Garage Moisture Problem

[cjthorley]

Hi Guys,

I wonder if someone can help me.

I have a single garage attached to my house in which I store a 1965 Mk1 Cortina.

The problem I have is moisture is forming under the car when it rains outside. I have sealed the garage and installed a dehumidifier which is working but fails to drop humidity below 80% when it rains out side.

The garage does not feel damp but you can clearly see moisture on the underside of the car and its wet to touch.

I dont really know what else to do.

Chris

 

[Lippyp]

Sounds like theres probably no damp proof membrane under the floor to stop water making its way through the concrete floor. Not an easy fix really other than dig it up and relay it. IME you either need a very well sealed gareg and a dehumidifier or plenty of ventilation to stop damp, having ventilation and a dehumidifier doesn't work as you're just pulling damp air in. I'm assuming all the gutters are good around the outside and any drains are clear. Is there a possibility you have a water leak under the slab from a buried pipe, does your water main come in that way?

Other solution would be something like a carcoon bubble job to create a sealed humidity controlled environment for the car. Might be cheaper than sorting the floor.

 

[pattenp]

Are you in a cold climate? Standard dehumidifiers do not work well when temps are below 60F. You may need a low temperature dehumidifiers or heat your garage some.

 

[Oldbear]

As pattenp asked "Where are you?" That would help a local member give you some local advice.

 

[djjsr]

The problem I have is moisture is forming under the car when it rains outside.

Do you mean on the concrete floor under the car or actually on the chassis of the car and the floor is dry?

 

[Tim The Tool Man]

A simple temporary (possibly permanent) fix would be to place a box fan at one end of the vehicle and blow air under the car. The moisture is accumulating there because there is no air movement.

I would be concerned about the underside of my tool boxes and/or mold under any work benches as well...

 

[JakeKohl]

Hi Guys,

I wonder if someone can help me.

I have a single garage attached to my house in which I store a 1965 Mk1 Cortina.

The problem I have is moisture is forming under the car when it rains outside. I have sealed the garage and installed a dehumidifier which is working but fails to drop humidity below 80% when it rains out side.

The garage does not feel damp but you can clearly see moisture on the underside of the car and its wet to touch.

I dont really know what else to do.

Chris

Chris,

You didn't say what area of the country you are from either - if you are in the southern US (where I am) and have been experiencing these giant temperature swings (38 F to 72 F in 24 hours), the concrete may just be sweating because it's colder than the air in the garage (like a nice glass of iced T).

Other ideas, are that you are getting moisture under the slab in the garage and it's permeating through...which doesn't exactly explain why it's more under the car (the sweating action does tend to explain this nuance better). Options may be to grade the ground away from the garage better to control the water or to pull up the floor, put in a vapor barrier, repour the floor. The may be some other sealer options but if you're getting that much water through the slab, the sealers will probably fail over time.

 

[gpalmer77]

Mk 1 Cortina and a damp garage = UK somewhere?

 

[Modifieddriver]

A simple temporary (possibly permanent) fix would be to place a box fan at one end of the vehicle and blow air under the car. The moisture is accumulating there because there is no air movement.

I would be concerned about the underside of my tool boxes and/or mold under any work benches as well...

That's what I do, except I use a higher velocity fan. In about 30 minutes the moisture is usually gone.

Keep the air moving, keep the door closed and add a small space heater.

Seems like a sudden temperature change, like 20 degrees, bring this condition on especially when there's high humidity. It happened here yesterday. We went from mid-40's-low 50's to mid-60's. Stuff turns wet, especially cold concrete floors and cold metal.

 

[Vinci]

Car Capsule

 

[kywildcat]

Was 70 and humid here in KY yesterday and my floor sweated bad. This usually happens in late March or early April every year. I always mop my floors up when this happens and throw the fans to them.

 

[justanengineer]

Car Capsule

BWAHAHA!!! Holy **** thats ridiculous. I hadnt seen that before, thanks for posting. Now I just need to clean coffee off the screen.

For a moisture problem, I would suggest heating/air conditioning your garage as appropriate to remove the moisture. Yes, there are times spring and fall where you dont "need" to do so for your own comfort due to temperature, but if you set the thermostat a lil hot or cold you can keep it dry year round...ASSuming of course that your garage is decently sealed, insulated, and has good windows/doors.

