should I put an extractor fan in my garage?

Are the air bricks actually clear or clogged up with crap?

Maybe, but I'd be surprised if it's really necessary?  If there's no sources of moisture then I would have thought some passive ventilation should be enough.  I'd just drill some more extractor fan sized holes and leave them empty if it's a problem.  The breeze blowing through 24/7 will shift far more moisture than an extractor fan on a timer.

Thanks

Are the air bricks actually clear or clogged up with crap?

good point . i shall check

I've got a similar problem: uninsulated single skin  detached garage with a tin lid, albeit with felting on the inside to slow condensation drop.

I had a spare solar-powered fan kicking around which I've fitted to get airflow through the space - I'd noticed lots of condensation on some nice steel cabinets I rescued from being thrown away in cold / wet weather, and want to stop them from rusting away. It's  not helped massively. I think this is a combination of poor airflow and poor insulation, but I'll be happy to be corrected.

This may or may not be good advice, but here's what I'm thinking of doing:

I replaced the roof with box profile agri sheeting about ten years ago and don't have the cash or inclination to go warm deck on a wonky (It's a trapezoid) shaped outbuilding. Should I jam a load of rockwool or similar up in between the rafters, then finish with a vapour barrier?

I don't have much hanging off the walls, so I was thinking of thermaboard cladding inside.

The whole damn thing will need rewiring as I'm certain a previous owner did it themselves in the days before Part P and it looks terrifying enough that I only ever really use the lighting circuit to run LED bars.

The whole damn thing will need rewiring as I’m certain a previous owner did it themselves in the days before Part P and it looks terrifying enough that I only ever really use the lighting circuit to run LED bars

I rewired mine after I realised that the previous owner had used some extension cable and buried it about 10cm's under the ground to provide the power to the garage. And yes it did put a spade through it but luckily I had turned off the power

I rewired mine after I realised that the previous owner had used some extension cable and buried it about 10cm’s under the ground to provide the power to the garage. And yes it did put a spade through it but luckily I had turned off the power

Ooof. We put a Tuin shed in at the end of the garden a few years ago, and dug an armoured cable in to get power to it fitted sockets and tails and a lighting circuit, then handed over to a sparky to check my work and do the bits that need a professional. He suggested running the cable to the garage, rejoining with a nice long tail and then on to the shed. Once I've got the garage sorted, they'll come back and wire the armoured cable into a consumer unit for the garage and then out again to the shed. I'm fairly sure the original cable out to the garage is at best 2.5mm T&E in a metal pipe, feeding into both a power and a lighting circuit. I very rarely use one socket in the garage for low current stuff and no more.

Would fitting an extractor fan help with getting rid of the condensation ?

I used to get puddles on the floor of my garage, put a fan in that runs 24/7. Now it's just a bit damp, and no rusty spots on tools.

I'll probably fit a humidity sensor and remote plug in there at some point.

I use a dehumidifier in mine. Stops any possibility of condensation especially as camping gear is stored in there as well.

Would an easy proof of concept be pointing a desk fan at an air brick or (maybe on a timer?) just to do a wee bit of  forced "extraction"  and see if there's any reduction in condensation?

A fan might help, it depends on the source of condensing moisture.

Condensation happens because the shed roof and/or walls radiate away heat at night and become colder than the air. If they drop below the wet bulb temperature (condensation point) of the air then condensation occurs.

If  the air in your shed has a higher moisture content than the air outside then it will suffer condensation more easily (higher wet bulb temperature).  This happens if there is rain leaking into the shed or you are bringing water in, such on wet bike tyres. In this case replacing the damp air in your shed with drier external air will reduce condensation - ideally with a humidity switched extractor fan.  Passive ventilation (air bricks) won’t help much on the cold still nights when condensation is more likely.

But if no water is being brought into the shed the air inside will be the same humidity as the air outside and ventilation will not make a difference. If condensation also happens on the roof or walls outside the shed when it happens inside, then this your problem.

If you can get a humidity meter, or a wet & dry bulb thermometer, you can measure what is happening inside vs outside the shed and so whether an extractor fan would help.

should I put an extractor fan in my garage?

Is he into trainspotting now?