The issue of water proofing the canvas of a folding camper, trailer tent or awning comes up regularly, and is featured in the FAQ section of our main web site.
The water proofing qualities of any canvas are integral to its ability to function properly. We do, however, need to be very careful as to how we look after it and protect it. For example, any cleaning products containing detergents will automatically compromise the integrity of the canvas, as will many treatments for mold, mildew, etc, and these need to be avoided, if at all possible.
With respect to waterproofing, generally, the advice has to be; “If it ain’t broke, don’t fix it”. Waterproofing solution should only be applied when the canvas is leaking profusely, and cannot be remedied using any other means, and should never be used purely as a preventative measure.
The cotton fibres in the fabric expand and contract, depending on their moisture content. As the fabric becomes soaked, it begins to swell, thereby plugging any microscopic holes in the canvas, and preventing water ingress, just like the wooden slats of a water barrel expand, and fill the gaps, in order to retain the liquid inside.
Water proofing solution plugs those holes in much the same way as the fibres do. Unfortunately, in doing so, it coats the cotton fibres, making them rigid, and preventing them from expanding when they become wet. This means that we have, effectively, removed the natural waterproofing qualities of the canvas. Once we have done this, it is only the water proofing solution that is keeping the moisture out. As the canvas flexes and moves, and is exposed to the elements, the water proof layer breaks down, and, as we have now destroyed the canvas’ own ability to keep water out, we begin to notice leaks appearing, once again. As a result, we find ourselves constantly re applying the solution, on a regular basis.
So. What is the best procedure when we spot a leak? Well. Most campers with non acrylic canvases will dry out, when placed in storage, for any period of time, and some will contract enough to allow water to start seeping in.
The best procedure is to set the camper up, and lightly spray it with a hose, until reasonably wet, allow it to dry a little, and then repeat, using a little more water each time. A normal canvas should self repair as it becomes saturated, and the leaks should disappear. On those rare occasions when it doesn’t, then you may wish to consider the application of the likes of Fabsil etc, which can be either painted or sprayed onto the canvas.