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Renovating a full-height basement can be a relatively easy and cost-effective way to add new living space to your house. But is your basement really a good candidate for a renovation?
If your basement isn’t high, dry and sound, you should correct these problems before starting renovations.
If you are planning a basement renovation, you should inspect your basement for possible problems.
- Must you stoop to avoid bumping your head on a beam or duct?
- Are there intermittent or permanent traces of moisture or mold on the floor or walls?
- Is there a persistent musty odour in clothing and other objects that are stored in your basement?
- Are there cracks as wide as a pencil, or that appear to widen or shrink, in the walls or floor?
If the answer to any of these questions is “yes,” you should include the costs of fixing these problems in your budget.
Photo by: John Burrows
Figure 2 Basement office
Preparing the Groundwork
Building permit
You must obtain a building permit if you intend to alter the structure of your house, increase the size of windows or exterior doors, or change the occupancy — for instance, by adding a self-contained apartment (see CMHC’s About Your House fact sheet
Secondary Suites for more information).
The building permit ensures that the changes respect minimum standards of health and safety. To make a good living space, a basement should be high enough to permit ceiling fixtures or fans with space beneath for a 1.8-m (6-ft.) tall person to stand. Most municipalities require a height of 2.1 m (6.8 ft.) from finished floor to ceiling before they will issue a building permit, which is also the minimum height required by most electrical codes for a ceiling light. Some jurisdictions permit limited obstructions, such as beams and heating duct bulkheads, within this space. Ask your building official what minimum heights are required.
Moisture sources
Dampness or leaks in the walls or floor must be corrected, because a damp or wet basement isn’t a suitable living space. Moisture problems can ruin even the most expensive renovations and make your basement unlivable. Damp walls and floors result from holes or cracks in the foundation, insufficient dampproofing on the exterior face of walls, poor drainage at walls and footings and site grading that slopes towards the foundation, insufficient dampproofing on the exterior face of walls, poor drainage at walls and footings and site grading that slopes towards the foundation (see
Figure 3). Wetness may also be caused by a high water table, which exerts hydrostatic pressure on the walls and floor. The following are ways to repair common sources of moisture.
Cracks
Although small cracks may be patched on the inside, large cracks and other causes of dampness are best repaired from the outside. This often means using heavy machinery to excavate around the foundation walls to the footings. Once the walls and the top of the footings are exposed, it is possible to patch small holes or cracks with water-resistant grout. If cracks are large or appear to be moving, you should hire a structural engineer to investigate and recommend repairs.
Drainage
Water can seep up through the basement floor, appear at cracks and holes and accumulate at the perimeter where the floor meets the walls. If this occurs frequently or seasonally, it may be the result of an improperly functioning foundation drain. The drainage tile or pipe around the footing may be crushed, plugged or missing, and should be repaired or replaced. The drainage tile should be perforated with holes to collect groundwater, and positioned so that its bottom is below the basement floor.
Some builders enclose the drainage tile with a geotextile “sock” to keep fine soil material from clogging the tile. The tile and sock should be covered with at least 100 mm (4 in.) of clear, crushed stone extending to a free-draining zone over the face of the foundation. A length of unobstructed pipe should slope downwards from the foundation drain to the storm sewer to carry away any water that collects around the footings.
Ensure that the foundation wall has an uninterrupted coating of bituminous dampproofing, or a waterproof membrane when there is hydrostatic pressure. The coating should extend from finished grade to the top of the footing and seal the joint between the wall and footing. Cover this with a drainage membrane or free-draining fill to provide the drainage zone mentioned above, and slope the backfill so it will carry surface water away from the foundation wall. As an added precaution, create a clay “dam” around the foundation walls just below the topsoil, to deflect surface water away from the house. Figure 3 shows a foundation drainage system.
Figure 3 Concrete foundation wall with insulated exterior face
Eavestroughs and downspouts
Eavestroughs collect water from the roof and rainwater leaders, or downspouts, and carry it to the ground. When the downspout fails to direct the water away from the foundation, or the grade doesn’t slope away from the walls, this water may leak into your basement. A simple solution is to extend the bottom section of the rainwater leader at least 1,200 mm (4 ft.) away from the foundation, and to adjust the grade around the foundation so that it slopes away from the house.
Window wells
Window wells can collect snow and water, and often contribute to dampness in basements. The base of a window well should consist of 150 – 200 mm (6 – 8 in.) of free-draining material, such as crushed stone, and must be at least 150 mm (6 in.) below the bottom of the window.
Window wells are places where snow and water will naturally collect. Install a length of drainage tile filled with crushed stone from the bottom of the well to the foundation drain, to ensure rapid removal of standing water from the well. As an added precaution, consider installing a clear plexiglass cover over the well if you don’t plan to use the window for ventilation. If the bottom of the window well is less than 1,800 mm (6 ft) above the footing, consult a geotechnical engineer about protecting the footing from frost action.
Figure 4 Window well at basement wall
Floor drains and sump pumps
Most basement floors in houses built after 1900 are sloped to a drain that, in turn, slopes to a sewer or dry well. It became common practice after about 1940 to install a ‘P’ trap in the drain, to prevent sewer gases from entering the basement.
If you intend to live in your basement, ensure there is a proper drain with a trap situated at the low point of the floor. The trap should be kept full of water to function properly and should be topped up periodically.
If there is no sanitary sewer in your vicinity, you may install a sump pit with a pump near the lowest point in the basement floor. The sump pit should be capped and sealed to prevent soil gases from entering. The pump should discharge to a dry well or to a location above ground where the water will not leak into the basement.
Backwater valves
A backwater valve is a device that automatically closes to prevent sewage in an overloaded sewer line from backing up into your basement. A properly installed backwater valve should be located to prevent sewage from coming through any fixtures in your basement, such as sinks, toilets, showers and laundry tubs. Installing a backwater valve may be expensive, but it can protect your basement renovation from serious damage, such as that which often occurs during periods of heavy rain.
Let's look at the basics first – the type of paint is determined by its thinner or binder.
