Expensive zinc or cheaper ply membrane like sarnafil for new extension roof??

[Olive324]

Hi, we are having a new extension to the back of our house and on the architects drawings we are having a zinc roof. After getting quotes from builders it seems that zinc is really quite expensive and they have suggested a single ply membrane such as Sarnafil as an alternative. Does anyone have experience of this? Does it look very different? I don't want to have the membrane if it looks naf and am wondering if we should just push the boat out and pay for the zinc. Any thoughts? Thanks

[LucyPie]

No advice but we are going through exactly the same for our extension roof as we want standing seam so will watch this with interest and post if I find anything that might help us both :) Googling images they do look very similar but haven't seen any single ply in 'real life' yet.

[PigletJohn]

I didn't think anyone uses zinc these days. It doesn't last for ever.

On my commercial premises we now have a synthetic rubber membrane on the flat-roofed part, after having lead stolen twice. I don't know the trade name, but flat roofers will have their favourite. As it comes in a large sheet you may get away without any joins, which reduces the chance of later leaks.

I believe it is available with a metalised coating which reflects sunlight.

If you have a stately home with standing seams and rolls intended to look like lead, you can get lead-plated stainless steel, though I doubt it will be cheap.

[LucyPie]

I was under the impression that zinc was very longlasting.

We have a large flat roof area to cover (56 sq m) so have been told that some roofing materials are not suitable.

We will also overlook it from the master bedroom so want it to look aesthetically pleasing hence thinking of standing seam which also looks very modern as well as suiting stately homes.

Our options to consider so far seem to be zinc, single ply, TATA steel Colorcoat Urban, Newell Prelaq Nova Plx metal ................ confusing yes!

[Olive324]

I thought zinc would be the longest lasting too! Anyone had it? Worth the money!

[PigletJohn]

I don't know how long zinc lasts, but it is a cheap substitute for lead, and older houses where it was used over bay windows and the like, I have seen it corroded away into lace. More holes than zinc. Roofers and builders sneer at it.

There is a way to calculate how long zinc lasts exposed to the weather, galvanisers have a table.

[OliviaBenson]

coated steel which has been made to look like lead might be a good alternative? It will be cheaper but look nicer.

[martymcfry]

Zinc will last longer than single ply I believe (25+yrs), it will also look better IMHO. I just recently went through this decision! We ultimately went for felt though :( We didn't have the falls required for zinc, which are less than lead but more than single ply or zinc.

rubber/single ply can look great with standing seam, but my concern was surrounding the asthetics - it can bubble up, and look truly awful unless laid correctly and by someone competent. Also I dont think it stands the test of time in terms of looking good a few years down the line.

Zinc is expensive, and not as widely used, but I believe the reasonf or that is that the machinery required to make the panels on site costs in the region of 10K - therefore you'll get many more roofers able to offer single ply as there is no such investment required in tooling. With zinc though you will need to lay a self healing membrane (not just plastic sheeting) - the one recommended by the zinc suppliers is expensive. You can get a cheaper zinc roof if you dont have it pre-weathered.

There are loads of brands of single ply, all slightly different colours and different thicknesses, every one will recommend different.

[Marmitelover55]

I thought GRP was the way to go for flat roofs these days? We ended up with a pitched roof in the end though.

[TheReturnoftheSmartArse]

We've got GRP on ours. Seems ok so far ...! The zinc option was rejected by the builders as it apparently corrodes very quickly. Had lead last time, which we had no problems with, but that was too expensive this time.

[TheReturnoftheSmartArse]

Sorry, Olive - I don't think yours is a flat roof, is it? I don't like flat roofs - the water's bound to stand, isn't it? We're onto our 3rd and haven't ever had any problems, but I'm always expecting it!

[Olive324]

No, ours is a sloping roof but not sloping enough to gave tiles. I'm confused by pricing as every builder we've spoken to has said that lead costs LESS than zinc. Aaarrgggh decisions!

[martymcfry]

Lead is a massive theft risk. I'd be worried to go on holiday if I had a lead roof!

[Olive324]

What about corrugated tin? Builder just been round to discuss and this is also an option. Any thoughts?

[PigletJohn]

it can't be tin. Does he mean galvanised corrugated iron, as used on old outbuildings before the invention of plastic?

[PigletJohn]

Here is a pic of what my BiL calls his tin roof (corrugated iron). It is getting a bit rusty.

UK builders are not usually skilled in doing neat detailing with it.

[Olive324]

Sorry, just checked. It's corrugated plastic coated steel. Been told where there is a building with it so I'll pop out at the weekend and take a look.

[PigletJohn]

very noisy during heavy rain, terrible in hail, quite noisy in light rain.

[Olive324]

Even if in has fitted insulation under it pigletjohn? Any other downsides? If you were roofing an extension which couldn't have tiles due to gradient, what would you have?

[PigletJohn]

I'd probably have a ply deck with synthetic rubber membrane, but I am not a roofer.

Insulation will muffle noise, but while a tiled roof has a gentle patter in rain, a metal roof (except lead, which does not resonate) makes quite a drumming.