It is fall and in most places rain is on the way or has already arrived. You want to be sure your RV or camper roof is waterproof and safe. If you have or even suspect you may have any leaks be sure to cover your unit with a suitable tarp until you can repair the leak.
Leaking roofs can lead to extensive cosmetic and structural damage that can be very difficult and expensive to repair. If you can catch a leak early you can usually take care of it and avoid the long term consequences. Leaks can be caused by several different problems. Impact damage from falling objects like tree limbs and hail is usually easy to find and can often be successfully patched without too much trouble, depending on the type of roofing material and the extent of the damage. Leaking seams or other failures in the roofing material from aging and/or weather can be harder to locate but are also very common. Leaking seams can be caulked or sealed; worn out roofing must be replaced. Another frequent source of leaks is around fixtures on the roof: roof vents, antennas, roof racks, and air conditioners. These can usually be taken care of by re-caulking but sometimes they must have the fasteners tightened or be removed and re-bedded to cure the leak. Re-bedding usually means replacing the butyl tape between the object the the roof. Roof A/C units may need to be removed and the gasket replaced to cure leaks around them.
The first step is detecting a leak. That sounds like it should be pretty straightforward, but RV roof leaks can often be very sneaky and the only signs may show up far from the source of the leak. Water will always choose the path of least resistance. Roof leaks may be the cause of wet or soggy floors and moldy walls. A leak in the roof may be completely contained by the ceiling and show up as streaks down the wall or puddles on the floor a long way from where the water is entering the roof. Sometimes the only noticeable symptom of a roof leak is a persistent foul smell caused by mold and mildew somewhere behind walls or ceilings. Excessive condensation may also be a clue that you have a leak somewhere that is allowing an unusual amount of water into the vehicle. Of course, some condensation is normal, especially in damp climates but if you begin to see a lot more than you normally see, you might suspect a leak somewhere. Some leaks are obvious, with water dripping from A/C panels or light fixtures every time it rains or you wash your rig. Some show up as damp or discolored patches on the ceiling or along seams. Streaks on the walls anywhere except below windows are an indication of a roof leak (streaks under windows can be caused by leaky windows). Sometimes you can do some tests to help locate where the water is coming it by watering the roof with a hose while someone watches inside. Take it slow, because it can take some time for water to make its way from where it enters through roof or seam damage to reach the site where it becomes visible on the interior. I have seen people try to use colored water to trace leaks but be aware any coloring the water may stain interior surfaces so use this technique very cautiously. You might want to test the colored water on an out of sight portion of surfaces where it might show up before you start. Even though you might be able to clean a surface from a short test, long term exposure from a test soaking through from the roof may cause permanent stains that are difficult or impossible to remove.
Leaking roofs often stain the ceiling. Sometimes you can remove the stains with household cleaners but really bad stains may require painting or refinishing. When repainting you will want to apply Kilz as a primer to seal the stains so they don't show through the finish coat. If the surface is damaged too badly for paint you might be able to install a new ceiling panel. The first choice would be to match the original panel. If that isn't possible pre-finished plywood paneling or FRP are good choices. FRP will be easier to clean. You will probably have to remove any light fixtures, vents, or antennas in the area to be replaced and remove all the moldings where the ceiling meets the walls or cabinets. Take care removing the moldings so they can be reused. If the moldings are damaged you may need to install new ones along with the new panels. It is a good idea to number the moldings and where they go to make it easier to reinstall them. You can either install a new panel over the old one or remove the old ceiling panel and replace it. Removing the old one reduces weight and gets rid of any old, rotten, smelly material that might cause problems in the future. It also lets you examine beneath the paneling to determine if there is any additional damage you need to address.
The most common source of RV roof leaks are seams, either along the edges where the roof meets the wall or between sections of the roof. These seams are usually protected by caulk, but caulk does dry out had should be replaced every year or two. The next most common problem occurs around fixtures that penetrate the roof, such as A/Cs, vents, lights, antennas, and roof racks. Most of these problems can be solved by removing the old caulk, cleaning the surfaces, and applying a generous coating of new caulk. As an alternative to regular caulking you might consider having the entire roof sealed. I did that with one of my motorhomes. The company guaranteed no leaks for 10 years and the projected life of the roof sealant was more like 20 years. I had the motorhome for many years (lost track of exactly how many) and never had any problems. The coating is one that is used on commercial buildings. It is white so it helps keep things cooler in summer. It can be rolled, sprayed, painted, or even dumped on and spread around. You can do it yourself but the effort it takes to properly clean the roof can be time consuming and having the guarantee may well be worth the cost of having the company do the installation. Besides that, being roofing experts, they will be able to better detect and correct any defects that might cause future problems. I believe the company I used was Minnesota Roofing Company, who came to southern California to do RV roofs in the winter when weather in Minnesota wasn't conducive to many roofing jobs. They would also sell the material for you to do it yourself if you want to do that.
When you find a roof leak, check the surrounding area for soft spots that would indicate dry rot or other structural damage. You may have to at least partially remove some part of the roofing and maybe the ceiling to effect appropriate repairs. Look for damage to the roof panels, ceiling panels, and any supporting infrastructure. Just fixing the leak and leaving the damage is a recipe for more problems. Damage can often occur far from the leak. A leaking A/C seal on my motorcycle trailer resulted in a rotted out roof panel several feet away where the water pooled around a roof A/C and eventually made its way past the aging seals. Rotted out roofing panels have to be removed and replaced. That can be a really big job, especially if the underlying structural support is damaged or if there are interior cabinets that might be affected by the repair. When replacing RV roof panels, match the paneling as closely as possible to the thickness and rating of the original panel. Then cover it with a matching roofing material. Most RV roofing panels are made of exterior plywood that is pretty easy to match up.
