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Fitting an Oversized Caravan & Motorhome Window Rubber


Caravan and motorhome double glazed opening window rubbers are designed to be fitted onto the wall of your van. Over time these seals can deteriorate and should be replaced to prevent water ingress and keep your van warm and comfortable. Water damage is costly to repair so replacing these sections before they start to fail is essential.

Before you can purchase a replacement section you will need to measure the thickness of the wall. This can be done by gently pulling the end of your current window rubber off of the panel. With the seal partly removed, you can measure the total thickness of the wall, including the wooden framework, outer skin and inner skin. This measurement should be somewhere between 25mm and 40mm.

Double glazed opening window rubbers are available in several different sizes. These products are manufactured to fit certain panel thickness. For example, CS4090 is designed to fit a 30mm panel and CS4091 is designed to fit a 35mm panel. This can be problematic when the thickness of your wall is between these two measurements, such as 32mm, and you are unsure whether a 30mm or 35mm seal will create the most reliable seal.

In this instance, we recommend that you purchase a seal slightly larger than the thickness of your wall. It is best practice not to try and fit a smaller section onto your van as stretching these window rubbers may increase the chance of water ingress. In the example above, you will want to purchase the 35mm seal for your 32mm panel.

When fitting an oversized caravan and motorhome window rubber, it is advisable to push the seal tightly against the outside of your van. This will create a tight exterior seal resulting in the additional 3mm space to be on the inside. This will leave you with two options;

Option 1: Keep the Gap

3mm gap between rubber seal and caravan wall

As the seal is pushed tightly against the exterior wall, the pre-applied mastic will bond to this surface and create a reliable seal. When stapled in place, the section is unlikely to move.  The additional gap left by the oversized window rubber inside the van can be left unfilled as will never experience rainfall.

These window rubbers are often manufactured so that the legs angle slightly inwards. Once fitted, you may find that this leg angles touches the inside of the wall completely hiding this additional gap.

Option 2: Filling the Gap with a Packing Piece

Using a packing piece of seal the gap on a caravan wall

Alternatively, it may be desirable to fill this gap with a packing piece if the inside leg does not touch the inside wall. To achieve this you can use our solid neoprene strip which is available in a range of thicknesses such as 1.5mm, 3mm and 5mm. This would need to be bonded or stapled onto the inside of the van to increase the wall thickness to suit the window rubber purchased.

For further information on how to identify and replace this window rubber, please view our Replacing Seals in Caravan & Motorhome Opening Windows technical help guide. These window rubbers are available in a large selection of sizes, designed to fit different panel thicknesses. See below to purchase a replacement rubber; 

CS1679  

To Fit 25mm Panel
10mm Diameter Bulb
 Single Fin Bulb

CS784

To Fit 25mm Panel
13mm Diameter Bulb
 Single Fin Bulb

CS1680

To Fit 27mm Panel
10mm Diameter Bulb
 Single Fin Bulb

CS785

To Fit 27mm Panel
13mm Diameter Bulb
 Single Fin Bulb

CS1681

To Fit 30mm Panel
12mm Diameter Bulb
 Single Fin Bulb

CS786

To Fit 30mm Panel
13mm Diameter Bulb
 Single Fin Bulb

CS4090

To Fit 30mm Panel
13.5mm Diameter Bulb
 Double Bubble Bulb

CS3002

To Fit 35mm Panel
12mm Diameter Bulb
 Single Fin Bulb

CS4091

To Fit 35mm Panel
13.5mm Diameter Bulb
Double Bubble Bulb

CS4556

To Fit 36mm-40mm Panel
10mm Diameter Bulb
 Single Fin Bulb
Tolerances for Dimensions on Drawings