How to Make a Window Sill

Posted by John on August 6th, 2012

Hope everyone had a great weekend!  Lisa and I were upstate in NEPA on Friday for an annual golf tournament that’s held in memory of my father.  It’s usually a great time and the proceeds are donated to a local charity.  This was the fifth year we’ve had it.  The tournament is organized and run by a committee of people that knew and worked with my father and they do a masterful job making it happen every year.  It’s a lot of work on their part and our family is deeply grateful for their efforts.  I especially enjoy seeing all those folks that knew him very well.  It’s nice to be reminded he was well liked and is still missed.

Even though golf is supposed to be a leisurely sport, it’s a long day on the course and it was pretty hot out.  We didn’t get back home until late and Saturday I was pretty sore all day (I golf like once a year).  Consequently, this weekend wasn’t that productive in terms of home projects.

We don’t have a lot of work left to do on our dining room wainscoting project.  We were able to squeeze in some time this weekend to get some painting done and if you’re following me on Instagram (john_ohfs), you were able to catch a sneak peek of the current progress.  We still have to do some touch up painting, wire the outlets and add the shoe molding (which we’ll be staining ourselves to save money).

Right before we added the cap and started painting, I made a new window sill since the old one was too small with the paneling on the wall.   When I told Lisa that I needed to make a new sill, she asked me if we could just buy one at Lowe’s.  If you didn’t know, you can’t really buy window sills.  You may be able to find some online, but the best way to get a window sill is to make them.  I’ll show you how we made ours and you’ll see it’s not terribly difficult.  It took me all of about 30 minutes to make ours.

Here’s how to make a window sill.

Once the paneling was completed under the window, I put this old sill back in.  I kept it and didn’t throw it out because I wanted to use it as a template for the new one.

You can see that the old one is too short on the back edge.  No problem.  I’ll just measure from the front of the old window sill to the window.  That’s how wide the new window sill will need to be.  For material, I bought some poplar.  The piece was a 1x6x8′ and cost around $20.  I almost always use poplar for painting projects.  It’s the same wood that’s all over the wainscoting.  It’s only slightly more expensive than first select pine, but it’s a hardwood, whereas pine is a softwood.  Does that make a difference?  I think so.  Over time, pine will be more prone to showing dings and dents and poplar may not.

To begin the replacement, I used my window sill router bit and routed a window sill profile on the entire front edge of that new poplar 1×6 I bought.  It’s better to put the sill profile on the entire board first before cutting out the shape of the sill.  You can cut the board first and then route it, but if you make a small mistake while routing it, you pretty much need to buy a new board.  If you make the mistake early, you can flip the board over and route the other side.

Once the profile was on the new board, I laid the old window sill over the new board.

I lined up the edges of the old sill with the edges of the new board and traced out the profile of the old sill onto the new board.  To make sure the new board would be the right size, I added some additional width to the back of the poplar piece.

Then I just cut along the lines I drew.  I used my table saw for the long straight cut along the back and my hand held jigsaw for the shorter cuts.  Once it was cut out, it installed with some shims, construction glue and finish nails.

I made sure to shoot at least one nail through each shim.  To remove the unused portion of the shim, I scored it with a box cutter and then cracked them off.

The gaps against the window will be resealed with painter’s caulk.  This new one actually sits a little lower than the old one.  You can tell by looking at the old caulk marks on the window.  Not sure why.  Don’t really care.

We’ll show you it painted along with the rest of the room very soon.

Ever install a window sill?  Do you need to replace any?  Get anything done this weekend?

Posted in Carpentry,DIY Projects. Tagged in ,, , ,

  • You're right, it doesn't seem too hard. Good work!

    • John_OHFScratch

      Thanks Whitney! Looking forward to your floors!

  • Man, I wish I had a garage or shop with power tools. I would have sooo much fun. You did a great job on the sill!

    • John_OHFScratch

      Thanks Lisa!

  • Kristen

    The sill looks like it was the original! Great job!

    • John_OHFScratch

      Thanks Kristen!

  • Johnny

    Hate to break it to you, but you actually can buy window sills online, there's various companies who sell them made to order.

    • Gabbie

      Hate to break it to you, but he didn’t say you couldn’t. He actually said “If you didn’t know, you can’t really buy window sills. You may be able to find some online..”

  • linda

    I’m new at DIYing and trying my hand at some projects. I may have missed it reading your blog but why did you put shims under the sill? Did it need to be leveled? Thanks.

    • John @ OHFS

      Yep. The sill just needed to be leveled a bit.

  • Sharon Macarty

    My husband replaced a window in an old house. There was still a problem. The window sill was not in good shape. I took a piece of wood, 6″ wide. I measured the length of the inside of the sill. I added 3″ in length to each side of the board. I carefully measured the width and length of the inside of the window. I used a small hand saw to cut the 3″ extension on each side. I sanded it, used min wax on the sill. To insert it, I used no nails or screws. I placed in. with one end extended up on the window at a slant. I brought the wood down slowly on the sill that was standing at a slant. I carefully moved it into place and it fits beautifully. The measuring was very important. It looks very professional. To remove it, I lift one end up and slowly pull it out. It has a perfect fit. I have had fun with my old house. It is turning out to be a show place. I am finishing it and it will be placed for sale soon. It is 5 miles to Bear Lake Idaho where there is crystal clear and good tasting water. Property there is extremely low priced.

  • disusbug

    Great work. How did you route it. Was it free hand or using a table.

    • John @ OHFS

      It was on a router table.