Drilling for an extractor fan, from the inside only

[Andy Dingley]

I need a 4" hole through brick, for an extractor fan. The ony problem is that its two floors up, and there's no access to the outside wall. It's directly above a small tile roof and the only place to put a ladder is about 6' to one side and too small to put a scaff tower.

Really I need to think of a way to core drill and fit this, working entirely from the inside and without dropping the plug.

Any bright ideas?

I can probably lay some plywood and carpet over the roof temporarily, just in case of falling masonry, but I'd rather avoid dropping anything big and heavy.

Thanks

[John Stumbles]

Been there, done that.

Core drill from inside. The plug *should* stay in the core drill (fingers crossed!).

Drop rope out through hole from inside.

Fit vent terminal to bit of 4" soil/vent pipe using stixall or similar sealant/adhesive - don't let it set as you'll need to allow a bit of wobble as outside wall and axis of hole bound not to be perfectly perpendicular.

Apply one-part PU adhesive to wall-mating surface of vent terminal.

Thread rope through pipe & loop around stick on outside of vent terminal.

Pull rope up from inside, reaching out through hole to help pipe & vent terminal in and to align terminal & bed it against wall, keeping tension on rope (tie it to something) until glues have set.

Repeat steps above applying industrial-strength Anglo-Saxon as it all falls apart leaving your hands coated with glue.

When adhesives have set release rope, attempt to remove any surplus glue via whatever access you do have, job done!

[dennis]

If you use a diamond core drill I wouldn't expect the plug to fall out, especially if its still got the pilot drill in. You would have to go easy on the last bit to avoid breaking the edges off. I doubt if a TCT core drill would do as well as they tend to break the edges if you try and breakthrough with them.

If you are any good at metal work you could always cantilever a ladder so the top bit goes where you want it. Maybe even fasten one of those odd three jointed "universal" ladders on top. Test it well before using it though.

[Nightjar]

That was certainly my experience of how it happened when I drilled for a ventilator from inside my bathroom. I did have access to the oustide, but didn't fancy standing at the top of a ladder holding an industrial drill gun one handed and I didn't have any scaffolding.

I found the anti-backflow shutter on the outside was large enough to cover any spalling.

Colin Bignell

[Steve Walker]

They are a little more expensive, but you can buy a vent kit that has an extractor fan, outer cover with seal and the 4" tube, where the 4" tube has grooves along the outer surface, designed to take screws from the end. This means that you can screw the outer cover to the tube, use a rope to pull it into place, squirt some low expansion foam around it and then when it has set, simply screw the fan to the inner end of it.

I used one of these as my ladders were trapped in the garage by my kit-car that had half the suspension disassembled!

SteveW

[John Rumm]

BTDTGTTS

Use a deep diamond core bit and there is no risk of the core falling out. I normally stick a thin SDS bit through first so that the pilot only needs guide and not actually drill. Once you are half inch into the wall you can lose the pilot altogether (sometimes they have a habit of working lose and getting in the way). Unless you have particularly thick walls then a 6" deep core plus the 8" or so arbour will normally get you through both courses from the inside.

As for the vent, long string and pull it up. To fix it helps if you have long skinny arms! A good sized bead of clear silicone on the back of the flange will not only waterproof the gap, but also fix it firmly enough without any other fixings.

Probably a good move just in case anything falls.