What did I just drill into?

Participant · 15 Jan 2014 at 14:37

I'm installing an extractor fan in our bathroom and I want to exhaust the steamy air through the attic space and out through the PVC soffit board. So I went up into the attic to look at the position of the rafters and measure where the hole needed to be.

Then I get my drill out for an exploratory hole, thinking I can just get an electrician's fishing rod up the hole to make sure it emerges into the loft space.

However, when I drilled through the soffit board, I almost immediately hit wood after the drill went through the soffit board:

Have I hit a rafter? If I have, I can't see how as I thought I'd measured it! Are there any other possibilities? When I push up on the soffit boards, there's some give before it hits something fairly solid but I presumed thos was just the soffit mounting to the sides.

I'm working under the assumption that my roof is probably constructed thusly:

and that I should therefore easily be able to put some 100mm flexible ducting between the rafter, roof, and joists.

WillyNelson · 15 Jan 2014 at 14:49

Maybe the old timber soffit if that uPVC has just been laid over it. Or maybe a substrate of board. I can't really see what that uPVC cladding is attached to unless there's something to bridge the gap between the rafters.

Nightglow · 15 Jan 2014 at 14:53

WillyNelson said:
Maybe the old timber soffit if that uPVC has just been laid over it. Or maybe a substrate of board. I can't really see what that uPVC cladding is attached to unless there's something to bridge the gap between the rafters.

+1

Sometimes I've fixed a extra bearer to the trusses,etc, just to give upvc soffit a bit more support.

Nothing of importance there to drill into & damage.

Participant · 15 Jan 2014 at 14:57

Thanks, so keep going with the drill you reckon?

Nightglow · 15 Jan 2014 at 15:06

No.

As your going to cut a 100mm hole, try drilling 25mm either side of the hole you drilled, as a joist is usually 50mm, should be able work out what your hitting & move your 100mm hole a bit this way or that way to clear it.

But, if you drill into clear space, measure 100mm from that hole & drill another hole just to make sure you have nothing else in the way & enough clearance for the pipe.

Participant · 17 Jan 2014 at 10:04

Success! The rod went straight through into the roof space this time:

Thanks for your tips.

However, I was still curious as to what I was hitting with the first drill hole, so I had a closer look in the attic, and I reckon it's the random batten nailed to the beam that you can just about make out to the right of the blue rod in this pic:

My 102mm hole will have to be placed pretty accurately if I want to avoid both the joist and the batten! Or I might get the wrecking bar out and get busy. That batten's not doing anything important is it?

This reminds me that I really must top up my attic insulation in the old part of the house!

Nightglow · 17 Jan 2014 at 10:10

Most likely just a noggin for the soffit, looking that photo, you should be ok without removing the noggin.

Just measure from joist to to cable pull rod, you only need to be 75mm from the joist, so it's easy to move you hole over a few mm if need be.

Look on Freecycle for insulation, picked up 18 rolls of 200mm insulation free last year, got about 450mm in the loft now.