The Triumph Dolomite Club - Discussion Forum

I built (or rather had built by a bicky) a singke skin brick garage. Yes, brickes more exoensive than blocks, but prettier and no need to render or paint.
This is a 30m2 jobbie, 2.5m high (I had the brickwork 2.5m high, and the roof joists on top!)
I did put a DPM in the base slab, despite the bricky reckoning it was a waste of time.

I got some slight second bricks, reused a good sized up and over door and reclaimed upvc back door and windows.. Roof was 200mm timbers with added firring (tapered wedges) on top. Then 18mm OSB3 and the £500 of fibreglass which I did in a day. Should last indefinitely....
Total cost was about 6K, whick includes a digger for the day and grab lorry, plus mixer mate concrete(more than self mixing by a couple of hundred quid, but much easier and faster, plus consistent mix)

I have siliconed the brickwork on the wall that gets all the weather, just in case. But garage is dry, and beautifully solid. To me it is a better investment tahn wood and not massively more expensive, plus easier maintenance.

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Clive Senior
Brighton

My new house used to be the show home and site office so it's carpeted and all the walls have plasterboard and paint on them. It's very smart but already my Mazda has left tyre marks on the carpet tiles! When I move the Dolomite it will soil the carpet with oil I'm sure.

Wood or brick? Oddly I always found my shed would get surprisingly damp in the inter and didn't breathe that well at all. To the point where I cut grille holes in it to promote better air flow. It improved it a bit but it would still suffer from condensation on the cold sides and roof. Perhaps masonry is better but the cost can get high. Wood or brick though would both benefit from insulation and good air flow to minimise dampness.

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Mark

1961 Chevrolet Corvair Greenbrier Sportswagon
1980 Dolomite Sprint project using brand new shell
2009 Mazda MX5 2.0 Sport
2018 Infiniti Q30

Good detail there guys thanks

Tony

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Membership 2014047

I served my apprenticeship as a bricky before I did my back in and no 4" skin will be waterproof without tanking or rendering and even then you run a risk. My timber and modern felt breathes and is completely dry but there are pro's and cons to each and every method, cost, time, your own personal skills, weather etc etc

My parents have a garage built with a single skin of bricks. Water seeps through when it rains on the side that faces the prevailing wind, so I'd avoid this building method myself.

Im going towards block structure with a cavity wall for insulation but still not decided, Ive got a load of work to do on the 'plot' first. Wish Id started earlier in the year lol

Tony

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Membership 2014047

Get a coat of silicone waterproofer on that wall. Cheap and easy to do, and it works.

Re insulation etc. Unless you heat the garage, all it will do is slow down how long the garage takes to cool eg when the sun goes down. That can help with condensation (it moves the dew point). However, far and away the most important aspect is good ventilation. And that makes insulation almost pointless!
Doing a cavity wall is real overkill on a garage, unless you have later plans to make it into a habitable space.

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Clive Senior
Brighton

Well if I get kicked out for too many car things it may serve a purpose


Tony

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Membership 2014047

Heating a garage to raise the dew point is very expensive. Far better to use a good desiccant dehumidifier. These work at very low temperatures and work as well at these low temps as high. They also provide a useful quantity of pure water which I use in my fish tank!

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Mark

1961 Chevrolet Corvair Greenbrier Sportswagon
1980 Dolomite Sprint project using brand new shell
2009 Mazda MX5 2.0 Sport
2018 Infiniti Q30

Regarding using a dehumidifier when I had a new garage built recently I was advised that this would be a waste of time without fully insulating the garage. I was told just make sure there was good permanent ventilation that allowed a good air movement to minimise condensation. They did this by having an apex roof with ventilation at the top and not sealing the tops of the walls to the roof. This keeps the water out but air movement over the apex causes a venturi air movement pulling air out at the apex and in between the walls and the roof base when winds are light and just blowing in through them when its stormy. I also open the door on good days to give it a bit of a boost as previously posted.

I have not seen condensation on the car but one disadvantage is dust and dead leaves comming in from the tree at the back of it.

Interesting topic. I am just planning a garage for a new property we will be moving to soon. I am planning on 6 metres by 12 metres to comfortably take 4 Triumphs and some gardening equipment.
Having had a timber garage at my current house I am now wanting to go for breeze block with render and a slate roof.
The timber garage has been great as far as dampness is concerned, but it does have very good ventilation. It used to cave a Coroline roof, but that used to drip condensation on me when working on the car in the winter. It also sagged when we had deep snow and the nail holes then allowed rain to get in. Now I have marine ply and felt on the roof. My main concern with timber was that there was a young guy in the village for a while who was an arsonist! A number of straw bales, sheds and caravans were set alight before he was "removed". But it made me think about welding, etc. I don't weld in my timber garage for that reason.
Our new house is in the middle of nowhere and can't be seen and when I contacted the planning authority I was told that I could build the garage without planning permission as long as the ridge height remained below 4 metres.
I am sure that rendered breeze blocks will last a lot longer than timber, too.

