Help! Too low for pitch roof?

[Swanny72]

Hi - having an extension done at the mo and the builder has been moaning And groaning about our roof design for a while- he said it's a really shallow pitch but the roofers been round and he can get it to work. He was going on about a 9 degree pitch- not sure if he was exaggerating though. Our current flat roof is 70cm below our bathroom window. The new vaulted roof which will replace this will be over a 362cm wide kitchen- so highest point at 181cm in . Is the pitch really going to be that bad?

 

[datarebal]

small kitchen! yes 9 is bad if you expect tiles or slate

 

[vinn]

A couple of things:
1. All calculations should already have been worked out when the plans were presented to BCO.
2.You say that the distance from wall plate to house wall - the going/run - is 3620mm
and the total rise is 1810mm. Am I right?

Then the pitch is 26.6 degrees.

 

[datarebal]

If the roofer can get it to work then it cant be such a low pitch.
if it was 25 + degrees then it would not take much trying.
how about a picture or two of the plans , elevations would be good?

 

[Ian H]

I think it's 70cm over 182cm, minus the ridge and flashing. Looking from the back would the roof be like this:

^

 

[Johnpaul Manning]

You really need to make sure that the pitch is correct. If it is 9 degrees do not put tiles on it and do not allow a roofer tell you its ok. Some trades people will tell you any story to get the job. If the roof is 25 degrees then yes it is fine. If it is 9 degrees I would suggest you put lead or copper on the roof alternatively you maybe able to go with a solid fibgerglass finish. Other alternatives would be torch on felt or similar type finish. There are also boards that Celotex specialize in called Celotex Crown up.

 

[Elastomeric]

Fibreglass is for boats.

 

[garyo]

I think it's 70cm over 182cm, minus the ridge and flashing. Looking from the back would the roof be like this:

^

Re reading I think you're right Ian. Ignoring ridge detail and hight-above-plate depth, that simple ratio gives 21 degrees, so the OP might be in with a fighting chance.

Presumably the ridge is directly in line with the bathroom window which is why it was mentioned, so they may need to be a bit check with the gap they allow for lead flashing upstand.