Workshop humidity control advice wanted

[Matthew N. Masail]

So I'm moving into an apartment soon which does not have a room for me to have a workshop, but the house is build into the rock so I do have a wonderful storage space with one wall being the outside wall of the house and the other is a natural rock wall...! how cool is that huh ? :) in any case it is long and narrow and I'm thinking it could make a good work space, the issue is that the concrete floor floods with about 2mm of water during winter, the landlord said the contractor is working on fixing it but in general it is humid much like a cave would be. since renting a separate space for a shop would cost me quite a bit, I'm considering the option of building a slightly raised wooden (Ipe) floor to keep me away from the water and buying a good system to balance out humidity. my main wonderings are:

1. The room is about 16 feet long X 6 feet wide. a dehumidifier that can take 10-20 liters of water out of the air per day seems to run about 700$. does anyone here have experience using one to control humidity?

2. I think it would be wise to buy a good Hygrometer to see what I'm up against. I'd love some recommendations. is this something where is pays to buy an expensive one?

3. any other thoughts on the matter? feel free to tell me what you think as I've never done anything like this before.

Thanks a lot,
Matthew

[Tony Leonard]

I've been running one in my shop for may years. My shop is 16x20x10 concrete slab and cooled by a window AC. I'm not sure what the capacity of the dehumidifer is. It is a typical big box store type though. The bucket is probably 1 1/2 gallons? I have to empty it almost dail this tie of year even with the AC running. I keep the AC set to a high temp to save evergy. Often wondered if I would be better off keeping it cooler and drier witht the AC? Anyway, it works just fine. The control for the dehumidifier gave up (twice) so I built my own. I keep the RH to around 50%. I only run it during the Summer. Not sure this will help you much. You might need to figure out how to calculate how much moisture you need to remove (at what rate) given the temp/humidity/volume. Perhaps there is an AC engineer on the boards that can help? My dehumidifer was only about $200 as I recall. Until the water issue is fixed though, you might be fighting a losing battle!

Tony

[Jim Koepke]

My problem with shop humidity isn't as bad as yours. One thing learned is dehumidifiers do not work well if it gets close to freezing.

A closed cabinet or other storage with a golden rod heater may be a solution worth consideration.

http://www.leevalley.com/us/garden/page.aspx?cat=2,2260&p=69378

Some sources have lower prices than Lee Valley. Most sources are gun or hunting supply shops and I am not up on any restrictions on their shipping to Israel.

There are other brands of these. The Goldenrod brand is the 'gold standard.'

jtk

[Jim Koepke]

Another thought, some dehumidifiers have an outlet to attach a hose for a drain so you do not have to empty the catch basin.

jtk

[Matthew N. Masail]

Indeed the dehumidifiers I looked at have an option for a hose. 1 1\2 gallons is about 5 Liters so the ones I'm looking at might be 2-4 larger than a regular box store ones, I don't know if I need that or not, but I will indeed consult the company before making a purchase of that size, I mean, I could get 2 sets of carving tools for that ! :eek:

I wonder if Tony is right though.... if there is water "underneath" my floor, is that a lost cause? I haven't made a shop there yet, I'm just exploring my options .

[Christopher Charles]

[Just went to post a reply but disappeared-apologies if a duplicate]

I'd guess that a dehumidifier would a bit like pushing on a rope--with standing water the constant evaporation would likely keep the relative humidity near saturation. Thus, may be better to focus on assuming high humidity and a system to keep tools in good shape despite that (good dust free storage, a goldenrod, etc.). The latter also has the advantage of being relatively portable...

Good luck with your genuine man cave!
C

[Allan Speers]

I would also consider trying to stop as much water & water vapor from coming up as possible. You say the landlord is working on that, but in what way? If just a pump, then there's still water underneath, which means humidity through the concrete.

I suggest putting some kind of sealer into the concrete. That way, if the landlord has some kind of pump system installed to keep the actual water table from rising into the area, you will be dry as a bone. You first need to fill in any major cracks, which is tricky but do-able. (the proper way to to grind a sort of "dovetail" shape into the crack, before filling it.)

I did my horribly-damp basement 2 years ago with Radonseal. (plus a french drain) The Radonseal soaks completely through the concrete slab, and chemically bonds with the lime, or something. I now I barely ever hear the dehumidifier kicking on. If I spill water on the floor, it beads up & rolls around. Just wonderful. I now plan on doing my garage-shop with the stuff. I've noticed that anything left on the garage floor gets massively rusty in a short time, even though there is no water. I've suddenly realized that this is ground moisture seeping up. (Duh!) The money spent on the chemicals should be far less than the dehumidifier electric costs it will save me over time.

Other products to condsider are "Conseal 100" and "V-Seal." I went with Radonseal primarily because (at that time) it was the only one specifically sold also for stopping radon, which I had a problem with. I think that JUST for water, V-Seal might be the best.

- But with any of these, it's a good idea to also use pumps, as too much water pressure can eventually cause new cracks to form.

