roofs. When you submit your plans to the regional district for planing and building approval, include outlines of future additions so they can alert you to any possible restrictions. For instance, the size of your septic field can be dictated by the number of bedrooms that you intend to construct. So you may want to plan for a larger septic system to accommodate future additions.

Roof top garden

My rental home in Castlegar has a beautiful view of the Columbia River. The problem is the tenants can only enjoy the view from the roof. Fortunately, it’s a flat tar and gravel roof. So I’ve been contemplating turning it into a roof top garden. Are there any drawbacks that I should anticipate?Certainly your plan to add an amenity area would enhance the aesthetics of your building and increase your property value. However, there are some technical concerns that you should consider which will arise when you apply for a building permit for this project.

The most obvious consideration is guardrails at the roof edges or at the limits of the defined “habitable” amenity area. You should consider how you are going to fasten those guardrails to the roof deck or roof fascia to provide sufficient resistance to the fall of a 95-kilogram person without compromising the seal of the roofing.

But the more complex problem is choosing an appropriate new roofing material. Unfortunately, conventional flat roof materials like tar & gravel or torch-on roofing are not designed for the wear and tear of foot traffic, chair legs, high heels, table legs or any assortment of objects that one could imagine on the roof during a summer roof-top gathering. As well, any roofing membrane warranties would probably become void under these conditions. So, the roofing membrane should be protected from direct pressure by installing “sleepers” that support an open spaced decking over the membrane. These “sleepers” should bear directly on to the roof sheathing (and supporting structure), not on the roofing membrane, so the membrane is not under the stress of point loads from the sleepers and the live load of the occupants and furniture. The sleepers will have to be “flashed” into a new roofing membrane. Although there are commercial roofing membranes that are designed to take occupant loads, tar & gravel or torch-on roofing are the least expensive flat roof residential alternatives.

When you apply for a building permit expect that the building inspector will ask you for assurances that the existing roof structure can support the additional “live loads” of people and furniture. Often, the only acceptable answer is a set of calculations and a letter from a registered BC civil or structural engineer who will review the existing roof assembly and accept it or propose structural modifications. You would then present this engineered design information with your building permit application and plans to the inspector for review.

Common new home after-purchase problems

We purchased a new house built by a contractor and sold through a real estate firm 18 months ago. This winter we’ve noticed cracks in the ceilings, especially in the hallway where the walls meet the ceilings. There are also several screw heads showing in the walls throughout the main floor. Are these serious enough issues to try and claim for repairs?I can assure you that these defects will not cause any structural problems in your home. These are “cosmetic” deficiencies that are quite common occurrences in newly constructed houses. You can expect that it can up to two years for these types of problems to occur as the building materials dry and the soils settle under the loads of the new structure.

However, this doesn’t mean that you have to live with these deficiencies. For instance, your description of the cracks at the hallway upper wall-ceiling joints sounds like a common problem called “truss uplift”. Truss uplift occurs because the bottom chord lifts, settles and twists seasonally. This movement occurs because trusses are constantly transferring live loads from snow, rain and wind to the exterior walls through the truss web members. If these bottom chords have been fastened to the top plates of the walls, the stresses of the seasonal movement will often cause the inside corner at this wall / ceiling joint to crack. In other words, re-finishing the cracks will not necessarily cure the problem. Part of the solution will be to go into the attic and remove the fasteners connecting the truss bottom chords to these wall plates.

The exposed screw holes are called “nail pops” in the industry. They are a common occurrence in newly installed drywall caused by building settlement and drying processes. They are easily repaired by tightening or resetting the screws, filling, sanding and touching up the paint. Any reputable contractor will be more than willing to and capable of repairing both the truss uplift and the nail pop deficiencies. These are the kind of common after-purchase problems that a builder expects to be called back to repair.

Concrete patio slab design considerations

We want to replace our wood deck with a concrete patio slab. The existing deck is about 18 inches above the ground and just about a 4 inch step down from our rear sliding glass door. We want to put the new concrete patio slab at the same height as the old deck so the step will be the same, but that would mean pouring concrete up against the wood wall. Is it okay to put the concrete in contact with wood?There are several design concerns with this proposal that you should consider before construction. To have the concrete slab 18 inches above grade would require a large volume of concrete, in other words, a slab 18 inches thick when a 3 inch thick slab would be sufficient. You could avoid this problem by pouring a three sided concrete perimeter wall first. Then, install backfill inside the curb wall with well drained, well compacted fill material. Then pour a concrete slab on the compacted fill.

