How Waterproof is your Van

Before using any more silicon on the van read this bit posted on the caravaners forum by the proprietor of a large repair organisation.

PeterD

For goodness sake remember, if you break or damage the window one day you will have to remove it some how. If it is sealed in with silicone or urethane then the chances of getting the frame off the van without destroying it are slim to nil, and you will damage the body of the van in the process. Why do you think the thing was originally fitted using a mastic or butyl type sealant? Because the manufacturer was concerned that the window would need to be removed one day. Later model vans have the windows siliconed or urethaned [Sikaflex] in because the manufacturers don't give a crap about the van once it has left their sight. Have some thought to the future, if you fit it with a permanent adhesive then that is what it becomes, very permanent. Butyl Mastic sealants, if applied properly should last at least ten years, and the unit will be easily repairable.

The same theory applies to painting the roof of vans with all sorts of painted on sealant, roof proof, bondcrete, thermocool or whatever. When the thing eventually leaks again, as it inevitably will, the repairer has an almost impossible job to reseal the unit quickly or economically. This painted on crap has to be removed first and that can be almost an impossibility in some instances. And don't think that the painted on crap will fix the leak permanently, it won't.

Silicon comes away quite readily if need be, but Sikaflex is somewhat permanent!

Motherhen

Sikaflex come in several types and can be used as the correct type doesnt set like silicone.
Also a neutral cure should be used as an acid cure will destroy stuff like fibreglass.

I worked as a roofer and we never used silicone beacause wherever there is movement it will pull off one side or the other.

We used a product called Secomastic which was a silver coloured sealer that never sets and is ideal on ducting and flashings on a roof because it allows two bits of metal to slide across each other without breaking the seal. .
There is a Sikaflex equivilent apparently.

I recently had to remove a window from my Roadstar and it has a sealant like this an I just smoothed it out and reinserted the window Hasnt leaked despite heavy rain recently.

Many years ago my old Franklin Arrow developed some bad leaks around the widows and roof,i remoned the windows and ally mouldings around the roof to find the mastic style of sealer had dried up and shrunk. i cleaned all the moulds,window frames and caravan walls/roof before using a mastic of some sort ( the name eludes me at the minute) but years after doing it no leaks and it was still tacky. But in saying that my 2 year old Jayco with fibreglass sides has what is called 'caravan silicon' used to seal everything up on it including the windows. it is apparently lots more flexible than regular silicones. time will tell i guess.