[Matthew N. Masail]

LOL I truly truly want to work there! something inspiring about having part of a cliff as a wall....

I'ts not just the tools, it's more the wood and finished produces. if I build a guitar in 100%RH, it will probably crack within days of taking it indoors..

[Allan Speers]

Say, this is the Neanderthal forum. I don't think electric dehumidifiers are allowed, are they? I mean, you have to plug them in.

You'd better get those hanging bags of salt, with the buckets underneath. Humidity control, the galoot way! :)

[Matthew N. Masail]

I would also consider trying to stop as much water from coming up as possible. You say the landlord is working on that, but in what way? If just a pump, then there's still water underneath, which means humidity through the concrete.

I suggest putting some kind of sealer into the concrete. That way, if the landlord has some kind of pump system installed to keep the actual water table from rising into the area, you will be dry as a bone. You first need to fill in any major cracks, which is tricky but do-able.

I did my horribly-damp basement 2 years ago with Radonseal (plus a french drain) and now I barely ever hear the dehumidifier kicking on. If I spill water on the floor, it beads up & rolls around. Just wonderful. I now plan on doing my garage-shop with the stuff. I've noticed that anything left on the garage floor gets massively rusty in a short time, even though there is no water. I've suddenly realized that this is ground moisture seeping up. (Duh!) The money spent on the chemicals should be far less than the dehumidifier electric costs it will save me over time.

Other products to condsider are "Conseal 100" and "V-Seal." I went with Radonseal primarily because (at that time) it was the only one specifically sold also for stopping radon, which I had a problem with. I think that JUST for water, V-Seal might be the best.

- But with any of these, it's a good idea to also use pumps, as too much water pressure can eventually cause new cracks to form.

Thank you Allan! I has asked but didn't know if there is a way to water seal concrete!
I don't think there is a need for pumps, right now it's summer and it's dry with just "cave" moisture, in the winter the water seeps in but I was told its only a very shallow layer on the floor, considering I'm "half way outside" that sounds not too bad to me. the builders are supposed to dig some kind of tunnel to redirect the build up of rainwater or something like that, and they said they will do it before the winter, so I'll just have to wait and see. I'm thinking a smart first step should be to get a good Hygrometer and hang it up once I move in.

[Matthew N. Masail]

Say, this is the Neanderthal forum. I don't think electric dehumidifiers are allowed, are they? I mean, you have to plug them in.

You'd better get those hanging bags of salt, with the buckets underneath. Humidity control, the galoot way! :)

I would bow my head with shame if you hadn't just admitted to owning one yourself ! lol we are modern Neanderthals

[ian maybury]

Not sure what your climate is like but +1 that you probably need to stop the water coming in Matthew, as it's unlikely that at the air change and water removal rates delivered by any reasonable dehumidifier could beat a large floor area evaporating water. Especially if the room temperature is any kind of comfortably warm at times. It'd also leave you exposed to a high risk of rust and other problems in the event of say a power failure or dehum failure too.

+1 also that care is needed with domestic dehumidifiers, in that as Allan their capacity often falls away to pretty much nothing as the temperature drops. Presumably because most are designed to remove moisture at normal living temperatures, and the refrigerant media won't evaporate fast enough to get the job done (if at all) down near (our) winter workshop temperatures. Which isn't to say that maybe there are not some different domestic types on your market capable of doing the job. Many don't have any meaningful tech data attached, so you can't even figure what it's capacity at its minimum operating temperature actually is - they tend (here anyway) to quote just a capacity at a fairly typical room temperature. Many don't have a %RH adjustment option either - it's entirely automatic and they may run some sort of fancy chip controlled algorithm that targets differing levels of % RH at differing temperatures to maximise economy.

Presuming inability to maintain a comfortable room temperature in the shop all of the time it's possible that a contractor type/one designed to remove moisture from the air in a recently plastered room to speed the drying might be a better bet, but definitely establish capacity at a given %RH (say 45 - 50% = 8% approx wood EMC?) curve down to your expected minimum workshop temperature before committing to anything. They tend (predictably) to be much heftier and quite a bit more expensive. Guys like EBAC do purpose designed workshop de-humidifiers i seem to recall too - a bit more expensive again but in materials/designed not to be damaged the potentially slightly acidic nature of wood dust.

If you want to really get serious about sizing the dehum it's possible to sit down with a psychrometric chart as used in air con. (somebody in the field might help out) Starting with baseline assumptions about outside temperatures and humidities, and ditto for internal and air change rates and water gain from people/floors/drains etc you can estimate the required water removal rates.

Watch out too for the possiblity of large volumes of hot and humid air getting into the shop when the doors open etc, and cooling rapidly on your rock face - this could possibly cause rusting problems due to condensation as a result of temporarily overwhelming the dehumidifier. Not sure how it plays out in practice (as in how much wood responds to short term temperature and humidity changes - maybe somebody has experience?), but it may be best from the point of view of properly conditioning wood to try to maintain fairly consistent %RH at least in the shop. Consistent temperature would likely be even better, but may be too expensive. ..

