Picture of Build a Window Seat with Storage
What's a bay window without a window seat?  An unfinished and underutilized space waiting to be transformed!  Building a window seat is a basic "build-in" project and here's how you can do it.    
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Step 1: Plan It Out

Picture of Plan It Out
Since bay windows are not all created equal, you'll need to measure the angles of the walls.  The standard is 135° but there are other variations and the "as built" angles will probably be different.  Walls are never perfectly straight, corners are never perfectly get the picture.  In the end, you don't have to be super exact since a piece of trim will cover the gap between the wall and the seat, but the angle needs to follow the wall.

How deep you'd like your seat to be is the next question.  I build this one to be 24" deep so we could use a rug runner instead of cushions.  Runners are 21"-23" wide.  How deep your seat is will also determine how wide it will be.  At 24" deep, mine turned out to be 8' 5" long.  Since sheets of plywood are 8' long it would have been easier to make the front shorter than 8' long and let the depth work itself out.  In that way you could rip an 8' piece of plywood for the front whereas I used 2 pieces.    

On I found a sketch of the framing for a window seat (pic 2).  The height they recommend is 19" with a 21" deep seat.  You can see from the drawing that a window seat is actually a short floating wall achored to 2x4 cleats on the wall.  The front can be wood, sheetrock or other materials since it is only decorative.  The one thing I did differently from the drawing was to place the 2x4s on edge as opposed to typical wall framing.  This makes a sufficiently strong wall and also creates a bit more storage space inside the bench.  

Thanks for the excellent tutorial - I never would have made this otherwise. I thought I'd share a few lessons I learned along the way, probably lessons mostly useful for the novice like me rather than the experienced DIYer.

Firstly, I had lots of 'slightly-thinner-than 2 by 4' timber left over from a previous project miscalculation. It's about an 30mm wide, and I was concerned at first this wouldn't be strong enough or might make aligning the top of the lid fiddly, but it worked out fine and it seems plenty sturdy enough for 3 or 4 people of average weight to sit on it. My only concern would be the pocket joints on the back to front bracing pieces, but mainly because I don't have much experience of them (bought a jig specially for this) so maybe I'm being paranoid. Definitely get a pocket hole jig if you don't have one - I bought just the jig for about £5.50 if you don't want the much more expensive whole kit and caboodle. As long as you have a clamp you don't seem to need the rest so I'm not sure I get why there expensive kits out there? Someone will let me know I'm sure.

Allow plenty of room for the extra depth that making panels will create. I used 12mm MDF, with 12mm MDF panels, so that's 24mm extra depth right there. Sorry if that's an obvious thing to everyone but, hey, I didn't add it on in my calculations! Maybe because it wasn't obvious in the design sketch above so I ended up slightly closer to being flush with the bay than I had intended.

I had originally added a profiled pine trim to the lip of the lid and the seat - see it in the third picture if you look closely. However, this inadvertently led to the lid having a kind of sharp 'blade' that would be sure to do some serious damage to any little, or even big, fingers trapped in the lid. I reluctantly tore it off and used a flat profile 18mm thick strip of rectangular profile pine (to match the 18mm thick MDF lid) and this is much much safer. See picture 4. I was worried it would look chunky and out of place but it doesn't, it looks just fine.

It also makes finishing off the corners where the mouldings all meet much easier - see close up (which still needs some touching up on the grey paint!).

The unanticipated depth of the panels meant it was more sensible, I think, to work 'backwards' from the front of the seat to the back, as any left over gaps at the back of the seat were easy to cover with trim. I wondered though if in any case it would be more sensible to work backwards from the front, as this way you are guaranteed a perfect fit at the front where people will see it.

A tip on the piano hinge - the one I bought was fairly cheap and had not much 'indent' for screws to sink in to it's depth - as the screw holes on each 'flap' of the hinge lined up with each-other there was a risk that the screw heads would bump in to each other when shutting the lid, so it wouldn't lie flat and flush. The simple trick was to only screw in on alternate holes, so the screw heads never met - it seems plenty strong enough still.

