Sagging roof issues and how to fix them
Roof Air conditioner
If you have a roof that is sagging on the inside and it passes all visual inspections from the outside, you should take a second look at the air conditioner. Each RV roof top air conditioner has a gasket underneath between the AC unit and the roof and these can sometimes develop leaks, even on fairly new RV’s.
Roof mounted air conditioners are very heavy units. They are subject to all the vibration, wind and the elements that occur during your ownership of the RV. It is quite common to find the roof area around the air conditioner sunken or sagging, especially on those RVs with soft roof construction. What happens is water can start to collect around the unit and then leak into the roof area.
To fix the issue, you need to determine the rafter spacing. On most soft roofs the rafter positions are evidenced by the indentations in the roofing material. Measure the distance between the centers of each rafter. It will usually be either 16 or 24 inches. Then you need to remove the air conditioner, but be very careful when lifting it off of the roof. Any old and remaining sealants could cause the unit to stick to the roofing material often creating tears in the metal. Be sure to clean off the old gasket and any sealant from around the 14-inch opening and remove any staples through the roofing material around the opening.
The next step is to cut some ¾ inch plywood strips and cut out the center for the air conditioning unit. You will now have approximately a 28″ X 34″ piece of plywood with an approximate 14-inch square cutout somewhere in the middle. Now, mark and cut the plywood in half longitudinally down a center line resulting in two, 14″ X 34″ pieces of plywood with a “U” shaped opening in each piece.
Insert each piece into the roof cavity through the 14-inch hole, underneath the sheet metal yet on top of the existing rafters. Slide each piece into position on either side of the 14″ opening taking care not to disrupt the roof insulation in the process.
Next, apply new sealant and a new gasket, and then reinstall the air conditioner.
The Fix- Create a support rib.
Sometimes with aluminum roofs on aluminum sheathed RV’s, the framing structure can use a little bit of additional reinforcement. This can be accomplished by adding a support rib that runs perpendicular to the existing roof support beams. If you are a handy person, this is something that you could do yourself, however it is very labor intensive and you need to know what you are doing. This does involve quite a bit of cutting and repairing as well as some carpentry skill. Basically in order to install a support rib, you will need to support the ceiling from the inside, using a ladder check the roof line ensuring that the roof has a nice natural curve to allow water run-off. Support the rib along the seam and mark it. Using a sharp knife, cut through the ceiling panel and foam insulation. Remove the aluminum molding and panel above the door, the rib can be easily anchored to the exposed framing on the door side.
RV sagging roof repairs- non Aluminum RV’s
The vast majority of RVs built today have a vacuum-bonded, solid roofing structure. Basically it’s a one-piece roof consisting of plywood decking on top, some type of insulation installed between the support rafters with a panel type of ceiling finish. The whole structure is built on a flat, vacuum table, glued together and set on top of the walls. The synthetic membrane is then installed once the roof is secured to the side walls.
The fixes described above do not apply to the more modern, one-piece, synthetic roofs like EPDM, TPO or fiberglass, unfortunately. The solution for a sold roof that sags is to first determine and rectify why it sags, then remove the rubber membrane and either replace the top decking with thicker plywood preferred, or simply install another layer of plywood over the existing plywood decking. Of course, this assumes all the rafters and support members are not damaged and remain intact.
Essentially you will be getting a new roof with this one, and we highly recommend that you get this work performed by a top quality RV repair shop like ours at Coach Specialists in Dallas Texas.