How to build a bay window seat with storage

a diy bay window seat with storage and cushion. A tabby cat sits on the cushion enjoying the sun.

For the longest time, I have wanted a window seat in our living room bay window. When Oli and I first rented our own flat, it was in a massive Victorian terraced house in Battersea, with really high ceilings and a huge bay window. There was a window seat in that window and I loved it. Ever since then, I have wanted one in our house. I found various guides and YouTube videos on how to build a bay window seat with storage, but nothing was exactly what I was after. So here is my version, a hybrid of various other guides I have read, and I hope it will help you with your DIY bay window seat with storage.

DIY bay window seat with storage
Just casually hanging out on my window seat

It was really important to me that we did not damage our original skirting boards. This guide is perfect for you if you have a period property and would like to build a bay window seat with storage, but you don’t want to damage your original features. This seat has been constructed around the existing skirting boards without the need to cut into or remove them. There is no drilling into the floorboards either. I totally get that some future owner may not want an MDF window seat, but hopefully will still want their Victorian features, so the seat can just be removed.

What style to go for?

I was torn between two styles. The style of my old flat which mimicked the shape or the window, or flat across the front. I like both styles but I slightly prefer those that follow the shape of the window. However, in the interests of getting as much storage as possible and also because I wanted an easier design to build, I went for a flat across the front style.

What you will need to build a bay window seat with storage

Tools

Where relevant, I have linked through to the exact tools I used (these are affiliate links, meaning if you shop through them, I will earn a small commission. I have only linked to products I have personally used in this project).

I always recommend Bosch tools. For beginners they are perfect – easy to use, quite lightweight and I particularly like that the battery can be used across the range you go for (note that the ‘green’ range is for DIYers and the ‘blue’ range is geared toward professionals (though I think more advanced DIYers is probably the real market). The ‘green’ batteries won’t fit ‘blue’ tools and vice verser. If I have stated the tool linked to is sold ‘bare’, it means it comes without the battery and charger, which you can buy separately. Remember the batteries are interchangeable between all tools within the range, so it’s fine to buy them bare once you own a couple of batteries. I have two batteries, so that one is always charged (that’s the theory anyway).

Bosch cordless mitre saw

Materials

  • Various screws – I used 3.5″ masonry nails for attaching the frame to the wall and then variously sized screws for putting the frame together (1.5″ to 3.5″ wood screws depending on the depth I was screwing into).
  • Rawl plugs
  • Sawn timber for the frame – I used 45mm x 95mm but with my mitre saw, I did have to turn it around as it was a little too thick to cut through in one action.
  • 12mm to 24mm MDF for the top (or ply which is probably better for the hinge – I’d use ply if I did it again). Make sure it’s thick enough for your hinge!
  • Piano hinge for the thickness of the MDF / ply top
  • 6mm MDF
  • Half dowels
  • Panel pins
  • Moulding pins
  • No More Nails
  • Wood filler
  • Caulk
  • MDF sealer
  • Paint of your choice, suitable for wood (I used Satinwood from Little Greene)
DIY bay window seat with storage

How to build your bay window seat with storage

I’ve broken this down into steps to make it as easy to follow as possible. I’d never built anything like this before and beginners can do it. Mine isn’t perfect but I’m really proud of it and it looks great.

Sketch your design

First and foremost, draw out a sketch of how you want the seat to look. This will help with measurements and working how much of everything you need to order. If you prefer to see things place to visualise, use masking tape to map out the seat in situ. I went for a straight fronted bench as I wanted a bay window seat with storage and this shape maximizes the storage space.

I set the window seat back a bit from the edge of the wall as it would have been too deep otherwise and look out of proportion.

Your window won’t be exactly the same size as mine, so I won’t list out all my measurements. Instead, the best thing to do is use the image below of my frame and work out your own measurements, then mark them onto your sketch. Once you are ready, cut your battens for the frame to size. I suggest doing these in stages, in case you need to make any tweaks to your design as you go.

DIY bay window seat frame

Build the frame

This is the most tricky part, but you’ll be pleased to hear it is easier than it looks and a beginner can certainly do this. I had never used a mitre saw prior to this project, so it is absolutely do-able!