The 18mm MDF is quite heavy - even this relatively small seat has a 1m wide lid which makes a room shaking slam if it falls shut. I 'borrowed' some Blum soft close door dampeners from my kitchen where there are 2 on every door - it turns out you only need one on each kitchen door for the exact same soft close effect so they were effectively spare. Even though they are very stiff, I need 3 on each side of the lid to be an effective little finger saver, and even then it won't prevent a smack on the knuckles, though I daren't try it. Adding the soft closers takes some fiddling - drill a hole though then for a screw hole, and position 2 near the hinge and one about half way down - this seemed to be optimal for my lid, but you mileage may vary. Warning: the momentum of the falling lid is pretty large so the lid will feel a force to 'pivot' on the dampers, effectively stressing and pulling 'up' on the back-most piece of the lid that holds the hinge in place, so make sure that has plenty of screws holding it down securely. While I did consider using 25mm MDF for the top, 18mm seems just fine and I can't imagine any amount of damping would hold a falling 25mm thick lid.

Finally, if you have shutters like those in the picture, I found that using a small round cushion at the back helps to stop people accidentally shutting the shutters by leaning back too far! Not ideal when you are trying to soak up the sun.

Thanks again for the instructable, I couldn't have done it without you.

kentdvm (author)  jojojolovell1 month ago
Beautiful! Nice job! Thanks for sharing!

Sharing was the least I could to repay your tutorial. I would urge others to give it a go, it really isn't as difficult as you might think with some planning and the right tools and materials for the job.

Just what i needed! I want to build a wide bench at the end of a hallway which otherwise would be wasted space. My enthusiasm outweighs my woodworking skill however your instructions are excellent and i can see myself being successful.
Before I begin, can i build the front frame just like a regular wall? Your 2×4s are faced 3.5" facing?
And thanks for mentioning that piano frames can be cut.
kentdvm (author)  anne.t.oreilly1 month ago
Great! Glad it was helpful. You can build the front frame like a wall and it would be even stronger. Yes, 2x4s are actually 1.5" x 3.5". Good luck. Share pics when conquer this project!
I realized later that you have the 2x4s positioned that way to improve your storage access.
My rectangular bench will be 46" wide and 28" deep. Do you recommend any changes to accommodate the extra depth?
kentdvm (author)  anne.t.oreilly1 month ago

I don't think you'll need to add any additional support. Not being an engineer, I would tend to test it for rigidity before installing top. If anything I'd guess you would be fine simply doubling the 2x4s spanning the top. A 2x4 on edge can support a lot of weight, but sit on it and see while it's still easy to add supports.

rshellem2 months ago

I made one over the last weekend and my wife loves it. I'm turning my formal living room into a play room for my two girls and the window bench will be perfect for toy storage. I just need to put my moldings on and I'm going to put a cushion on top

kentdvm (author)  rshellem2 months ago
Sweet! Nice job. I think you'll really enjoy the storage and use of the space.
UdyRegan2 months ago

I've never really been very fond of window seats - it's a good space for extra storage, but it really depends on whether the layout of your house can accommodate it or not.

jklavens6 months ago

This looks awesome and very easy to follow! My one question is: why is there a gap on either side of the face frame? The outer stiles are not flush with the outer edges of the rails. It looks pretty, so is it just for esthetics? Thanks!

kentdvm (author)  jklavens6 months ago
Thanks! The main reason was I didn't want to rip the edge at an angle to match the wall. I thought it would look okay offset so I rationalized being lazy and not messing with it. I like the look but at the same time it creates a little recess which is harder to paint, caulk, etc. If I had a "do-over" I'd probably rip the angle.
skunkworkx.7 months ago

Those sections aren't asymmetrical—which means one half is different from the other. You simply made the sections two different sizes, But both the left and right halves of the face section appear the same.

kentdvm (author)  skunkworkx.7 months ago
You are correct. It is symmetrical, but not uniform.

these are great instructions! Is it possible to build this as a removable bench, rather than securing it directly to the wall?

kentdvm (author)  Colleenpimentel1 year ago
Sure it could be movable. You would need to build a frame for the box and could use 2x4s & 2x6s. The back frame could be build similarly to to the front. Then the build would be pretty much the same.
cbunyan1 year ago
Many thanks - this has been really useful to help me get my head around what I need to do.
kentdvm (author)  cbunyan1 year ago
Glad to help and share. Once you get started it goes pretty quickly. Good luck!
briser31 year ago
I've included pics of my finished work. Well, almost..... I still need to do a final painting over where I patched all of the nail holes. But you can see how it came out.

