Almost every window well we make is named by three numbers in the same order — width × projection × height. Get those three right and ordering is trivial. Get one wrong and the well either will not drop into the hole or leaves a gap you have to fill with something.
Here is how to take each one, and what to do when the numbers disagree with each other.
Width: along the wall
Width runs horizontally along the foundation, parallel to the wall. Hook the tape at one side of the window opening and run it past the other side.
You want the well wider than the window, not the same size. A well that stops exactly at the frame leaves nowhere for the sash to swing and nothing to seal against on either side. Six inches of clearance past the opening on each side is a reasonable working figure for a standard basement window, more if the window swings outward.
Our widths run from 36″ to 96″. If your measurement lands between two stock widths, take the larger one — a well slightly wider than needed is a non-issue, a well slightly narrower is a return. You can filter the full catalogue by width once you have the number.
Projection: straight out from the foundation
Projection is how far the well stands out from the wall, measured perpendicular to it. This is the number people get wrong most often, because it is the one you cannot eyeball.
Projection matters for two separate reasons:
- The window has to open. A casement or awning window that swings out needs the projection to clear the sash at full travel.
- Egress, if the room is a bedroom. The National Building Code wants 760 mm of clear space in front of an egress window. A 30″ projection gives 762 mm and clears it. A 24″ well gives 610 mm and does not.
We stock projections from 12″ through 36″. The 12″ and 16″ wells are utility sizes — laundry rooms, storage, mechanical — and are not intended for a bedroom opening. If the room is a bedroom, start from the egress-ready sizes and read what the code actually asks for.
Height: down from finished grade
Height is the vertical drop from finished grade down to where the base of the well will actually sit. Not to the window sill. Not to the bottom of the window. To the bottom of the hole.
The lip of the well should finish at or just above grade so surface water runs away from it rather than over the edge into it. If the well is short, you get a step down into the well at ground level that collects everything.
Stock heights run to 42″. Where the drop is deeper than that — common in Winnipeg, Saskatoon, Fort McMurray and anywhere else the frost line runs past two metres — two wells of matching width and projection stack and fasten together. Order both and say so in the order notes so we can match the flanges.
If the hole is already dug, measure the hole
This is the single most useful rule on this page. Where an excavation already exists, its dimensions govern, not the window's. The hole is the thing the well has to fit into. A well sized to the window that is two inches wider than the excavation is useless until somebody goes back with a shovel.
So: open excavation, take all three numbers from the hole. No excavation yet, take width and projection from the window and its clearance requirements, then dig to suit.
Two mistakes worth naming
Copying the old well. A steel well that has been in the ground twenty years has usually spread at the top, settled at the base, or both. Its current dimensions are a record of how it failed, not a specification. Measure the window and the excavation instead — there is more on this in replacing a rusted window well.
Measuring the glass. Width is taken across the rough opening, not the pane. On an older basement window the frame can be several inches wider than the glass, and a well sized to the glass will not clear the frame.
When nothing on the list matches
We roll and form every well at our own plant in Calgary rather than buying them in, so a size we do not list is a quote rather than a refusal. Send us the three measurements and what the well is for, and we will price it.
Quick reference
- Width — along the wall, past both sides of the opening, round up to the next stock size.
- Projection — out from the wall; 30″ minimum if the room is a bedroom.
- Height — grade down to the base of the excavation; stack two wells past 42″.
- Existing hole — measure the hole, not the window.
Got your numbers? Shop all 213 window well sizes, or read how to install it before you dig.
Code figures here follow NBC 9.9.10.1. Provincial and municipal amendments vary, so confirm the requirement with your building department before you order.