RV Roof A/Cs are sometimes the source of leaks because of gasket failure, even if the visible signs of leakage are some distance away from the A/C. The gaskets are relatively inexpensive and not too difficult to replace. If you start seeing moisture or discoloration on the ceiling around your A/C it is probably time to replace the gasket. Early replacement can prevent additional damage that can be costly to repair. Almost RV roof air conditioners fit a 14"x14" opening in the roof and most, but not all, use a universal 14"x14" gasket. Be sure to disassemble the unit far enough to measure the old gasket before ordering a new one. I recently had to work on a 20+ year old unit that needed a non-standard gasket. Amy in our local RV store (Gary's RV Store in Springfield, Oregon) spent a lot of time and effort attempting to help us find the right gasket. She eventually sent us to her supplier, Airxcel, manufacturers of Coleman Mach Series and Maxxair air conditioners. Their customer service was very quick to respond and helped us find the right gasket.
Another cause of leaks around roof A/Cs is sagging. Roof A/C units are fairly heavy and if the roof was not properly structured to support the weight sagging will result. This causes any water that falls on the roof to pool around the A/C and the sagging often compromises the gasket seal between the A/C unit and the roof. If the roof has sagged you will need to upgrade the structural supports to restore it to level and properly support the weight of the A/C. Be sure to remove all damaged supports and replace them with securely anchored new material. Unless you have reasonably good carpentery skills and the proper tools this is probably best left to professionals.
If your roof is structurally sound you probably only need to replace the gasket. Over time gaskets, which are under pressure from the weight of the unit and from tightened fasteners, get compressed to otherwise begin to deteriorate resulting in leaks. If you have a manual for the A/C follow the manufacturer's instructions to remove the A/C and replace the gasket. Lacking a manual, you will first need to remove the interior shroud. Doing so might allow you to confirm if the unit is leaking. If you decide to replace the gasket you will need to locate the fasteners (bolts or screws) that secure the interior base plate to the bottom of the A/C. You will probably have to unplug wiring too. Then lift or tilt the A/C up out of the way. The old gasket should be stuck to the base of the A/C. Remove the old gasket and any residue completely and carefully clean the mounting surface before installing the new gasket. You can usually scrape the old gasket off with a putty knife and clean the residual adhesive with solvent. Take care not to spill solvent on rubber roofs! While the roof where it sits is exposed use a level or straightedge to determine if the mounting platform has sagged. If there are any low spots you will need to correct the structural defects before proceeding. Then attach the new gasket to the bottom of the unit and lower the A/C back into place and reinstall the base plate on the inside to snug it down and secure it to the roof. Plug in the wiring and reinstall the interior shroud. Be sure to carefully inspect the roof and supporting structure and make any necessary repairs before reinstalling the A/C.
The use of caulk, silicone, or liquid sealers along with the A/C gasket is not recommended. The gasket is designed to compress and form a tight seal. Any added sealers may interfere with its normal function and sometimes may actually damage and destroy the integrity of the gasket.
A few RVs have a domed roof that helps keep water from accumulating under A/C units, but most have flat roofs. If yours has a flat roof and water tends to puddle around the A/C you might be able to build up a little platform around the opening to help it shed water. This would be easiest to do if you were removing and replacing the roofing but you might be able to do it without removing the roofing if you have good finish carpentery or cabinet making skills to make the shims necessary. The shims should create a flat, level platform at that extends outside the roof opening far enough to support the entire A/C gasket. Then you will need tapered shims from the flat platform extending a few inches to support the roofing. Making and installing those tapered shims could be a bit of a challenge unless you have the right wood working skills. The mitered corners will have to taper in two or even three dimensions!
Most roof A/Cs are designed to fit a standard 14 x 14 roof opening. Make sure you know the size of the old gasket before purchasing a replacement gasket. Standard gaskets sell for around $30 or less; premium gaskets can cost over $50. However, given the high value of many RVs and the high cost of repairing water damage it may be a good idea to opt for the premium gasket if you have the budget for it and plan to keep the RV for any significant length of time, but I have seen standard gaskets work perfectly well for 20 years or more. I had to replace the gasket on a very old unit that needed a gasket
that was about 15"x 151/2" inside dimensions and with shipping it cost
over $90! NEVER attempt to replace or repair a leaking gasket using caulk or silicone sealer. It might work for a little while but you can be sure it will fail a lot sooner than making a proper repair by replacing the gasket with the correct one. The solvents in some sealing compounds could damage the gasket causing even more problems.
Prevention is always better than repair! Many roof problems can be prevented by proper preventative measures. Regular inspections for deteriorating caulk or damage can help you seal seams or repair holes BEFORE they start to leak. Avoid loading heavy or sharp objects onto an RV roof and make sure you have sufficient clearance before driving under trees where low-hanging branches might damage the roof. Be careful when walking on an RV roof and make sure there is no sharp debris caught in the tread on the soles of your shoes. Standard seam caulking should be inspected frequently and typical maintenance schedules call for stripping it off and redoing it about once a year. Some roof coatings, such as those supplied by Minnesota Roofing, may reduce the need for frequent caulking. When inspecting the caulking be sure to examine all the seams (including those where the roof on some RVs wraps down over the side wall) and around all vents, antennas, etc, that project through the roof.
Dry up!