Cutting a hole in an external wall

[Matt G]

I'm thinking of knocking a hole in an external wall for venting the exhaust of our portable air conditioner as I'm not keen on dangling the vent out of a window. The unit came with what appears to be a simple externally mounting flange with a seperate lid to cover it up when not in use. I can see several problems with this though.

- The flange is wide open with no grille or slats or anything on the outside. I can imagine all sorts of undesirable weather and wildlife finding its way indoors.

- The flange being externally mounted and not very deep means that the hose would have to be stuck through a rough hole in the internal wall (concrete block, I assume), across the cavity, and through a hole in the external (brick) wall. Would there be any problems with bridging the cavity in this manner?

- The AC unit may be moved away from its present location over winter. This would leave a gaping unfinished ugly hole in the wall, exposing the cavity to the room, and leaving only the thin plastic lid on the outer wall as a barrier to the cold outdoors.

Is there available a kit that provides a nice clean aesthetically pleasing duct through a wall ,that can be closed at both ends to keep the outdoors from getting indoors and that won't cause problems with insulation?

Also, what tools would I need? This seems to be an excellent opportunity to get my wife to agree to the purchase of a decent SDS drill ;)

Matt.

[Huge]

I have one of these.

I bought some 6" ducting to go through the wall and an external louvre grill for the outside. The flange goes *inside*.

I haven't had any. I foamed the duct into place with expanding polyurethane.

I made a piece of square ply, cut a circular hole in it, painted it white, mounted the flange for the aircon on it and screwed it to the internal side, covering the ducting.

I don't get problems with insulation. I thought about gluing some polystyrene to the inside of the flange cover, but I couldn't find the Round Tuit.

I'd go for it. Cutting a 6" hole through a 9" brick wall by hand is a PITA.

I can post a digital piccie, if required ...

[PoP]

I did this job earlier this year.

Once I had fitted the external flange (which had an integral plastic door opened by the pressure of air coming from within) I bought a small sheet of fine wire netting from the local garden centre. From that I fashioned a small mesh grill which I araldited to the flange.

1/4in mesh, doesn't have any impact on the ability of the flange to export air, but suitably small to prevent wildlife from coming in.

To be honest I bought a 107mm plastic hole liner which was designed for the job. Cost about a tenner if I remember correctly.

I tried drilling the 107mm hole with a core drill and my trusty black and decker 650w drill. Pretty soon volumes of smoke emerged from the drill, a quick visit to the local DIY shed saw the purchase of a 900w SDS drill, and it pushed thru the hole no problem at all.

In my opinion you won't be able to do this sort of job without a suitable drill, and the average home drill won't cut the mustard.

PoP

[nightjar]

Try looking at the ventilation accessories sold for Vent-Axia or Expelaire fans. They feature all sorts of louvres, anti-back draught flaps, cavity bridging kits etc., in a range of different sizes. If your hose is 100mm, you can find similar bits in most DIY sheds too.

I would go for hiring a diamond core drill and the drilling machine to go with it. It makes a much better job of holes of 100mm and above.

Colin Bignell

[Huge]

I have the materials to do this, but never bothered. Nothing has entered the duct after 2 years.

[PoP]

Related, but not directly.....

Our house is now about 8 years old. Last winter (about January time) we had a couple of really cold nights. Wife and daughter heard scurrying sounds above their bedrooms. We'd never had this before.

Got local pest control in, they confirmed that one rat had made its way into the roof space, and then departed. Apparently just looking around. Believed to have climbed up the inside of the drainpipe to reach the loft. Confirmed when pest control lifted the access panel in the back garden - chewed snail shell which is the way a rat gets to the contents of the shell (they go in the side door to get the squidgy contents, not the front door).

Anyway, moral of this story is that just because you haven't had problems yet doesn't mean that you might not have in the future. It took nearly 8 years before we got a rat problem (one rat, visited on two nights). And that seems to have come about because our local Tescos (about half a mile down the road) were having some significant building work done, and that had disturbed the rat population who were looking for new food sources.

I'd recommend putting that grill on even if you haven't seen a problem yet. If ratty does get inside your house he's going to make a bee line for any food supplies (kitchen obviously), and the first you might know about it is rat droppings. Ratty might set up a nest in an inaccessible place and it could be very costly to eradicate. Applying that grill would be an insignificant cost.

PoP