Trish Bongard Godfrey

How Low Can You Go? Lowering Your Basement

13 May 2015
Trish Bongard Godfrey

Living space is at a premium for most of us, and one of the most practical places to capture more space in your home is the basement. When most of our houses were built, 80 or 100 years ago, basements weren’t designed for living. They were functional spaces, designed for furnace and plumbing connections, basic storage, and for getting the foundation below the frost line. But these days, a basement is considered an integral part of most homes.

A finished, livable basement is a great investment in your home – one you’ll be grateful for when it comes time to sell. Lowering your basement 18” can transform a 5’8” spine-crunching laundry room into a 7’4” living space. Instead of using it to store your bike in the winter, you could put in a comfortable rec room or a much-needed second bath. Instead of hiding boxes of tacky gifts from your in-laws in the basement, you could hide your teenager down there, in their own suite – they’ll love the independence. And of course, a basement apartment is an option for earning extra rental income.

Lowering a basement is specialized work. Find a skilled contractor with expertise in underpinning and waterproofing basements. You’ll be trusting these professionals with the foundation (literally!) of your home, so do your research. Choose someone with experience, make sure they have proper insurance, and ask for references. A qualified and trustworthy basement contractor should also help you sort out the necessary permits for your reno.

An engineer will assess the depth to which your basement can be dug. The biggest limiting factor will probably be cost – basement lowering is a big job, and shouldn’t be done on the cheap. From estimates I’ve seen, underpinning (digging down and rebuilding the foundation wall in sections) can cost between $300-$500 per linear foot. Bench footing, another method of basement lowering, is less expensive but may add less space. Sometimes both methods can be combined in one job – be sure to discuss all your options when getting quotes from contractors.

Waterproofing the basement is vital. Especially if there have been problems with moisture at the current depth, take steps to prevent more dampness after the basement is lowered. It doesn’t get drier the deeper you dig! Interior waterproofing is economical and effective in the short-term, but the best long-term solution is to fully waterproof the basement on the outside. Consider installing a sump pump (if you don’t have one already) to protect against flooding. Also, if your new basement is lower than the main waste connection from your home, a sewage ejector may need to be installed.

There are lots of factors to consider when planning this reno, but if you’re hurting for more living space, it could be the perfect solution.