So I have a period correct two bay garage .... made in the model T era. This means it's really small, just enough room for a T with the top up. It is unheated.
Now here in the Northeast we have four seasons with fluctuations in temperature and relative humidity. My garage has a concrete floor. So, when there is a sudden change in temperature the dew point can result is condensation on the floor and anything metal. Aside from heat ... which is not an option ... would there be a floor covering that might be good for this application; laying down sheets of plywood for instance?
I have a friend with the same issues, He has tried for years to solve it to no avail.
His quick solution was to buy blue tarps and lay them flat on the floor and then drive the car on top of the tarps.
This does not solve the dew point [problem but keeps his cars from drawing the moisture under his fenders and chassis.
Being from Rhode Island, near the water. I deal with this problem often. In the springtime particularly. The garage is cold, and the cars are cold. Come mornings the door is opened and damp, warmer air enters the garage and turns the car into a sweating beer can. The side of the engine block runs like a river. Clutches rust up. Brakes rust.
In my unheated garage, I keep it shut as tight as possible. Letting the contents warm slowly. Having large windows that allow sunlight to warm the cars helps too. Keeping the cars slightly warmer than the surrounding air keeps them dry.
The best floor would be wood, with an air space below it. This keeps the humidity from flowing up though the cement floor. Having epoxy over the concrete floor also helps in this regard, but does not stop condensation from the air.
As long is it us not freezing, you can run a small dehumidifier with an outside drain. You can set that on a thermostat so it does not come on when it is too cold.
I struggle with these issues every year.
Put down a poly vapor barrier and then a wood floor. Could be plywood, old boards, or whatever. Concrete sweats too much up here in the cold areas. I have three sheds and all have wood floors.
Mark, before I moved into this house and when I was into 60's / 70's cars, I was outside in gods garage. A friend of mine used tarps on his garage floor to try and keep moisture at bay, I figured I'd try them outside. Works just as well, I had zero issues with things rusting on my cars. I think any type of poly vapor you can put down will be your best solution for what you have to deal with.
Brendan and Erik's idea of a wood floor over it is a really good idea too. If you buy sheets of plywood, you can work on it and even when its chilly out, you will not get yourself or feet cold as it will provide some insulation of sorts.
In my current garage, I am lucky not to get condensation on the floor at least, I have an old carpet remnant that was tore out of a room down. People walk in and are almost astonished I have a "carpeted" garage
Has any one tried to keep air moving across the floor all the time with small fans? Just curious
Being old construction, there's most likely no vapor barrier between the ground and the concrete like they do now. This means that the concrete will wick moisture from the ground forever and be a constant source of humidity.
Covering with plastic or tarp is a temporary fix. I'm not sure that any of the modern "paint-on" coatings will survive over moist concrete unless it's allowed to dry. You might check on the epoxy coatings and see what they recommend but I would expect adhesion problems.
I built a garage to the dimensions in one of the period publications that was touted as being specifically for a Model T. I had a slab that was formerly a patio and used that as my floor. I assumed it did not have a vapor barrier under it so I laid heavy plastic over the concrete and then put down treated lumber sleepers and 3/4" plywood over that for the floor. I did not use any insulation and left the studs and roof rafters exposed. I made sure there was plenty of ventilation through the eaves and at each end and I also ran a box fan on low all the time that I had on the floor behind the car. Never had an issue with moisture up north. Cold in the winter and hot in the summer but no moisture issues.
Aww just carpet it.
I don't know if a dirt floor causes the same problems as concrete but, I also used a tarp and there are no problems.
This is kinda like putting on your underwear backwards. Do you
try to stuff different things in them to make them fit right, or do you
take them off and do it right ?
In this case, you take the concrete out (installed before the plastic)
and put the vapor barrier down FIRST. That means on the dirt, UNDER
the concrete. THEN you do a nice concrete floor !
try a layer of plastic then a cheap piece of indoor /outdoor carpet does wonders and if it gets wet it dries fast keep a piece under my motorcycle all the time high humidity in florida works fine
I know you said that heat is not a option, but consider using this product (https://www.uponorpro.com/~/media/Extranet/Files/manuals/QuikTrak_InsG_9-00.aspx ?sc_lang=en)
In conjunction with perhaps a roof top mounted solar thermal panel. It can all be operated from a 12 volt solar electric panel
I have used this product
What about replacing it with a new building with a new floor and more room? Bud.
Before I spent any money on the floor, I would check with a materials engineer who will probably tell you that any water coming through the concrete is very low compared to the water coming from the warm outside air as it cools overnight. A fan connected to a timer (or to a humidistat) might be the better option, but each building and its environs will be different. The water appearing on the concrete (or on the car) is mostly from condensate in the air.
Hi Mark, I have a building with very little moisture problem. I would place good quality vapour barrier on the concrete and then strap ( no need to fasten them to the concrete. Fasten boards to the strapping and the air will circulate. There will be very little moisture. People used to keep cars in the barn also and the hay would help control the moisture. I have had great luck with the plank floor over air and vapour barrier. It also keeps the Flywheels on my gas engine from rusting. Cheers, John
Maybe a dehumidifier would help while still costing less than what heating or redoing the concrete would?
Trying not to be technical, just suggesting a thought 'outside-the-box' for re-construction or new...
Consider the soil you're on top of. i.e. - Clay sub-soil is going to hold moisture more than sand.
Think about laying down styrofoam foil-coated house sheeting, with the concrete floor on top - (Be aware, concrete flat-masons will cuss about it 'running'.)
Even without heat or a heated floor, it helps to keep the concrete from 'sweating'.
I did this (1" thick) when building our walk-out lower-level home over 20 years ago. Much warmer floor and no moisture problems!
From Marv's FWIW Dept.
Put some fans in there to keep the air moving, makes a big difference.
There is a forum called the Garage Journal and they have a flooring section that covers what you are looking for .
Kurt Baltrusch has it right. MOST of the water is coming from the air and not the concrete floor.
I've been going with oscillating fans on timers. Living in IL the humidity is always high.
An exhaust fan on a humidistat or timer, or at least a switch will solve your problem. Could be as simple as a bath fan, might need more than one.
When I put the concrete floor in the work shop in 1978,we put styrofoam sheets on the gravel & covered the styrofoam with heavy plastic,then poured the cement.Have never had any problems with condensation under the cars.Chadwick,I know of a person who put carpet on a wooden garage floor to stop condensation.Well a little gasoline leak & a spark from the booster cables & this gentleman lost all his antique cars & a 100 year old plus garage.
Kurt is right. The earth under my concrete floor is well drained sand and very dry so ground source moisture is not a problem for me. If I allow the garage to heat up and cool down by day and night temp. changes or heating for only a few hours I will get condensation that will rust my tools and whatever else is rust prone. Although not always practable keeping temp. constant will mitigate condensation. Otherwise a dehumidifier is likely the best answer.