Max using a jigsaw to cut out a template for the new plywood van floor

How to Build, Insulate & Lay a New Plywood Van Floor

| Our Citroen Relay Van Build

Like most things have done with the van build so far, the van floor took longer than expected. It is however a crucial part of life, having a floor, so, let that inner carpenter out because here’s a detailed ‘How To’ for all you keen van converters.

If you’d prefer to watch, here’s our video…

To use the existing plywood van floor or not?

We could have used the existing plywood floor as it wasn’t in too bad a condition, but the perfectionists inside us won that battle and decided we could do it better. But we did keep the existing van floor as a template, which did help, a little.

If your van floor is in good nick and it fits well, save yourself a million trips in and out of the van fitting new wood and keep hold of it.

Fitting your van floor support battens

We decided that the more support battens for our van floor the better, because this means added strength and support for the weight of our kitchen and seating, when they go in. Now we know we can screw into the battens and not just the ply floor.

Tom marking out measurements on a wooden batten for the floor

Like most van floors, our Citroen Relay’s floor is (annoyingly) corrugated, so we placed the battens on the highest parts of the van floor, to ensure we had sufficient depth and space to add insulation.

We used 50mm x 25mm battens at 3 metres long which covered the length of the floor.

Once Tom had cut them to size and planned the layout we cleaned the area beneath each batten and secured them in place with Sikaflex. We DID NOT use any screws because we didn’t want to create any more holes in the van. Sikaflex is super strong and came with lots of recommendations. So, we trusted the reviews and liked the idea of not screwing into the van any more than necessary.

Top tip: We added a batten along the edges of the doors as this will be a well-used area and can do with as much support as possible.

Tom vacuuming the floor with a Henry Hoover
A tube of Sikaflex adhesive lying on the floor and on a recently glued wooden batten

Cut & fit your van floor insulation

We used the Xtratherm Pitched Roof Insulation Board (25mm x 1200mm x 2400mm) to fill in between the battens.

Close up of Tom cutting the insulation board with a stanley knife for van floor

We found that the best way to cut them to size was to measure, (measure and then measure again) then draw your line and cut with a 9mm Stanley blade. You can use a metal ruler along your line if you need an edge. But a consistent sawing motion, with the blade at an angle worked well.

As with most van-related cutting, if you’re not confident, aim for bigger than smaller. You can always cut or ‘nobble’ bits off, but it’s harder to add bits on.

Foam party! Fill the gaps with expanding foam

Now you have the battens and insulation in your van floor, it is time to fill any gaps.

Tom filled all gaps between the wooden battens with expanding foam. And when asked what technique he found most helpful he said: “fill it with just the right amount”. This is totally useless as it is entirely obvious but, all I know is that you hear through the grapevine that the saying ‘the more the merrier’ does not apply to expanding foam. So, all I can tell you is, go easy and don’t apply too much.

Once dry, we trimmed the excess foam off with a Stanley blade.

Complete your vapour barrier

Go big or go home. Not necessarily true but when it comes to a vapour barrier we did go for it. We know that many other converters have used the aluminium foil tape along their battens to complete the vapour barrier (the insulation board has a foil outer layer which acts as a vapour barrier) but the aluminium tape is quite fiddly, and we had a whole roll of Vapour Barrier so Tom just went for it. Then, we covered up all the edges with the aluminium tape. I say ‘we’; Tom did most of it and I swooped in at the end for the big finish.

Don’t lose your centre line

Before you cover battens up with your vapour barrier and plywood, ensure you somehow mark where the centre of each batten is, so when you come to screw your plywood in, you are hitting the batten rather than your insulation.

We marked the centre line of each batten with a pencil on the end batten. Once the plywood was down, we used a string to mark out the centre line of each batten on the plywood and then screwed the floor down along those lines.

Fit the new plywood

You can use your original plywood as templates but don’t expect your new pieces to fit first time. They might, but they might not. A problem with relying on the old van floor is that it might not have fitted that well to start with, plus the floor is now raised due to your battens and insulation so the shape may have changed.

Max using a jigsaw to cut out a template for the new plywood floor

This is where the task of ‘nobbling’ comes in. Because fitting the new ply is especially difficult in the corners, around the wheel arches and in any rounded areas, but we got there in the end. I don’t recall the exact amount of times we moved the pieces of plywood in and out of the van, but it was a lot.

Top tip: Measure, measure, and measure again before cutting your new plywood. Don’t simply draw around your old plywood template and cut.

Before we started on the plywood floor, we added a plywood strip along the batten next to the sliding door.. This was to raise it up to the same level as the other battens. (You can do it this way, or simply use a thicker batten.)

Securing the van floor

We used three pieces of plywood, the two middle pieces meeting down the centre batten and the third across the top, like a ‘T’ shape. Because the top piece didn’t have a batten to be secured, we used a ‘scarf joint’ so the top piece would overlap the other pieces. This gives the edge of that top piece more support and means there is less movement.

To secure the new plywood van floor in place, we used wood glue along the inside edges and then screwed it into the battens below.

Close up of Tom using the electric screwdriver to drive a screw into the new plywood van floor
Max uses an electric screwdriver to screw in the new plywood floor

We also filled the small gaps in between the pieces with wood filler. And we will be laying a Luxury Vinyl Floor on top later on. (We will make a separate video on how to fit the vinyl floor. So stay tuned!)

Congratulations, you made it. Hopefully, you now have a better idea of how to build a van floor but if you have just completed yours, go jump around on it with joy!

What do I need?

Here are some key products we used… (As an Amazon Associate I earn from qualifying purchases.)

Thank you for reading our blog, we hoped you enjoyed it and we certainly hope it was helpful. If you did, and you haven’t already checked out our other blogs, please stick around. Or find more videos on our YouTube channel, where you can leave your questions and comments and follow our van build series.

FAQs

What is a vapour barrier?

A vapour barrier is a layer added to the inside or ‘warm side’ of your insulation that prevents any humidity or moisture (i.e. caused by breathing or cooking) from reaching the outer layer or ‘cold layer’ of your van and therefore preventing condensation from building.  

Why is aluminium foil a good vapour barrier?

Aluminium foil prevents vapour diffusion, which means it does not allow moisture to pass through it, making an excellent choice as a vapour barrier.

Do screws securing the battens break the vapour barrier?

Yes, technically it does, but the holes created are being filled, tightly, with screws, so there shouldn’t be any gaps and your ‘barrier’ should still be very much intact.

Do you have to screw your van floor battens down?

No, we chose not to. Instead we used Sikaflex, which is a ‘Three in One Adhesive, Sealant and Filler. We didn’t want to create any unnecessary holes in the van that could possibly lead to rust later. Plus, the plywood floor, kitchen and seats are going to be screwed into the battens, that along with the weight of everything means those battens aren’t going anywhere!

Should I insulate my floor?

You don’t have to, but our thought was, if you’re going to insulate the walls and ceiling why let the floor be your weak link. You can always open windows and doors if you’re too warm but if your van is cold then that is a problem. Also, insulating doesn’t only mean it keeps it warm, but it means that when your van is cool, it can also help to trap cool air in when it is warm outside. 

What size Plywood should I use for a van floor?

We used 12mm plywood as a good compromise. We wanted something thick enough that it is durable and strong but not too heavy because we still need to lay our luxury vinyl flooring on top.

What size insulation foam board should I use for a van floor?

Our insulation board is 25mm deep; for us this worked well because we attached our battens to the highest points on the floor, which meant the insulation went in between, in the low areas, sitting flush with the top of the battens. 

What size battens should I use for studwork in a van conversion floor?

Our battens are 25mm x 50mm x 3000mm. 

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