Garage 2/2 (Flat Roof Weatherproofing)

[dpm_dpmartin]

Hi,

This is the second question I've asked about my garage with a flat roof.

I would like, in preparation for winter, to spend a bit of time getting my garage into tip-top condition.

I have this flat roof on my garage...

And I'm wondering what is the best product out there for me to use in covering this... by "product" I'm thinking of something that comes in a can, as the roof appears (to me, at least) to be quite stable... I'm not looking to install a new roof.

I've seen, in Screwfix, the product called Isoflex Liquid Rubber on page 97, which says it's good for roofs and lauds the fact that it's "5 times more flexible than bitumen"... which I'm guessing is a really good thing.

Does anyone have any experience of this product and is it a good buy? Would something else be more suitable?

Can I paint straight over all those annoying loose pebbles, and get them stuck in place, or will I need to brush them all off first, paint then (possibly!) put them back on.

Why did the previous owner or the person who built the garage put a load of loose pebbles on there in the first place anyway?

Other alternative products I've seen...

Thompson's 10 Year Roof Seal
Cementone Flexacryl - this comes in grey as well
Flag Roofix - this comes in white!
Black Jack Roofing Emulsion - to be used in summer only, it says

...any advice as to what I should be using would be really helpful.

 

[bryanpar]

the pebbles are there for a reason.they absorb the heat from the sun and stop the roof felt underneath going soft with the heat.if there is nothing wrong with the roof (ie not leaking) why do anything at all. you would have to remove the pebbles to coat with a bitumen then re apply the pebbles to roof

 

[dpm_dpmartin]

Thanks.

It's really not me making work for idle hands... I know we had a bad winter last year and it might be the same again. There are parts where the roof has lost some pebbles (due to wind) and I've only had the house since June and I reckon the thing hasn't been looked at for many years... so I wanted to do the job (especially as I've housed various things in the garage that I want to keep safe and dry).

I did not know that about the pebbles, good to learn, shouldn't they be stuck down? Are they supposed to get blown around, and off, in the wind?

 

[dpm_dpmartin]

Are these solar reflective coatings (paint) any good? Would that allow me to ditch the pebbles and have a smooth roof?

 

[alan333]

The pebbles (chippings) keep the roof getting hot as per bryanpar said, but years ago they had a second purpose which everyone seems to have forgotten in modern times, ie fire spread prevention. The theory is that when a burning ember from next door's house landed on your roof, it didn't set your house alight. My personal theory is if the fire is that close then your house is going up anyway.

I can't tell from your pic but it's probably a felt roof. If the edges are mineral surfaced like what you often see on hut roofs, and there are lap joins at every metre or so around the edges...then it's felt. If it's a thick, grey smooth-ish surface with no visible joins anywhere, like a walkway on a 70's shopping centre, then it's asphalt. It's uncommon to have chippings on asphalt.

The chippings should be stuck down, although they could be anywhere between well stuck into the surface, to lying loose on the top. I haven't came across a product which would successfully work over chippings, they'd need to come off. Also remember if you move them into a big pile at one end that pile will be heavy, so the roof could collapse. If they're well stuck then removing them involves bashing them off with a spade, and this damages the top felt layer. Even if they're not well stuck it leaves a lot of dust etc, which any new product would struggle to adhere to. You need to torch the whole roof to "burn" the bitumen surface back up.

To rejuvenate the roof...remove the chippings, burn up the surface, make good any defects and, if the surface is sound enough, lay a new layer of good quality felt over it, and re/do all the edges. Then painting with bitumenous solar reflective paint won't do any harm.

Again i'm with bryanpar here, if it ain't broke don't fix it. Post a few more pics of the edges and upstands, they are where most felt roofs go faulty first, so are a good tell-tale as to condition.

 

[dpm_dpmartin]

I took a couple more pictures... the pebbles have gone in some areas and they are mostly loose (it feels like, to me).

Not sure what upstands are, but the corner areas do seem fine. Well, the two that I have easy access to, that is.

Do these help?

And...

 

[alan333]

In the pic in your first post it looked like the roof joined to the brick wall, upstands are where the felt would have gone up and into that wall. I can now see there are no upstands.

Judging by the drip edges the roof doesn't look too old, and looks pretty professionally done too - the corners are mitred, the welted drips look good, and the cuts are straight.

I'd leave it alone unless the loose chippings were a bother. You could try sweeping an area and see how good the surface is for solar reflective paint instead. Or you could stick the chippings down with chipping compound or similar.

 

[dpm_dpmartin]

Ah, I see... no, that's a different house and there's a big air-gap. I'll look into chipping compound... learning new stuff all the time.

 

[dpm_dpmartin]

Where does a person like me buy both solar reflective chipping and chipping compound?

My usual suspects - ToolStation, Screwfix, B&Q appear to be drawing a blank - unless I'm searching very poorly. I think I've seen lots of varieties of chipping (various colours, stuff from the Cotswolds etc.) on the Wickes website... but they're over £120 a bag... it might be a [very, very] big bag, but still...

Any hints appreciated...

 

[dpm_dpmartin]

OK, this looks interesting... reflectance mentioned. Different colour, but I could mix it in and change it to a nice off-white over time (to better match the sides).

http://www.specialistaggregates.com/roofing-white-limestone-p-2082.html

 

[alan333]

Where does a person like me buy both solar reflective chipping and chipping compound?

The chippings don't need to be solar reflective, it's the fact that there's a layer of cold stones on the roof which stops the sun getting through. I typed "roofing merchants sheffield" into Google and got quite a few results. Maybe try phoning a few and see who is the most helpful or has the best prices/delivery etc?