Q Should I protect my motorhome floor with underseal?

I am looking to Waxoyl the underside/ doors, etc, of my new motorhome, Should I do the underside of the floor? Or would this hold water in if I had a leak inside and cause the floor to rot?

David Dransfield

A

In the case of a panel van conversion with a steel floor, then yes, using some form of wax underseal or a stone chip paint, will help protect it. In the case of a coachbuilt motorhome, which will be made of either plywood or plywood face with plastic or aluminium, the answer is it depends on a few factors.

Plastic doesn’t need additional protection. Aluminium does corrode in time, so a layer of stone chip might be helpful, but it’s a lot of effort for a minimal benefit and you will need to apply an etch primer first, otherwise the stone chip will not bond well to the aluminium.

In the case of a plywood floor, unless you have an internal plumbing leak or a failure of a window seal, you should not be getting any water coming from the inside to the outside. Plywood floors usually fail due to water ingress from the underside, especially around the joints to the side and rear panels. It’s also common for them to fail around the inner wheelarches from all the water and road debris flung up by the tyres and wheels.

So, protecting the plywood floor around the edges of the ’van and the wheelarches – or perhaps installing some form of spray guard or mud flap – is the key thing to do. But I wouldn’t use Waxoyl or any other underbody sealant or spray that is not recommended by the motorhome manufacturer. It depends on the products used to treat the floor – some manufacturers insist on specific products and it may be part of the terms and conditions of your warranty.

If it’s out of warranty, then a breathable product for wood may be the thing to paint on it. Removing mud and salt from the underside regularly is a wise thing to do, too.

Peter Rosenthal