MVHR Supply and Exhaust Holes - Retrofit

[mike2016]

Hi,

I was just wondering if I should have any structural concerns before having 2 x 180-200mm holes drilled in my gable end wall at the base of the attic floor. The chimney will sit in between the holes with a 2m+ gap between them. I don't want the chimney sagging in a few years if I compromise the structure in any way....?! Any ideas / concerns I should raise before this goes ahead? I've marked a possible location but they will probably be a little further apart in the end. Thanks. 

[MikeGrahamT21]

Firstly, those holes are likely too close, as you've stated. I don't see how it could cause any issues myself, the weight of the chimney will be focussed on where the stack vanishes inside the masonry.

 

Secondly, any chance of removing those air bricks and use those holes instead? Saves drilling

 

If you are concerned, perhaps consider the roof tile vents instead.

[mike2016]

Thanks - the air bricks go into the upstairs bedrooms - the attic is very low and a 28 degree pitch, you can't stand up in it. Tile vents is the alternate but has its own set of issues, mainly I like holes in my roof even less than my walls!! One more problem to monitor down the road with leaks etc, it's a 22 year old house and I don't trust the membrane under the tiles to handle any small leaks. Just the thoughts of diamond drill bits and I'm wondering if the cavity block wall will suffer as a result, probably not but was interested to see what others think.....

Cheers

 

[MikeGrahamT21]

I would say going through the wall will be fine. Circular holes are the best for structural integrity also.

[Russell griffiths]

Core drill will be fine, I take it those old vents will be blocked off.