Spring Series: Keeping your basement dry part one
Part One: Preventing
By March and April, most Canadians are anxious for spring to come. But for those whose basements leak every year, spring can mean unwanted stress and expense.
Keeping your basement dry can be a daunting task. There are so many possible causes that diagnosing the problem can be overwhelming for homeowners. We’ve put together a collection of posts to alleviate some of that stress by giving you tips to diagnose and deal with unwanted water. Read on for Part One: Preventing!
A quick disclosure: Part One is going to cover the “big fixes”. Not all basements will need such serious intervention. In fact, in most homes already have these systems in place, but we figured we would get the tough stuff out of the way early! Stay tuned for parts Two and Three, which will offer advice about maintaining these systems to keep them running effectively!
Damp Proofing
Damp proofing is a type of moisture control system made up of two layers of material. The first layer of protection, usually made of tar, is applied directly to the outside of your foundation to keep water from reaching interior spaces. The tar is typically sprayed or painted on and, because it’s nonporous, it keeps groundwater from penetrating your porous, concrete foundation. The tar is then wrapped in a high-density polyethylene membrane to keep stray gravel, pebbles or even ice from scratching away the tar.
Damp proofing should be done during the construction of the home and has been part of the Building Code for decades. Unfortunately, this doesn’t guarantee that homes, even new ones, are adequately protected. Some builders will cut corners to save money, leaving your home vulnerable.
One well known shortcut is to cut the tar with gasoline before applying it to the foundation. The tar goes much further, but the gasoline will evaporate leaving behind a tar layer that’s far too thin. The tar will often seep into the concrete rather than create a strong outer barrier, and water will find its way in through the weak points. Because the tar is then covered by the polyethylene membrane, it’s very difficult to catch this short cut during the inspection. This is a common source of wet basements in our area.
When we build new homes, our damp-proofing product of choice is Resisto. Resisto is a tar product that comes in sheets with a strong adhesive that sticks to your foundation. Rather than painting or spraying the tar on, we wrap the foundation creating a thick layer of tar to keep water away. We install Platon high-density polyethylene membrane over the Resisto to produce a strong moisture control system that keeps your basement dry.
Eves Troughs
Picture your home from a birds-eye view. Let’s say the dimensions of the house are 25ft by 40ft, giving you roughly 1000sq ft of roof protecting your home from rain and snow. How much precipitation will fall on a 1000 sq ft area?
Let’s say you have a modest 8 inches of snow on your roof when spring hits. If we convert that 1000 square feet to 144 000 square inches and multiply it by 8 inches of snow, we have 1 152 000 cubic inches of snow. We need to factor in that when snow melts and becomes liquid, we’re left with about 1 cubic inch of water for every 10 cubic inches of snow. So, we’ll divide 1 152 000 by 10 for a total of 115 200 cubic inches of water. There are 231 cubic inches in a gallon, so let’s divide 115 200 by 231. That makes the total runoff for this 1000sq ft home 498.7 gallons, or 1887.8 litres of water, and that doesn’t include any springtime rain!
Your eves trough system is what carries this water off your roof and away from your house. A proper system will not only carry water away from the foundation, but will discharge in a culvert or low-lying area where the water will drain away from the house. This keeps the water from saturating the earth around your foundation, which minimizes the risk of seeping through into your interior spaces.
Weepers
Damp proofing will keep the ground water from seeping through pores in your foundation. Eves troughs will displace the water coming off your roof so that it doesn’t fall against your home. But what about the ground water that arrives at your home from other sources? Enter, weepers.
Many homes, especially those in low-lying areas, will always have excess ground water. That water collects against the foundation where it should be stopped by well installed damp proofing. Your weepers are what stop that water from pooling outside of your home and carry it away from the building. This is especially important if you have basement windows that are low to the ground as they’re vulnerable to pooling water against the home.
Weepers work in much the same way as your eves troughs, just underground. We install a perforated, High-Density Polyethylene tube (the same material that’s used over the tar for damp proofing) with a cloth wrap (our favourite product is called “Big ‘O’”). We place it underground, just below the concrete line in your basement, and run it around the perimeter of your home. The tube collects the ground water while the cloth keeps sand and other particles from clogging it. The system dumps the water into your sump pit (more on sump systems later in this series!) where it’s pumped away from your home, adding another layer of protection against leaks.
Which System is Best?
All of them. When we talk about water management, we’re using an umbrella term (cheesy pun very much intended) that encompasses all three of the smaller systems mentioned above.
Each of them solves one problem: the eves collect and drain the runoff from your roof so that it doesn’t pool around your home (systems 1 and 2 in the image below), the weepers carry away any groundwater that finds it’s way to your foundation from other sources (system 3 below), and damp proofing keeps any remaining moisture from entering your home through your foundation’s pores (system 3 below).
Each of them will divert a portion of the water there are no guarantees against Mother Nature. The best way to protect your home is through redundant systems, which come together to create an effective water management system.
The drawing above illustrates a water management system with several redundancies to ensure your basement stays dry all year. Systems 1-3 are discussed in this post, 4 & 5 to come! Image credit to Chris Carman: Construction Artist Extraordinaire.
Stay Tuned…
Thanks for reading Part One of our 2019 Spring Series on Keeping your Basement Dry! We’ve covered preventative measures (AKA the “big fixes”). Next week we’ll be talking about maintaining your systems and things you can do yourself to keep your basement dry!