Best way to protect an old but apparently sound flat roof
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Murgatroyd
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Best way to protect an old but apparently sound flat roof

by Murgatroyd » Mon Sep 27, 2021 6:00 pm

I want to extend the life of an asphalt flat roof that will be 23 years old next month. There are no leaks in it, and cracks in the felt where it goes over the long edge of the roof were sealed last year with bituminous sealant.
Recently I noticed some cracks in the felt at the bottom of the upstands so I sealed them with scrim tape and Acrypol+. I also covered the earlier repairs with a coat of Acrypol+ as I had the tin open.
In order to facilitate inspection of the roof I swept up and removed the chippings that had been laid on the felt originally (along with the accumulation of moss, bird droppings, and general dirt), and discovered that a substantial amount of them had become embedded in the roofing material.
My question is: How should I proceed, in order to further extend the life of the roof? The embedded chippings make covering the roof with Acrypol impracticable, and I've no desire to start scraping them off.
Would flooding the roof with a suitable material be a reasonable approach? If so, what should I use? Or would simply replacing the old grey chippings with more reflective ones be adequate?
I would add that there are no spongy or saggy areas on the roof; I can walk on any part of it without feeling as though I'm going to drop in unexpectedly.
The object of the exercise is to head off trouble at the pass and not to repair existing leaks, because there aren't any.
Attachments
The Acrypol looks blue in the pictures but it's actually grey.
The Acrypol looks blue in the pictures but it's actually grey.
The cracks I mentioned are under the drainpipe.
The cracks I mentioned are under the drainpipe.

stoneyboy
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Re: Best way to protect an old but apparently sound flat roof

by stoneyboy » Tue Sep 28, 2021 10:48 pm

Hi mufgatroyd
At 23 years your roof has lasted well.
You could try sweeping off all loose gravel, pouring a spirit based bituminous adhesive on the roof and brush in well, once the coating becomes tacky spread some new clippings.
This all needs to be done in dry weather.
Regards S

Murgatroyd
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Re: Best way to protect an old but apparently sound flat roof

by Murgatroyd » Wed Sep 29, 2021 11:38 am

Thanks very much for your response.

Could you suggest some specific products that would be suitable? I'm not expecting product endorsements but it would be helpful to be advised about the pros and cons of various manufacturers' solutions to the problem by someone with experience in such matters. I don't have access to specialist equipment and I don't have the knowledge or skill to use it if I did, so applying said product needs to be within my modest capabilities.
The roof is about 18 square metres in area, if that's relevant.
If the roof needs to be dry to ensure good results then it looks as though this will be a job for next year, as I imagine a roof that's warm as well as dry would be that much better for obtaining satisfactory results.

stoneyboy
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Re: Best way to protect an old but apparently sound flat roof

by stoneyboy » Wed Sep 29, 2021 10:14 pm

Hi mugatroyd
I’d suggest the solvent based Black Jack or something similar applied with a soft bristle yard broom. Roof needs to be absolutely dry so the paint can penetrate around stuck on stone chippings. You need a non sunny day or the paint will dry too quickly and the top coating of stones won’t stick. If you can find chippings with no fines these are best.
Regards S

Murgatroyd
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Re: Best way to protect an old but apparently sound flat roof

by Murgatroyd » Sat Oct 02, 2021 11:22 am

Thanks again for your interest and input.

I'm assuming that "fines" means small fragments and dust mixed in with the chippings themselves, so I'll watch out for that when I'm buying. I'm intending to use white chippings if possible, because of their better solar reflective performance.
The original ones seem quite small, resembling cat litter in size. Would you advise larger chippings, and if so how big should they be?
You mention that the stones need to stick to the top coat, which infers that they need to be applied while the latter is still wet, or tacky at least. Why is this? I can't tell if the old chippings I removed had originally been stuck on and come loose over the years, or hadn't been stuck on but had sunk in here and there over the course of various hot summers. However, I can foresee considerable scope for me getting into a bituminous mess if I'm working with paint that isn't completely dry...

One (hopefully) last question: Would you advise the use of a primer before applying the actual top coat(s)?

Many thanks for your help.

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