10mm or 25mm over fascia vent

[lee2lee]

I'm having a new roof, I have bought 25mm over fascia vent, but would prefer 10mm, any down side to the 10mm?

The reason is the bottom tile is going to rise up with the vent under it and I don't want it coming up too much.

Thanks

 

[noseall]

Use 25mm and a shallower fascia. We have had to trim a fascia in the past to accommodate the OF vent. Awkward though, using a circular saw sideways on.

Not seen 10mm OF vents. Prolly don't admit sufficient air unless supplemented.

 

[garyo]

Should you bother using them if it's a new-build extension with permeable breather membranes all over the roof? Admittedly I have done in the past as a belt-and-braces approach but I'm not sure they're strictly necessary?

 

[noseall]

Should you bother using them if it's a new-build extension with permeable breather membranes all over the roof? Admittedly I have done in the past as a belt-and-braces approach but I'm not sure they're strictly necessary?

During extremely cold weather and when a fully occupied house is burgeoning with moisture, many breather membranes cannot cope. It is always sensible to include OF vents. They are discreet, inexpensive and easy to fit.

"I have breather membrane therefore I cannot have condensation issues" is a myth.

 

[garyo]

"I have breather membrane therefore I cannot have condensation issues" is a myth.

Interesting. So what would you typically find in a bovis (etc) new build?

 

[noseall]

Interesting. So what would you typically find in a bovis (etc) new build?

Home condensation is idiosyncratic. Two identically built houses can yield differing results. It's more about occupancy than build quality although poorly fitted loft hatches and general robustness of the build does have a wee bit of influence.