# Forum Home Renovation Sub Flooring  Installing Vents/Knocking out Bricks-help please!!

## martyjames

Hi 
I hope this is in the correct section. I am going to install a ducted fan system under my house to get damp air out from under the house. I will need to knock out bricks in a double brick wall to put vents with attachments for ducts in. Is it safe to knock a few bricks out in double brick walls without fear of the wall weakening/collapsing?? probably a dumb question but better safe than sorry!! 
thanks in advance 
cheers 
Marty

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## Compleat Amateu

Yes you can, but no more than 2 in a row.  If you take out 3 you risk the cracking the joins at either end of the unsupported brick above. 
This will be one bad job, especially as your walls are double brick, so get tools to help you: A big angle grinder - the less mortar join you have to cut out by hand, the better.  One with a blade deep enough to go the depth of the brickwork is good, but be careful, angle grinders that big will grind you if they jam in the brickworkA (hand) block saw, for cutting the remains of the mortar joins (you'll ruin it, but I haven't found any other way)A bunch of (say) 4mm masonry drill bits, for easing out the corners of the "hole" to start withMasonry chisels and hammerKneeguards if your holes are close to the ground.  Kneeling on broken brick is just murder!Good luck and I hope your mortar is soft .. mine wasn't

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## jago

If its a circular hole for you pipe work to the vent... go hire yourself a diamond tipped core cutter from Kennards or the like or if you know a plumber get them to do it,5 minute job nice neat hole. :2thumbsup:

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## GeoffW1

Hi, 
Have you considered simply installing a lot of double size mesh vents, these  Brass Mesh Vents 
As you see, you can get them in various layouts, including 2 x 1 brick. You don't have to have one on the inner skin of the cavity wall either, just the matching opening, which need not even be exactly in line with the vent (can be 1/2 brick out). 
If you have 2-3 of these on the exterior wall of each room, below floor level, it will do wonders. I did this with a Federation home which had dry rot and damp underfloor, and the problems disappeared. 
Cheers

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