[Dave Beauchesne]

Matthew:

Several good replies from the gang.

As a HVAC guy, I have much experience with humidity problems / control, but the issues where I am are lack of humidity due to colder climate location. I can't say I have experienced working with a rock wall!

Some things to remember:

Humidity always moves from a more humid locale to a drier locale. If there is water at 100% relative humidity under your concrete slab, and it is 90% RH in your shop, the moisture will travel towards the drier locale, very rapidly. Water vapour will travel through an untreated concrete slab or cinder block wall like it wasn't even there.

Paint is useless ( even oil based ) UNLESS it is formulated to be impervious to water vapour. Specific epoxy formulations work well, and the Radon impeding product looked very promising to me. The proof is in the result: dehumidifier ran much less.

As for the sizing of a dehumidifier; the problem will not go away if there is an ' unlimited ' amount of moisture available. I would wait until the ' pooling water ' problem is remedied: hopefully they can channel the rain water away. As stated, if you have a situation where you can ' hydraulic ' or have water pushing up on your slab from below, disastrous consequences can occur. There are physics involved here, and water is a powerful medium in many way.

Pumps keeping water away from not being able to be in contact with the slab may be the best solution. If there is a vast amount of potential water vapour ' right there ' ( under the slab ) it will find its way into the drier shop.

Good luck!!!!

[Tom Stenzel]

Say, this is the Neanderthal forum. :)

Can't get more Neander than a cave for goodness sake!

-Tom

[Joel Goodman]

I doubt you will dehumidify standing water -- the important thing is to figure out why it's there and how quickly it will return if you pump it out. I would put a small sump pump in the lowest spot and see what happens. A friend had to have channels cut in the concrete to make a low spot for the sump pump and redirect rainwater away from the house to have a dry basement. If there is a lot of water coming in you will not solve the problem without redirecting it.

[Matthew N. Masail]

Thanks so much guys, I understand now pretty much what I need to do if I want to work there, this was a great help.

[Stanley Covington]

I don't know your landlord, but in my experience, when they say the "contractor is working on it," they often mean they have talked with a contractor, but the cost was too high to actually do anything about the problem in your lifetime.

It is a safe bet water is ponding on the concrete slab because of positive groundwater pressure pushing it up around the slab's perimeter, or through cracks in the slab. The only certain resolution is to relieve the pressure. If the concrete slab is placed on soil or gravel, you may be able to solve the problem yourself, but if it is sitting on rock, then the problem is much more difficult.

Assuming the slab is on soil or gravel, buy a sump pump with an automatic float switch. Then buy three or four feet of plastic sewer pipe or storm drain pipe big enough to contain the pump and switch. Layout a circle at the centre of the slab matching the diameter of this pipe plus 2 or 3 inches extra. Use a hammer-drill with a masonry or concrete bit to drill holes around and just inside this layout circle. Break out the concrete with a hammer. Use a stone chisel to clean up the edges of the hole. Use a post-hole digger to dig a hole in the soil deep enough to accommodate the pipe, pump, and switch. The deeper the better.

Drill holes in the sides of the plastic pipe to allow groundwater to enter. Wrap the pipe in geotech fabric (filter fabric) to keep soil from slumping into the pipe, but allow water in. Place the pipe in the hole, with the edge of the pipe recessed below the edge of the slab enough to allow a lid to rest on the edge of the pipe, and flush with the top of the concrete. Fill the gap around the pipe with sand or fine gravel, and place a couple of inches of larger gravel in the bottom. Place some grout around the perimeter of the pipe to from a nice solid lip for the lid to rest on.

The lid can be a pre-made plastic product to match the pipe, or you can make one from concrete with rebar or reinforcing wire, or even exterior grade plywood will work if you are willing to replace it periodically.

The pump is connected to an outflow pipe that comes up through the lid and runs over the surface of the slab, but a better solution is to cut a groove in the concrete using a grinder with an abrasive (or diamond) blade and chip out the waste with your stone chisel. Place the pipe and cover it with an inch or so of concrete or grout to make a level surface. The power line to the pump can likewise be inset into the slab in the same method using plastic or steel conduit to protect it.

The outflow pipe needs to get outside the building, or to an internal drain, but I don't know your layout, so can't give better advice other than to remind you that there is a limit to how far your pump will be able to move water vertically. Confirm the vertical distance you will need to pump the water before you buy or do anything.

When the pipe fills with water, the sump pump will turn on automatically, and pump out the groundwater. When the water level in the sump drops below a certain level, the pump will shut off automatically. This arrangement is used very commonly and should keep the water level far enough below the slab to prevent water intrusion. No guarantees, though.

There is no permanent way to prevent water or vapour from penetrating through a slab using a top-coat on the slab. They all either wear off, or blow off, over time, and water/vapor gets in again. But if you are willing to re-coat periodically, there are probably some good products in your area.

Keep in mind that water is eternally patient, finds every weakness, and never rests. It always has its way in the end. We can only divert it for a time.

Stan