Keep caulking the roof seams
The most common reason for leaks in RV roofs is failed caulking.
Over the years, I have seen many examples of damage from water leaks in RVs. Many are so badly damaged that constant water intrusion has caused a roof to collapse. In three separate cases in the last year, the rubber roof membrane is the only part of the roof remaining with gaping sections where the plywood roof structure has disintegrated. Water usually enters the roof at a point where a roof vent or skylight is set. Caulk cracks and over time, water gradually seeps and pools under the roof membrane. It eventually soaks the ply sheeting and wood frame causing total failure.
Cracks and pin holes in caulking can appear in as little as one year. A newly manufactured RV can easily have pin holes and cracks in roof caulk. The causes could be poor quality caulk, tree damage, cracks from twisting of the RV on rough roads, ageing caulk, or caulk applied in extremely high or low temperatures and by not following manufacturers’ instructions.
With so much water damage observed in this last few years, I recommend roof inspections at least annually. If you suspect you may have been near trees, check the roof soon afterwards.
The customer who owns the motorhome in these pictures said she did not think there were any leaks to worry about. I suggested I would climb up just to check because she could not recall when it was last inspected. Most of the caulk was okay, but there were some places that needed immediate attention.
The solution is simple. Brush the roof down to remove loose dust and leaves. Remove flaking and degraded caulk with a plastic scraper or use an oscillating tool with a scraper attachment very carefully. Wipe the cracks and open pin holes with rubbing alcohol. Apply self levelling caulk to horizontal surfaces and non-sag caulk to vertical and sloping surfaces. Always use an RV grade caulk and never use household grade caulk. Household grade for windows and doors may be silicone based which is difficult to reapply. RV and other roof grade caulks are suited to regular topping off. It is also easier to shave or scrape any flaking old caulk. Silicone caulk fragments and will not allow new caulk to adhere.
After application, check for any minor gaps or pinholes and apply another layer of caulk to fill the gaps. Take care to apply caulk in such a way that it will not hold water in small pools.
Where do the pin holes come from?
Pin holes form from air bubbles either trapped within the caulking cartridge or when caulk is overlapped too quickly. The pin holes appear while the caulk is setting, so if it is possible, check the caulking after an hour or more.
Image of newly applied caulk, filling all gaps, cracks, and pin holes. Soon the bright white caulk will weather off and will not stand out against the original caulk, and give a long lasting seal against water.
4 Comments on “Keep caulking the roof seams”
Phil Odion
I am wondering if I should remove and replace the line of caulk in the small gap where my rubber roof of my class A RV meets the rain gutter? Thanks so much.
Alan ONeill
Hello Phil, I have done this. It is a temporary, but necessary repair because it will seal this gap and prevent water from entering the screws that hold the rain gutter to the wall. You may have to review this annually because depending on your environment, you may have to do this every year, due to cracks forming in your new very thin bead of caulk. If you recoat the roof, you can apply caulk then coat this gap with some of the roof coating. The longer lasting remedy is to completely remove the gutter, check all screws and replace the rusty ones, then clean and apply new butyl to the back of the rain gutter and refit.
US Roofer
Well said! Poor quality caulk makes pinholes and gaps and due to dirt and bad weather conditions RV roof leaks happen. Butyl MS Caulk(https://www.rvroofmagic.com/butyl-ms-caulk.php) is the ideal sealant for roofing, siding, and other construction & industrial applications.
Alan ONeill
Thank you for your suggestion. I have not used Roof Magic, but all and any attention to details on roof sealing is always better than no maintenance at all. In my mobile RV repair business here in San Louis Obispo County, I have seen many cases where owners have never had the roof inspected.