HELP - want to build a roof terrace


11 Feb 2010
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United Kingdom
I just got my planning permission through for building a roof terrace. I already have a flat roof but its leaking so just decided to get planning to make it into a roof terrace.

I've spent the last couple of weeks doing research on the Internet and have come across many roof systems but am confused as to which one is better for a roof terrace. I've had a few roofers over to provide an estimate and their approach for the roof terrace, they have all suggested a different approach so now I’m really confused. The rafters and etc. are sound and do not need replacing, just need a waterproof and walkable roof.

The options I have been suggested are; single ply (like Sarnafil), EPDM rubber, Liquid Plastics (fibre glass), and Asphalt. Some of the guys I have spoken to say Asphalt is hard waring and will last long and is suitable for a roof terrace. Another roofer swears by Liquid Plastic / Liquid Applied (fibre glass) roofing system, according to him single ply roofs are sh*t as they can easily get pierced .I’ve also seen a few videos on you tube for Single Ply roofs and they appear to be an absolute nightmare – too many leaking problems.

I’m concerned that Asphalt and fibre glass based roofs may expand and contract and may result in leaks and cracks.

Is there anyone out there that has a roof terrace or balcony or even someone who has hands on experience of working with above mentioned materials who can provide some sound advice.?
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If you plan to deck over the area or use paving slabs you can use any of the above materials. As with all of the materials mentioned they will all last well provided they are detailed and built correctly. Realistically single ply may be uneconomical on a small roof such as this so I would think you can take that one out of the equation anyway. I presume building regs are to be involved? To get a good fixing for the handrail will need very careful detailing to get it to look good and ensure it doesn't fall off! Your existing roof structure will very likely need to be beefed up, not only to be able to resist the loadings expressed upon them for the handrail fixings but because your roof was probably never designed to work as a floor. Building control may well expect an engineered solution rather than a guess by a builder. Unless your builder is directly familiar with terraces such as this you would be wise to seek advice from a structural engineer.
You obviously need to ensure you have a sound/watertight roof before you go creating a roof terrace.

Liquid Plastics and Tor Coatings are 2 reputable companies that I know about and have been about for a number of years. Tor Coatings have guarantees with their system for up to 25 years (I believe that Liquid Plastics have a similar guarantee plan), and so long as the system is installed correctly you can extend the guarantee - for example , say you take out a 15 year guarantee all that needs to happen at the end of 15 years is for a new top coat to be applied to obtain an additional 10 year guarantee. Also the material is breathable, and you should not get problems associated with vapour - if you see some roof finishes they have something akin to bubbles pushing up - this is the vapour trapped behind the roofing membrane.

Check out the companies web sites for further details and to get quotes.

Depending on your available budget you should consider insulating the roof with PIR insulating board which has a high vapour resistivity prior to installing whatever weatherproofing system you decide to install.

You can then lay your paving slabs - you will need some shims to pack up and perhaps provide a small void space under the paviours to allow rainwater to drain away - there are proprietory systems on the market, regretfully I have no details to hand!

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guys, many thanks for you comments and advice. I now feel I have a good understanding of what I need. I just need someone to do me a good job now - I've been speaking with some local roofing companies and am making progress.

With regards to building regs, they have already looked at the roof, rafters and etc. and have said they are happy with it and the current rafters/joists are strong enough to be used as a roof terrace. I'll need to build a wall at front instead of a railing, the wall will just go on top of the existing wall so that should be okay, gonna use cavity trays to ensure water doesn't run down the cavity.

once again, thanks for your help.

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