Hi everyone,

I've been going around in circles looking at flat roofing options, from economical EPDM £6k to Single Ply PVC £22k, and struggling to make a decision as i know it is an important one. I am concerned with EPDM not lasting due to the glued seams and shrinkage which seems to be the most common complaints. I found a product that a local installer uses called Resitrix, which seems to eliminate my EPDM concerns as it is heat weldable and much thicker than other membranes at 3.2mm. I was hoping to get some insight from people who have installed flat roofs and thoughts on different products.

Here is a link to resitrix (any info from people who have used it would be really helpful).

https://www.resitrix.com

I'd be interested in opinions on the current state of flat roofing options too. I always find it difficult to make an objective decision, partly because of the number of options out there.

Some questions

- Does one of PVC or EPDM have a clear environmental advantage?

- Again from an environmental point of view, what about fibreglass - worse or better than membrane type systems?

- Small-scale builders nearly always want to do fibreglass or built-up felt on flat roofs, instead of membranes. This is usually because they can do it themselves instead of getting in a subcontractor. It usually seems to be a cheaper option on small jobs because of this. In terms of longevity, do felt or fibreglass really perform that badly?

- Are manufacturer-backed warranties (sometimes offered by membrane system suppliers) worth the paper they are written on?

Torch on is usually the cheapest with two sometimes three "X" layers. There are also lots of detailing pieces available to give a neat look. I've used it on several small areas, with an OSB sub base.

In our previous house we built a garage alongside the existing garage and converted the latter into a workshop and utility room. The total roof area of the combined building was about 35 sq.m. (5m x 7m). This was a "flat" roof with a pretty minimal slope as I recall (about 2.5 degrees) and had fibreglass covering. When we sold the place in 2007 the roof was about 17 years old and was fine. My wife is in touch on Facebook with the folk who own the house now and as far as I know they have not mentioned any problems with the roof which I think they would have done as they have done a lot of work modernising the utility room. So the fibreglass must be coming up to 30 years old.

Admittedly I have no experience of EDPM or PVC but I would recommend fibreglass, not least because you can walk on it without any fear of puncturing the surface! Not sure if that is the case with the other materials?

Edit: just had a look at the Resitrix videos. Looks good stuff, would be interesting to see examples of actual applications.

Posted By: jms452

Posted By: lineweight- Does one of PVC or EPDM have a clear environmental advantage?

Plastics with Chlorine in have nasty decomposition products and are not currently widely recycled.

and just to be clear - the C in PVC stands for chlorine and there's no C in EPDM.

Posted By: jamesingram
Greespec as ever lays it out neatly

The problem I have with greenspec is that it never really gives you an objective answer (perhaps because that's impossible).

For example, if I compare PVC with EPDM,

- EPDM has 3 positives and 4 negatives listed
- PVC has 3 positives and just one negative.

One reading of that might be that EPDM is more problematic, but I don't think we are supposed to consider the pros and cons listed each to be equally weighted. It's mentioned for PVC that for "many designers" it's rendered "unacceptable". But this information isn't really very useful - what am I supposed to do with it?

Of course, I could spend a day, or a week, reading up on PVC and all the arguments pro and against, and come to my own conclusion. But the fact is that no specifier or designer can do that for every single product and material they come across. Even if they were technically competent to do so and make a good judgement, there's not the time to do that and also actually design or build anything.

I don't know what the solution is. But looking at Greenspec often doesn't leave me feeling any more confident about making the best decision.

No - it's not specific to Greenspec. But Greenspec tantalises with the possibility that it can remove doubt from the process, when it can't really.

That's not to say it isn't useful.

Whatever the material, the installation seems to be the key. I've a friend whose glassfibre roof failed after around 5 years, while a garage roof I specified with a high-spec 3 layer felt around 1990 is unexpectedly still going strong.

I've a (very) small tower roof to do next year, and for that I'm currently inclined to go for mastic asphalt, if the cost is reasonable, with an inverted design (insulation + tiles on top).