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1959 TR3A, 1970 Triumph 1300, 1974 Toledo
Thanks Photobucket

If rendering over lightweight blocks, you really want to use "rend-aid" to help prevent issues later. I wouldn't render direct onto them (though many people still do!)

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Clive Senior
Brighton

It might help if we clarify a few points here for Tony and any of the others considering building a garage.

All the air around us has moisture in it and as the temperature drops towards freezing the amount of moisture the air can hold drops. You will often hear the term “Relative Humidity” which refers to the amount of moisture in the air compared to what the air can hold at that specific temperature. When the air cannot hold all that moisture, it condenses as dew.

If you take the situation of an unheated garage then as the air is gradually cooled while maintaining the moisture constant content, the relative humidity will rise until it reaches 100%. This temperature, at which the moisture content in the air will be saturated, is called the dew point. If the air is cooled further, some of the moisture will condense.

Now if you understand all that then let me make some comments about the types of construction proposed here.

Timber walls. Fine particularly if they are not continuous and allow ventilation to the outside for as the air cools inside the garage that warmer, near saturated; air will probably pass through the walls to the outside and be replaced by cooler less saturated air from the outside. If the timber walls are continuous then the dew point, the point at which the condensation forms is likely to remain within the wall itself and that moisture will be absorbed by the timber. Unless the timber is treated or is of a type that can cope with moisture then it will eventually rot. (Probably not within the lifetime of the structure proposed here). However condensation can, and will, still form on the underside of the roof.

Double brick or block walls. The dew point will always be towards the outside of the wall and in the case of the double brick the condensation will run down the inside of the outer brick wall.

If you look very carefully at the photograph of Geoff’s “reasonable sized shed” you will see the flexible lining under the iron roof. The prime function of that lining is to form a vapour barrier. Condensation will be forming under the iron roof and will be dripping down onto that vapour barrier which will then carry it to the outside edge of the roof where it will be discharged into the open.

Here is a photo taken in my garage/shed cum workshop. If you look up at the underside of the roof you can see the vapour barrier which shows lines which mimics the shape of the corrugated iron roof above it. All the condensation forms above the vapour barrier and below the iron roof and is carried to the outside as it is in Geoff’s shed.

There are various types of vapour barriers available, from, as Geoff describes - foil backed continuous plastic sheeting, through to bituminised paper based products (which I have used).

I would always use some such product under any roof (even my wood shed where I store my wood for the winter fires which is open on all sides has it under its roof) and I would always put something under the floor slab (in this country it is usually plastic sheeting) as well, to stop the damp rising up from below.

Tony says he is erring towards a cavity wall of some sort which should work. I would recommend that no matter what sort of roof he eventually selects that he places a vapour barrier under the external roof skin and if it is a concrete floor, a vapour barrier under that.

He will then have a nice dry space in which to store and work on his cars.

Robert

Cheers for that Rob, I'd not heard of a vapour barrier before so I'll look at that too

Tony

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Membership 2014047

Sorry, but I have to disagree with most of this.

The vapour barrier will actually stop water vapour in the air, in the garage/shed, from meeting on the cold surface of the underside of the corrugated sheets. So condensation will not form above the vapour barrier and below the corrugated iron sheets, as stated. Unfortunately, as the vapour barrier is mostly touching the corrugated sheets, the surface of the barrier will be almost as cold as the sheets and the condensation will just form on the underside of the barrier. In this case the vapour barrier will have little, or no effect. It would have been better, although still not ideal, to have fixed the barrier to the underside of the purlins and taped the joints, then at least there would be an insulating air gap in between the sheets and the barrier, and the surface of the barrier would have been relatively warmer and less likely to form condensation on its surface.

Vapour barriers in building construction are mostly used to stop interstitial condensation (condensation that forms within the thickness of a wall wall/roof structure) and should be placed towards the inside of the building. For example, if you have a roof consisting of corrugated sheets, with Rockwool insulation between the joists/rafters, and a boarded ceiling, then a layer of polythene above the ceiling boards will prevent condensation forming where the dew point is reached within the structure. This might be within the Rockwool insulation, or on the lower surface of the corrugated sheets, depending on the inside humidity levels and temperature, and the external air temperature.

Vapour barriers, or more accurately Damp Proof Membranes, are always a good idea under a concrete floor slab, and, if possible, turn them up the walls and link them into the Damp Proof Course. Heavy gauge polythene is best for this.