 

[Kevin54]

If you can get your meathooks on one somewhere, pick up a furnace blower and set that up to blow under the car. No one really knows why some concrete sweats and some don't and it doesn't have anything to do with a moisture barrier. My floor doesn't have a moisture barrier underneath and my floor has never sweat. My son's doesn't have a moisture barrier underneath, he's on a hill, and his will sweat so bad that he needs to take a squeegee to it in the summer. The cause is high humidity and a cold slab causing the moisture and not necessarily moisture coming up through the slab from underneath.

Moving air will work better than a dehumidifier. You could also park your car on top of a sheet of visqueen (plastic sheet) to make a barrier between the floor and the underneath of the car.

 

[plym49]

You need some air circulation. Use a fan at ground level - the lowest speed should be OK - that gets some air moving at ground level.

If that is not enough, add some vent to the outside.

You don't have your dryer vented inside the garage, by any chance? If you do, vent it to the outside and that will solve your problem.

 

[Mr H]

Here's my solution..........

My Garage is damp and cold - its made from concrete walls and floor - damp all over - its a mess - even the roof leaks a little! The car was getting very damp and I was worried about the paintwork/rust plus its a convertible. I bought myself a Carcoon - it keeps a constant flow of air over the car. The car comes out exacately the same as it went in - no damp/dust/rodents!

The worse thing for a car can be a rapid change in temperature or humidity- which can cause condensation to form. Simply keeping an airflow over the car stops this from happening - I can even put the car away wet and within an hour its dry. Last week I opened the garage and there was condensation on the OUTSIDE of the unit after 3 days of non stop rain! - inside the car was untouched.

It might seem a little OTT but stops any issues that may cost a hell of a lot more to get fixed. Got mine customised in size to aviod the "up and over" door

The unit has a metal frame - unzip the back drive in a zip back up - it takes 15 seconds. When you no longer need it you can get back a far ammount of your money from ebay.

 

[Too_Many_Tools]

Hi Guys,

I wonder if someone can help me.

I have a single garage attached to my house in which I store a 1965 Mk1 Cortina.

The problem I have is moisture is forming under the car when it rains outside. I have sealed the garage and installed a dehumidifier which is working but fails to drop humidity below 80% when it rains out side.

The garage does not feel damp but you can clearly see moisture on the underside of the car and its wet to touch.

I dont really know what else to do.

Chris

Moisture only condenses on the coolest item.

Heavy items like cars and machine tools have a resistance to quick temperature changes...and because they are cool the warmer moisture condenses on them.

Keeping the vehicle several degrees above the dew point will prevent any condensation.

I will mention that many of the problems people have in regards to this are self induced because they just can't leave the damn doors SHUT. If one keeps the doors SHUT, there is almost NO condensation problems when you see drastic outdoor temperature/humidity swings.

 

[Pluribus]

Sooner or later this thread is going to go here, so I might as well do it.

 

[Kevin C]

My old garage always had a damp slab. Part of it was that it had not vapor barrier and the other was that it was cold. The other part was the building was old and leaked a lot of air. Winter air in the Portland OR is pretty damp.

I found that the cold slab kept the floor of the car cold enough to cause condensation on the cars floor. Not only was the slab wet but the carpets always stayed damp. I figured this out when I tried to dry a car out with wet carpets. After I dried them with heat lamps and fan I let the car sit in their for a few days only to find they got wetter.

The new shop with insulated floor does not seem to have that issue.

Plus two on getting some air circulation. I used a small electric heater set on low aimed under the car to get things to dry out. Not a permanent solution but it worked. Another option is to raise the car up a bit for storage.

 

[Buford T. Justice]

I run a large shop fan and 5k hung electric heater in mine, seems to keep things pretty dry.

 

[c39er]

Moisture only condenses on the coolest item.

Heavy items like cars and machine tools have a resistance to quick temperature changes...and because they are cool the warmer moisture condenses on them.

Keeping the vehicle several degrees above the dew point will prevent any condensation.

I will mention that many of the problems people have in regards to this are self induced because they just can't leave the damn doors SHUT. If one keeps the doors SHUT, there is almost NO condensation problems when you see drastic outdoor temperature/humidity swings.

All of this is 100% right on! I never open my shop doors on wild cold to warmer temp swings till the shop and concrete equalizes. No sweating on the slab and metal.

 

[Modifieddriver]

Moisture only condenses on the coolest item.

