MVHR Supply and extract holes, advice please

[crispy_wafer]

I've to core 5" holes through brick&block for the supply and extract, access externally is a bit tricky as it's about 5m up in the air.  I plan on doing this from the inside out.  I'm a bit scared of making a mess of the external brickwork, any tips?  Also with the mind of doing the job right, I dont want to just wang the pipe through the wall stick the cowl on and leave it, what's an appropriate way to seal up and make an airtight seal around the penetration.  Any products I should use to make a proper job of this?  Curious to know what others do?

 

 

[joe90]

I core drilled mine from the inside till the pilot drill penetrated the outside, then using the pilot hole finished from the outside which stops brick bits flaking off. (We did still have scaff up tho). Just sealed inside where the airtightness barrier should be.

Edited June 29, 2022 by joe90

[Nickfromwales]

Loads of speed, next to zero pressure whilst drilling, and a good diamond bit shouldn’t break out.
 

If they’re very hard or very soft bricks you’ll need a tower scaff and do as per @joe90 did. Fail to prepare, prepare to fail. Simples.   

[markocosic]

Light pressure and speed as @Nickfromwalessays...plus a cowl with a large flange to hide any mess...

 

Are you drilling a table end in the loft space? If so I'd say there's no need to seal that particularly.

[Iceverge]

I pilot driled all the ways through. Then stitch drilled from both sides and chiseled out to finish. didn't have a 200mm core and love suffering. 

 

It was a PITA.  all done pre plastering. 

 

Made the hole good with some sand and cement and airtightness paint. 

 

 

 

 

Edited August 13, 2022 by Iceverge

[crispy_wafer]

It's still on my to do list.  It's up on the gable end, so going to hire a niftylift to get up there.  A couple of bits of gutter that the roofers put up have slipped loose so will hit that at the same time.  Was rather hoping the roofers would come back to sort the gutter, then I could drill from the inside and use their ladders to fix the cowling in place on the outside.