So,

My glorious mancave is finally built, only took about 4yrs…

But now that it’s up and watertight I’ve noticed it’s getting damp, specifically on the roof and top 2 breeze blocks of the highest wall (sloping roof).

I’m assuming that this is due to a lack of ventilation, despite having a brick sized gap on one upper (but not top of roof) corner.

So, if I put in an air brick on the opposite bottom corner (above DPM) do we think that will be enough?

Or should I add more airbricks/perhaps a fan to get the air moving?

Or do I need to add some ventilation at the very highest level of the roof?

Sloping roof (conduline corrugated on OSB), breeze block walls, no insulation, 7m x 2.4m x 2.8m, concrete floor (10yrs old, no damp coming through).

Other more expensive options are heating/dehumidifier/insulation.

I’m rarely in there, so heat wise a fan heater is fine for occasional use, but don’t want bikes / tools etc getting rusty and damp.

Positive input appreciated!

I had the same issue in a garage. I ended up putting in 3 airbricks fairly high up. It seems to have cured the condensation on the ceiling issue that we had.

I used these Proper brick ones look nicer but these seem to exchange more air than the traditional brick ones

No idea sorry but having no insulation in a garage for me was enough for tools to get condensation on them and go rusty.. even if you’re not in there I’d personally have put in a small amount of insulation

I have a sectional concrete walled, asbestos roofed garage which was almost like a rain shower when cold outside. I have stuck some foil bubble wrap stuff to the roof and its almost cured it. The floor still condensates as times still, considering a new surface for this, but don’t want to spend too much as I doubt the roof will last too long.

Moist Mancave

They write themselves sometimes, don’t they.

Best not google the title at work 😀

In the short term, applying a light coating of light oil to tools could help to inhibit rust?

Yep some WD40 or similar is ok for the hand tools, but also plan on storing some powertools in there which is more of an issue.

I’ll try a couple of airbricks, still not too sure on the ideal postion of these though, high/low or both?

Don’t write off using a dehumidifier if the air-brick doesn’t help. We converted a two-storey, stone-built out-building into a home office / kit-store / gym / turbo cave and before we properly sorted the pointing, the infill in the walls absorbed a fair amount of moisture. I now just run a dehumidifier to keep on top of things and it works really well. Hope is that it’ll eventually dry out the walls completely, but it works well enough that it’s no longer an issue for us.

Had considered a dehumidifier + small greenhouse type heater to keep the chill off the air initially (with some polystyrene type roof insulation), but for as little time as I actually spend in the shed the energy use would be difficult to justify.

Is your out building now airtight(within reason) or do you also have some ventilation (air brick / trickle vent etc)?

I’m still surprised that I have an issue given that mine isn’t anywhere near airtight now with a physical hole in the wall, but still looks like a possible airflow issue for me.

Is your out building now airtight(within reason) or do you also have some ventilation (air brick / trickle vent etc)?

It’s insulated to building standards specification, but because I have a wood-burner upstairs, there’s a vent direct to the outside downstairs which I shut off when I’m not using the burner.

For perspective, when we moved here, the bathroom which was the upper level of a built-on extension to the house was seriously cold with condensation issues even with a semi-permanently opened window. Turns out there was no insulation – apart from a long dead rat – in the ceiling cavity / under the roof. Insulating it made a massive difference. Much warmer space and no condensation issues.

I was surprised at the impact insulating the roof made, definitely worth considering.

The dehumidifier only switches on when humidity reaches a pre-set level, mostly it doesn’t run which cuts running costs. Just need to empty the collector once a week or so. Varies depending on the weather.

On the flip side, my shed is very very well ventilated – there’s gaps everywhere – and my woodworking tools and nice power tools and machinery have zero corrosion after 3 years

Best not google the title at work

It’s actually disappointingly disappointing.