But, there is also a problem with this proposal as well as your own suggestion. The fill and / or the concrete are in direct contact with the wood frame wall of your house. A basic good building practice rule in construction is “never put concrete or soil in direct contact with wood”. For instance, all your exterior lawns and gardens should be at least 6 inches below the bottom edge of your wood frame walls. All concrete sidewalks should also be six inches below wood walls.

Concrete is not impervious; it is a moisture sponge. Any concrete surface, including sidewalks and patio slabs, will soak up water and transfer this moisture to adjacent wood materials. You could install a waterproof peel-and-stick gasket (blue skin) on the wood wall before you backfill and pour concrete, but this is fundamentally risky. Anytime you have wood in contact with soil and /or concrete, especially on the exterior of a building (with no heat source to dry the moisture), you have a recipe for problems. Even though the peel-and-stick may turn back water, there is a significant risk that condensation from the warm interior in contact with the cold exterior concrete and compacted fill will cause rot in this area of the wall. I recommend that you keep the patio slab at least 6 inches lower than the top of your existing concrete foundation wall and slope the slab away from the building foundation. Then install a set of stairs with a landing to your sliding glass door. This design will ensure many years of trouble-free outdoor living for you and your family.

Sags and dips in roof

We have a cabin on Christina Lake. This year’s project was to add an 18 ft. x 24 ft. second floor sleeping loft for the kids. I built the roof with 2 x 8’s and they are supported at the middle of each rafter with short walls that separate the bedroom space from the attic so there’s plenty of support for the rafters. But when I look at the roof from the outside there are sags and dips when you look along the length of both sides of the roof. Does this roof need more support in the spots where it’s sagging?This is a very small roof structure. In fact, with the mid-span support of the walls (“pony walls”) you could probably have constructed the roof rafters from using 2” x 4” or 2” x 6” rafter stock. However, I should mention that the size of rafter materials a person chooses is dictated by the snow load in the area in which you build. In other words, the sizes I am suggesting for your application will not necessarily be adequate for Rossland and may be too large again for Nelson’s north shore. There are generic tables available to select rafter sizes that suit your location, and your local regional or municipal building inspector will be able to provide this information. However, the roof you have constructed is over-built by far. So, you don’t need to worry about structural failure or additional re-enforcement.

Most likely, the sags and dips in your roof are the result of a common error that can be attributed to inexperience. A simple trick can avoid this problem next time. This trick is called “picking the crowns”. When a carpenter lays out his materials for a floor or roof, he “eyeballs” all the stock on the ground first. He looks down the length of every board for the “crown” because there is usually a bow in every piece of lumber. Then each “crown” is marked with a penciled arrow and turned in a common direction as it gets laid up on the wall or floor line. This way there can be no mistake when the carpenter pulls each board up for installation. He knows all the “crowns” are facing one direction, and as a double check, each board has an arrow. With all the “crowns” facing up there is no way a roof or floor will show sags or dips when the project is complete. Although there is no structural weakness in the roof you built, you will have to live with the misperception and accept that the defect is only aesthetic.

This article is dedicated to the memory of Paul Findley, a talented and highly respected local contractor and skilled carpenter tradesman, who will be missed among all his colloquies in the construction industry. Our condolences to his wife and family.

Determining the risk tree roots present to foundation

We purchased a house about 2 years ago. There is a 12-14-year old Douglas-fir ‘hedge’ about 7 feet from the side of the house (on the neighbour’s property) – the trees are about 3 feet apart and there are lots of them – all the way along the fence line. Among the Douglas-fir are a couple of maple trees starting to grow as well. The trees do afford some shade along the side of the house and the chickadees love them! Our questions: what damage can be caused to our foundation walls by the roots of these trees and how can we guard against any damage? Is cutting the trees down the only solution?Tree roots can adversely affect building foundations. However, there are many variables to consider when trying to determine the risk tree roots present to a foundation. For instance, the first consideration is the proximity of the tree(s) to the structure. Obviously, the bigger the tree is and the closer it is planted to a foundation, the more risk it poses to the structure. I have consulted an arborist on your circumstance and he has advised that Douglas fir trees and maple trees have root structures that can easily reach your foundation at 7 feet distance. So, here are a few things to consider.

