Garage condensation

[IanM]

I can post a video of empty garage but this site needs it to be hosted somewhere right?

In the full-editor, there is a picture icon for posting photos.

[hmg66]

Evening all, been a while.

Mainly because I bought a 200 year old farmhouse a year ago so have been busy getting it to a certain point.

Plenty of outbuildings, one of which is a good sized main garage which is where I will be building up my ‘73T if the bodywork guy ever gets his finger out.

Problem is, there is mad condensation on all inner surfaces. One wall is stone (shared with an old byre beside garage) and other three walls are single layer block. Roof is galvanised corrugated tin, floor is concrete and freshly prepped and painted this summer.

The weather has been variable recently with big swings in temperatures and humidity so it may be that today is the worst combination of cold walls and warm, humid air. Every surface is wet. I’d really like to do something about this before I start to use the garage for the 911. I have a few months to sort.

So, hoping some of you have older properties and have dealt with something like this? I’m thinking solution for the walls would be a new inner wall using insulated blocks with a standard cavity. Or I could ‘clad’ the inside of all four walls with some sort of insulated board on battens? For the roof, I’m thinking replace tin with modern insulated profile. I guess there is nothing to be done with the floor.

In the meantime, do you think more ventilation will do any good? There are no external windows, just a big old pair of hung rolling doors.

Thoughts and advice appreciated!

Cheers,

Al

I have a detached unheated garage built twenty years ago to the then building regs standards.

Slate roof, brick and block insulated cavity walls, insulated and DPM concrete floor etc

Whilst it’s dry and certainly no visible condensation to the fabric of the building the recent weather conditions with rapid swings in temperature have meant that both classic cars stored there have had some condensation when under an indoor cover.

It’s happens every time we have these swings in temperature so I just take the covers off for a couple of days… short of heating it and running some sort of dehumidification system I’m not sure it could be avoided.

Even the professional storage barns that people pay large monthly rents for seems to be nothing better than this construction wise.

[Cortina]

I have the same issue with old buildings - part of your problem is the recent weather .... 15C variation in 24 hours is NOT normal.
I just live with it - happens about once every two years or so. Let the air in and wait !

[deano]

I haven't read every post below, but in my opinion all you need is more ventilation by the sounds of it. Ideally from front to back of garage.

Building regs for houses or extensions now 'require' 25,000 square mm per metre of ventilation, which equates to a 25 mm high opening along the full width of the building, front and back, or the equivalent opening in air bricks or mechanical ventilation. The link below shows a possible solution, and has a telephone number for condensation advice.

https://www.permagard.co.uk/perma-vent- ... 1YQAvD_BwE

This amount of opening area will work for your garage too, or a loft, or anything else.... though a lower value might be OK for a garage I dont know.

I learned this the hard way just a couple of weeks ago, resulting in mould on the underside of a partly constructed flat roof because I had not gotten around to ventilating it yet. Bone dry since then

Someone please correct me if I am wrong, but my impression is that dehumidifiers do not work in cold weather. This is based on my use of the chemical ones that you can buy from the supermarket, not electrical versions...

[Flat 6]

So I'm stuck between a strategy of stopping the humid outside air getting in (more efforts to seal roof and doors) and letting more air in (ventilation).

Letting more air in is definitely the easier option! Before last weekend's major condensation hit I had actually ordered four aluminium louvred vents and was debating whether this was the right way to go or not.

I suspect it's a case of either:

1/ getting it pretty well sealed and then using a combination of heat and dehumidifier to keep the garage closer to how you would keep the house or

2/ treating it like a leaky old garage and just keep the air moving - garage will be close to external air in terms of temperature and humidity.

As a point of reference, the attic of the main block of the house is a 'cold attic'. There is no liner under the tiles, although we plan to remove and replace the existing material (asbestos). There is a 'Nuaire' positive pressure blower in the ceiling of the front hall that blows filtered air from this attic into the house as a mechanism to avoid damp. We don't use it because of the asbestos tiles but the solution generally seems well regarded for old houses. So someone somewhere has concluded that it is a good idea to blow air from a cold/ drafty attic into a damp house to reduce damp. For me, that kindof supports the ventilation route than the 'seal it up' route?

Thanks all for interesting replies - clearly I am not alone in this situ!

A

[stichill99]

A friend built an insulated tin sheet shed and it has a 6 foot by 3 foot vented sheet in the end wall. Slatted so rain doesn't come in and I am amazed how dry his collection of cars and bikes stays. My home built breeze block shed has damp problems as I never put a dpm below the floor and damp rises through the floor. I extended it and put dpm below floor and 2 block vents in back wall and it stays bone dry. For me ventilation is the key!

[neilbardsley]

I must admit I thought that some airflow was needed?

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