Replacing extractor fan question

[rodderstrotter]

I'm replacing an old 100mm extractor fan. The old fan had a small amount of plastic vent hose, not suitable for this fan as the backdraught flaps get caught. I've managed to obtain a plastic duct, but don't fancy cementing it in, as it's awkward & will make a mess of the tiles. I want it fitting solid, as the fan clamps inside the tube. I was thinking of using something like no-nails in a plastic cart, but I'm not sure if the gap would be too big to fill with it. The OD of tube is 103mm, 115mm hole. Any suggestions what I can use? Sorry if it's a stupid question

 

[riveralt]

I'm replacing an old 100mm extractor fan. The old fan had a small amount of plastic vent hose, not suitable for this fan as the backdraught flaps get caught. I've managed to obtain a plastic duct, but don't fancy cementing it in, as it's awkward & will make a mess of the tiles. I want it fitting solid, as the fan clamps inside the tube. I was thinking of using something like no-nails in a plastic cart, but I'm not sure if the gap would be too big to fill with it. The OD of tube is 103mm, 115mm hole. Any suggestions what I can use? Sorry if it's a stupid question

You can always use expanding foam - just make sure the duct slopes away from the fan.

 

[PrenticeBoyofDerry]

Yes expanding foam will help fill the void, and having the duct sloping slight downward toward outside is good advice, but do not make the slope too much as this can often prevent the fan unit fitting flush to finished wall.

 

[rodderstrotter]

Thanks for the advice. I have used foam before, great stuff as long as you're careful!
The hole is pointing slightly in, but there's enough slack to at least level, and hopefully point to outside