Not all tree roots damage foundation walls. Some roots simply turn away when confronted with an impervious wall. For instance, if there is little moisture in the soil between your house and the hedge there will be less incentive for the tree roots to travel over to your foundation. In other words, water this area of your yard less and consider landscaping with dry-land plants or bark mulch or decorative rockery.

Tree roots can find their way into existing cracks in a concrete wall and slowly force the crack to spread. Then water penetration is likely. So check your foundation wall adjacent to the tree hedge for existing cracks along the exposed face of the concrete wall. If you find any cracks, dig down beside them until they taper out. Then patch and fill these cracks with concrete crack filler like “Xypex”. If your basement is unfinished, consider patching all visible cracks on the inside of the wall as well. Before you bury or cover any of this work, take photos of the cracks and the repairs you have completed. Then monitor these areas occasionally for signs of movement from the possible pressure of tree roots.

Another more labour intensive deterrent to tree roots involves excavation. You can consider digging a trench several feet away and parallel to your foundation to the depth of the footings. Then install vertical galvanized, corrugated metal roofing sheets… Backfill the sheet metal wall with the soil you removed and the tree roots should be deterred indefinitely.

Another issue to consider is the principle of property management. In other words, the landscaping and building(s) on one property cannot adversely affect the use and enjoyment of adjacent properties. This is where you may need those photos you took of the crack repairs. Documentation of changes to your property is the most convincing evidence if dispute resolution is necessary.

Sloping floors a common problem in additions

I recently purchased an older home with an office addition attached to one side of the original house. Now we’ve moved in I find that the floor in the office is so unlevel that my chair rolls away from my desk. I’m thinking of going into the crawlspace under the addition and jacking up the whole addition, but this seems like a lot of work. Are there any other options to level this floor?Sloping floors are a very common problem in additions such as yours. Often, the problem is caused by a mistake made when the concrete foundation for the addition was cast. Many builders tie the new addition foundation and framing to the original structure in an attempt to gain structural integrity. However, the original building finished settling years ago, while the new structure continues to settle, except of course, for the new portion of foundation and structure that is tied to the original building. This contact point between the two structures acts as a “hinge” while the new addition settles at the furthest wall parallel to the “hinged” wall. No matter how hard the builder tries to achieve a floor that is level and at the same elevation as the original floor, this new settlement defeats his attempts. Often you will see cracks in the new concrete and drywall in the addition at this “hinge” point. And I’ll bet your chair rolls to the new parallel outside wall.

I think there may be easier ways of re-leveling this floor than raising the leading edge of the addition. Although tying a bungee cord from your chair to the desk would be cheap and easy, there are slightly more expensive and permanent options that you may consider. For instance, if the floor is significantly “out of level” you could start by removing the finish and sub-flooring in the addition. Then, install tapered shims on or across the floor joists. Next, re-install the sub-floor and finished flooring.

If the difference between the high and low elevation is small you may also be able to use a self leveling floor compound available at your local building centre. These products “float on” with a trowel and permanently bond to the sub-floor, creating a hard wedge that re-levels the floor and provides a new surface for the finished flooring of your choice. These options will also avoid the potential for cracking drywall walls and ceilings and window glass that can occur if you attempt to raise the whole structure.

