materials for flat roofs

Have a look at http://www.rheinzink.co.uk/. They do a wide range of products and there is one for every situation.

A 9 degree pitch isn’t that flat at all, zinc can be used on pitches down to 3 degrees and other materials can go to much lower pitchs. For a small job like this zinc would be alot more awkward to use and expensive than membrane sheet/built up layer materials (which are available in a much wider range of colours than in the past).
Why did you choose zinc in the first place? And what’s the span of the roof.

as regards insulation, there’s a great irish made product called EcoQuilt made by SmartR Insulations Ltd in Dublin. It’s a reflective material. Its’ really easy to use, clean etc. and its perfect for retro-fit, attic conversions, extensions etc. The websire is http://www.smartrinsulations.com If you’re looking for an insualtion it’s a good one to go with, especially with the energy ratings for houses coming in soon.

Firstly Zinc looks absolutely fantastic on a low pitch roof, especially if you go the whole hog and incorporate the guttering, downpipes etc and be careful with the edge detailing to make it look as thin as possible.
However, it’s a pretty awkward system alright – the underside of the zinc has to be ventilated and a lot of control is needed at the joinery stage of the roof construction so that the Zinc contractors can come and do their job properly. It probably isn’t worth the hassle unless the roof is going to be quite visible.
It’s also quite expensive! A (fairly large) zinc roof component and the guttering and downpipes came to about 10% of the total cost of a house I’m just finishing which is pretty rough. However, I reiterate it does look fantastic!

Most people I think would use lead in your situation. It needs venting behind, but the main thing is that you can get hold of it & someone to lay it. Rheinzinc is a product for bigger projects really.

@BTH wrote:

However, it’s a pretty awkward system alright – the underside of the zinc has to be ventilated and a lot of control is needed at the joinery stage of the roof construction so that the Zinc contractors can come and do their job properly.

As long as it is detailed right, it can be just as simple at the joinery stage. Using rafters without full fill insulation can be the easiest way to achieve ventilation and use spaced boarding instead of conventional ply under the finish. Decide now before it becomes a problem when you change your mind and you are trying to adapt.

But as BTH said it is more expensive. And as for a lead roof. Don’t even bother. Lead is far too ductile, thats why it is used for flashing.

How would you space boarding underneath the zinc Bren88?
Ths site says zinc has a lifespan of around 100 years when used on roofs – pretty impressive. Would copper be the same?

http://www.vmzinc-us.com/content/37/

@ren wrote:

Hi,
I am currently building a single storey extension and the pitch of the roof will be approximately 9 degrees with 3 glazed panels. I have considered using zinc on the roof but want to know if there are any special requirements for ventilation. Is it a suitable material for a domestic extension, does it retain heat and how will it change colour over the years? Can rainfall be heard with a metal roof? Does anybody know of any other material that is aesthetically pleasing for a low pitch/almost flat roof? I have heard about Nordman roofs but think they might be too “plastic” as they don’t age and apparently have quite a glare. The house is a 1950’s mid terrace and the existing roof is tiled. Any advice is greatly appreciated.
Thanks
ren

I was looking at an existing extension for someone recently that had obviously been built by the previous owner himself. 215mm rendered single skin block , no insulation, concrete tiles to a roof of approx 10 degrees (min recommended pitch 35). If Building Control has a scope of responsibility as they do in the UK it would have to be pulled down.

ANYWAY, the point being that recommended min pitches are arse coverers. I assume that this roof will be visible from your own upstairs windows? If so, go the extra hog and use a nice material – i’m using rheinzinc on my own extension. If you pick a product you can get a whole pile of manufacturers details for the proposed build-up that will clear up all the vent etc. Use an insulation with a good sound rating and you should be all right with noise

@Graham Hickey wrote:

How would you space boarding underneath the zinc Bren88?

A small c.4mm gap is left between the boards and they are fixed to the rafters. That site you posted, VMZinc.com, are another market leader. The following is taken from their website and is on basic structure under a zinc roof.

