Recommended expansion gap between roof batten abutting a brick wall.

[epsilonGreedy]

I have a small roof over a single storey room where the ridge abuts to the main house 2-storey brick wall at 90 degrees. The run from ridge to fascia is short i.e. 2m and will require about 11 2 x 1 battens each side butting up to the two storey wall at 90 degrees.

 

I assume some expansion air gap is recommenced between the 22 batten ends and masonry wall?

 

The final truss below next to the main house wall has a clearance of 40mm. The longest batten length is 4m. There will be a lead soakers from ridge to fascia. I will be using slate and a halves alternating at the abutment. The code-4 lead roll for the soakers is 240mm wide.

 

I understand a 3mm gap between natural slates is standard industry practice. However the slates at the abutment will need to be about 5 to 10mm (I assume) back from the wall to accommodate the 90 degree bend of the soakers that will be formed around a block of wood at (guess) a 5mm radius.

 

Please ignore the black arrows in the image below, they were for another question. This question relates to the roof abutment next to the main cavity wall on the right.

 

 

[markc]

Timber does not expand much along the grain, only across it.

If you want to leave a couple of mm  that will be fine

[epsilonGreedy]

7 minutes ago, markc said:

Timber does not expand much along the grain, only across it.

If you want to leave a couple of mm  that will be fine

 

 

Ok good to know. A dark slate roof can get very hot which led to my concern about the battens expanding lengthways. I don't want them fighting with the brick wall on a hot day and popping off the trusses under stress.

 

So a few mm it is. A smaller gap does lessen the chance of a batten splitting open at the end grain near a truss fixing nail.