Detached garage moisture/slight mould

[AidanGee93]

Hi People,
Looking for some tips, moving into a new home in a week, got a detached Garage with a proper apex roof. The garage itself is doubled bricked (outer house brick, air gap then breeze block) wooden studs and plasterboarded.
I'll attach pictures...but the garage seems decent enough for what I'm looking for i.e. store all my tools, a basic home gym, a ceiling hung punch bag and general storage I.e. lawn mower, strimmer, bikes etc.
I live in Scotland, near Glasgow and want to control the humidity in the garage as don't want tools to be moisture damaged in future, also looking to use this garage as a work area to cut timber for any DIY down the line and would be ideal to leave timber in the garage during renovation but don't want it to become damaged with the moisture.
You can see in the pics that it looks to be rusted screw/nails showing through the plasterboard? Obviously moisture has got to these but I'm looking to control it so any tips.
I have noticed the garage has two lower vents to the west side ( that's the prevailing wind in this area). And the current owner has taped one up which I imagine is to stop drafts maybe. I know since being built (2001 roughly, all new build estate houses along with the garage) the owner had put new front doors to make it more air tight so think Air circulation may be a big factor?
Was looking to uncover the 1 out of two current lower vents and add another two opposite wall for air flow, also adding one high vent each side (west and east) as I know warm air rises...so thinking this would give good air flow and get humid air moving?
Looking to put an extractor fan in aswell on ceiling in the center so it sits in the loft with ducting (mainly for when cutting wood or using the gym).
These air vents are obviously good for airing the room but wondering about temperature as would no doubt get cold, similar temp to outside and I hear a damp house is a cold house, so just looking for any suggestions. I don't want to put heaters in as such a waste of money for wat I plan to use the space for. Dehumidifiers seem good but are they necessary if proper ventilation?
Cheers guys.

[Nickfromwales]

That lot needs to come off. Do it properly, once, and it'll be good for the duration. I'd do insulated plasterboard, dot & dabbed, and seal every nook and cranny with closed cell expanding foam. Then you'll not need anywhere as much airflow (cold damp air btw) as you think you do.

[AidanGee93]

20 minutes ago, Nickfromwales said:

That lot needs to come off. Do it properly, once, and it'll be good for the duration. I'd do insulated plasterboard, dot & dabbed, and seal every nook and cranny with closed cell expanding foam. Then you'll not need anywhere as much airflow (cold damp air btw) as you think you do.

Thanks Nick, the more I look at it the more I think the same strip it back to the breeze block and do it right, I'm thinking down the line fresh studs, insulate then plasterboard it, that way I can place sockets where I like as well as right now they are randomly on the wall. This garage is unheated btw and won't be heated, would you recommend using a vapour barrier over the insulation before plasterboard?...heard mixed opinions about trapping moisture etc.

As with vents on opposite walls high and low for cross airflow and letting cool air in bottom for warmer air to escape through top...you reckon a lot of the air coming in would be carrying moisture and not really do much good?

I do want it done right so will rip it all down but rather get everything on paper with regards to vents, vapor barrier, insulation etc etc. do it properly once like you say

[AidanGee93]

1 minute ago, AidanGee93 said:

Thanks Nick, the more I look at it the more I think the same strip it back to the breeze block and do it right, I'm thinking down the line fresh studs, insulate then plasterboard it, that way I can place sockets where I like as well as right now they are randomly on the wall. This garage is unheated btw and won't be heated, would you recommend using a vapour barrier over the insulation before plasterboard?...heard mixed opinions about trapping moisture etc.

As with vents on opposite walls high and low for cross airflow and letting cool air in bottom for warmer air to escape through top...you reckon a lot of the air coming in would be carrying moisture and not really do much good?

I do want it done right so will rip it all down but rather get everything on paper with regards to vents, vapor barrier, insulation etc etc. do it properly once like you say

Btw, closed cell expanding foam...would it still be needed if when I replace plasterboard I plan to skim it all anyway...so closing where the boards meet with scrim and plaster 

[Iceverge]

Why not just fill the cavity with bonded beads? 

 

https://www.greenwood.co.uk/continuous-extract-dmev/unity-cv2-gip

 

For air quality and humidity control I'm a big fan of these.....er.....fans.....

 

eBay has them for handy money regularly enough and they're very effective and near silent. 

[AidanGee93]

7 hours ago, Iceverge said:

Why not just fill the cavity with bonded beads? 

 

https://www.greenwood.co.uk/continuous-extract-dmev/unity-cv2-gip

 

For air quality and humidity control I'm a big fan of these.....er.....fans.....

 

eBay has them for handy money regularly enough and they're very effective and near silent. 

Thanks for input, definitely going to remove all the plasterboard, new studs and insulate so mind made on that one. Just looking for air control tips and appreciate you're comment with the fan. I will put and extractor fan in the loft with ducting leading from ceiling vent to external loft wall...as plan to do a lot of sawing in there in future for things like MDF wardrobes, fances, decking etc...allows me to work if raining which 90% the time it is.

