For various tedious reasons, there’s not really anywhere obvious I can run a dryer vent except through the garage door. Is this a feasible idea?

If not, can the dryer be vented through the roof? There is a pre-existing vent for an extractor fan that isn’t used,

If not, can the dryer be vented through the roof? There is a pre-existing vent for an extractor fan that isn’t used,

Don’t see why not (without seeing pics), just make sure that water can’t get back into the duct.

I presume there would need to be some sort of water trap? Would a booster fan be needed?

I presume there would need to be some sort of water trap? Would a booster fan be needed?

Without seeing what’s there, I dunno, but a cowl built off a small and waterproof upstand should do it.
Without seeing where the drier is, I dunno, but I imagine not a problem as hot air rises.

As it happens, the dryer is more or less directly below the vent – all I’d need to do is cut a hole for the trunking through the garage ceiling.

Where is the existing, yet unused vent for an extracor fan of which you spake?
Or one of these.

Or look for a flat roof cowl, if it’s a flat roof.

Do you have the dryer or would you be prepared to buy a new one anyway.

Condensing dryers are brilliant. No venting required. Plonk it where you want and just dry clothes in it.

Where is the existing, yet unused vent for an extracor fan of which you spake?

Straight up (ish). Plasterboard ceiling/plywood loft floor between it and the dryer.

We currently have the dryer. When it blows up I would rather have a condenser, but of course the kids will be bigger so it won’t be on quite so much…

Yes, we did this for the gas tumble dryer in our last house. Fitted by a Gas safe registered laundry specialist, no less.
We just had a plastic vent cover and flexi tube ducting.
We didn’t need to open the door to get the bikes in and out as it was barn doors, you could if you needed to though.

We just had a plastic vent cover and flexi tube ducting.

Have just been to do a spot of measuring. About 5m from dryer to garage door, or 3.5 m up to roof vent.

Through the roof and make sure it’s watertight.

Aye, sounds like it’ll be easier; if I can get away without a booster fan then there should be less of a lint issue…

What length duct comes supplied with the drier? Manufacturer would be best bet for finding max duct lengths.

Zanussi website failing to be helpful.