Heavy items like cars and machine tools have a resistance to quick temperature changes...and because they are cool the warmer moisture condenses on them.

Keeping the vehicle several degrees above the dew point will prevent any condensation.

I will mention that many of the problems people have in regards to this are self induced because they just can't leave the damn doors SHUT. If one keeps the doors SHUT, there is almost NO condensation problems when you see drastic outdoor temperature/humidity swings.

I agree with keeping the building closed. I'm on my wife's *** because she can't seem to understand what happens. Open the O/H garage door to let the dog out!!!!!!!

 

[crewchief888]

we've had some MAjOR temp swings over the past week, from single digits to +60* F

yesterday was the only day i even felt like being i the garage in a couple weeks.

it really looked like i had turned a spinkler on


i've always had an issue with the floor being damp, especially in the spring,
(i know theres no vapor barrier under the slab)


but holy sheeet
it was at least 15 degree colder in the garage, and everything was sweating,
condensation was literally running off my toolboxes

 

[rburke65]

So I guess the location of the OP is still a mystery, huh?

 

[Hotrod barn]

I noticed that since I have been working on my barn that now when the temp. Gets close to the dew point that my tools and Torino are getting a little condensation.that ***** ,all my machinist squares and mics. Have started to rust.my barn needs heat and air circulation.watch the dew point and heat it if you can .
One day Last week the dew point was 3,my tools got wet.
The dew point changes every hour by the temp. and relative humidity.

 

[Too_Many_Tools]

I noticed that since I have been working on my barn that now when the temp. Gets close to the dew point that my tools and Torino are getting a little condensation.that ***** ,all my machinist squares and mics. Have started to rust.my barn needs heat and air circulation.watch the dew point and heat it if you can .
One day Last week the dew point was 3,my tools got wet.
The dew point changes every hour by the temp. and relative humidity.

Correct..it is the DEW POINT that matters...and it changes.

If the item in question has a temperature ABOVE the dewpoint, it will not have any moisture on it.

If it is at the dew point or below...it will be running with moisture.

Years ago I bought a very new expensive machine tool, bought it home and cleaned all the oil and grease off of it. Left for a few hours during which we had a big upswing of temperature and moisture...and when I got back the entire machine was rusty.

Not happy.

It took days to repair the damage.

Now I use products like LPS3/Boeshield to cover any valuable iron.

It means repeated cleanups but no more damn rust.

Rust never sleeps.

 

[olytdi]

Yes, dew point.

And, every time you bring a wet car into the enclosed space, you've got to get that water into the air and then the air is more humid inside than outside. As such, if you're going to introduce water into your enclosed space regularly, you need to have a means of either removing moisture from the air (dehumidifier) or removing the moist air (ventilation).

That said, warmer air holds more moisture so you can cheat by raising the temperature of the air and getting the water moved from where it is concentrated (on the car or on the floor) and into the air where it is more "equitably" distributed.

As for weeping, seeping concrete floors, I've found that a slab can transfer moisture from beneath it if there is a high enough water source at pad level (which isn't that common). Usually, moist floors are the result of temperature differential between the slab and the air. Warm air hold a lot of moisture that will condense on your cold slab.

So what's it all mean? Second law -- there's no free lunch. You've got to manage how much water you bring into the space, the temp of the air, and ventilation.

I was having a damp shop problems with damp floor. What I did to successfully deal with this is two pronged -- I installed a ceiling fan that blows directly down on the slab and made a ventilator on an outside wall whereby the intake is 1 inch off the floor and the exhaust goes outside through the wall. This low speed ventilator is made from 8 inch duct and an inline duct fan that operates off of a humidistat. It comes on automatically when the humidity reaches a chosen point and draws air right off the floor. No more moisture problem whatsoever. The ceiling fan helps get whatever moisture is on the car or on the slab into the air then out of the shop. You can always add heat to this equation and the air will hold more moisture that way as well. But then you start to have the problem of removing warm air through ventilation which can be expensive.

A vapor barrier under the slab is a great idea and should be standard on a new pour. I forgot to do it on my slab but am convinced that the dampness I used to get was due to condensation. My slab sits on three feet of crushed rock and is higher than anything around it so I don't think there's water pressure pushing up from below.

Hope that helps!

 

[Too_Many_Tools]

Yes, dew point.

