Minimum angle for roof

[MrD]

Hi,

What would be the minimum angle for a ridge beam and rafter type roof?

Would 10 degrees but too low?

Thanks
MrD

 

[MikeG.]

This is going to depend on the type of roof covering, rather than the construction. The construction can be beefed up to take virtually any angle. So, what is going on the roof........sheet materials, tiles , thatch, turf?

Mike

 

[MrD]

Hi Mike,

That would be useful to know I guess!

It would be shingles from a company called katepal. I have them and a roll of very heavy duty underlay and a tub of bitumen sealer. The underlay alone looks better than most of the roof felt you see in wickes so although the shingles are probably not designed for this angle I am hoping the underlay and loads of sealer will keep the roof dry.

I do have some breathable roof membrane I could put under the underlay as well?

I am beefing the roof up but just trying get get a low angle to keep in with the new planning rules (<2.5m height near a border)

Thanks

 

[MikeG.]

Hang on a minute!

I'm not sure that is the new rule.............I think that is just for flat or monopitched rooves, and that pitched rooves get a higher permitted level. Do check first before you end up with a compromised building.

Not my department, you understand.......

Mike

 

[MrD]

I have checked it and although there is some confusion it is a maximum ridge height of 4m with no part higher than 2.5m within 2m of a border.

Anyhow I think the roof will be waterproof with all the measures I am taking but how would you beef it up?

 

[MikeG.]

I would need the span dimension, and the basic roof design (ie rafters with joists, trusses, rafters with purlins, rafters with structural ridge etc.......) to be able to comment on that.

Mike

 

[MrD]

3m span. Simple rafters with joist. Rafters 2 by 4. ridge 2 by 6. Ridge length 4.4m

Thanks

 

[MikeG.]

I'll look at this later if I get the chance.......

 

[MrD]

Thanks!

 

[Oldman]

Not sure if this is helpful or not:

Bitumen Roof Shingles strip form. Roofing Shingles are applied directly onto the shingle underlay on roofs with a roof pitch between 15° and 45° or directly onto the roof structure on roofs with a roof pitch above 45°.
Not for use on roofs with pitch of less than 15 deg.

 

[MrD]

Thanks Oldman,

The supplier of my shingles (Katepal) suggest approx 12 degrees as the min. My roof is around 11 degrees. So should be ok!

The Katepal stuff is great if anyone else is thinking of using shingles. Very good quality.

MrD

 

[jobie]

Hi I’m building a summer house it’s going to be used all year round so eventually I’m going to insulate it. What could I use to insulate it on top of the roof boards under the Bitumen shingles keep it dry and is in expensive.
It’d a flattish roof  Many thanks in advance

 

[MrD]

Hi Jobie,

I will be insulating my underneath the roof boards - between the rafters using rockwool - then putting 9mm ply to form the ceiling.

I am not sure what you could use between the roof boards and shingles.

Hope that helps.

Mr D

 

[Dibs-h]

Hi I’m building a summer house it’s going to be used all year round so eventually I’m going to insulate it. What could I use to insulate it on top of the roof boards under the Bitumen shingles keep it dry and is in expensive.
It’d a flattish roof  Many thanks in advance

Probably be better starting your own thread as this thread isn't really about roof insulation nor summer houses. Also people sometimes just read the subject and based on that may not read the thread.

 

[ProShop]

Dibs-H,

You could use roofing underfelt, either mineral or the more modern breathable type. Works very well and not expensive (well the mineral type isn't). I assume your using it as a sandwich so to speak .

 

[CWatters]

Dibs - If the insulation is going on top of the rafters you are building what's called a "warm deck" or "warm roof" construction. I would use Celotex or Kingspan which is quite expensive but it's twice as good as polystyrene so only needs to be half as thick.

I'm no expert on bitumen shingles but I thought most have to be nailed as well. Wickes recomment nailing into 18mm T&G boards. Those could be fixed to the rafters through the insulation using long screws.

 

[Dibs-h]

Dibs - If the insulation is going on top of the rafters you are building what's called a "warm deck" or "warm roof" construction. I would use Celotex or Kingspan which is quite expensive but it's twice as good as polystyrene so only needs to be half as thick.

I'm no expert on bitumen shingles but I thought most have to be nailed as well. Wickes recomment nailing into 18mm T&G boards. Those could be fixed to the rafters through the insulation using long screws.

I think the last 2 posters have got me confused.

This thread is about the min angle for a roof and I was just politely pointing out to the poster before me (Jobie) that he would be better starting his\her own thread than posting unrelaled questions on someone esle's thread (MrD's).

My roof construction is all sorted thanks to Mike G and a few others. Thanks for the advice tho!

Cheers

Dibs