Guides/Fitting Windows

Build Guide

Fitting Windows in Your Campervan

A comprehensive guide to choosing, cutting, and fitting windows in your van conversion — covering bonded, rubber seal, sliding, and fixed options with step-by-step instructions.

Difficulty: Intermediate Cost: £80–£400 per window Time: 2–4 hours per window

Window Types Brand Comparison Tools Needed Step-by-Step Fitting Tips & Common Mistakes

Before you cut: Fitting windows is one of the most permanent steps in a van conversion. Once you've cut a hole in your van, there's no going back. Take your time planning window positions before picking up the jigsaw.

Windows are one of the most transformative upgrades you can make to a panel van conversion. They bring in natural light, provide ventilation, and make the space feel infinitely more liveable. However, cutting holes in your van body is a significant step that requires careful planning and the right technique.

This guide covers everything you need to know — from choosing the right window type for your build, to comparing the major brands available in the UK, to a detailed step-by-step fitting guide that will help you achieve a professional, watertight result.

Window Types

Bonded Windows

Brand Comparison

Brand	Origin	Price Range	Best For
Dometic	Swedish	£150–£400	Premium brand, excellent quality and finish.
Carbest	German	£80–£250	Excellent value for money.
AGS	German	£60–£200	Budget-friendly option.
Seitz / Heki	German	£120–£300	Part of the Dometic group.

Dometic

Premium brand, excellent quality and finish. The S7 and S9 series are particularly popular for Sprinter and Transit conversions. Double-glazed options available.

Pros

✓ Excellent build quality

✓ Double-glazed options

✓ Wide size range

✓ Good UK availability

Cons

✗ Most expensive option

✗ Can be overkill for budget builds

Range: S4, S5, S7, S9 series · Price: £150–£400

Carbest

Excellent value for money. Very popular in the UK van conversion community. Good quality seals and frames. Available from Kiravans and Van Conversion Supplies.

Pros

✓ Great value for money

✓ Good quality seals

✓ Wide availability in UK

✓ Popular community choice

Cons

✗ Not as premium as Dometic

✗ Fewer size options

Range: Carbest RW Style, Carbest RW Motion · Price: £80–£250

AGS

Budget-friendly option. Good for those on a tight budget. Quality is acceptable but not as refined as Carbest or Dometic. Available from various UK suppliers.

Pros

✓ Most affordable

✓ Decent quality for price

✓ Good for budget builds

Cons

✗ Lower quality seals

✗ Less refined finish

✗ Fewer premium options

Range: Various bonded and rubber seal options · Price: £60–£200

Seitz / Heki

Part of the Dometic group. Good quality windows popular in motorhome conversions. Less common in panel van conversions but excellent quality.

Pros

✓ Motorhome-grade quality

✓ Excellent seals

✓ Good insulation

Cons

✗ Less common for panel vans

✗ Higher price point

Range: Seitz S4, S5 series · Price: £120–£300

Tools & Materials Needed

Jigsaw with metal-cutting blade

Angle grinder (optional, for tidying edges)

Drill with metal bits

Masking tape (lots of it)

Marker pen / scribe

Measuring tape and ruler

Safety glasses and gloves

Rust treatment primer (e.g. Kurust)

Bonding adhesive (e.g. Sikaflex 252 or 221)

Masking tape and cleaning cloths

Isopropyl alcohol (IPA) for surface prep

Primer/activator for adhesive

Suction cups (for holding window during bonding)

Sealant gun

Bodywork filler (for any gaps)

Step-by-Step Fitting Guide

Plan Your Window Positions

Mark out where you want your windows before cutting anything. Consider: privacy (avoid windows directly opposite sleeping areas), ventilation (position for cross-flow), aesthetics (symmetry looks better), and structural ribs (avoid cutting through structural ribs in the van body). Use the window template provided with your window to mark the cut line.

Tip: Tape a piece of paper to the van wall and trace around the window template. Step back and check how it looks before committing.

Prepare the Cut Area

Apply masking tape around the entire cut area — this protects the paintwork from the jigsaw and gives you a clean surface to mark on. Mark the cut line clearly on the masking tape. Double-check your measurements. Remember: measure twice, cut once.

Check for wiring, fuel lines, and structural elements behind the panel before cutting. Use a torch to inspect the area.

Cut the Opening

Drill a starter hole in one corner of your marked cut line (large enough for the jigsaw blade). Insert the jigsaw blade and carefully cut along your marked line. Cut slowly and steadily — rushing causes the blade to wander. Keep the jigsaw plate flat against the van body.

Wear safety glasses — metal swarf is sharp and dangerous. The cut edges will be razor-sharp.

Tip: Use a fine-tooth metal cutting blade (18–24 TPI) for a cleaner cut. Lubricate the blade with cutting oil.

Treat the Cut Edges

File down any sharp edges with a metal file. Apply rust treatment (e.g. Kurust) to all bare metal edges immediately — bare metal will rust within hours in UK weather. Allow to dry fully. Apply a coat of primer over the treated edges for extra protection.

Skipping this step is the #1 cause of rust problems in van conversions. Don't skip it.

Dry-Fit the Window

Before applying any adhesive, do a dry fit of the window to check it sits correctly in the opening. Check the gap is even all the way around. If the window doesn't fit, now is the time to adjust the opening — not after you've applied adhesive.

Tip: Use masking tape to temporarily hold the window in place during dry-fitting.

Apply Adhesive (Bonded Windows)

Clean the bonding surface on the van and the window frame thoroughly with isopropyl alcohol. Apply primer/activator to both surfaces if required by your adhesive. Apply a continuous bead of Sikaflex 252 or 221 around the window frame — approximately 8–10mm bead, 10mm from the edge. Work quickly as adhesive starts to skin within 10–15 minutes.

Sikaflex is extremely difficult to remove once cured. Wear gloves and protect surrounding areas with masking tape.

Tip: Sikaflex 252 is structural (for bonded windows). Sikaflex 221 is a sealant (for sealing around frames). Use the right product for the job.

Fit and Secure the Window

Press the window firmly into position. Use suction cups to hold it in place while the adhesive cures. Apply even pressure all the way around. Remove any excess adhesive with a cloth dampened with white spirit before it cures. Apply masking tape around the perimeter to hold the window in position.

Tip: Don't move the van for at least 24 hours while the adhesive cures. Ideally leave it 48 hours.

Final Sealing

Once the adhesive has fully cured (24–48 hours), apply a bead of Sikaflex 221 sealant around the entire perimeter of the window — both inside and outside. Smooth with a wet finger or sealant tool. This provides a secondary waterproof seal.

Tip: Test for leaks by running a hose over the window before fitting your interior. Much easier to fix now than after the build is complete.