Old plastic vapour barrier causing moisture problems

About twenty years ago I built a two bedroom addition on the back of our house on a concrete foundation and crawlspace. I had heard that the building code required a vapour barrier on the underside of the floor joists. So, after I insulated the floor joist cavities I stapled a loose fitting plastic sheet to the bottom of the joists that hangs down the sides of the concrete foundation walls and ties into the vapour barrier on the ground of the crawlspace. It also helped to support the insulation. A week ago I went into the crawlspace to pull some new speaker wires to the second bedroom and I found that all my sill plates are rotten and the top side of the plastic is soaking wet. What the heck is going on?There was a very brief period of time, about the time you built this addition, when the Code required a plastic vapour barrier on the underside of a floor assembly in a crawlspace. This requirement was removed when Code authors found that the vapour barrier was trapping moisture in floor cavities, just as yours has done. Often the moisture was simply from a bucket of water or an overflowed sink that spilled and drained through the flooring. Sometimes the moisture would be from condensed humidity that collected over time on the top side of the vapour barrier.

In your circumstance, it is likely that the water on the top side of the vapour barrier has been migrating across the vapour barrier to the exterior walls and draining on to the top of the concrete walls where the rim joists sit. Years of constant wetting will inevitably cause rot in any untreated wood lying on wet concrete.

The problem you describe is predictable in light of what we know today about building technology. Unfortunately, the problem will be quite expensive to fix. You will have to remove the vapour barrier and then remove and replace all the rotten sill plates. You should also check your rim joists and the ends of your floor joists. Often, when sill plates are rotting, adjacent wood components like rim joists and ends of floor joists are also rotting. Repairs will likely involve jacking up the existing floors and temporarily supporting them (re-shoring) until the new sills (and rim joists) are installed and the floor is re-set. If the ends of the floor joists are also rotten, consider “sistering” new joists to them rather than pulling them out and replacing them. This will save you considerable effort and time in a lengthy and difficult job.

Leaning chimney in the attic

We purchased a heritage house in Rossland last year and I just got up into the attic last week. It’s a big stand up attic and much to my horror when I got up there I saw a brick chimney that I didn’t even know we had. The scary part is that it is really leaning a lot from the point where it comes through the attic floor to the point where it goes through the roof. I’m worried that it’s going to fall over. Should I plan on taking the chimney down before it falls down?Often, in older houses, chimneys that used to serve wood cook stoves or wood burning furnaces get buried inside walls during renovations. So, it’s not unusual to find a chimney in your attic that is not obvious throughout the rest of your new home. You may consider the potential for removing a wall and exposing the brickwork as a feature in your heritage house.

The leaning chimney in the attic is probably nothing to be concerned about. Here’s a quick way to dispel or verify your concerns. Take a two-foot builder’s level and go back into the attic. Put the level on one of the horizontal mortar joints between two courses of brick. If the mortar joints are level, the lean on your chimney is probably intentional. Often a mason will deliberately construct an offset in a chimney because he wants the chimney to exit through the roof in a specific location.

For instance, bringing the chimney through the ridge of the roof is a better strategy than exiting at a low point on the roof. The ridge exit avoids the potential for snow build-up on the backside of the chimney, reducing the pressure and flashing complications a lower exit can create. So, offsetting the chimney in an inconspicuous location like the attic is common practice for an experienced and skillful mason. However, do check the condition of the brick mortar joints when you are checking the joints with your two-foot level. Make sure the mortar is not powdery, weak and crumbly. Also, look for long lines of cracks in the mortar. If you see signs of deterioration or significant cracks in the mortar, you should consult a masonry contractor to inspect the integrity of the chimney for you.

Post & beam deck supports with pre-cast footing blocks

I will be constructing a backyard deck soon. Is it okay to support the deck posts & beam with those pre-cast footing blocks I’ve seen at building supply stores?The only way to be sure that your deck will not rise and fall with the seasonal freezing and thawing ground supporting it is to dig holes and pour concrete footings and pier foundations below the level that frost can affect them. If you use pre-cast footing blocks without digging holes the outer edge of your deck will rise and fall seasonally making the deck connection at the wall of your house act as a hinge. Eventually the hinge will weaken and any roof structure over the deck will also be adversely affected. Your house probably has its foundation below the level of frost. It is considered good practice and well worth the extra effort to also cast your deck footings below frost so the two foundation are both frost protected.

