What is the best flat roofing system?
I want it to last as long as possible without maintenance. Cost is not an issue. Subsequent access will be extremely expensive, so it needs to be bombproof, or at least sun and rain proof, for decades.
Christian.
Lead, probably, good for 70-80 years but the area you are doing (you don't say) may make this a bit expensive.
Lead?
If nothing else make sure it has a decent fall
About 16 sq m. Do you think lead might be too heavy? I doubt I'd get much extra weight past the BCO, particularly as we're not sure if the house has foundations at all.
How are large flat roofs done with lead? Do they just solder the joins?
Christian.
It will the minimum fall allowed, I'm afraid. Every cm matters.
Christian.
Copper? I think it's lasted longer than 80 years on cathedral domes.
It's a bit vulnerable to physical damage of course, but glass is almost immune to weathering and corrosion. How you support it might be more difficult.
Waterproofed concrete with turf gowing on top? Add enough turf and it would be moderately bombproof :-)
Owain
I wouldn't have thought this would be a problem: Code 5 lead (5lb/ft2) would be lighter than the traditional 3 layers of felt + chipping
No, no, no! Lead moves quite a lot with temperature so the secret of constructing a roof that will last for decades is to detail it so that the individual pieces can move.
They are laid in sections hammered over round wooden formers at the section edges. The next section is layed and hammered back over the first (and the wooden former). [Picture binary sent separately to Christian].
I've got asphalt topped with GRP reinforced lightweight concrete tiles on my roof terrace. The architect reckoned this would have a *very* long life. However, the exposed bits of asphalt do need painting white every few years.
For just a roof, how about zinc?
Would I right be in saying that it would take about 400kg of lead at about
1.70 per kg? That would be a reasonable cost, if I've got the sums right.However, it does seem like a lot of weight. Are you sure that alternatives weigh similar amounts? What about GRP? Is it any good? Is it lighter? I'm worried about weight because I want (a) the walls to still be standing and (b) to have minimum rafter depth.
Christian.
I've found Polyroof 185, which looks like a premium GRP solution, with a 20 year insurance guarantee and 30 year expected life. Anything involving asphalt will not work. There's no way it can be painted/rechipped/patched at anything like a reasonable amount of money. It's got to be fit and forget.
I think it would be a fraction of the weight of lead, so might provide a solution if the BCO doesn't allow lead because of the weight on the 1909 foundations (assuming there are any). There's already suggestions that the party wall can't be built up in brick, but may have to be timber framed.
Christian.
Well, it wasn't a DIY job (sorry) so I don't know the weight. The alternative (as someone else has mentioned, was Zinc (well it's some alloy or other). I was quoted 30-40 years for that AFAICR.
The weight you suggest sounds about right from my recollection and the point load is far less than someone standing on the roof. I can stand on this one without any give at all. The supporting timbers for the dormer roof (from the drawings) were 100x38 SC3 at 350mm centres (3-4m long).
Bob
Think that's quite conservative. Next door has a zinc flat roof over the rear addition. Replaced recently. And the lady who lives there - age 75 - was also born there, and can't remember it having been replaced before.
I have a zinc tray on the flat roof above my bay window - which I replaced some time ago. And it looked very original to me. The house is Victorian.
In message , Christian McArdle writes
Dunno, but ISTR that my wife's nan has it on flat roof that was done sometime ago, i could check up on this.
What about Butyl rubber? This stuff is supposed to have a long life (as in decades) My FIL had his flat roof done in this, but only a couple of years ago.
is one place I know of.
Hi,
Thick thick (1/4"?) fibreglass, with white pigment for UV protection and/or gelcoat on top.
Maybe get a roofing contractor to do it, but with double or even triple overlapped layers of the normal thickness, carried over any edge flashings. Either that or read the guarantee very carefully...
Does the Polyroof system state what weight the fibreglass is or how thick it is?
cheers, Pete.
In article , Christian McArdle writes
You reckon it's a lot of weight for the founds but a quick calc on the weight of the walls shows they're probably a just under a couple of tons(*) each so
200kg extra per wall doesn't seem too much to bear.(*) Your 16m2 guessed to be made up as 4m square, single brick construction, 2.5m high, based on a single brick in my hand 21cm x
6.5cm weighing 2.5kg.
Actually, it is double brick and about 5m high. However, the status of the foundations is unknown, so the BCO may be wanted to keep the extra weight down. In fact, he'll probably insist on exploratory investigations and underpinning. If underpinning is required, then we might as well do everything as heavy as possible, as the foundations are then a known quantity.
OTOH, we're a bit worried that underpinning would scare off ignorant potential purchasers.
Christian.
In article , Christian McArdle writes
He seems to be being a bit silly worrying about an extra 200kg when the walls themselves must weigh over 5tons each (4% extra loading). You're the man on the ground, but maybe presenting the figures could get you out of a bit of work, particularly if the walls are original (they've lasted X00yrs so . . .), less so if you're building them up.
Then you are not underpinning, you had the foundations 'reinforced' to guarantee they could take the extra loading ;-)
Lead does sound nice btw.
We got a fibre glass flat roof done by these people a few years ago and they did a very good job...
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