DIY bay window seat with storage

The frame is tricky because of the angles and needing to get everything level – your period floors probably are not! There are a couple of ways you can measure the angles. You can use an angle finder or you can do what I did and use two pieces of card to create a template and measure the angle from there.

When attaching each batten, you can make it extra strong by also using No More Nails as well as screwing into position.

Wall battens

Position where the top of the frame will sit, starting with the middle batten. When considering where to position the batten, you should account for the MDF lid and also any cushion you may put on top. I used the height of our sofa seat as a guide.

DIY bay window seat with storage

Attach the first batten using 3.5″ masonry screws and heavy duty rawl plugs. Use a spirit level to make sure the batten is straight.

DIY bay window seat with storage

Next, attach the two battens to the outer bay window walls, always using the spirit level to ensure they are level. Remember period properties are usually pretty wonky. By the way, the angled cuts on my outer battens should have been at the front for the MDF to sit against. Whoops! It didn’t matter in the end, but you can learn from my mistake!

DIY bay window seat with storage

Top front batten

Next, cut a length for the front of the frame. You will need to cut at a angle as illustrated in my picture and you will need to measure this based on your window. The easy way to do this is to hold your length of wood under the out wall battens and make a pencil mark where you need to cut. As always, use the spirit level to measure regularly that everything is level.

DIY bay window seat with storage

When you are ready to screw in place, first use the pocket jig to make holes at an angle for the screws to sit in. The pocket jig is really handy, as it ensures the screws sit tight in place and the screw heads don’t stick out. Once you have made the holes with the pocket jig, fix the batten in place.

DIY bay window seat with storage
A pocket jig is used when you need to drill in at an angle

Vertical battens

Next, cut at least three pieces of wood to size to position between the floor and the front batten. I made mine a really close cut and knocked them into place with a hammer. This is because I didn’t want to drill into the floor, so I wanted really firm pressure. You could add brackets to attach the battens to the floor if you prefer, of course. I used my countersink bit before screwing the battens into place from the top. I used three, but later, after adding the bottom front battens (below), I added more (between the top front batten and the bottom front battens) to make it easier to attach my panelling.

DIY bay window seat with storage

Bottom front battens

Next, add the bottom battens. I screwed these into place at an angle, using the pocket jig first.

DIY bay window seat with storage

Seat battens

Then you need to add some battens to secure the front and back of the frame. I used the pocket jig again and screwed in at an angle. In hindsight, I would add only one batten in the middle rather than two. I did this because I thought it would make it stronger, but it wasn’t really necessary and makes accessing the storage space tighter, so go for one (I will probably adjust this at some point in the future).

DIY bay window seat with storage

Use the mitre saw to cut angled battens. You can hold the length of wood under the frame and mark with a pencil exactly where to cut.

DIY bay window seat with storage

Floor battens

Finally, I added battens from the front of the frame to the back wall to hold in place if it gets knocked. These were cut to fit very snuggly and I didn’t screw them in place, but just knocked them into position with a hammer.

I didn’t do this, but if I were to build another, I would paint the frame at this point.

Attach MDF cladding

Next you need to attach the MDF cladding to the front of the frame.

I used panels of 6mm MDF for the front of my seat, but you could get one long panel cut to size. If you opt for this, be sure to get it cut to the widest measurements (i.e. wall to wall rather than skirting board to skirting board).

DIY bay window seat with storage
It doesn’t matter that there’s a gap here because of the step below. If you aren’t panelling you’ll
need to cut to the shape of the skirting board at this point

Scribe the shape of the skirting board

As I did not want to remove the skirting board, I opted instead to scribe the shape of the skirting board onto the MDF using a scribing compass. You can watch YouTube videos of people doing this to get the idea.

Once you have drawn the shape of the skirting board onto the MDF, you need to cut it out using your jigsaw. I highly recommend you practice cutting intricate shapes out first.

DIY bay window seat with storage

The MDF will now sit nicely against the skirting board.

