I own an old cinder block and cement 2 car garage. The trouble is that when the doors are shut, the humidity probably goes up to 100% inside. This seriously plays havoc with anything inside the garage (tools for example will easily rust). Needless to say, I do not keep any cars in there.
There was never any method installed for ventilating the garage. Would a fan or 2 help? What about those vents you see so often on builiding rooftops? (the cylindrical ones with the conical top.) I’ve heard that calcium chloride is great for absorbing moisture but would I need a couple of barrels of it each month?
I would like to know any ideas the SDMB membership may have.
Pick up some zeolite pouches, easy to find at the pet or hardware store. Zeolite is a magical volanic mineral that absorbs stuff, including humidity. Just hang them up and they will do the rest.
Every month or so, take them out and put them in the sunlight and they will release everything, and can be reused.
Is all of the block above grade? What is the status of grading around the garage, e.g. does the soil profile promote drainage? Are there rain gutters? Do the downspouts have leaders to take rainfall away from the foundation wall? Are the soffits vented? Is there a ridge vent? Answers to these questions will help to get you pointed in the right direction.
danceswithcats
The garage is perfectly level with the soil and there is only one downward grade - the front asphalt driveway. The garage is just as I described it - cinder blocks and cement (okay wooden doors) - NO gutters, downspouts, soffits, or vents.
Ventilation of some sort would seem to be in order. My garage (shared with 5 other tenants) has ceiling vents and it is always dry in there.
Here is some info on attic vents and while not exactly what you are on about notice the first sentence:
While you do not have a to draw moisture up form as above your garage still can (and obviously does) collect moisture. Keeping a good flow of air through it should help a good bit. Properly done I do not think you even need powered fans and normal airflow might do the trick but talk to garage builder or someone whou would know to be sure (my garage holds six cars so it is sizeable and all vents are passive).
Nope…they look like the one in the picture I posted…mostly. Mine are silver (unadorned aluminum) and the one in the pic looks like it might have a solar array on it the may power a fan. Just guessing but it looks like that to me. Mine are totally passive. Essentially a pipe extends a bit out of the roof and then a hat, like and upside-down baking pan sits over it. That keeps the water out. Inside is a bit of screen to keep bugs and animals out.
Simple but effective.
They also, of course, help vent exhaust fumes from the cars…in my case that is probably more important than anything. Not enough to vent someone sitting in there with the doors closed and running their engine but plenty to take care of the bit of exhaust that gathers before people exit…times 6 cars I imagine that might add up to enough to be not good to leave without ventilation.
Note that the thing I linked to suggested some sort of two-tiered vent system. Not much air will leave the top vent without a way for new air to replace it at the bottom. I doubt you need much but probably something to allow air in (ala a clothes dryer exhaust vent except it lets air in). If the garage doors do not seal particularly well perhaps enough air can leak in that way but I’d think an intake vent would be needed.
It’s fairly easy to install a ridge vent, if you’re at all handy. Getting gutters and downspouts put up will help also, rather than having rain saturate the ground next to the block. Also, is the block sealed in any way on either side? If the outside is still plain block, there are a number of good waterproofing paints and sealers that you can use to reduce water absorption by the block and improve appearance.
The first style I thought of was something like this one. You might call it semi-passive - no power, but the slightest bit of wind turns it and draws up air from inside. Granted, they’re a lot more conspicuous than other vents, but I hear they work well.
As Whack-a-Mole says, you might want a vent at the bottom as well. Just make sure it has a good screen on it to keep any local wildlife from moving in.
Only one problem with that idea. Almost every coating manufacturer starts out by telling you to apply to a clean dry substrate which is free of bond-breakers. They often advise performance of a “patch test” which is nothing more than a piece of 4 or 6 mil clear poly about a foot square that is sealed to the slab for a day or so. Beads of moisture indicate conditions which may cause bubbling or disbonding of the coating. If a certain amount of moisture is permissible, you would then need to perform a quantitative test using anhydrous calcium chloride.
Where do you live? Climate won’t make as big of a difference as it would with a finished building, but it may still matter.
Also, how is the garage constructed? Besides having block walls, how else is the garage built? Is the roof a gabled or hip roof, or is it flat? How far does the roof cover past the walls? What type of roofing material was used; metal, composition shingles or cedar shingles? How well sealed is the space when all the doors and windows are closed?
Beyond that, are there any signs of dampness on the outside of the garage? I mean, things like mildew on the lower parts of the walls, moss or mildew on the roof or places where water pools on the ground near the garage after a rain.
Finally(!), does the humidity seem to get worse from season to season, does it get bad after it rains, does it happen overnight or is it just bad all of the time?
My first guess would be that water is wicking up from the ground through the concrete floor and blocks, but I’d like to know more about the rest of the building.
First order of business is to loacate and eliminate the external source of moisture. From your description I assume it is plain, unpainted block which gets a fresh supply of moistue from each and every rain. If so a thorough coating with “UGLI” paint will make it water repellent.
Second be sure there is adequate drainage all around the slab to prevent wicking of moisture up into the block.
Third provide adequate ventilation to dry the building out and keep it dry.
Calcium chloride in considerable quantity would help, A few packets would be useless.
Good idea but…
SORRY to say a few pouches of Zeolite would only be of use in a closet or other small area. Also too expensive for a large area like a garage.
It could be used as a dessicant, but would require a large quantity. It would be much more efffective and much cheaper to properly ventilate the garage.
It is a saturated liquid after use and is discarded. Disposal is another problem with it.
A flat roof itends to collect rain water and if not water tight and well drained, i.e. pitched to drains or if in poor condition it could be the source of your moisture.
The high humidity will interfere with or extend the time of getting things dried out but once dry should not be a serious problem.
I live 2 miles from the Pacific - the house has the garage on the ground level, and the living area is buit over it.
The furnace is in the rear, and the space above is always heated - if I leave raw steel even next to the furnace, it rusts. If I leave it away from the furnace, it is iron oxide within 3 months.
Cinderblock is purous, flat roofs (how does it shed snow?) are bad news, and lack of ventilation just seals the tomb - the only ways to keep raw steel rust-free in those conditions:
Tear it down, and start over - you will need a moisture-proof enclosure - good luck, as that will also mean air-tight.
Add a large heat source - vents aren’t going to do diddly, and chemicals will surrender immediately. If you weren’t in such a humid environment, I’d recommend the “GoldenRod (tm?)” dehumidifiers - they can protect the immediate area (used to keep aircraft instruments dry during storage), but if your situation is anything like mine, they will also go belly-up.
Use LPS/ACF-50/ at least WD40/ on everything you want to keep rust-free. These are all temporary, spray-on coatings - the LPS and ACF-50 will go a year before needing replacement, and in the case of anything like a shovel, file, saw, etc., usage will destroy the coating immediately.
Learn how to blue steel and Alodine ™ aluminum - and never even think about storing bags of concrete (anybody want 60 lb. bricks of Sacrete ™)?
There is a reason surplus airplanes are stored in deserts, check out Mojave, CA - tiny town, flat terrain - upon approaching on the ground, the first thing you see are the vertical fins of transport-category airplanes. Ever see a 747 buttoned up in the desert?