Finishing your basement is a great way to increase the living space — and value — of your home, but before you hire someone to install that new bar, home office or family room, make sure your basement is absolutely dry.
Concrete is used to build virtually all basements, and concrete is porous — it's filled with tiny air pockets that water can move through. At the same time, the ground around your basement is loaded with moisture looking for a place to drain. If there is an opening in your basement's moisture barrier, water will find it and end up on your basement floor. Or, it can seep in over time and cause mould and rot that you may not even be aware of behind your new walls and under your flooring.
Building standards and materials for moisture control weren't as good in the past as they are today, so you often find older homes with wet basement problems. Newer homes are built with better moisture protection, but that can still fail as it ages or because of the effects of ground movement or changes to the home.
In an unfinished basement, the first signs of water infiltration are visual. Look for water pooling or for wet stains anywhere on the walls, especially after a rain. Look for white efflorescence, which is the salt residue left when water wicks through concrete walls. If you see anything like that, you have a moisture problem.
Even if your basement passes the visual inspection, you may still have too much moisture in the walls and floor to cover them with drywall and flooring. Do this test: Tape a piece of clear plastic to the wall and/or the floor. If you get condensation in a few days, you have a moisture problem.
What goes into making a basement waterproof? Almost all of the moisture protection now required by the building code is applied on the outside of the concrete wall. The code requirements vary slightly from region to region, but the basics (and don't forget the code is the minimum standard) include a drainage membrane against the wall, sprayed-on waterproofing material, properly functioning eavestroughs and downspouts that direct water away from the house, and weeping tile at the base of the foundation wall.
You should also make sure your soil is graded so it slopes away from the house.
If water is getting into your house, one or more of these things are not functioning properly or were never properly installed in the first place. The weeping tiles may be old and broken or blocked up. Large tree roots sometimes break into the drainage system and plug it, causing water to back up and get into the house. Your yard could be directing water toward the house instead of away from it. You may find your basement only leaks when there is an extremely heavy rain — but even if that happens once after your basement is finished, you have a huge problem.
Some of these problems can be dealt with fairly easily. You can redo the landscaping. You can have your drains scoped to see if there are tree roots plugging them, or if there are other problems. (Believe me, that few hundred dollars will be the best money you spend before finishing your basement.) The downspouts can be lengthened so they expel water farther away from your foundation.
If you still have water problems, you may be looking at excavating around the house to inspect and/or replace the weepers as well as check your foundation. Foundation repair contractors can repair damage as well as waterproof the exterior of your basement walls with spray-on waterproof coatings and drainage membranes.
These solutions are the best, but they can be expensive, so the industry has developed some solutions that work from inside the house and cost less. Most are terrible — waterproof paint, a baseboard that doubles as a water collector. Forget about them. The only one I will accept is an interior weeping system hooked up to a sump pump. But make sure the pump expels the excess water far enough away from the house or it will find a way back in.
Even if you don't have evidence of water problems in your basement now, you can still develop them — depending on the way your contractor finishes the space. If he uses traditional stud framing with batt insulation and a vapour barrier, you will almost certainly end up with condensation and moisture build up behind your finished walls. You need to create a thermal break between the cold concrete surfaces and the warm air in the basement so that condensation never forms. (I'll talk about this in more detail in a future column.) Don't start your basement renovation until you are confident your moisture problems are solved, so you won't have to do what I do every day — rip everything out because someone didn't do it right the first time.
Mike Holmes is the host of Holmes on Homes on HGTV. E-mail Mike at mikeholmes@holmesonhomes.com or go to www.holmesonhomes.com
