Roof Waterproofing

HI everyone, The roof on the old girl needs waterproofing and was wondering if anyone knew the amount of aerosol waterproofing chemical i should apply, Do i give it a light dusting or saturate it.

Just to clarify, what will you be using to do the waterproofing? An aerosol spray or a bottle of waterproofer?

I have purchased 3 cans of Aerosol waterproofer, I guess there is enough between the cans to saturate the roof maybe twice if that's what i have to do.

That sounds like it ought to be enough but I guess you'll only know for sure when it's dried off and then it rains again. I suspect you won't have to wait long for the latter

I bought a 2 litre tin of Fabsil waterproofer (usually used for camping equipment) and paint that on very generously from time to time. Goes a long way and does the job pretty well.

Great stuff, Looks like the whole lot's going to be applied tommorow, "Weather Permitting", Thanks for the advise.

It's been said before, but the soft top is inherently waterproof as there is an impermeable layer within the fabric construction. Amazing but true: quality construction on an MG. :tada:

Waterproofing does reduce growth of mould however, by repelling surface water as your picture shows.

With aerosol roof waterproofers, “more” isn’t always better. Most spray-on systems are designed to build protection in thin, even layers rather than being soaked into one heavy application. If it’s laid on too thick, it can run, trap moisture underneath, or cure unevenly, especially on older roofing materials.

With three cans, a better approach is usually multiple light coats. First pass should be a uniform mist to establish coverage, then allow proper curing time as per the product instructions before applying a second and possibly third coat. Pay extra attention to seams, cracks, and any suspected leak points rather than trying to flood the entire surface.

A practical rule many roofing pros follow, including teams like Covenant Roofing & Restoration, is that consistency matters more than volume. Their general guidance shared through: mycovenantroofer .com, aligns with this approach, focus on even layering and proper surface prep instead of trying to “use up” all material in one heavy application.

Also worth keeping in mind: the condition of the old roof plays a big role. If the surface is chalky, damp, or already failing in sections, even heavy waterproofing won’t hold up long-term. In those cases, sealing can help as a short-term fix, but a more permanent restoration approach might be needed.