Flat roof advice please!

badmumof1

ahh george you telling me that the designers of bluewater, american air museum dexford and many may more were wrong to go with glass fibre roofing and should have gone with felt?
glass fibre will outlast any building and is stronger than felt.

George_Bray

badmumof1 wrote: »

ahh george you telling me that the designers of bluewater, american air museum dexford and many may more were wrong to go with glass fibre roofing and should have gone with felt?
glass fibre will outlast any building and is stronger than felt.

OK to be fair, I must admit that if both solutions were the same cost, I would at least consider fibreglass. I hold fibreglass in the highest regard as a strong material, e.g. for certain car body repairs. But for roofs, I'm not sure there's too much evidence of fibreglass roofs having lasted for 25 years or more (yet), and still looking good, as my old felt roof did, even though I decided to replace it. My questions would be, could a fbreglass roof crack and is it affected by the sun's UV rays, etc, etc? 25 years+ is a long time.

To clarify, I'm talking only about hi-performance torch-on felt. Wickes do sell it but you can get even better stuff from a specialist, as per my materials cost of less than £400, of which only about £300 was for the felt itself. The bitumen (a superb material) is 'built-in' to the felt.

I'm confident that hi-performance torch-on felt is such a great, long-lasting solution, that I would not pay a penny more for a fibreglass roof. And what thickness of fibreglass, too? There are options and various quality levels. And will they just lay the fibreglass on top of the old felt as a botch job? Is that how the fibreglass people could present a seemingly low price, initially?

badmumof1

They DONT lay glass fibre on top of old felt, our whole roof was taken off and redone with brand new boards and wood.
I believe the same materials are used to make boats and ponds and boats have salt water and rocks to contend with.
we have approx inch and half of glassfibre and i dont think you can get anything stronger and more durable than this.
Remember i have had this put on a balcony so its got to be tough to be able to be walked upon which felt would be no good.
The bitumen stuff that was up there before melted in the hot sunshine and then cracked in the winter from the cold so we were left with holes in the roof good job we didnt have insulation between otherwise that would have gone rotten and caused more damage.
i guess to sum up its like deciding between wood facias or plastic
wood you would need to treat where as plastic you wouldnt.
just like the glassfibre you wouldnt need to do anything or worry but felt you would have the worry of it melting or going sticky and moving then forming cracks in the winter so it needs repairing

pedro67

niallmoran wrote: »

Hi folks

We've just bought an old cottage with a bigish (approx 35m2) flat roof extension that needs replacement (sagging boards, old felt covering etc) and the roofing contractor that did a pre purchase check quoted £5k + vat. for a new 5 layer felt roof with coolag insulation.

I thought that this seemed quite high so am planning on replacing it myself in the summer. After lots of reading i've decided on a fibreglass roof (mainly cause i'm used to GRP boats!) and want to build a warm roof construction.

My shopping list includes all the fibreglass material (approx 500 quids worth), CSR3 18mm decking but i'm struggling to find out what insulation board i should use (and where to source it!) for the warm roof construction as it can get a bit chilly in Dundee!

I've come across composite board that includes a 6mm ply top but i'm unsure how to use this....do i still need my 18mm deck? How do i attach it to the joists? Do i need noggins?

Can anybody point me in the right direction with this? I'd be most grateful for any help

Cheers
Niall

Hi Niall,
I've just struck a deal with a local reputable family business in Ayrshire to have my flat garage roof re-surfaced with firestone epdm. The area to be done is 13sq/m and it works out very reasonable. Google this, research the product and find a company local to you, get a quote and you'll be pleasantly surprised. A fibreglass system will inevitably crack under extremes of temperature, I'd avoid it like the plague. Good luck matey.

Poppycat

Our bay and porch was done with Firestone EPDM and is guaranteed for 20 years, its much cheaper than fibre glass and not much more than felt

EPDM is used to make ponds and is glued to the roof

George_Bray

badmumof1 wrote: »

They DONT lay glass fibre on top of old felt, our whole roof was taken off and redone with brand new boards and wood.
I believe the same materials are used to make boats and ponds and boats have salt water and rocks to contend with.

It's true they shouldn't lay fibreglass on top of old felt, any more than laying new felt on top of old felt. But I found a posting on the Internet from one worried householder, whose contractors had done just that, so I'm sure it does happen.

Here's a good website which supplies the materials for a glassfibre solution but, I say again, I fear this ain't gonna be as good value as top quality felt which I reckon could last at least as long as fibgreglass, and perhaps longer. People with glassfirbre hulled boats and canoes are forever attending to 'issues' with the fibreglass.

http://www.cfsnet.co.uk/project-roofs.html

alanobrien

Felt done correctly can last for years. Our old roof about the same size as yours lasted over 28 years and we had to replace it late last year. I looked at glass fibre a friend has one and swears by it. The only problem they had was a slate dislodged from the roof in a storm cracked it but thats easily repaired. I also looked at EPDM which is easy to DIY but UV stability and embrittlement always concern me with these so in the end we fitted a new felt roof. These are polyester based these days and the density of the layers vary. Overall cost including decking and insulation replacement was £2k in the South east.

upbeat_2

I have been given quotes from between £2800 and £4800 including VAT for a flat roof. Its hard to get a like for like quote as they all use different materials. My roof is basically my garden so I have to have something non-slip. I think I will go with fiberglass. There is fiberglass on it already but wasn't done properly first time round (about 20-30 yrs ago). Im in the house 3 yrs. Can anyone give me any other suggestions for a replacement flat roof which can be used as a garden. I was thinking of putting decking on the roof once it has been repaired. If anyone has had similar job done I would love to hear your story and if it was a success. Thanks

woodbutcher_2

Not going to get into the whole felt vs fibreglass argument but if you are going to use your roof as a garden with decking and plants then you need to get structural calcs done to make sure your roof can take the load.

FIBAMAN

My first time on this forum, so hello everyone.
I could not resist having some comment here as I have been in the grp business for the last 18 years. I will state straight away that I am not plugging for business (my market area is petro chem, LNG, offshore etc).

Look at the basic facts, felt whatever quality is based generally on bitumen. Bitumen deteriorates with UV exposure so some applications will last considerably longer than others depending on location and orientation. It softens with heat and stiffens with cold, often the source of cracking. It has little or no mechanical strength and is applied by hot torch usually (safety hazard). Advantage - cheap.

GRP roof systems are only as good as the skill of the applicator, so choose wisely.
The systems I have seen usually utilise cheap orthophthalic resins so their material costs are fairly low, what you will be paying for is the guarantee. You could try hagging with these guys as some of the costs I have seen bandied about are ridiculous. I have been involved in jobs with very high spec resins where the grp is lining areas subject to hydrochloric acid and the like for an applied cost of £60 / sq mtr. Cheaper resins are perfectly suitable for roof applciations but I would guess material costs would be less than £20 / sq mtr.
Finally, ensure that your grp system includes a surface tissue, which will give a better finish but also improve the weather resistance by 25 - 30%.

The material that we manufacture loses between 1 - 2% of resin weight in 10 years.
The inclusion of a tissue also acts as an indicator as to when the top surface is reaching a stage where maintenance is required., achieved by brushing on a topcoat.
As to insulation I can point people in the right direction if they pm me