Flat Roof

lnos1

Hi,

I am wondering if someone could point me in a direction of the best ways to construct a flat roof. I have a flat roof on the main roof of a house with slates on 4 sides (there is no centre ridge along the roof - house more or less square!). I have heard about using fibreglass as a long life time solution. My understanding is that felt is cheap but doesn't last that long. Do people use metal anymore? I find it hard to find stuff on google.
Also, how would it be joined to the slates? Is it possible to have a smooth joining or would some ridge have to be contructed? I would be worried about leaks in a few years.
All advice is very much appreciated (or diagrams ).
Thanks

OBrother

You could use lead or zinc sheets, both are relatively expensive and are specialist jobs. you could also use EPDM membrane, google this and you will get lots of possibilities, there is also asphalt which you will see on the flat roofs of the old school and public buildings. With any of these or fibreglass, it is the quality of detailing by the designer and the experience of the trades man that make all these systems work, so get people who know what they are doing and are willing to give a guarantee.
You should also be wary of using poor quality plywood as a deck below any roof, and it is best to use what is called a warm deck, where the insulation is above the timber. all of these items need careful detailing by someone who is qualified to do it.

lnos1

Thanks for that.
Would it mean lead and zinc are the best as they are the most expensive, followed by fibreglass and EPDM membrane? Am I right in saying asphalt is the worst?
When the flat roof is part of the main house, and there will be an attic underneath, would you still use insulation? At the time of planning, the architect convinced us to go with the flat roof rather than having a gulley/valley. He said drainage would be a problem with that. Now I am left with a flat roof and not convinced it was the right choice.
Has anyone seen or done a flat roof on top of a hip roof?
Thanks

OBrother

Lead and zinc can have a life span of 60 years, depending on pollution locally, asphalt is probably 30 years and EPDM 20, fibreglass is not really around long enough to accurately say. I assumed that the flat roof was over a room so it is optional where to put the insulation.
This type of flat roof detail is more common than you might think, it is best to keep the flat part slightly lower than the ridge level for both aesthetics and finishing detail.

lnos1

Thanks OBrother,

If it lower than the ridge (its hipped roof on four sides), how would the water drain out?
Also, how would I find details of this roof being done somewhere else? Is there a book you would recommend?
Thanks again

OBrother

Inos
to make the water drain out you are going to have to take it down internally or at least partially internally, you need to talk to the original designer or another designer and have it detailed up.

landcrzr

Try contacting a kingspan rep about standing seam. They have plenty of standard details and may even mark up a drawing if you have one of the house. Have a look here.

http://www.kingspanpanels.ie/Products/Roofs/Kingzip

lnos1

Thanks Landcrzr, do you know the lifespan of that kingspan product?

sydthebeat

lnos1 wrote: »

Thanks Landcrzr, do you know the lifespan of that kingspan product?

GUARANTEES
Kingspan TOTAL Panel Guarantee on the structural and thermal performance up to 25years
and coating guarantee up to 30years.

from here

and remember a guarantee isnt an 'end of life' indication.

landcrzr

Just be aware also that a guarantee or 'life span' greatly depends on the correct installation of any product. Ruberoid make some perfectly fine bitumen based roofing felts, but they must be installed correctly if they are to last. I think you need a good roofing contractor as much as a good product.

joejitsu

the torch on felt any of the leading suppliers sell these days are all 20 year gaurantee...
the actual material will easily last double that as they speed up the aging process in a lab and proven to last up to 50 years...20 year gaurantee is so because the roofer will also be 20 years older and chances are he wont still be dong it!!!
asphalt is the best bet but slightly more expensive but doing the actual job mite have complications as regard to height and acess to roof...
hope this helps!

sydthebeat

joejitsu wrote: »

the torch on felt any of the leading suppliers sell these days are all 20 year gaurantee...
the actual material will easily last double that as they speed up the aging process in a lab and proven to last up to 50 years...20 year gaurantee is so because the roofer will also be 20 years older and chances are he wont still be dong it!!!
asphalt is the best bet but slightly more expensive but doing the actual job mite have complications as regard to height and acess to roof...
hope this helps!

seriously? who ever told you that!!!!

muffler

joejitsu wrote: »

the roofer will also be 20 years older and chances are he wont still be dong it!!!

And why wont they be doing it? Because they have all ****ed off emigrated to Canada

joejitsu

30 years experience told me that...u obviously dont know anything about it!

sydthebeat

joejitsu wrote: »

30 years experience told me that...u obviously dont know anything about it!

touchy there
let me go one step further by saying that an installers guarantee is worthless, unless the installer is registered, certified and insured.

The only guarantee that is worth anything is the product manufacturers guarantee, and the wording of same will be designed so that the installer should be fully trained, insured etc.

the idea that a products guarantee time limit is such that it runs out when the contractor who installed it leaves the profession is frankly hilariously ridiculous.

engineermike

sydthebeat wrote: »

touchy there
let me go one step further by saying that an installers guarantee is worthless, unless the installer is registered, certified and insured.

The only guarantee that is worth anything is the product manufacturers guarantee, and the wording of same will be designed so that the installer should be fully trained, insured etc.

the idea that a products guarantee time limit is such that it runs out when the contractor who installed it leaves the profession is frankly hilariously ridiculous.

A caveat to the product manufacturers guarantee - is it specific to our climatic conditions or not ? - I.E. - Irish agrement approved.
Some industrial flat roofing solutions are versatile with 'box profile' metal sheeting and epdm / or plastic type - sealed seam covering above the sheeting.
Fibreglass - although it hasn't the track record of the other systems mentioned and is subject to poor workmanship errors as is all envelope detailing - connection detailing etc. - However If it were my flat roof I would be swaying towards fibreglass as its application is semi fluid allowing for good seals at outlets or up stands etc. I see a lot of it on new extensions & apartment balconies.
Further more they make boats out of it, and fibreglass kept the water out all those years I was doing the Liffey decent and trashing my canoe over the weirs. Its easy to repair. Ticks a lot of boxes!!
Bitumen / torch on felt, FORGET ABOUT IT! - run a mile. Life span is 10 years plus in my experience. Check with your insurer if you can even get cover on a flat felt roof as many do not offer cover and those that do have clauses that the flat roof must not be more that 20% or thereabouts of the total roof area.

Another query, what is your arch tec. or engineers advice and specification on the flat roof detail ? They are required to inspect and sign off - so surely they have input on this decision / or can advise you properly.
mike f