Flat roof coverings

[wakey77]

Hi im planning to do a flat roof extension on the rear of my property and after being put right about the construction of the roof itself ive started to look at roof coverings the main 3 being.
Felt (3 layer system)
Firestone rubber
Fibre glassing

I would like to do the roof covering myself as i do have a little experience ive used the firestone rubber a few times and also the 3 layer felt.

I like the rubber as its really quite easy to use is strong and does,nt easily leak its also easy to repair however after time it doent look so good with the imprint of the deck showing through.

The felt i also like it looks good but doesnt seem to last as long as the rubber roofs

Lately ive been looking at grp fibre glass roofing it looks quite simple to use looks good and im told it lasts a very long time providing it doesnt see much foot traffic.
so im thinking the fibre glass might be a good option but is it simple enough for a 1st timer to use and what is your experience of it or preffered roof covering.

Any comments would be greatfully received.

 

[xdave]

My personal preference, having used all three methods, is the rubber. I use hertalan easy weld with/or easy cover and have never had any issues with the deck showing through. For a warm roof I use 15mm class 3 structural ply on top secured every 200mm at the perimeter and 300mm elsewhere through the insulation to the deck below it, with a 5mm class 3 hardwood ply across the top with staggered joints. I also use the 5mm for any upstands as it is much easier to get a strong bond with it and it protects against mechanical damage.

If you have the funds and the aesthetics would work then consider installing an extensive green roof over the rubber as it will increase the service life considerably by masking it from UV. It helps to cool during the summer too. It can help to retain heat during the winter, but not when wet.

I haven't used rubber for long enough to compare its durability to a felt system, but on easy of installation alone I would choose it over felt. It's clean and easy and you can use a heat gun rather than a torch which is easier to control.

With GRP you can get a good finish as a DIYer with a bit of practise but it is the most fiddly method and the tooling costs make it the more expensive option. You'll pay for disposal of any excess resin or catalyst too. It is much more easy to make mistakes with GRP if you are not very thorough. For longevity consider an epoxy top coat rather than a polyester for water resistance. If the roof is big enough for expansion joints then I wouldn't DIY it and would choose a flexible covering.