Drying out the garage

I'm not taking away your booze, not that kind of dry out.

Last spring we completed a three car garage here in Houston. Floors are sealed and painted, walls all fancy and nicely finished. A great spot to work. I recently came in though and found that my soft tool-bag (one of those heavy duty tool box bags) was all funky and had mold/mildew growing on it. It was sitting on the floor. So this is high humdity Houston and we get afternoon showers with regularity in the summers/fall.

So is that humidity enough to cause mold/mildew and if so, what do I do about it? I noticed that where the garage door closes there is that apron area that stays wet far longer than the slab outside. Can i set the garage door to not close so tight, to let air flow there? Or is there something I can do to keep that area dry.

I do a bit of wood working and had looked at an airfiltration system. Would something like that, set to cycle on a few times a day, be enough to keep the air moving in the garage? Last option is a window unit set to cycle and pull humidity out.

Thanks

Air flow, ventilation. Gotta get some air moving in there.

Dehumidifier
Is there insulation on the walls and ceiling?

That what I was thinking. Something as simple as a box fan "might" help.

Since its Houston, probably something as simple as a window mounted air conditioner would help drop the humidity in the garage. Bet in that neck of the woods you could find a cheap, used one to stick in the window to help out.

Was that tool bag sitting on the floor? Cement doesn't fully dry for ages and I'd bet it's giving off dampness, sealed/painted or not. Getting stuff like that off the floor can't hurt.

But, yeah, fans, air movement, AC, dehumidifier, they'll all help.

And set everything you can, up on wood blocks- this will allow air to circulate and evaporate from the slab faster, and without condensing on idems sitting on top of the slab. You didn't mention if there was a vapor barrier installed under the slab or not.

Moisture moves from wet to dry and warm to cool. Being that Houston is basically one big (hot) swamp (not unlike the cool one I currently live in), and has very high humidity year-round, the window air conditioner isn't a bad idea. It will help minimize the space humidity when you are in it, which mother nature will then try (successfully) to equalize. Painting the floor won't help- moisture drive will lift most anything, even epoxy. Welcome to Houston.
You will have to make sure the ground around your structures doesn't dry out. You most likely have highly active clay soils that the house and garage are built on. These clays expand and contract significantly with moisture change. It's unlikely your builders did proper subgrade preparation and built an engineered, moisture-conditioned soil pad for your structures or even drilled concrete piers that the geotechnical engineer said they had to do in order to keep moisture-related slab movement to less than 1". (That's what we attempt to design to.) I'd bet that they didn't even strip the topsoil before they put down the cushion sand and poured your slab. You most likely now have a nice moisture reservoir under your garage slab with lots of organic material in it. Keep soaker hoses going around all of your building perimeters if it starts to dry out. Now ya got even more moisture for your garage slab to deal with. At least the cracking brick, warped door frames and cracked drywall will be minimized.
Keep stuff that absorbs moisture elevated off the floor, especially your turning stock. Sticker it too. Invest in a good moisture meter and check your stock before you chuck it in the lathe!

When I lived out in the dirt I built a nice hermetically sealed dirt free 8x16 building to keep my bikes. As soon as the sun hit the walls on a sunny day the cold of the bikes and the quickly heated non ventilating air turned a mess that looked like I took a spray bottle of water to everything. Stuff rusted fast. Crack the garage door provided you wont get a mouse or rat invasion, and put a $20 box fan against one of the wall vents and see what that does to circulate some air.

Air conditioner or dehumidifier is the solution. Being that you in Houston the AC might be better because the dehumidifier puts out air warmer than the intake air, but it is dry, and doesnt require access to outside. I have a 50qt Frigidaire dehumidifier and it has no problem kicking the humidity down from 85 or 90% in my 1500 Sq foot house +1 car garage in a few hours, if I left it on im sure it would do fine. Its amazing how much moisture you can pull out of the air.

damprid. Can get it on amazon or at Wally world. Works quite well. And super inexpensive.

I've planned to get or build a dust system, ie blower in a box with some filters hung from the ceiling. Would that create enough air movement?

I have a window with the plan to put in a window unit, but I would REALLY like to get one I could put on a timer to run 20-30 minutes every few hours. So finding a unit that can be programmed or plugged into a programable outlet is tough.

Just ordered a garage door seal kit to keep the water from coming up the apron.

Your proposed dust system will not provide enough air circulation. In your location I'd use a small-medium pedestal fan in each corner to get all the air in the garage moving. I'd also forget about the timer and go with an Energy Star large-capacity dehumidifier with a relative humidity setting. It will run until the RH point is reached. The window AC unit will be fighting a loosing battle until you air seal and insulate the structure shell (use the Energy Star recommendations, not your local building code).

Dehumidifier +1 - I am in DC and had the same issue last year with the humidity. I have a mini-split HVAC unit and used to only turn it on when I was in the garage. Mold started on the bikes, seats, most anything plastic; it just plain sucked. Since then I leave the HVAC unit on dehumidify and no issue since.

Sorry I failed to respond to some of the earlier questions.

The construction involved the removal of an existing parking slab, full scrape and a moisture barrier. So no topsoil under it. yes there is the normal fat clays of Houston. Before sealing the slab I did the plastic test and had no moisture through the slab. The walls are all insulated with R13. There is an apartment above, so there is an R20 barrier between the floors for sound as much as insulation. The garage door is not insulated. everything else got spray foamed and sealed up tight.

I'm not sure if that impacts the type of equipment we would need to deal with the humidity. I am getting the dust system anyway and do intend to put a window unit in at some point since it is half shop half garage and summers are too brutal. I guess a third appliance wouldn't be the end of the world.

Which split system do you have? I just saw one, Shark AC, that is not a bad price for the size. the Mitsubishi systems seem pricey. The prices I saw were on par with a nicer window unit, but with the option of having it on a programmable thermostat.

I'm guessing your roof is leaking

I doubt it. 1st floor garage, second floor apartment. all new construction

I have a dehumidifier in my garage/workshop. It cures dampness especially this time of year when the vice would have condensation on it.

Added benefit is lots of distilled water for coolant mixes, laundry iron and a final rinse for the car to avoid lime marks!

Same problem happening in my garage (similar setup.. shop downstairs and finished office space upstairs). Poured slab over 10 mil vapor barrier.

I'm wondering how effective a dehumidifer will be being that the shop has a garage door. The door is sealed pretty good (barely any light comes through) and the structure has housewrap.

Would love a 3 head split HVAC system, but that's a whole nother level of $$$.

An AC would be nice here too, but I think it might be like using a wrench as a hammer. Sure it works, but you're going to end up ruining your wrench.


I wonder though if an AC operating 1-2 hours a day would do it, or if it would need to be on much longer.