DIY bay window seat with storage

Note that if you are going to add panelling, like I did, you only need to scribe the top piece of MDF. It doesn’t matter if the bottom bit isn’t flush against the wall as no one will see this.

Attach the panelling

I think window seats look better with panelling, whatever style you go for. I opted for three panels, with one larger one in the middle. I cut 6mm MDF strips to size using my mitre saw (though you could get these cut for you in a DIY shop) and attached as above using No More Nails and panel pins. I clamped in place for an hour or so to get a really close bond. You don’t need to keep it clamped this long, but as with all my DIY projects, I did a little a day during lunch hours and baby nap times!

DIY bay window seat with storage

Consider an air brick

You may wish to build an air brick into your design. I didn’t bother for two reasons. 1: the rooms has been replastered with gypsum, so it can’t breathe anyway (and in hindsight, I would have gone for lime, but equally, it’s not the end of the world) and 2: there is still circulation from the holes I have cut to access the lid. If you do go for an air brick, I have used these elsewhere in the house and they are lovely and come in a range of attractive designs.
DIY bay window seat with storage

Attach the seat / lid

I used 12mm MDF for this, but you could also use ply. I bought four panels which I then cut to size. This worked well as I need 2 x triangle sections on each side which are fixed in place and 2 x opening panels in the middle to access with storage beneath. The main feature for this window seat is the storage, so having a big opening section was important and I really think you’d be missing a trick if you sealed the whole thing shut.

DIY bay window seat with storage

You can either cut the panels flush to the front of the seat, or add a little lip. I cut mine flush and then added a half dowel at the end, which gave a perfectly rounded finish.

Cutting the angled sections

A cheats way to do this is to fold a piece of A4 paper diagonally over to create a triangle that sits with its hypotenuse along the edge of the bay window, as shown below. You then use this as a template, draw on your line and cut with a mitre saw.

Position everything in place before fitting

Position your four panels in place before fixing the two triangle pieces in place. This helps ensure a good fit. Also, it’s best the panels have a little bit of give between them rather than being a really tight it as they may expand a bit. I certainly found that mine did after sitting in place a while.

Also, paint everything before fitting it – much easier than bending yourself at impossible angles like I had to!

Fix the triangle panels in place

Fit your two outer panels in place with No More Nails and screws in at angle using the pocket jig. Where you are able to screw straight down (i.e. at the front), use a countersink bit first so the screw doesn’t stick out.

Fill over your screw holes and any joins in the MDF or gaps with woodfiller. I smooth mine over with a damp cloth after filling and then used my sander to sand back to a really smooth finish. Also, as a side note, let’s not be snobby here. If you aren’t a professional carpenter, it really doesn’t matter if your cuts aren’t perfect. Filler is your friend and once painted I promise you, no one will notice.

DIY bay window seat with storage
Wood filler fixes all!

Make sure everything is painted nicely at this point, before adding your opening lid sections.

Cut opening lid panels to size

You will need to cut your panels to attach the hinge. Make sure you account for anything that could get in the way of the lid, for example, my window sills stick out a lot – you don’t want this to stop the lid opening fully and therefore limiting access to the storage below. A cut about a third of the way in should be fine in most cases.

DIY bay window seat with storage
Mark out where to cut your opening panels

Attach piano hinges

I bought my piano hinges online here. They cut them to size (for free) which was very handy. Make sure you understand which way the hinge will open before screwing it on. I don’t know how, but I got it wrong about 5 times!

DIY bay window seat with storage
DIY bay window seat with storage

Add decorative elements

Finally, add any decorative elements. I ran a half dowel along the front of my bench for a nice curved edge.

DIY bay window seat with storage

I also added decorative moulding to the inside of my panels. I found it really easy to cut to size using a mitre cutter.

Final thoughts – bay window seat with storage

My bench isn’t perfect, but as a first ever DIY carpentry job, I’m happy with it. And also it shows you can have a go just to learn. I love my perfectly imperfect bay window seat with storage and I hope you’ve found this blog useful. If you fancy finishing your new bay window seat off perfectly, head over here to find out how to make a window seat cushion to sit on top.

DIY bay window seat with storage
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