sealing fibreglass

[prue]

Ant, is there anything to seal fibreglass, our roof on my old Roma is seeping with the heavy rain we have in Scotland, I have tried wax, OKE wax was recommended by boat owners but it was awful it left streaks and dirty marks when it was dirty andI had a terrible time getting it off. The roof is not leaking but the roof is always damp and I think the fibreglass is now porous. Thanks Prue

[ant]

Hi Prue.
It's very unusual for the GRP on a Romahome to go porus, that's more of a boat problem when what's called "osmosis" occurs and the GRP allows water to seep through it. Normally the GRP has to be submerged in water for some time before that occurs. There are some paint on laquers that can be used that might stop a very slight seep. some boats get whats called "epoxy" treatment that has the same effect as a laquer, namely blocking the pores in the gel coat of the GRP. The absolute cure is to have the gel coat removed, the GRP dried out properly and more gel coat applied, this however would be a very expensive remedy ( several £1000's). It may pay to ask at a local boat yard what products are available apart from the heavy wax you've already tried. Whatever you decide to do the GRP must be absolutely dry before you try anything otherwise you're wasting your time and money.
Ant

[barry5933]

Oct 26, 2009 22:02:17 GMT prue said:

Ant, is there anything to seal fibreglass, our roof on my old Roma is seeping with the heavy rain we have in Scotland, I have tried wax, OKE wax was recommended by boat owners but it was awful it left streaks and dirty marks when it was dirty andI had a terrible time getting it off. The roof is not leaking but the roof is always damp and I think the fibreglass is now porous. Thanks Prue

I have a 30 year old fibreglass boat that lives almost permanently afloat all year. Osmosis is a well known problem where moisture seeps INTO poorly laid up GRP (fibreglass to you and me) from the outside and reacts with uncured resin constituents. The result is blisters on the OUTSIDE of the skin. Water does not seep through the GRP even when fully immersed.

You do not say whether the dampness is permanently obvious, when the van is in storage or only when it is being used, but I suspect the dampness inside your roof is more likely to be internal condensation, caused by inadequate ventilation.

Having spent 5 weeks in Scotland earlier this year in almost continuous rain, I can visualise the situation of the moist air inside the van condensing on the inside surface of the even colder roof panels.

The usual remedy is through ventilation to keep the inside and outside temperatures roughly equal. This obviously becomes more difficult when you are using the van and warm, moisture breathing people are ensconced inside with vents closed to keep the weather out.

Somehow, you need to keep the air moving to remove excess moisture without causing excessive draughts. How to achieve this is an age old problem. We never used to suffer condensation when we had draughty wooden windows and open flues in our houses, but that's another story.

Barry