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Sealants & How To Fix A Leaking Caravan

Article by Peter Smith - Caravans Plus
Read Time: 5 mins

Water entry can cause serious damage to your Caravan or Motorhome. It is important to check your seals regularly against fatigue and degeneration. It is imperative that the seals on your Caravan or Motorhome remain 100% water tight, else you could be up for some very costly repairs.

Over the years many types of sealants have been used to not only join components used when manufacturing the caravan or RV, but also to seal against water and dust penetration.

Water damage to caravan

Left: Large areas of damage to internal wooden frame.

Internal panel damage

Right: Ply panels will get damaged even with aluminium frame or sandwich panel

1. Butyl Mastic (Ezycaulk Cartridges)

For many years caravans were sealed using a a Butyl Rubber / Mastic or sometimes known in Australia as Caulking compound.

This type of sealant is a non-hardening, water and dust proofing compound that forms a tough skin but should remain permanently soft and sticky beneath.

There have been many versions of this caulking compound that have been used by Caravan manufactures since the 1960's. Many dry out and crack leaving a gap that water can penetrate and cause damage to the walls and ceilings.

Some caravans were also built where the caulking compound was too soft and tended to run out and drip during very hot weather.

Despite these problems it is still often the best solution to use a quality proven caulking compound where you know you will need to remove the items that are being sealed.

It can be a popular choice for those who are restoring a vintage caravan and would like to keep everything original. It is useful on vents that are removed to access items behind.

Caravan Sealer

The main advantages are:

The main disadvantage:

Caravans Plus Recommends Ezycaulk for:

  • Vintage Restoration
  • Removable components or panels where closed cell foam tape is not suitable

    Cartridge Z Bond Ezy Caulk, White, 500g, Paintable, Removable

    Cartridge Z Bond Ezy Caulk, White, 500g, Paintable, Removable

    43 In Stock Now.

    2. Silicone Sealants

    Silicone sealants have been widely used by for many decades now. They allow for greater flex than the above mastic products. They are considered to be a step up in technology from Butyl Mastic sealants.

    There is a large range of silicones for different jobs. You may have noticed there are silicones for plumbing, bathroom/kitchen, glazing to name a few, yet not all silicones are the same.

    a) Silicone Sealant V2 - Acetic cure

    There are many silicones available from your hardware store that are suitable for your bathroom and kitchen areas. In wet areas, ensure you select a product that is anti fungal. The Acetic cure silicones like V2 release acid while curing which facilitates etching of the surface and a superior adhesion to smooth surfaces like glass and ceramics.

    This is NOT recommended for the external seal of joints on Caravans & Motorhomes.

    b) Silicone Sealants V60 - Neutral Cure

    Bostik's V60 white glazing silicone is used by a number of the major caravan manufactures in Australia for sealing the outsides of their caravans. In some cases, it has been re-packaged and sold as Caravan Sealant.

    For the most part, a caravans outer shell is sealed using Neutral cure Silicone. The ACETIC silicones release acid while curing, and while it gives superior bonding to certain surfaces like ceramic and glass, it can cause corrosion to the painted and powdercoated surface and soft metals like the aluminium. We do NOT recommend ACETIC for Caravan and motorhome sealing

    Silicone to seal caravans

    The main advantages are:

    • Gives a stronger adhesion so can be used as a glue (within limits)
    • Allows for greater joint movement than Ezycaulk
    • Maintains strength and elasticity for life

    The main disadvantage:

    • It is permanent, must be cut or peeled off to remove.
    • It is not paintable

    Caravans Plus recommends V60 for:

  • New roof joints
  • New corner moulding
  • Removed and cleaned corner moulding
  • Installing hatches

    Not recommended for doors and windows - see foam tape

    Cartridge Silicone V60, WHITE, 300g. Caravan Body

    Cartridge Silicone V60, WHITE, 300g. Caravan Body

    25 In Stock Now.

    To see our full range of sealants, click the link below

    3. Polyurethane Sealants (Sikaflex or Matrix Cartridges)

    Polyurethane sealants are becoming more common place within the industry. As more caravans and RV's shift towards fibreglass panels, the use of single component polyurethane sealants such as Matrix FC or Sikaflex 221 is increasing.

    This product is used for making joints between panels with a high joint strength. It also has excellent UV, chemical and weathering properties.

    This type of sealant displays excellent adhesion, chemical and weathering properties, as well as the added advantage over traditional silicone in that it is both sand-able and paintable. Interestingly, it is also anti fungal.

    a) Silyl Modified Polymer (SMP)
    The most commonly used product in this range is Simson ISR 70-03 based on (SMP). It is highly used within the United States RV and motorhome industry, particularly by some of the more well known motorhome manufacturers.

    Matrix FC

    Matrix FC

    Sikaflex 221

    Sikaflex 221

    ISR 70-03

    ISR 70-03

    The main advantages are:

  • They give a very strong adhesion so can be used as a very strong glue
  • Allows for even greater joint movement than silicone
  • They can be sanded and painted
  • Maintains strength and elasticity for life

    The main disadvantage:

  • They are permanent, must be cut or sanded to remove.
  • They are more expensive than silicone
  • The strength may be a disadvantage when repairs require dismantling

    These are not currently stocked by Caravans Plus, but are recommended for joints with fibreglass sheets, and where permanent strong adhesion is required for structural strength. They also provide a waterproof seal.
    For more specifications about product...Click here.

    Was this helpful?


    • comment-avatar


      I have found the Sikaflex 11 FC to be an excellent sealant & adhesive, I use soapy water on my finger as a tool to smooth out & finish the sealant, the FC is for fast cure.

    • comment-avatar


      I'd like to see you offer cans of the liquid rubber and polyerethane roof sealant to do the whole rv roof.

    • comment-avatar

      cindy hart

      do you have liquid rubber for my fifth wheeler roof

    • comment-avatar

      John Corcoles

      I redid my motorhome with sikaflex and within two years it had dried and cracked. I am now going to use a silicone non acitic type.

    • comment-avatar


      Can you suggest a liquid rubber membrane for the roof of a caravan

    • comment-avatar


      Our van is a hybrid(used to be expanda but now there is no bed where it expands and expanda door is just large open door. How could we reseal the door so that we can still open and use the door but have it sealed in the gap? (I hope this makes sense)

    • comment-avatar


      Is it practical or even possible, to successfully repair a caravan roof that has hail damage ?

    • comment-avatar


      how to paint caravan roof& what product

    • comment-avatar


      How to you replace a rubber seal in top vent

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