Rust in the shop

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Forum topic by Teddytim1 posted 03-04-2018 04:34 PM 913 views 0 times favorited 6 replies Add to Favorites Watch
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5 posts in 2119 days

03-04-2018 04:34 PM

Topic tags/keywords: rust humidity hygrometer vapor temperature insulation vapor barrier

I have an older home in Central Pa with a brick carriage house that I use as my wood shop. In the shop I have several massive antique woodworking tools which have large heavy metal components. As the seasons transition, it is not uncommon to be very cold one day and warm with extremely high humidity the next. The shop was not heated and the shift in temperature and humidity was playing havoc with condensation on the cold equipment. As fast as the rust formed, I would dive into rust removal efforts, and it was / is driving me nuts.

From reading on the subject I’m learning the concrete floor and brick walls both soak up water via capillary action and then they release the water as vapor into the shop space. The doors are also not helping as they droop and need to be rebuilt. To combat this affect wedge the doors shut as best as I could and I purchased a commercial dehumidifier and a space heater. The heater is set for about 45 degrees. The warmer temperature does not stop the vapor, it just makes it warm vapor. The heating is so the equipment doesn’t initiate condensation by being colder than the air. As a plus the warmer air helps make the dehumidifier more effective.

I was about to put up a vapor barrier, [a huge task of taking down gypsum and peg board, insulating, and stapling up poly before putting the peg and gypsum back up] to reduce vapor coming from doors, floors and breathing bricks [Not a “B” Movie] and such when I had my mind scrambled by too much woodworking dust.

First off, because it is a shop, it does not have a houses’ normal sources of water vapor such as AC, fish tanks, showers, bathing, dish washer steam or small dogs breathing and so on. I was feeling good about the vapor barrier [which would hold vapors in as well as out], and then it hit me, the wood in a wood shop holds water. In fact, for wood, too dry [Low moisture content] is a bad thing. The building needs to hold a target relative humidity (RM) of around 35% for the wood to hold a moisture content (MC) of 7%. Being the simple guy I am, what I really need, is a shop building that will release humidity if it is too high and hold it if it is too dry. Now I am confused. Should I be putting in insulation with a backing? Is the poly the right thing to do? Is there a way to just slow the vapors? I need advice. Can you help me?

-- Tim

6 replies so far

View bilyo's profile


1112 posts in 1874 days

#1 posted 03-04-2018 05:15 PM

What is happening is that on cool/cold nights, your tools are getting cold and then when the temp/humidity rises in the morning, the moisture in the air is condensing on the cold tools. The single best and first thing you should do is properly insulate with vapor barrier just as if you were doing your home. Also, seal up your doors and windows. This alone will help greatly in minimizing the indoor/outdoor temp changes and help prevent the condensation. It will also greatly improve the effectiveness of what ever heat/dehumidification you have.

I have posted this before, but have not gotten any feedback as to whether it works for others. As a temporary measure, run a small fan during the season when condensation is a problem. The moving air will help prevent the condensation from occurring. It doesn’t take much.

View HarveyM's profile


106 posts in 2794 days

#2 posted 03-04-2018 06:02 PM

Some paints are rated as vapor barriers I.E.

I don’t know how effective it would be in this case, but it’s an easy alternative to gutting your shop.

I too would try circulating the air prevent condensation.

-- Just a Duffer

View CaptainKlutz's profile (online now)


3168 posts in 2266 days

#3 posted 03-12-2018 12:36 AM

The key to stopping condensation is eliminating the event(s) where shop temp falls below dew point of air, or preventing dew point rise above the temp in shop. Easy in principle, hard to execute in real life. Buy a temperature/humidity monitor and mount it inside shop. Having data helps you understand what is happening.

Simplest way to control condensation is temperature control.
But you need the shop temp held above dew point. Depending on where you live and humidity levels, this means mean keeping the shop at 65-70+ degrees F year round. Adding air circulation will also help achieve a more constant temperature in the shop. Note that temperature control alone will not stop condensation. If you live in topical environment, dew point can be over 80 degrees! Only way to reduce temperatures required to stop condensation events is controlling the moisture level.

Best way to control condensation events is humidity control, which requires control over exterior moisture permeation.
First on list is sealing up the work space to stop unwanted air exchange. So seal up those doors/windows like your regular living spaces. Once you control amount of outside air exchange, you can attempt to control the inside humidity with de-humidifer.
Second area to consider is unsealed wall/floor surfaces. If you have framed walls that are unfinished, then install some plywood or drywall on the walls (be sure to follow local buildings codes as garages have requirement for min thickness and fire ratings). Just adding an air space to outside will help reduce moisture levels and aid in controlling condensation. Adding insulation will make it less costly to heat the shop above dew points. You can add moisture barrier under interior drywall, but vapor barriers work best on outside to help reduce moisture in wood framing. If you already have finished walls, then focus on concrete, as concrete is a sponge. If the outside is wet, the inside will be wet eventually, unless the surface is sealed. Coating the floors with epoxy sealer and brick walls with waterproofing paint stops the moisture intrusion and will help to reduce work shop dew point.

Once you have sealed up your work space to minimize moisture permeation, condensation events will typically only happen when you open doors during rain storm, and shop is below dew point. Those can usually be controlled by small heater and de-humidifer (or a HVAC System for control in tropical/severe climates)

Best Luck.

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

View Teddytim1's profile


5 posts in 2119 days

#4 posted 03-12-2018 02:23 AM

I agree with everything said. I wish it would be more along the lines of leave to aspirin on the work bench and that should cure it. Looks like the shop is in for a major rework.

-- Tim

View Fresch's profile


489 posts in 2693 days

#5 posted 03-12-2018 03:04 AM

I run a paddle fan 24/7 .

View Pizzadave's profile


125 posts in 854 days

#6 posted 03-12-2018 03:51 AM

I have a similar issue with my shop. It’s in a garage and it does have a vapor barrier although I only run heat when I’m in my shop. Therefore, rust tends to show itself from time to time on my cast iron tables and such on my machines. I have found something that takes the rust off, seals the metal and lubricates without residue on my work. It’s pretty amazing stuff.
Seal 1 is the name of it and they use it mostly for gun cleaning but I have found that it does wonders for all rusty items. Spray it on. Let it sit. Rub it off with cloth for minimal rust and I’ve had to use a sequence with steel wool down to 0000. I know this doesn’t really answer you post but it may help to get rid of the rust. Not to mention… it’s 100% non toxic. Hope this helps.

-- Dave, NY, It works-It really does!

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