Flat roof repair on a 3 x 4 metre kitchen extension

Almost 29 years ago we had a kitchen extension built with classic asphalt roof construction and it's now that time...again! to have it repaired.

This time, the need for a radical repair was prompted by some of the kitched ceiling plaster board collapsing one morning just before Christmas last year when the weight of the sodden rock wool insulation had become too much for the sodden plasterboard to bear.

The need for immediate repair seemed rather urgent until we got an overpriced quote from a local roofing firm whereupon we realised it could wait till roofing firms had stopped pricing themselves out of the stratospheric prices they were using to moderate the seasonal peak demand on their services.

That first quote of £1782.00 +VAT (green mineral torch on felt!!!) with an additional £726.00 + VAT for the fibreglass (GRP) option was a little bit skewed by my asking about increasing the slope of the fall, thus guaranteeing the extra costs of reboarding and new timbers that were included in the quote.

I now realise that there's absolutely no need to increase the fall when proper materials are competently applied (the modest amount of pooling was largely the result of the way the asphalt layers had been overlapped on the gutter edge of the roof, raising a lip preventing complete drainage into the gutter.

With my new found awareness I was able to ask a couple of roofing firms in the past couple of weeks to provide quotes. The first of these, about a fortnight ago produced a much more reasonable quote of £1060.00 (VAT inclusive) for an epdm rubber roof, considerably cheaper than that very first winter time quote of £3009.60 for a GRP roof.

The second of the two recent quotes was for a mere £767.00 for a GRP roof (laminate with 2 x 1.5 fibreglass, whatever that means), cheaper yet again! In fact just over one quarter of the winter season price we had been quoted.

As a result, I've been googling for more information in regard of GRP roofing repairs and I'm not really any the wiser as to the pros and cons of each system (epdm rubber or GRP)

The timeline is a bit hazy but I guess about 14 or 15 years back the leaks had become so problematical it just had to be properly repaired. At that time, I was able to rope my SiL (who had served time as a roofing apprentice) into helping me repair the roof.

When we lifted off the rotten cheap 'n' nasty chipboard used by the original building contractors, I _insisted_ on replacing the s**te with decent marine grade plywood sheeting (a decision that, at this stage, seems to have paid off).

It's now apparent that my biggest mistake on that first repair was on failing to insist on NOT using asphalt and bitumen as the weatherproof 'membrane' materials, a mistake I intend to most vigourously rectify _this_ time round.

My research efforts have led me to consider epdm rubber as the best solution which, in 20/20 hindsight, I can't believe I hadn't insisted upon the first time round - I guess it was considered to be too "avante garde" at the time and my SiL felt more comfortable with the traditional asphalting technique he'd grown up with).

As I mentioned, I have a choice between epdm rubber and GRP and I can't decide what the pros and cons are. I'm hoping to get some more considered opinions from the regulars in this DIY newsgroup before I make any further decisions on this matter.

The costs are obviously important but I'm prepared to go for a more expensive option to avoid savings based on false economy.

Reply to
Johny B Good
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I can sympathise as this happened to us. Our solution was to fit a 17.5 degree pitched tile roof. Can you get enough height to do this. I've replaced the garage roof in the same manner and the only problem in 35 years has been the lead flashing cracking in a gulley as I was not aware of the length limitations on lead gutters. Bitumen solved that problem very quickly.

Reply to
Capitol

I'm pretty certain that would raise planning permission issues as well as add considerable expense.

I know that _both_ GRP and epdm when installed properly will outlast asphalt roofing by a decade or three. In both cases, puncture damage can be easily and effectively repaired if the need ever arises.

The 30 year manufacturer's warranties of epdm rubber encourages the contractor to offer 10 and 15 year warranties on the whole job (there are some epdm covered flat roofs still going strong after 40 years suggesting that epdm might be good for half a century or more).

I'm not so sure that GRP can do quita as well in this service, despite its waterproofness being well proven in small craft construction (30 and 40 foot sailing yachts, aka Tupperware boats), hence my question.