And, every time you bring a wet car into the enclosed space, you've got to get that water into the air and then the air is more humid inside than outside. As such, if you're going to introduce water into your enclosed space regularly, you need to have a means of either removing moisture from the air (dehumidifier) or removing the moist air (ventilation).

That said, warmer air holds more moisture so you can cheat by raising the temperature of the air and getting the water moved from where it is concentrated (on the car or on the floor) and into the air where it is more "equitably" distributed.

As for weeping, seeping concrete floors, I've found that a slab can transfer moisture from beneath it if there is a high enough water source at pad level (which isn't that common). Usually, moist floors are the result of temperature differential between the slab and the air. Warm air hold a lot of moisture that will condense on your cold slab.

So what's it all mean? Second law -- there's no free lunch. You've got to manage how much water you bring into the space, the temp of the air, and ventilation.

I was having a damp shop problems with damp floor. What I did to successfully deal with this is two pronged -- I installed a ceiling fan that blows directly down on the slab and made a ventilator on an outside wall whereby the intake is 1 inch off the floor and the exhaust goes outside through the wall. This low speed ventilator is made from 8 inch duct and an inline duct fan that operates off of a humidistat. It comes on automatically when the humidity reaches a chosen point and draws air right off the floor. No more moisture problem whatsoever. The ceiling fan helps get whatever moisture is on the car or on the slab into the air then out of the shop. You can always add heat to this equation and the air will hold more moisture that way as well. But then you start to have the problem of removing warm air through ventilation which can be expensive.

A vapor barrier under the slab is a great idea and should be standard on a new pour. I forgot to do it on my slab but am convinced that the dampness I used to get was due to condensation. My slab sits on three feet of crushed rock and is higher than anything around it so I don't think there's water pressure pushing up from below.

Hope that helps!

Great post!

I had a relative who put up a wonderful shop, insulated with fiberglass and I swear had every tool made by man.

He also made a practice of driving vehicles full of snow and ice into the shop...letting the furnace do the melting...and let the water drip into a pit underneath.

15 years later...the garage rotted from the inside out...the high moisture laden air had condensed on the fiberglass insulation, soaked it and there was dry rot everywhere. The shop was gutted and rebuilt.

We also had a continuing problem of tools rusting...if they sat in a drawer undisturbed...they would be found with a layer of rust.

The lesson I learned...if you introduce moisture into the shop interior you better be voiding it to the outside if you value your shop and tools.

 

[Pluribus]

Have had the same issues with moisture in my shop, so I now use a 110-volt oil filled electric heater on the 600-watt/low setting during the winter. I figure that just by heating minimally, it will help keep it dry enough. When it gets warm, I'll switch over to using a dehumidifier. It sure was an ugly surprise when I noticed all my shelving was growing mold. For a while last year, I was drawing over a gallon a day out of my 550 square foot shop with the dehumidifier. Thankfully, I didn't have most of my good tools stored in there.

 

[Tarnished]

I too have this interior rain forest problem. My shop is in an old barn which is quite open to all the elements and can't be effectively closed up. So this week when it went from 20* to 70* everything in the shop was WET! Floors, machines, tool box, even the wood benches had a coating of water on them.
Can wright my name in the condensation

Floor so wet I can track myself

I have been fighting this for years, and don't know of a way to prevent it. Best I can do is turn on a fan to move air around and dry what I can. As others have said, this is caused by thermal mass of the cold concrete (and machines) being hit with warm humid air. Result=Condensation.
It is especially distressing to watch your lovingly restored machines RUST within hours. I try to keep everything metal coated with Johnson's wax, or paraffin & mineral spirits as best as I can, but things still rust and have to be redone.
360 days of the year I love my old barn, but those other 5 days really have me longing for a new, sealed, insulated, heated, cooled, dust free well lit place that I see in some of your shops shown here.
John Rusting away in Ohio

 

[Hotrod barn]

I am off today and after reading this again I am afraid to go out to my barn...Ii rained like crazy here yesterday.

 

[Modifieddriver]

To protect bare metal parts and equipment I use a product called RUSTLICK. I buy it from WW Grainger. About $32/gal. It'll treat parts and it'll keep them free from rust for several years. Great for those long-term projects.

What I've done on several parts of the shop is place some cheap old 4x8 plywood, T1-ll siding and even heavy duty thick cardboard under the cars. Creates a moisture free area on the floor. The car might still get condensation on it, but less from the bottom.

