Garage shop moisture problems

[Stephanie and Tim]

Hi all!

We moved into our new house a few months back, and I promptly filled both garage bays with my tools. Now, as spring approaches and I'm itching to spend more time out there, I'm noticing a lot more rust showing up. My previous shop, also in a garage, had no moisture problems at all - unprotected cast-iron tabletops never showed any rust at all. Now my drill press table is covered with a layer of rust. No pitting yet, and I'd like to take care of this pretty quick.

Details:

Garage is a standard two-bay deal with two aluminum overhead doors. Floor is concrete, that appears to have had a second layer poured over the first, but in any case it's in lousy condition - full of craters. The concrete seems to be pretty low grade stuff - it chips easily, and sounds sorta hollow in several places. Walls are concrete block to about 3 feet with some cracks, and unfinished two-by above that. The rear wall is partially below grade. The front is obviously at grade. Siding is board and batten. Ceiling is open to the trusses. Overall, the structure isn't particularly tight, there are some visible openings.

Questions:

1. I'm not sure if fixing the weatherstripping, trim, etc. is a good idea or a bad one. If I make everything tighter, will I just be keeping more moisture in, essentially creating a big sauna?

1. I'm thinking about putting in a plywood floor over 1x2 or 2x2 sleepers, as the underlying floor is pretty trashed. Will this help with moisture problems?

2. Ideally, I'd like to also finish the walls to some degree. As it's a shop, I think I'd probably want plywood walls rather than wallboard, so I can attach whatnot to the walls without really worrying about it. Is this a bad idea? Should I go with wallboard instead?

1. Like many folks, I've got a couple of tons of crap stored in the rafters of the garage. From a moisture control standpoint, how much should I worry about the open ceiling?

Thanks!

-Tim, who is well versed in furniture building, but woefully underedumacted in basic construction....

[TURTLE]

This is Turtle.

When you have a moisture problem in a building of any kind. The cure is to have a air flow through it and exchange outside air for the room air. There maybe a hundred cures for this but one would be to get you a roof type attic vent-o-lator used for attics and it will be the one that is for side wall discharge of attic air. You will have to get one that has the Humitity control setting on it and set it at 90% RH and keep the R.H down below 90% RH. Anytime the humity gets above 90% in the room area. The fan will come on and exchange the damp air for drier outside air. If you keep the room at 99% RH or less the tools should not rust. Now just thinking about it 70% RH might be a better setting. Now if your heating or cooling this area. this may become a problem doing this when your tring to heat or cool the area.

Just some thoughts here.

TURTLE

[Joseph Meehan]

What that "new" house new to you or newly built? New concrete lets off moisture for months after it is put in. That could be your main problem.

Was the old garage block or frame? That can make a difference as well.

Are you sure there are not hidden leaks?

That said, you may need to keep water off the walls and seal the floor. I suggest a water repellent for any outside walls. I would guess a good garage floor paint would do a lot to reduce moisture coming up. BTW you can tape a piece of plastic or foil to the floor and come back in a day; remove it and if there is moisture on the underside, you have moisture coming in from the floor.

Also keep in mind that weather conditions from one year to the next can make a difference as well.

[Edwin Pawlowski]

Perhaps if you put a moisture barrier first it would. Othewise it will just serve to rot the plyswood.

Again, moisture barrier. Insualtionalso, regardless os where youlive. It will help keep heat out in the summer also.

Are you getting moisture from seepage or is is just condensation in the "cage" of cool air fromthe masonry and the warm spring air comingin? I've seent he top of my tablesaw rust right before my eyes on spring day when the garage was cook and I opened the door on a warmish, but rather humid day.

To get rid of the rust on your tools, Top Saver is fantastic. Best rust remover I've ever seen for tools. $20 from most good tool dealers. It also give some protection, but Thopsield T9 is a better protectorant.

[nospambob]

[Tom Baker]

First, I think Mr. Meehan is on the right track. Concrete can add moisture to the environment for a long time. Depending on construction any of the materials in that garage can pass moisture. Concrete can also pass moisture from the earth below. Concrete block (CMU) can pass a lot of moisture if not sealed on the outside / wet side. Moisture can enter the CMU from contact with the ground, rain, leaks from the top.

The plywood floor on sleepers won't solve a moisture problem. The sleepers are in direct contact with the slab and should, by code and common sense, be treated material. They will be out of sight and out of mind and inaccessible for inspection. Plywood should be no better or worse than gypsum board for the walls. Any water or moisture infiltration should be stopped at the outer surface of the wall and neither is going to help an interior moisture problem. If the garage is attached to the house, the common wall should be fire rated. The easy way to do that is to add a layer of 5/8 Type "X" gypsum board. I know of no reason plywood cannot be attached over the gypsum board. The open ceiling should not be a problem. The roof might become a problem if you choose to heat the interior of the garage.

Tom Baker

[ameijers]

I'll almost bet the block wall on the uphill side isn't sealed, and you are getting groundwater keeping the block damp. And if they double-layered the slab, it may have been to deal with a ponding problem. (Your 'hollow-sounding' comment suggests slab may have been undermined, and you have a spring channel running under the garage.) Before you throw any money fixing up the inside, figure out where the water is coming from, and make it go elsewhere. Seal the wall, put in a drain tile and drywell, regrade back yard, add gutters, whatever it takes to keep water from parking against the outside of the block or under the slab. May be worth paying a engineer or basement repair guy for an expert site survey and recommendation- your garage is a half-basement, so they are familiar with what causes problems like yours. And yes, any time when the lower part of the wall is buried and cooler than the top sun-exposed part of the wall, condesation is going to be a problem.

aem sends....