Clean and dry 100 to 150 mm wide, 18 or 24 mm thick softwood boarding, according to the rafter centres.
Any wood treatment products (fungicides, insecticides) must be dry and completely neutral in relation to VM ZINC®.
The roof boards are fixed perpendicular to the direction of the pitch leaving a 3 to 5 mm gap between them.
They are securely fixed to the structure.
Maximum difference in height of 1 mm between roof boards.
The deflection measured under a rigid 600 mm long straight edge cannot exceed 2 mm in all directions.
The roof board nails are countersunk in order to avoid any contact with the VM ZINC®.

Hmmm..Well if lead is too ductile, its been used (traditionally & otherwise) for years, perhaps not on such low pitch. How are you lot managing to get hold of Rheinzinc in such small quantities without a lot of bowing & scraping?

Local suppliers and fixers can be very interested in smaller jobs, especially if they are a little bit out of the ordinary – Going by the guys I used for my project over here in the West anyway. They have done some major copper and zinc cladding projects but were more than happy to look at the smaller jobs as well… May be the architectural connection at work though as well because they will definitely be getting my recommendation on any future larger jobs i’d be working on…

@L1 wrote:

Hmmm..Well if lead is too ductile, its been used (traditionally & otherwise) for years, perhaps not on such low pitch. How are you lot managing to get hold of Rheinzinc in such small quantities without a lot of bowing & scraping?

Lead is normally only used for flashing on roofs. It doesn’t have to to large project, or Rheinzinc for that matter. Standard plain zinc sheets can be used. For a simple flat roof it would be childsplay. A sheet metal worker could easily finish the seams on site.

@Bren88 wrote:

A small c.4mm gap is left between the boards and they are fixed to the rafters. That site you posted, VMZinc.com, are another market leader. The following is taken from their website and is on basic structure under a zinc roof.

Clean and dry 100 to 150 mm wide, 18 or 24 mm thick softwood boarding, according to the rafter centres.
Any wood treatment products (fungicides, insecticides) must be dry and completely neutral in relation to VM ZINC®.
The roof boards are fixed perpendicular to the direction of the pitch leaving a 3 to 5 mm gap between them.
They are securely fixed to the structure.
Maximum difference in height of 1 mm between roof boards.
The deflection measured under a rigid 600 mm long straight edge cannot exceed 2 mm in all directions.
The roof board nails are countersunk in order to avoid any contact with the VM ZINC®.

i thought the build up had to be boarding/deck on top of 50mm battens (for vent gap) on breather membrane on rafters.

if the board is directly on top of the rafters then there is no ventilated space open at the eaves and the breather membrane cant drain into the gutter…?

@Bren88 wrote:

Using rafters without full fill insulation can be the easiest way to achieve ventilation and use spaced boarding instead of conventional ply under the finish.

There insulation between the rafters isn’t fuly filling the space. A c.50mm gap is left and this gives the ventilation cavity. If you want to fully fill the space for achieve a better U-value then batten are needed.
But as I said, the non-full fill detail is easier.

Hope you don’t mind me resurrecting this thread but I’m looking for opinions on an alternative my architect has suggested – something called ‘Modified Bituminous Asphalt’.
Has anyone got any experience of this system? Has it been used widely in Ireland? Difficult/Easy to install? Price?

I was originally thinking about a Zinc roof on my building too (this is a house with a 45 ft span) and all my previous experience with any kind of asphalt roof has been horrible. They leak, they deteriorate, and they look ugly!:(

A well installed , with good falls to drain , asphalt roof is a very good spec . However you might like to consider a multi layer torch on felt system where the top layer includes a copper sheeting . If correctly specified you wont need to ventilate the roof and it does look good. Try Moy Materials for samples , spec details , recomended installers and warranty

It might be worth looking at http://www.metseam.com, they are based here also.