Recommendations for Low slope roofing options please

[Tofer]

We are building a house on the seafront with a modern style, low pitch (12 degree slope) roof, necessary for various design reasons.

 

1. We've considered metal sheet but are concerned about corrosion, although Bluescope say it should be OK with their 0.4mm aluminium coating. Some have insulated the underside of the sheeting with spray foam for thermal & noise resistance, also integrity reasons as the clip lock fixing system (we liked) was used and they were unsure of the resistant to strong winds with this system.
2. Another consideration is corrugated fibre cement sheets - we like the 'Prima product and colour range but it is only recommended for roofs over 20 degree pitch. Would a continuous bead of silicone between tiles be sufficient to resist leaks on our 12 degree pitch? We've seen other products in corrugated sheet which claim to be OK down to 10 degree pitch, but don't have a great range of colours.
3. The obvious choice looked like being the asphalt shingle roof (guaranteed to 10 degree pitch), but I'm not a great fan of the appearance and am very concerned with installing it in the rainy season as a moisture / termite resistant OS board, which is used as the base, is going to get saturated and then the workers will proceed to install the underlay asphalt sheet and shingles as they just want to get finished and go. Will it dry out satisfactorily from beneath? I've also seen the manufacturers websites showing possible defects, e.g. curling up, cracking and blistering, which are all very off putting.
4. Our favourite is the SCG 'Ayara modern' tile, but is only good for slopes over 25 degree pitch. The local supplier told us there was some sort of underlay used on a modern example shown in their catalogue on a low modern style roof using prestige tiles, but couldn't show us or explain adequately for us to understand. Anyone have any ideas?

 

We have talked to the suppliers / manufacturers but are unsure of their technical acumen and motivation.

 

Contributors opinions and knowledge / experience would be very much appreciated - thank you.

 

[Kwasaki]

1 hour ago, Tofer said:

Another consideration is corrugated fibre cement sheets - we like the 'Prima product and colour range but it is only recommended for roofs over 20 degree pitch. Would a continuous bead of silicone between tiles be sufficient to resist leaks on our 12 degree pitch?

 

If you like Prima cori roofing it will be OK at 12% if sealed as you say laps and side laps.

Get the longest sheet lengths that are available and increase end cover laps more than recommended.

[Kwasaki]

Traditionally, a minimum roof pitch of 20° was recommended in BS 5534, but modern tiles and slates have now been designed for applications as low as 15°. It is uncommon to find a roof below 15°  but for those very low pitch applications, there are interlocking clay pan-tiles available, suitable for use down to 12.5°.

[Tofer]

18 minutes ago, Kwasaki said:

If you like Prima cori roofing it will be OK at 12% if sealed as you say laps and side laps.

Get the longest sheet lengths that are available and increase end cover laps more than recommended.

Thanks for your response.

 

Unfortunately the Prima range are only 650mm long and with proprietary clips give a 150mm overlap. We could overlap say 200mm with standard clips or screws but anything more would not look so good as there would be little of the tile remaining to show.

 

Our builder and the supplier are sceptical about using silicone at the joints as they reckon it will only last a couple of years or so. Dilemma!!

[Tofer]

3 minutes ago, Kwasaki said:

 

Traditionally, a minimum roof pitch of 20° was recommended in BS 5534, but modern tiles and slates have now been designed for applications as low as 15°. It is uncommon to find a roof below 15°  but for those very low pitch applications, there are interlocking clay pan-tiles available, suitable for use down to 12.5°.

Thanks again. Do you know which clay pan-tiles are suitable for that pitch.

[Kwasaki]

10 minutes ago, Tofer said:

Thanks again. Do you know which clay pan-tiles are suitable for that pitch.

In the many home building Thailand stores  e.g. Home-mart,  Global Hse etc etc there are a selection of interlocking roof tile which are the same profile as shown in link below.

 

https://www.pinterest.com/pin/671740100639973912/

 

All that's needed in these low pitch roof applications is a properly installed roof underlay of which there's many types these days.

This is a bit OTT but an example.