Sagging support beams

The beam supporting my carport / deck roof are sagging. They are made of two pieces of 2”x6” lumber. Should I replace them or just repair them somehow?In the construction industry a laminated beam is no less than three pieces of lumber. Two ply beams are lentils or headers and usually span smaller openings over windows and doors. So your lentil should be a beam. To be able to tell you the exact size the beam should be would require more detail about the length of the floor joists, the spacing of the supporting posts and other loads the beam may be supporting. But as a general recommendation consider re-enforcing the beam by adding one or two more 2”x6” boards nailed or bolted to the existing beam. You will also need to increase the size of the posts under the beam to ensure that all the 2”x6” laminations bear fully on the posts. Also make sure the new 2”x6” beam joints land directly over the centres of the posts. You can also add additional posts by jacking up the existing beam and then slowly releasing the pressure on to the new posts.

Cut an opening in wall for window

I have a small bedroom window and a beautiful view of the lake that I cannot see. If I cut a larger opening in the wall for a bigger window how can I be sure that I won’t hit any electrical wires, plumbing pipes or gas lines?It is quite uncommon to find gas lines and water lines buried in an exterior wall of a building. However, you’re right to exercise caution when cutting into any wall in your home. The safest way to proceed is to find a wall stud near the outside edge of the new window location. Outline the “rough opening” of the window on the interior drywall, then cut and remove just the drywall or plaster covering. Remove any insulation from the cavity and the location of any wires, pipes and other mechanical services will become apparent.

You will need to install a new lintel (header) above the larger window to carry the load of the roof or floor and roof load above the larger opening. This will mean installing some new wall studs. The overall size of the lintel will be determined by the size and amount of load that it carries. The only accurate way to determine the size of this lintel is to refer to a handy little book called The Span Book, published by The Canadian Wood Council, available in most book stores or ask your local contractor or building inspector for advice. Remember that gable end walls of roofs are often not load bearing, so this may decrease the size of the lintel you require.

Small porch and deck addition on mobile home

This fall I will be building a small porch and deck addition on my mobile home. What type of footings and foundation should I construct under this project?If your mobile home is supported by wood or concrete cribbing that are situated right on the soil surface, the same strategy can be applied to your proposed addition. The principle behind this suggestion is quite simple. Your mobile home moves and shifts as the frost in the bearing soil under it expands and settles from winter to summer. The cribbings settle and shift, often losing their contact with the steel under-carriage of your home. This is why mobile home manufacturers and installers recommended that you re-level and install cribbing shims under your mobile home at least every other year.

If the addition and deck you construct have their footings below frost any structural connection between your mobile home and the addition will act as a hinge. Your original home will continue to rise and fall with the seasonal frost but your new addition and deck will remain stable below frost. Any structural connections between your original home and the addition will be stressed and may eventually loosen and fail due to this hinge affect.

If you construct the addition and deck without any structural connections to your original home then you could consider installing the footings below frost. However, mobile homes are often moved so the addition and deck would be much more permanent and difficult to re-locate. As well, if you are renting the space in a park many mobile home park owners prefer that you construct additions without permanent footings so that they can be readily dis-assembled.

Cracks in concrete walls

There are two cracks in our basement concrete walls. One crack runs vertically in the middle of the wall and one runs diagonally from the bottom edge of a window. The cracks are about ¼ inch at the widest points and the vertical crack leaks water in the spring. Any suggestions?Vertical and diagonal cracks in concrete are quite common especially at windows. Often these cracks are annoying but structurally harmless. Cracks that run horizontally are less common and are often more serious when considering the possibility of a structural failure. However, it is still a good idea to monitor vertical and horizontal cracks especially when they are ¼ inch or more. You’ll want to know if these cracks increase in size over time.

To do this, tape or glue to each side of the wall adjacent to the crack 2 small pieces of overlapping paper. Make sure only one end of each paper is fixed to the wall. Put a continuous pencil mark across both paper tabs. Check the continuous pencil mark periodically to see if the pencil mark has separated. If it has, you know the crack is still increasing in size. You should consult a structural engineer if this is the case to determine the cause and possible remedies if required.

If the cracks are stable you can patch them with products such as Zipex, available at any local building supply company. This usually stops the water from seeping through the wall. You may also have site drainage problems that can be corrected which will in turn decrease the volume of water against the wall. See previous articles for information on site drainage or contact your local building inspector for advice.