We need to add ventilation holes to an existing building. The holes will be core-hole drilled through a limestone brick wall. The bricks have crevices. The contractor is acting stupid and obstructive or I would ask them. How would one mount a short (24 cm lond, D= 300mm) piece of round air duct into the core hole? Simply put in? Sikaflex all around? How about risk of moisture creeping in?

My first idea is to let the duct sick out 1 cm on both sides, and to grout the wedge with sikaflex. Criticisms? Better ideas?

  • $\begingroup$ You haven't told us anything useful. How about a blueprint showing what you are doing? $\endgroup$ – Phil Sweet Jun 7 '19 at 9:40
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    $\begingroup$ A slope to the outside? $\endgroup$ – Solar Mike Jun 7 '19 at 9:53
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    $\begingroup$ Sounds like you want the DIY stack exchange? $\endgroup$ – Jonathan R Swift Jun 7 '19 at 10:30
  • $\begingroup$ "The contractor is acting stupid and obstructive..." Double check that it's the contractor. Perhaps the contractor has years of experience and doesn't want their name attached to a failure. $\endgroup$ – TimWescott Jun 7 '19 at 17:51

In a project which was a mixed use 5 story building including a movie theater in LA in 1988 we needed similar set up.

For under-floor ventilation in the theater we created concrete subfloor channels with service access hatches and sloped to drainage with flex insulated double wall ducts running through opening to vertical registers on the riser of steps on the isles.

I have been there a couple of times since for minor structural changes required by other anchor tenants, but have not heard of any issues with floor ventilation system.

I don't think you need anything around your duct, makes it easy to replace if needed. Just make sure you have drainage for potential condensation.


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