Repair a leaking motorhome roof

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We bought our motorhome in Spain and I do not think it has seen much rain as it has been stored in a garage and used in generally dry climates. Earlier this year we drove to the UK to visit our family, friends and the amazing CamperJam festival near Telford. Sadly our motorhome developed a leak after a couple of heavy downpours in the UK. I guess it was not used to the damp weather there.

Damp in motorhomes and caravans is something that needs to be sorted quickly otherwise lots of expensive and hard to fix damage can occur. You also get a musty, damp smell after a while. If you are buying a motorhome with that smell – walk away!

Discovering the leak

Our motorhome had been at a friends storage unit for a couple of days. We went over the next day after a big downpour and around the main Heki 3 rooflight (the rooflight over the dining area) was a discoloured area on the ceiling. And if you did not spot the marks on the ceiling, there was also a puddle on the dining table. At least this made it easy to identify the culprit. Sometimes it can be very difficult to trace a leak. It might only appear when the rain is coming from a certain direction, or like this case when it is really heavy rain.

Most leaks occur around windows and other items like TV aerials. It is usually the result of sealant drying or lifting over time creating small gaps. Even a tiny gap is enough to let a lot of water in, and do a lot of damage if not spotted in time.

Fixing the leak

Whenever I have had leaks on motorhomes before, the only solution is to completely remove the source of the leak. Just blobbing a load of silicon over where you think the problem is located, is at best a temporary solution, and quite often does not work.

If you go to a caravan/motorhome service place to get it repaired expect to pay a lot because it is labour-intensive. However the materials are quite cheap, and the work is not difficult so if you are remotely handy you can save yourself hundreds of £/€ doing it yourself.

What you will need

  • Basic tools, like screwdrivers
  • Step ladder if working high up
  • New sealant – we used W4 caravan non-setting mastic strip from Amazon.
  • A metal scraper
  • Rags
  • Alcohol cleaning solution

The sealant cost less than £20, and the whole thing took us about three hours.

Removing the roof light

Firstly, we had to remove the leaking roof light. It is a big (and expensive) piece of plastic so be careful with it! Take your time, remove all the screws and use your metal scraper to get between the roof and the roof light. After nearly twenty years, this was very stubborn. Just persevere freeing a bit at a time, trying not to put too much pressure on the plastic parts of the rooflight.

We were able to do most of the work from within the motorhome – standing on some steps. The bit where the hinge of the opening was we could not reach from inside, so had to stand outside.

Eventually the unit was freed, and we carefully lifted it out of the opening and put it carefully to one side. I am not going to sugar coat the fact, that at this point it looks really bad. You have a huge hole in your lovely motorhome!

The next step is the most important (and messiest). You need to remove all the traces of old sealant, both on the roof and on the roof light. We had a couple of metal scrapers and set to work. This step took about an hour.

The bits on the roof light were the worst to do, because there was a lot of intricate parts which needed the sealant to be picked out with a screwdriver. The roof in comparison is a flat surface so just needs plenty of hard work with the scraper.

Do not worry to much about the stubborn bits, as your alcohol-based cleaner can be used with the rags to clean all the awkward bits. Make sure to give all surfaces a final polish with a dry rag to remove any residual cleaner or sealant.

Refitting the roof light

The next step is to use your non-setting mastic sealant tape stuff. It will stick to anything it comes into contact with, including itself.

Go easy with the mastic tape because it sticks like something nasty on a blanket. Probably should of said before now, but do not wear your best clothes to do this job!

Just take your time, and cut sections off the roll and stick it to the roof opening until you have it everywhere you need it.

When you are happy with the sealant tape, grab your roof light and hopefully with and extra pair of hands, lower it onto the sealant. Give it a press down to firmly seat it into the mastic. Most roof lights have clamps that grip from the inside so as you screw everything back together, it should squish down onto the mastic and hopefully seal everywhere!

Congratulations if you got this far! You can either wait for some rain, which in the UK will not be long, or get a bucket of water and test your work. I am happy to say that ours has a had a couple of good downpours since, and so far everything is bone-dry.

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