Reply to
Johny B Good

Almost 29 years ago we had a kitchen extension built with classic

I had an asphalt roof replaced at our last house with some sort of high tec torch on rubbery stuff. I can't remember what it was called but the chipboard deck had to be replaced at the same time and the pitch increased.

The pitch increase was easily achieved by adding long wedge shaped timber cut from lengths of 3x2 to the top of the old joists. The 3 inch increase in height along the house wall was all that was needed to ensure full run off.

That roof then lasted the 21 years we continued to live there.

Mike

Reply to
Muddymike

Whatever that rubbery stuff was, it seems unlikely to have been epdm rubber since that's normally glued to the boarding (if not ballasted) and never torched on.

If, in the unlikely event, it turns out that the existing marine ply boards do need replacing, I'd certainly have the roofers fit wedge strips to the joists to add an extra 3 inch fall otherwise it would be an unnecessary expense if the boards are still sound (none of the roofers thought the boards were unsound when inspecting the roof).

The slight extra fall certainly mitigates the effect of minor leaks in the roofing membrane by eliminating standing water after a fall of rain but the real solution is to reduce the risk of _any_ leaks altogether. Epdm rubber fullfills this far better than conventional asphalt coverings, as does GRP (but I think maybe not to quite the same extent).

Any repairs that might arise out of damage caused to epdm and GRP are more amenable to DIY efforts and more longer lasting than with an asphalt covered roof (no hiring of blow torch and boiler or the use of extremely expensive acryllic based sealant to effect what would be a temporary repair before being forced to relay a new covering a year or two on).

Using either of my current options (epdm or GRP) eliminates the main cause of ponding which was the raised layer of asphalt from the necessary overlapped joint just by the gutter edge which will render the need to increase the fall rather redundent.

Don't get me wrong, if the existing boards have to be replaced, then I will insist on the wedges being added (there's nothing wrong with a belt and braces approach - just as long as the braces don't cost a small fortune).

As things stand, in the absence of any advice regarding the relative merits of epdm versus GRP, I'm leaning toward the epdm rubber roof repair option.

Reply to
Johny B Good

Is epdm a DIY option? My flat roof is coming up to 30 years old so will need replacing soon. Although asphalt, it was properly done using marine ply and the correct fall. Access is good.

Reply to
Dave Plowman (News)

IME planning permission is almost always granted for a flat to pitched roof conversion.

Reply to
Capitol

Even if it makes it higher than surrounding roof lines? Sounds like a good way of getting round planning - build with a flat roof then apply to change it. ;-)

Reply to
Dave Plowman (News)

Out of all the DIY options, epdm seems to be the most DIYable of all and I was tempted to diy the job except I suspect my lack of fitness would get in the way of doing a thorough job (or even doing it at all!).

is worth a look. Rubber4Roofs seems to be a good supplier for complete epdm rubber roofing kits.

The problem is my missus doesn't trust me to diy the repair and would prefer to get a professional in. I have to say, she has grounds for such doubt and, quite frankly, I don't fancy running up and down a ladder all day long and slaving away at such a task.

Having decided that we needed to select a roofing professional to affect the repairs, it's basically deciding between an epdm roof repair at £1160.00 or a GRP one at £767.00. With just shy of 400 quid saving with the GRP option, I was wondering whether the epdm option can justify the extra cost over GRP.

In both cases, the cost of overlaying the existing boarding with sheet wood after the old asphalt layers have been scraped off has been included which is at least indicative of competence by the roofing firms concerned.

Reply to
Johny B Good

Is epdm a DIY option? My flat roof is coming up to 30 years old so will need replacing soon. Although asphalt, it was properly done using marine ply and the correct fall. Access is good

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Reply to
funandtechno

I laid EDPM underneath the green roof on my shed. It was very easy.

It might be useful to have a second pair of hands on a larger roof.

Reply to
Martin Bonner

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