If you've ever been in a real old parking garage or barn with a wood floor, you'll find the moisture is not a significant problem. I've seen "barn-find" cars stored in old downtown parking garages with wood timber floors. Underneath looks great.

 

[Tarnished]

To protect bare metal parts and equipment I use a product called RUSTLICK. I buy it from WW Grainger. About $32/gal. It'll treat parts and it'll keep them free from rust for several years. Great for those long-term projects.

ModDriver: Can you tell us more about Rustlick. Grainger has a lot of listings for corrosion inhibitors by these folks. Which are you using, and is it an oil base produce or what?
Thanks.

 

[socapots]

X2 on the rust lick info

 

[Modifieddriver]

ModDriver: Can you tell us more about Rustlick. Grainger has a lot of listings for corrosion inhibitors by these folks. Which are you using, and is it an oil base produce or what?
Thanks.

It feels like some sort of an oil base and has a slight brownish color, but looks almost clear when you put it on.

I buy it by the gallon and put it in a plastic spray bottle. Use it full strength. It flows right out and covers real good. Has kind of a sweet smell. You'll find that smell in many machine shops, 'cause that's what they use on their equipment.

I use a fair amount to preserve parts I buy. Some of the stuff I treated and stored 7-8 years ago is still preserved. A quick trip through the parts washer or a blast with Purple Power takes it off.

Rust Lick #631 1 gallon Grainger#1C187 $42.80

12 oz. spray Grainger#1MKN5 $14.33

Catalog says good to prevent rust indoors for 2 years. My experience has it lasting longer.

It doesn't take much to coat a part, so a gallon will last a long time if you spray it and forget it.

 

[Too_Many_Tools]

I too have this interior rain forest problem. My shop is in an old barn which is quite open to all the elements and can't be effectively closed up. So this week when it went from 20* to 70* everything in the shop was WET! Floors, machines, tool box, even the wood benches had a coating of water on them.
Can wright my name in the condensation

Floor so wet I can track myself

I have been fighting this for years, and don't know of a way to prevent it. Best I can do is turn on a fan to move air around and dry what I can. As others have said, this is caused by thermal mass of the cold concrete (and machines) being hit with warm humid air. Result=Condensation.
It is especially distressing to watch your lovingly restored machines RUST within hours. I try to keep everything metal coated with Johnson's wax, or paraffin & mineral spirits as best as I can, but things still rust and have to be redone.
360 days of the year I love my old barn, but those other 5 days really have me longing for a new, sealed, insulated, heated, cooled, dust free well lit place that I see in some of your shops shown here.
John Rusting away in Ohio

Machine tools are tough to protect.

In your case...paint any nonpercision surface...on machine ways should be bare and have those protected by LPS3/Boeshield.

You can cover machines and heat them...if they are above the dew point moisture will NOT condense.

Bear in mind allowing the condensation to continue is destroying your machines from the inside out.

I seen many fine vintage cars ruined by poor storage...they rust/rot from the inside out.

 

[Too_Many_Tools]

Have had the same issues with moisture in my shop, so I now use a 110-volt oil filled electric heater on the 600-watt/low setting during the winter. I figure that just by heating minimally, it will help keep it dry enough. When it gets warm, I'll switch over to using a dehumidifier. It sure was an ugly surprise when I noticed all my shelving was growing mold. For a while last year, I was drawing over a gallon a day out of my 550 square foot shop with the dehumidifier. Thankfully, I didn't have most of my good tools stored in there.

Want to guess how much mold is on the backside of your walls and ceiling?

Learn how to calculate your dew point is and heat the area above that temperature.

 

[Too_Many_Tools]

I agree with keeping the building closed. I'm on my wife's *** because she can't seem to understand what happens. Open the O/H garage door to let the dog out!!!!!!!

You need to educate her.

Can she let the dog out the front door of the house.?

If the dog inside the garage, you need to build a dog house...pets inside a garage raise its humidity.

 

[ericburns4]

Using fan beneath the vehicle and blowing air under the car, would help.

 

[Oldbear]

So I guess the location of the OP is still a mystery, huh?

He seems to have started the thread with his one post and then fled the area...

Good example of why us new guys should fill out some information on our profiles.

 

[Oldbear]

And I wish i could get a moisture problem... "Udder Cream" hand lotion is am important tool in my tool box... its as dry as a popcorn fart in the shop.