Finishing your basement this winter: what to sort out first

Most of a basement renovation happens below grade and out of the weather. Framing, insulation, drywall, ceilings, flooring and the bathroom don’t care whether it’s snowing outside, and a basement finished over the winter is ready before the spring thaw and the summer, when families tend to use the extra room most.

The catch is that a few parts of the job do depend on the season. Anything that involves digging outside, cutting the foundation or pouring concrete outdoors is easier before the ground freezes. Water problems are easiest to spot in the wet months, not in the middle of a dry January. And the holidays slow down suppliers, offices and everyone’s calendar, including yours.

That’s why we like to plan winter basements in the fall. If you’re reading this in late October or November, you’re in the right window to sort out the pieces below before the cold sets in.

Fall rain is the best test your basement will get before spring. After a heavy rainfall, go downstairs with a flashlight and look at the corners, the bottom of the walls, around the windows and wherever pipes come through the foundation. The City of Toronto points out that a damp floor in the corners can mean the weeping tile isn’t working properly.

Winter can hide a problem. Once the furnace is running, the air dries out, and a wall that was damp in October can look fine in February. The water hasn’t gone anywhere; it comes back with the thaw. That’s why we want to hear what your basement does in the wet months, not just what it looks like on the day of a visit.

If you’re not sure whether moisture is coming through the concrete or condensing on it, tape a square of clear plastic tightly to the wall or floor and leave it for a day or two. Droplets under the plastic point to moisture coming through the concrete. Droplets on the room side point to humid air meeting a cold surface. Neither one rules out a finished basement, but each changes what goes behind the new walls.

• Photos after a heavy rain, with the date
• Any staining, white powdery deposits or peeling paint
• The corners where the floor meets the walls

A few basement jobs start outside. Some can still be done in winter, but frozen ground, snow and cold concrete make them slower and harder, so we try to deal with them first.

Not every basement needs a building permit. In Toronto, finishing the basement of a house generally doesn’t need one when there are no structural changes, no new plumbing and no second unit. Add a bathroom, change the heating, underpin, build an entrance or create a second suite, and a permit is required. Electrical work is a separate process. Almost all of it has to be reported to the Electrical Safety Authority, and anyone you hire to do it must be a Licensed Electrical Contractor.

We’ll tell you at the walk-through whether your plan needs a permit, and if it does, get the drawings started early. Toronto reviews complete house applications within 10 business days, but complete is the important word, and a package that comes back with comments takes longer. The statutory holidays at the end of the year slow everyone down, so it helps to have the application in well before Christmas.

Ordering works the same way. Windows, doors, vanities, specialty tile and some flooring take a while to arrive, and suppliers get busy before the holidays. Choosing those items early means our crew isn’t waiting on a box when the walls are ready. If you’re picking a new floor, our guide to floors in heating season explains why it should sit in the house for a while before it goes down.

Winter adds a few practical jobs. Drywall, lumber and flooring arrive in bulk, and a cleared, salted driveway and path make deliveries safer for everyone. If the basement has its own door, it’s usually the best way in, because it keeps materials and boots off your main floor.

Salt and slush are hard on finished floors. We lay protection from the entrance to the basement stairs and keep it down for the whole job. We’re also happy to plan around where you park, where the snow gets piled and where a disposal bin can sit without blocking the driveway when the plow comes through.

Think about heat as well. The basement needs to stay warm for drywall compound, paint and adhesives to set properly, and the product labels give their minimum temperatures. If part of the heating system is being moved or extended, plan when that happens so the rest of the house stays comfortable on the coldest days.

In summer you’d open a window while the paint dries. In January that isn’t practical for long. Health Canada lists paint, glue and varnish among the building materials that release volatile organic compounds, and its advice is simple: increase ventilation when you use them, and choose products that give off less where you can.

In a winter basement, that comes down to a few habits. Pick low-emission paints, adhesives and sealants, and read the label before you buy. Keep the basement door closed while products cure, and run the bathroom exhaust fan or another fan that vents outside, so fumes leave the house instead of drifting up the stairs. If your house has a heat recovery ventilator, keep it running. Anyone sensitive to smells, along with babies and pets, may be happier spending the painting days on the floors furthest from the basement.

Flooring adhesives, grout sealers and finishes on wood stairs deserve the same care. We schedule them so they have time to cure before anyone needs to walk on them, and we’ll tell you ahead of time which days will smell the strongest.

Health Canada recommends keeping indoor humidity between 30 and 50 per cent. A basement that used to sit cold and empty behaves differently once it’s finished and heated. In winter the air down there usually gets drier, but drywall compound, paint and concrete patches all release moisture as they dry, and cold water pipes can still sweat. Health Canada suggests drying those pipes and insulating them with foam.

Spring and summer are the real test. Warm, humid outdoor air reaches a cool basement and the humidity climbs. Health Canada recommends running a dehumidifier in damp areas such as basements, with the windows closed while it runs. We plan for that while the basement is being built, leaving a spot for the dehumidifier near a floor drain or the sump so it can drain on its own, with an outlet beside it.

An inexpensive hygrometer from a hardware store is worth having. Check it a few times through the winter and again in June. If the reading stays above 50 per cent, deal with it before mould gets a chance.

This isn’t a schedule, because every basement is different, but it’s the order we follow for a winter project.

1. Late fall: watch and fix outside

   Watch the basement through the fall rain, take dated photos, and sort out downspouts and any other outside work before the ground freezes.

2. Before the holidays: decide and apply

   Settle the layout and what the basement is for, get a written estimate, and submit any permit application with complete drawings.

3. Early winter: order and protect

   Order windows, doors, fixtures and flooring, and set up floor protection, dust barriers and the delivery route.

4. Mid-winter: build

   Repairs and rough-ins come first, then inspections, insulation, drywall and ceilings, with the basement kept warm for the finishes.

5. Before the thaw: finish and test

   Flooring, trim, paint and fixtures go in, and the dehumidifier and its drain are ready for the first humid weeks of spring.

Our basement renovation page covers layouts, bathrooms, ceilings, second units and pricing. These guides and local pages pick up where this one leaves off.