Ran into an old timer who said it's the best way to go. In the northern climes the concrete will sweat pretty bad in the fall and spring so he would lay a sheet of plastic under the car to hold the moisture down. Anyone else heard of this???
Yea if the garage particularly has a lot of ventilation and the inside temp follows the outside temp fairly quickly. For example in the spring and fall it is not uncommon to have large temperature swings. If the temperature inside of a garage changes quickly enough with the weather, the floor and everything else will sweat. Heavy plastic or even better a tarp does help keep the moisture contained at least from the floor. My garage is insulated and sealed pretty well and it will take a couple days before a sudden temp change outside has a significant change in temp on the inside. This is a slow enough process to avoid condensation. If it has been cold for awhile, then warms up, if I leave the garage door open everything starts to sweat within minutes so as much as I'd like to let warm air in, I do not. The best thing to do is keep a small fan running all the time to keep the air moving. This will help prevent condensation.
Jeff, I live in Chicago and store my car in MI. I usually put a tarp down and then a sheet of plywood. Seems to work fine. JB
I asked this same question 2 days ago to a long time car builder/collector and he says the plywood under the car is more important than the plastic. Okay to do both but the plywood was more important as the plastic will still allow the concrete under the car to sweat and it will act to trap the moisture but it is still present. The plywood will help to contain the moisture into the concrete? He said that's why when you see an old "barn find" car the undercarriage isn't rotten out as the moisture stayed in the ground, dirt floor, or in the barn floor, wood. It's usually the cars that have been kept in someone's concrete floor garage for 20-30 years that the undercarriage is rusted/rotted.
Its the speed of the change in temperature of the air that causes this condensation effect. I don't see it hurting to add plastic and or plywood under the car, I would. A couple times Ive opened the garage door in the morning when its cool in there, and the humidity in the air from the outside will condense on the car almost instantly. I'll pull the car out and it evaporates pretty quick as soon as the sun hits it. For long term storage though, Id go with the plastic at least.
warmer moist outside air , cooler inside temps , open up that garage door or whatever and the moist air sweeps in and contacts the floor and it "sweats" (condensation ) . water does not sweat through concrete . they made boats out of concrete in dubya-dubya II my dad said . thats if your place is kinda tight , if not its just a slower process . my barn is far from air tight up stairs but its usually dry feeling - a little hay left over/wood floors/air flow ? good storage . but down stairs i keep pretty tight , stays pretty good but i run a small dehumidifier 24/7 . before the dehumidifier water/condensation would run right off of the car and other stuff would feel dampish . and dirt floors = bad . del
the other problem that exists is this- since most garages do not have plastic laid on the stone base before the concrete is poured, u also have moisture rising from below through the concrete and leaching out the lime in the concrete. i lay a sheet of plastic on top of the concrete floor and then a tarp on top of the plastic.
I have cousins who jointly own a flawless '66 Mustang that has been in the family since new. It spends winters in a gigantic plastic bag that is charged with Nitrogen. One problem is that the bag is not mouseproof. The nitrogen kills the first mouse to chew it's way in, but the second mouse gets to build a nest in the car. They had a convertable top damaged by mice. The solution was to put a bunch of D-Con bait traps in the garage. No rust, no mice.
A 2 mil clear sheet that you would use for house painting works great. It's very cheap, under $3.00. You can also go to Home Depot and buy a giant carpet remnant. I bought a large 15' x 9' outdoor carpet for about $15.00, and it works great as a moisture barrier, and also feels great when I have to crawl under the car. Definitely put something under it though, especially a concrete floor, and especially in a Chicago climate. I knew someone that stored their 69 H/O on concrete for years, and even after warming him about the concrete floor, he wouldn't listen. After about 15 years, and never driving the car, the chassis was a ball of rust, exhaust pipes rotted away, and he had to have it all restored.
So, that's why they put the green cap on tires filled withe nitrogen. So, the mice will know not to chew into those tires.:eek2: :Brow:
Hi Bham, I cannot resist mentioning that I simply don't understand folks who pay extra for Nitrogen in their tires. The Earth's atmosphere is 79% Nitrogen! The best that can be done is about 97-98% Nitrogen in the tire anyway. ou:
