Home & Garden

Fill in basement window

  • Last Updated:
  • Jul 25th, 2010 9:15 pm
Aug 26, 2003
414 posts

Fill in basement window

I am looking for some advice on how to fill in a basement window.
It is currently under a deck and very little natural light comes through.

I will be finishing my basement and covering up this window.
My foundation is poured concrete and the window opening is 40" x 18".

I have researched a few options.

1. Fill in with concrete block and parge.
2. Build a 2x4 pressure treated frame and use concrete board flush on the outside.
3. Build plywood forms and pour concrete into the window.

The problem I have is accessibility from the outside is very limited so whatever I do an interior solution would be best.
I would need to rip up all of my deck boards to access the window from the outside.

Has anyone done this before and have any suggestions?

My main concern is once I cover up this window, I want to make sure it does not leak since it will be behind drywall.
2 replies
Sr. Member
Nov 24, 2002
890 posts
The only true way to water proof it is from outside. As far as closing it in, the easiest thing to do is brick it in. Brick or cinder block works best, and is the easiest. Concrete is too messy, and too much work. The opening is already structurally sound.

There's lots of great products and home depot/lowes to make brick/cinder block water proof (blueskin).
Sr. Member
Oct 7, 2007
502 posts
You won't need to fill with concrete since the structure has already been designed for an opening so all your doing is basically filling the void (no need for structural strength in the material filling void). The easiest way to do this is to use concrete block and have it waterproofed from the outside.

Then when you go to finish the basement, you would do the same spray foam/ insulation and vapour barrier.