roof fall on a garden room

[freddiemercurystwin]

You should ensure you end up with a minimum 1:80 following any sag. Don't build it with 1:80 because you'll end up with less eventually.

 

[mrrusty]

I’m a bit tight for head room in here

Unless there are specific reasons not to, why don't you pay the £3-400 and get planning so you can go a bit higher? You can get planning with hand drawn drawings and downloadable location plans. It isn't difficult.

A very low ceiling is IMHO oppressive and spoils much of the benefit of having the extra space.

 

[Jupiter01]

You make a very valid point re. Planning permission @mrrusty. I’ve not done it due to time and expense to be honest. Was planning to have this complete before the winter sets in.

I am not proposing that I use 4x2s for the roof. Will definitely be using 5x2s but was checking whether the extra timber at the front could be less than 50mm. Clearly as this roof slopes down to the back, the ceiling space will be reduced.

 

[nickjb]

Just make it 50mm higher at the front. Nobody is measuring it with that level of accuracy.

 

[Jupiter01]

I plan to calculate my 2.5m from the ground up to this second top plate on the front (giving me the 50mm slope). The back wall will be 50mm lower than this.
Since I am extending the front roof by 40-50cm, that will take me slightly over the 2.5m at the edge of this extended roof. Wil that matter do you think?

 

[Jupiter01]

Just fix one wall plate higher. Minimum fall for an EPDM roof is 1:80 but this is the absolute minimum so I wouldn't skimp on joist size as you wouldn't want a puddle in the middle, thinner (than 18mm) OSB decking is fine, my garage has 9mm with joists at 400 centres and I haven't gone through it yet.

I was going to go with 11mm OSB on the roof with 5x2 rafters at 400 centres. Will that be okay for me to walk around whilst I am fitting the rubber roof?

Also, do I need to leave expansion gaps when installing this OSB board on the roof? Apparently its required for the floor...

 

[Jupiter01]

I was going to go with 11mm OSB on the roof with 5x2 rafters at 400 centres. Will that be okay for me to walk around whilst I am fitting the rubber roof?

Also, do I need to leave expansion gaps when installing this OSB board on the roof? Apparently its required for the floor...

Can someone give me a steer on this please

 

[mrrusty]

Yes you need a small gap between OSB sheets of about 3mm to allow for a little expansion. I think I would prefer 15mm OSB TBH.

 

[Jupiter01]

Yes you need a small gap between OSB sheets of about 3mm to allow for a little expansion. I think I would prefer 15mm OSB TBH.

Just a 3mm gap on both floor and roof OSB? No need for foam or any other substance in this gap.
Happy to go with 15mm OSB for the roof