Roof angles

[anchorpointmax]

I've just put up a small front extension and this week had a crack at putting up the timber roof frame. The building inspector came out yesterday and agreed it was good but then I started to pick his brains about roof tiles. My main roof tiles are 'redland 02 plain brown tiles' and on my plans the extension is to match these. The problem I now have is that the pitch of the roof is 27% and the inspector has told me it has to be 35%.
After a second look a 35% angle will take the roof line up past my 1st floor window.
I can get an angle of approx. 32% at 2.5 courses below my window sill but this leaves little room for my lead.
It's also been mentioned about using a product called 'onduline' to put on instead of the felt.

I'd be grateful if anyone can advise on angles for my current tiles or if there might be an alternative tile that `i can use on the 27% pitch (that must be similar to the plain tile)
Cheers.

 

[noseall]

it is true indeed that plain tiles will deal with a minimum pitch of 35 degrees.

on a 100mm headlap, virtually all concrete interlocking tiles will deal with your pitch.

why not consult your architect or planning and see if they will allow a similar colour/textured tile to suit the pitch.

i would be nervous about using an incorrectly pitched tile with a weathering underlay system.

 

[anchorpointmax]

Cheers for that noseall.
can you tell if there is a plain tile made from concrete that will do the job and if so what's the difference between that and one from clay?

 

[noseall]

you can buy concrete interlocking tiles and you can buy clay (less common) interlocking tiles. an interlocking tile will deal with lower pitches than plain tiles.

you can also buy clay plain tiles and you can buy concrete plain tiles.
whether they are concrete or clay they will still only deal with pitches as low as 35 degrees.

'tis not the material from which the product is made but the fact that they do not interlock.

 

[^woody^]

Look at the sites of Marley or Redland for recommended pitch for each tile.

While you are there, you will see concrete interlocking tiles with have a very similar appearance to plain tiles - Marley Duo comes to mind.

If you want a lower pitch than the tile's recommended one, then either ask the manufacturer to supply confirmation that your proposed pitch is OK (the BCO will accept this) or plyboard the rafters, fit one layer of mineral felt with sealed laps and then lath and tile it.

From a planning point of view, the tiles do not have to be a perfect match - in most cases just a colour match is enough

 

[noseall]

or plyboard the rafters, fit one layer of mineral felt with sealed laps and then lath and tile it.

then proceed to put lots of holes through the mineral felt when nailing the lathes.

 

[^woody^]

Which the bitumen tends to self seal

Granted its a bit of a waste of time, but it makes the BCO happy.

I've never had a satisfactory answer of a BCO, when asked if this nonsense is necessary when the normal felt copes adequately with the small amount of rain which could potentially get under the lap.

Its just seems like of of those things which was banded about the BCO office as the 'right' thing to do, and so becomes 'the requirement' over time.

 

[SurreyRoofingEstimator]

If you just need a similar tile to plain tiles you could change the tile to something like either of these;

Redland Duoplain
Marley Ashmore
Forticrete Gemini
Sandtoft 20/20 (this is clay)

If you need to keep the plain tile specification and almost guarantee no leaks look at Onduline, this is a corrugted bitumen sheet that (with plain tiles) is fixed to a 20mm thick ply which is laid over the rafters, the batten is then fixed directly over the Onduline which acts as the underlay, any water that gets through the tiles (generally wind divem rain) will drain onto the Onduline and make it's way to the gutter down the troughs.

 

[iaink]

i have same problem,my roof is only 12 degrees
but marley have a tile called malvern that goes down to 12 degrees