Verge overhang - minimum size

[garyo]

I'm building an extension with a gable wall at each end. My double pantile roof tiles run uninterrupted from one gable end to the other, so my roof has to be a multiple of these sizes.

Due to the width of the tiles and my preferred depth of soffit overhang, I'm trying to minimise how much the verge cement board will overhang the fascia boards.

I've read recommendations not to go below 40mm to avoid wall discoloration, but I'm not sure what's this is based on and whether it only applies to situations where the cement board verge overhang is directly off the brickwork rather than also having a soffit? It's a single storey extension so not the tallest building in terms of weathering.

Thanks

 

[^woody^]

50mm tends to be the minimum to avoid drips and the staining you mention, but the more the merrier. And its the same whether there is a barge board or not.

 

[garyo]

50mm tends to be the minimum to avoid drips and the staining you mention, but the more the merrier. And its the same whether there is a barge board or not.

Thanks. So even with a 250mm wide soffit, then a 170mm upvc fascia cap that will form a big drip edge on the bottom, this is a concern?

 

[^woody^]

Yes. Consider reducing the ladder overhang instead.

 

[datarebal]

tilt the under-cloak slightly lower on the outside edge.

not enough overhang will bite you in the future.

 

[garyo]

How much shunt can I expect to have on a Marley Mendip or a Redland Grovesbury? They're listed as having a cover width of 298mm and 300mm respectively... is that at max shut (compression) or at some mid-point and they will go 2mm either way?

 

[datarebal]

you get more with the Redland and it varies tile to tile a little

 

[catlad]

If you are trying to minimise have you considered the continuous dry verge 5m profiles?

 

[garyo]

If you are trying to minimise have you considered the continuous dry verge 5m profiles?

I don't like the look of dry verges. However, it's just occurred to me that Redland do a half tile for the Regent, so if I stagger one of those in at each course near the verge then that will let me achieve 50mm cloak overhang without making the soffit depth look unmatched.