There are three main types of roofing used on American Motorhomes.
The first roof construction used from around 1970 – 1990 had a similar construction to those that are used today but in the early days they used aluminium for the final skin. These roofs tended to be very reliable and 30 years later can still be found water tight and in good working condition.
The main disadvantage of these roofs was the noise; when it rained the water was very loud on the aluminium, and on top of this the aluminium prices started to rise.
From 1990 onwards a rubber membrane was used on the outer layer, proving much quieter than the aluminium counterpart. This meant that the roof construction needed to be changed from using separate 6ft x 4ft sheets into using one large piece of board. The reason behind this was simple; when the membrane was used with separate boards, the joints showed, and if one of the boards raised then it was likely to result in damage to the membrane.
The one piece of board used now is called Oriental Strand Board (OSB), which is laid on the roof and then the membrane is bonded to it. A non petroleum based sealant is used to seal up the skylights and cappings. The problem with OSB is that if any water reaches it then it will disintegrate the board, separating it and then drying out into dust. The advantage of having the rubber membrane, as stated before, is that it is much quieter than the alternative aluminium. Obviously, the rubber membrane has its disadvantages, such as:
- The membrane tends to chalk, so when it rains it will leave streaks down the bodywork. As most paints are full body paints, the streaks are very obvious on a dark coloured RV, needing lots of elbow grease to remove!
- The rubber membrane can be easily damaged by overhanging tree branches. When this happens and is not noticed, the OSB can become very wet very quickly.
- The membrane needs regularly maintaining to remove tree sap and bird droppings which can eat into the rubber.
If a leak is spotted quickly, they can be remedied at a minimal cost, however when they are left the cost of repair rises exponentially. Some manufacturers still prefer to use the rubber membrane roofs, but others have moved onto a new type; the fibreglass roof.
The fibreglass covered roof again has the same basic construction as the rubber and aluminium roofs but with the main difference that the covering is fibreglass. One way in which this is achieved is by using one sheet of fibreglass, bonded to the OSB and slotted in the roof rails along the side. The other way uses 2 sheets of fibreglass joined along the middle, again bonded to the OSB and slotted in the roof rails.
On the whole the fibreglass roof is fairly reliable, as you don’t get the streaking effect you get from the rubber membranes and they are not as easily affected by tree branches, however they tend to be noisy when it rains.