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Community and Q&A

Material for Interior Window Sill

etting | Posted in General Questions on

I closed off the framing in the double walls around my windows with OSB.  I’ll finish the sides and top surfaces with drywall, but I expect to need something tougher for the interior sill, which is around 5-1/2″ deep.    My very low budget on this house is devoted to energy efficiency and air quality, so I want to spend as little as possible on the window sills without using anything that might outgas like some kinds of particle board.  It doesn’t need to be beautiful.  Any suggestions?

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  1. Expert Member
    Akos | | #1

    I used PG poplar painted to match the walls. Reasonably affordable and durable.

    1. etting | | #2

      Thank you, Akos. What is PG poplar? (Google doesn't know.) Roughly how much did you pay for it?

      1. Expert Member
        Akos | | #13

        Depends on how thick of a stock you are getting. The 1x stock is pretty cheap, similar price as trim per linear feet. 5/4 or 2x is more expensive but you also don't need all that much of it. Look at your local lumber yard or trim depot, they will be much cheaper than box stores.

  2. Expert Member
    DCcontrarian | | #3

    PG= paint grade

    1. etting | | #4

      Thank you, DCC. I generally don't know anything until I read it somewhere.

      1. Expert Member
        DCcontrarian | | #6

        None of us do.

  3. 5Stud | | #5

    A friend of mine used 5/4 cedar decking because it was so easy with the rounded edge as the bullnose and at the time fairly cheap for little labour. One cut.
    It looks a little worse for wear 5 or 6 years later, mostly staining, but since it is the full width of the opening, very easy to replace as long as you don't overfasten it

    1. etting | | #7

      Thank you, 5Stud. Decking boards are an interesting idea, and some kinds that would be safe indoors are fairly inexpensive.

    2. canada_deck | | #9

      Cedar is quite soft. If you anticipate that you might be placing stuff on the sills or that pets might scratch them, I'd aim for something harder.

      1. etting | | #10

        Thank you, canada_deck. Of the deck boards, the composites look best to me, as they're inexpensive, don't require paint, and should be pretty tough.

        1. canada_deck | | #16

          One problem with the composite deck boards is that the insides don't look like the outsides so if you plan on having this protrude beyond the wall, it won't look good.

  4. jollygreenshortguy | | #8

    I suppose it depends on your specific situation. But I've used simple, inexpensive white glazed tiles on a number of windows. The bright white reflects light nicely into the space. They're easy to keep clean, and I can put things like flower pots on the sill without having to worry about it.

    It's also the kind of small DIY job that adds a nice touch to a home.

    1. etting | | #12

      Thank you. I can see the appeal. It may be more work than I would take on at my glacial speed.

  5. Expert Member
    BILL WICHERS | | #11

    Poplar is probably the cheapest hardwood, and it holds up reasonably well, it just doesn’t stain well. Painting is no problem. If you have a trim router, you can easily use a round over bit to get a nice edge on the boards. If you want a more durable wood, you could go with oak or maple, but either of those will be significantly more expensive than poplar.


    1. etting | | #17

      Thank you, Bill. The 40' I would need of 1x6 poplar runs $129 at the local big store.

    2. Expert Member
      Michael Maines | | #21

      Poplar can take stain very well, if done right--I've seen faux-finishers make it look indistinguishable from black walnut, and I'm a wood nerd. Or leave it unfinished--I did that with a sunroom once and the color changed fairly quickly to a beautiful chestnut brown, with no hint of the green tinge it has when freshly cut.

  6. Expert Member
    MALCOLM TAYLOR | | #14


    If what you want is something cheap and fairly durable, go into a lumberyard and see what primed finger-joint trim they stock. Any of the wood ones they sell will be hard enough.

    1. etting | | #18

      Thank you, Malcolm. I was pleasantly surprised to see that the local big store has it, as finger-jointed products seem to be much rarer in the US than in Canada. It looks like a high-quality product, pricier than other options I'm considering at $51.88 for 1-1/4 in. x 7-1/4 in. x 84 in., but not wildly so.

      1. Expert Member
        MALCOLM TAYLOR | | #20


        I wouldn't pay a premium for it. I only suggested it because here it is often the lowest price reasonable alternative.

  7. Patrick_OSullivan | | #15

    Minor point: this is more accurately known as a window "stool", not "sill". If you take a look at any lumberyard's trim catalog, they should have a couple different profiles of window stool, likely in primed pine or poplar. These will have the advantage of having less sharp edges facing the interior (vs. some flat stock). As mentioned, you can also do a simple profile yourself. Just depends on how much work you want to do.

    1. etting | | #19

      All very good to know, Patrick; thank you.

    2. Expert Member
      Michael Maines | | #22

      I'd say it's more precisely called a stool, or stool cap, but it's not incorrect to call it a sill or interior sill. Sill is just used for so many other things that it's an imprecise term. Outside the US, English speakers often call what we call wall plates sills. Then there are the window rough sills and the exterior sills, or sill extensions.

  8. Expert Member
    Michael Maines | | #23

    I'd consider a local softwood, such as that used for framing lumber. Around here that's spruce or hemlock. When new it has too much moisture to use as a stool cap; it will shrink and warp, but if you let it dry and then run it through a thickness planer it can be a lovely finish material. Or you might find salvaged framing lumber that is already dry, with more character than new material.

  9. etting | | #24

    I ended up buying 1 in. x 8 in. x 8 ft. Primed Finger-Joint Pine Board that came out to roughly $20 per board with free shipping from Home Depot. It looks as if it will do nicely.

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