 

 

[Tofer]

We originally designed our roof thinking we would use the 'Sopralene stick roll of granule covered bitumen, hence the low slope (OK to 4 degree), laid in the vertical direction and joined at the roll sides over a bead to replicate the appearance of a standing seam roof. Having visited the supplier we later decided it was not so practical as it relied only on the sticking aspect with no mechanical fixings thereby relying on the OS board structure being very clean - a bit difficult to guarantee in this environment, so raised the roof pitch from 7.5 to 12.5 degree to facilitate bitumen shingles as an alternative finish.

 

We we also wanted to maintain as much sea view as possible above our roof from our rear plots for the next phase of villas. Also we were constrained on the planning side by the orbortor as we can only build 75m2 per block with a min. 4m space between within the 30 - 50m zone from the high tide mark, so have to split the roofs to shade ('cover') the 'link'. The overlapping modern style, low slope roof seamed to be the perfect solution to avoid valley gutters or flat roof sections linking traditional panachart roofs. 

 

In hindsight more advanced planning and research would have been sensible, but we were not in country at the time and had to get the building permit as a matter of urgency as the orbortor were threatening a rule change to exclude any building within the 50m zone instead of the 30m zone, which would have killed our personal villa plot. 

[Tofer]

15 minutes ago, Kwasaki said:

In the many home building Thailand stores  e.g. Home-mart,  Global Hse etc etc there are a selection of interlocking roof tile which are the same profile as shown in link below.

 

https://www.pinterest.com/pin/671740100639973912/

 

All that's needed in these low pitch roof applications is a properly installed roof underlay of which there's many types these days.

This is a bit OTT but an example.

 

 

Thanks again. I see this roof used the SIP panel, is that available in Thailand?

 

This is exactly what I was thinking of for the Araya type roof we liked but thought it would get a bit expensive and as you say, a bit OTT. Certainly should be belt and braces with tile and counter battens, although I would run the sarking / roof felt over the counter battens for added security.

[Kwasaki]

25 minutes ago, Tofer said:

I see this roof used the SIP panel, is that available in Thailand?

l personally wouldn't use any roll type roof finish covering in Thailand.

 

We built many moons ago and we are northern located,  l would say nowadays in Thailand your can get just about any buildings materials from ground up now.

 

I don't bother looking much but someone like Global house l would think can supply just about anything you want,  if not there's many other outlets that could.  

 

[Tofer]

2 minutes ago, Kwasaki said:

l personally wouldn't use any roll type roof finish covering in Thailand.

 

We built many moons ago and we are northern located,  l would say nowadays in Thailand your can get just about any buildings materials from ground up now.

 

I don't bother looking much but someone like Global house l would think can supply just about anything you want,  if not there's many other outlets that could.  

 

We don't have GH in the South that I've seen so far. I'll check on line, thanks.

 

We've scoured the merchants around Krabi, Phuket, Surat Thani, Trang even some recommendations in Bangkok and only come up with the options I mentioned. I'm sure they are all offering pretty much the same stuff, it's just difficult getting any trustworthy / knowledge based advice. 

 

I tried being clever and using my UK product knowledge and directions to local (regional) suppliers, but this turned out horrendously expensive, e.g. Centor sliding folding doors in Malaysia  with those fancy horizontal roller insect screens, who quoted about half our entire build budget just for the doors / Windows....

 

I think you're right about availability of most products but cost is a consideration, particularly with the weaker pound hitting our budget with a 20% reduction, and the capabilities of our local contractors. After much angst I've finally consigned my design aspirations to the bottom drawer and realise we just have to get it built, particularly as our 4 year building permit deadline is closing in.

 

Very good of you to lend your moral support and technical advice, much appreciated. Hope you are enjoying your home in the North.

 

Cheers.

 

 

[Kwasaki]

Well good luck,  roofing has been nearly all my working life & your 1 2 & 4  are all possible as for what sounds like your other high end build products l feel GH could provide something to your taste.   

http://www.yellowpages.co.th/en/profile/521971740132001

There's a Global Hse in Bangkok too.
 

[Tofer]

40 minutes ago, Kwasaki said:

Well good luck,  roofing has been nearly all my working life & your 1 2 & 4  are all possible as for what sounds like your other high end build products l feel GH could provide something to your taste.   

http://www.yellowpages.co.th/en/profile/521971740132001

There's a Global Hse in Bangkok too.
 

Many thanks. Maybe I'll put my dress shorts on and have a trip up there...