I recently purchased a Swift Major XL for a very low price due to the fact it has quite a damp problem in some of the walls. I did some research before I made the purchase and thanks to all your posts (especially you Wizard), I decided that I am competent enough to do the repairs. I have covered with tarp and stripped out the damp wall and foam boards. On doing so. I noticed a few pin holes in the skin. These are small holes and are randomly spread over the one side (6 holes max). My question is: Can I seal these from the inside with fibreglass/epoxy/sealant before putting foam boards back on? As they are so small I don't really want to cover the outside with sealant/stickers etc.
I am documenting my repair and will hopefully join The Fixed It Club one day.
My assumption is these are corrosion spots caused by the interaction of the steel of fixing staples or nails on the aluminium skin. In damp these work as a battery at the expense of the aluminium; however as you are replacing the substrate wood etc these particular points will not be there to cause further damage.
I would just smear the back of them with a bit of the Sikafix bonding you intend using on remaking the seals. Like with a palette knife. If large use an off cut of thin aluminium sheet to cover them. Don't use any other metal patch than aluminium, as almost any other metal you can readily access will cause more problems.
On rebuilding try to avoid any contact between the screws/nails/staples you use and the skin, because any damp such as condensation will start another point of corrosion.
I did check if there was any metal staples, fillings, etc when removing the polystyrene. I couldn't see any. The holes are not behind the substrate wood.
It was so wet behind the foam that I guess the tiniest bit of metal was have started corrosion.
I do have another question: I have noticed that the folded aluminium wall has started to become unstuck from the sheet bellow it. Is it ok to use Sikafix to bond these back together before adding the foam boards or should I use roll mastic?
I do have another question: I have noticed that the folded aluminium wall has started to become unstuck from the sheet bellow it. Is it ok to use Sikafix to bond these back together before adding the foam boards or should I use roll mastic?
If as you say the aluminium was exposed to so much damp any impurities in or on the surface could well initiate pitting.
On the above question I would tend to lean towards Sikaflex, as I am not a fan of most 'mastics'. The exception might be if it is evident expansion needs to be accommodated, and here on the expanse of caravan side that might be a function of the folded joint. I would quiz a friendly van repairer for a steer on that, unless one comes forward to help on here.
We also had pin holes in our van due to damp. We used a cold weld called J B Weld to fill the holes in. We have had no problems with these holes since filling them. We purchased the cold weld from Ebay if thats any help.