Fitting windows to your van conversion

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Fitting windows yourself is a bit scary – you are cutting large holes in the side of your van – but it isn’t actually as difficult as you might think.

The secret, as always, is measure twice, cut once.

Here are a few photos illustrating the process of fitting a Dometic / Seitz S4 motorhome window (eBay⇒) to my van.

1. Decide where the window is to go and mark out the cutting line.

Check the window positioning on both the inside and the outside of the van before you start to cut. Note where the anti-vibration struts are on the inside of the panels – these are a pain to cut through but can safely be removed:

Positioning the window - using a template on the outside and checking the position with the window frame on the inside
Positioning the window – using a template on the outside and checking the position with the window frame on the inside

2. Cutting a hole for the window

To do this nicely requires two tools – an electric drill with a hole-cutter drill bit (eBay⇒) and a jigsaw with a metal cutting blade (eBay⇒).

The installation instructions for your windows should specify the size of the hole cutter you need to make the corners.

Here’s how it goes. Corner holes drilled, lines marked and taped up with masking tape (eBay⇒) to prevent the jigsaw guide scratching the paintwork:

Window corner holes cut
Window corner holes cut

Three sides cut now – apply some extra tape to help stop the cutout flapping while the jigsaw cuts the last side. Having a second person to help here is useful – they can hold on to the cutout from the inside to help keep it still:

3 sides now cut - one more to go
3 sides now cut – one more to go

Once the hole is cut, use a file to smooth down the edges and then paint the bare metal with some red oxide paint (eBay⇒)  to make sure they do not go rusty — you do not want rust creeping outwards from your window frames.

Remember also to clean the metal filings thoroughly from the outside of your van – an airline is good for this if you have one, otherwise a vacuum cleaner and/or a magnet can be used.

(If you do not clean the metal filings off your paintwork, they will embed themselves in the paint and go rusty, giving your van’s paintwork a rather speckled appearance. Don’t ask how I know this… if you do make this mistake, the metal particles can be removed with a car valeting product known as ‘detailing clay (eBay⇒))


3. Building the frame

This stage may differ for different types of window and different types of van body. In this case, the windows are Dometic / Seitz S4 windows (eBay⇒) being fitted to a panel van body.

Because they are designed to be fitted to caravan and motorhome bodies, which are of a sandwich construction and approximately 1″ thick, an additional frame is required when fitting these windows to a panel van, whose walls are only a couple of millimetres thick.

What’s required is a wooden frame, fitted to the inside of the van like this (full details come with the window’s installation instructions). The idea is to make the wood plus the wall of the van around 1″ thick:

Fitting a Seitz window - wooden frame
Fitting a Seitz window – wooden frame

4. Fitting the window

This stage is surprisingly easy. All that should be required is to push the two halves together and then screw them together (see your instructions for specific details).

Remember to use some Sikaflex adhesive (eBay⇒) under the outer window frame and then to seal around the edge of it after fitting with some more sealant/adhesive.

Click image to find out more about the Sikaflex Adhesive

This is especially important with panel vans as the sides of these vehicles usually have some slight curvature, which you have to fight against – hence the importance of sealing the gaps.

Fitting the two halves of a Seitz window together

That’s it! The first time I fitted these windows I was nervous about it, but it turned out to be a relatively pain-free job. I would recommend having a DIY-competent friend to do it with if possible.

Once your windows are fitted, you can insulate and panel around them.

Next: Carpet lining and flooring

Back to Conversion Guide Index

Disclaimer: All material is provided for information purposes and is my opinion only. I can take no responsibility for the accuracy, suitability, reliability or safety of the information in this guide.

12 thoughts on “Fitting windows to your van conversion

  • very informative , i have a fiat ducato swift kontiki, some toerag has broken the windows ,my question is can i use caravan windows on this vehicle , any help greatly appreciated,,,,jon

    • Bad luck… you may well be able to use caravan windows – they are the same in design and fitting as most motorhome windows. It will be a question of whether you can get the right sizes, colours (frame and the window itself – these vary) and fittings. Some motorhome converters use bespoke sized windows in their conversions. If this is the case, then you may have to purchase replacements from Swift.

      I would probably contact Swift for a quote for the parts in any case, as at least they should be able to provide exact replacements, even if they cost a little more. They may also advice on fitting, if needed.

  • hi .. regarding the above. do u wood panel ur van, before fitting the window or do u put the woden window frame in then the window, and then wood panel the whole van?

    • Hi Phil,
      Good question! I think it’s best to fit the window with its wooden spacer frame first, then panel around it. When I bought my van, it was already panelled out as it had been a work van.

      So when I fitted the windows I removed the panelling, fitted the window, then cut a hole in the original panel and refitted it.

      Hope this helps,


  • This was great, thanks so much. Helped me put in two roof vents in a fiberglass roof.

  • Alan McLean

    I have a Movano minibus with holes already cut. Can I get Windows to fit exact?

    • Hi Alan,

      Not too sure about this. I guess that as it’s a minibus you’ll be able to find glass replacement windows in the correct size as they’ll be standard fit for the Movano. But I don’t know if you’ll be able to find double-glazed motorhome windows such as Seitz units. They do come in a lot of different sizes, so it may be worth phoning round some suppliers to ask.

      Cheers, Roland

  • edward huntley

    hi good straight forward guide. Do you know how much over hang the outer frame of these windows have over the cut out hole size.

    • Hi Ed, I can’t remember now, it was a few years ago. From memory it’s probably an inch or more, but the fitting instructions are pretty good and explain in detail how to do it all.

      Cheers, Roland

  • Hi I intend fitting window to my boxer and as planning on using 25mm insulating panels on the side can I cut through these and use as the spacer instead of wood ?

    • Hi Craig,

      This could work, but I’m not sure how hard/dense the insulating panels are. The only problem I can see would be that when you pull the two halves of the window frame together (inside/outside) they might crush the insulating panel. This might not be a problem — it’s been a while since I did it and I’m not familiar with the insulation you’re using.

      Regards, Roland

  • I’m fitting shower door glass already in a frame to my van will that be ok


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