Thank you for the awesome instructions. We were looking for ideas for a window seat, looked at yours and decided this was exactly what we wanted. The bonus was the terrific step by step instructions.
I spent about $250 for mine, and that included a new floor register and the ducting needed.

Thanks again!
kentdvm (author)  briser31 year ago
Wow! Awesome job! Glad it was helpful.
incandenza1 year ago
Thanks, that's very useful. Much appreciated. I'll check if those Kreg jigs are available in the UK.
incandenza1 year ago
Great job, and instructions. Can I ask a dumb question? (I'm pretty new to home improvements). In the front wall, how are you attaching the 5 blocks to the horizontal 2x4s?
Many thanks
kentdvm (author)  incandenza1 year ago
kentdvm (author)  incandenza1 year ago
Thanks! Not dumb at all. I used a Kreg pocket jig with 2 1/2" screws. In the 3rd pic you can see 4 oval holes in the face of the vertical 2x4. These are holes you drill using the Kreg jig which allows you to drive the screw. The screw enters the other board roughly midline and doesn't exit the other board. Very strong joint especially with glue. I use the jig more for 3/4" thick boards but it will even work on 1/2" boards. It is an easy and quick joinery system I would highly recommend. I use it for virtually everything.
rbookser1 year ago
I built a window seat this week using this design as a basis. I had a floor vent to contend with so I used a 8" base on the interior frame and just elevated the bottom of the face frame to allow for a vent. The whole thing looks very similar to your and my wife and daughter are ecstatic with the result. The bead-board sandwich is so easy to do and it made this a very usable, attractive and solid. Thanks so much!!!
kentdvm (author)  rbookser1 year ago
Awesome! Good job. We love ours too. Changed our kitchen!
Thanks for sharing the comprehensive step-by-step DIY techniques. They are easy to follow and the end results are amazing. A storage space under a seat is a really smart idea as it is a combination of 2 useful functions. The storage can be used for multiple purposes like for magazines or throw pillows that people often use while sitting on the window seats and enjoying the scenery.
DIYDragon2 years ago
I love these built in seats! I need to find a place to put one in my house. :-) Great instructable.
stephenf2 years ago
Very Nice. I like window seats - great places to read!
pinchebob2 years ago
Nice job both with the construction and the explanation.
kentdvm (author)  pinchebob2 years ago
wa7jos2 years ago
I built something like this for my son's house. The front of mine is made like a cabinet front with 2X4 structure supporting the top. In the cabinet front are 4 raised panel doors. The small ones on the end are decorative, but the two larger ones in the middle are operable leaving some storage space. I put a 1" thick bull nose across the front for strength. Then we had some cushions made to fit the top.
wa7jos wa7jos2 years ago
kentdvm (author)  wa7jos2 years ago
I like it! Nice job. I thought about making doors on the front but finally decided a lid would work better for us. Ours is surprisingly comfortable with just the rug although cushions might be in the future. Thanks for sharing!
janandrews2 years ago
This is great! Now I want a bay window so I can have a window seat.
heibert2 years ago
Great job! Thanks. May be i try to make same at my house.
Ohgeez this looks like the window seat set up I illustrated for this children's book for a woman close to Toronto. Almost a splitting image except there was also an a window at the top, the room was white and it was a stormy night. Spooky! :o
Takelababy2 years ago
Very nice
melmomma62 years ago
Beautifully done! It's just what I was looking for. Thank You for posting.
kentdvm (author)  melmomma62 years ago
Thanks! I know you'll like it;)