I know ventilation is good for getting stale air out and fresh in but just don't want it freezing...seems pointless. Heard 2 vents in opposite walls for a cross air flow, and 2 on top for warm air to escape...open to suggestions 

[Nickfromwales]

8 hours ago, AidanGee93 said:

Thanks Nick, the more I look at it the more I think the same strip it back to the breeze block and do it right, I'm thinking down the line fresh studs, insulate then plasterboard it, that way I can place sockets where I like as well as right now they are randomly on the wall. This garage is unheated btw and won't be heated, would you recommend using a vapour barrier over the insulation before plasterboard?...heard mixed opinions about trapping moisture etc.

As with vents on opposite walls high and low for cross airflow and letting cool air in bottom for warmer air to escape through top...you reckon a lot of the air coming in would be carrying moisture and not really do much good?

I do want it done right so will rip it all down but rather get everything on paper with regards to vents, vapor barrier, insulation etc etc. do it properly once like you say

It's a cold space, eg outside of your thermal and heated envelope, so going for the insulated plasterboards will decouple you from the cold block wall. I'd choose this over batten and boards as you lose less internal space, but if you want to DIY then battening may be the way to go.

 

You don't use plaster and skirting boards to become 'airtight' (draught-proof in this instance), as then air is already free-flowing behind the boards and insulation aka thermal tenting, so a bead of foam top/bottom/sides will work wonders.

 

I'd say looking at the ceiling that needs dropping and stuffing full of rockwool too, but if there's a room over it it should already be there (and also be fire rated plasterboard?). If it has a leaky garage door then obvs there's got to be a point where you just accept this space will never be 'warm' tbh. In my man-shed/office I have not bothered and just flick on a fan heater (2kw) for instant heat but only when needed, cheap and easy.

 

For ventilation, if you you'd probably be better off sucking air out of the house and forcing it into the garage, so it leaves via the garage door, as that air won't be freezing cold or have lots of moisture in it.

[AidanGee93]

6 hours ago, Nickfromwales said:

It's a cold space, eg outside of your thermal and heated envelope, so going for the insulated plasterboards will decouple you from the cold block wall. I'd choose this over batten and boards as you lose less internal space, but if you want to DIY then battening may be the way to go.

 

You don't use plaster and skirting boards to become 'airtight' (draught-proof in this instance), as then air is already free-flowing behind the boards and insulation aka thermal tenting, so a bead of foam top/bottom/sides will work wonders.

 

I'd say looking at the ceiling that needs dropping and stuffing full of rockwool too, but if there's a room over it it should already be there (and also be fire rated plasterboard?). If it has a leaky garage door then obvs there's got to be a point where you just accept this space will never be 'warm' tbh. In my man-shed/office I have not bothered and just flick on a fan heater (2kw) for instant heat but only when needed, cheap and easy.

 

For ventilation, if you you'd probably be better off sucking air out of the house and forcing it into the garage, so it leaves via the garage door, as that air won't be freezing cold or have lots of moisture in it.

Cheers for you're tips, I get you now with the foam top/sides/bottom then can plaster it. See the current set up is studs and plasterboard so when I replace it I'll possibly add a slightly thicker stud (room for insulation) and plasterboard as I'm happy with the space even if loose a tiny bit with bigger studs.

The ceiling is quite high I thought this too but happy with the height...if get up the small crawl space loft above it and add plenty insulation. Will height of the garage be an issue regarding moisture/mould in future?

Regards to sucking air out the house...I understand you're point just don't see how I could do it as the garage is about 2.5m off the gable end of our house, plus that's a path to back garden...also even if was a way it's into the living with closest room?

I will keep my eye on the garage door next heavy rain fall but had a rough check and seemed no sign of previous water ingress. Thanks for you're tips I appreciate anyone's input with some knowledge behind them 

 

[AidanGee93]

1 minute ago, AidanGee93 said:

Cheers for you're tips, I get you now with the foam top/sides/bottom then can plaster it. See the current set up is studs and plasterboard so when I replace it I'll possibly add a slightly thicker stud (room for insulation) and plasterboard as I'm happy with the space even if loose a tiny bit with bigger studs.

The ceiling is quite high I thought this too but happy with the height...if get up the small crawl space loft above it and add plenty insulation. Will height of the garage be an issue regarding moisture/mould in future?

Regards to sucking air out the house...I understand you're point just don't see how I could do it as the garage is about 2.5m off the gable end of our house, plus that's a path to back garden...also even if was a way it's into the living with closest room?

I will keep my eye on the garage door next heavy rain fall but had a rough check and seemed no sign of previous water ingress. Thanks for you're tips I appreciate anyone's input with some knowledge behind them 

 

Worth mentioning I would like to use the crawl space loft for storage, nothing delicate would go up there for storage. That's probably another topic tho