Skip to comments.Moisture Sealing An Unfinished Concrete Floor - Advice Please!
Posted on 02/27/2014 5:11:03 AM PST by newb2012
Looking to moisture seal my unfinished basements concrete floor as a measure to cure and prevent mold in the house. Appreciate any suggestions, sources and references - about what kind of sealant to use etc.
If unfinished, find a downstairs roughed-in plumbing pipe for a sink, toilet, floor drain, etc. and then wire an outlet near that. Buy tubing, adapters, etc. and connect to a good capacity dehumidifier and keep it running. One with an adjustable humidistat is nice.
I did that in my basement and it is always below 50% in the summer and 30% or so in the winter....it will work for mold, and rust (I keep my guns there).
There is a product called “Anti-spalling compound” It contains linseed oil and a drying agent. I have used it on exterior walks and been very happy with it.
http://www.garagejournal.com/ Go into the forum, entire section on preparing and sealing concrete floors.
Was a vapor barrier put down before the concrete was placed?
Check with Your local Paint Store (Sherwin-Williams, etc) a lot will depend on the age of the concrete- the newer the worse time You will have, the older the better.
Concrete is always curing.
You can check with Home Depot, etc but they don’t just deal in coatings.
That’s ALL a paint Store does.
Prep is VERY IMPORTANT!!!
You will be using a 2 part coating but get the Pros at the Paint Store to help You.
If any of your guns have wood ‘furniture’, be careful not too keep the humidity TOO low. I’ve heard it can cause the wood to dry out and crack over a long period of time if the air is too dry. I don’t have this problem as ALL of my firearms have black plastic/polymer that makes them look “dangerous” to Liberals and idiots(please pardon the redundancy).
At minimum, an epoxy-based paint (pricey) and a good dehumidifier after it's applied.
If it's a new-ish pour, you'll need to wait for it to fully cure .. do a web search on recommended times.
Regardless how smoothly it was troweled, etching is recommended before any paint's applied .. etching = acid solution, most commonly muriatic.
Conversely, if the basement space isn't used for much beside storage and the moisture isn't such that things fall apart down there,
investing in a good 70 quart dehumidifier (w/ hose > floor drain) may be enough to obviate the need for messing with paint, etc.
My Garands I have oiled with unboiled linseed oil, as with the carbines and 1903s....others have been sealed pretty well, too. In the 10 years I’ve been doing this, no cracks or splits yet...(fingers crossed):o)
Use a two part epoxy paint it’s kind of expensive but in the long run it will last. I know Sherwin William has it but Home Depot and Menards and Lowes probably have it too.
Good advice regarding the local Paint Stores. Most of the people at ‘Big Box’ type hardware stores tend to not have any real idea about what they’re selling, and earn a little over minimum wage. I believe the only requirement to work in those places is having the ability to lift 20lbs, give authoritative bullshit answers, and fog a mirror. Hiring people that have actual real knowledge of their in-store departments would cut into profit margins, which are about ALL that matter for such places.....
Keep in mind that if you are having moisture being drawn through the concrete due to temperature/humidity differentials, putting a barrier seal is difficult to completely stop.
A low quality product may only make your problem harder to fix in that the moisture may build up behind an inadequate seal. That "paint" may then make it tougher to put down a better product later.
My point, based upon my father's experience with the same problem, is don't try to cut corners on your first attempt. It will make the real fix that much harder.
Do your research. Some folks have found more success running dehumidifiers in the basement.
My dad didn't find anything that worked until he spent the money on a good epoxy-type paint (expensive and a challenge to lay down quickly before it cures). The two cheaper types he tried first only created him more problems as they split and cracked as the moisture built up behind them from inadequate sealing.
They worked at first, but did not last over time. And then they had to be fully removed to get a good seal for the next product.
Poor cleaning of the surface will likely prevent good sealing as well. The best is an acid product made for cleaning concrete prior to sealing. I used these in factories where I coated floors to help with cleaning. Eventually I convinced my Dad to try what I suggested, but only after a couple years of failure with lessor products.
Good Luck! It can be a big job. Be SURE to get force ventilation through your basement (window fans) before the acid clean or the epoxy paint. You don't want to pass out down there in it, nor do you want those fumes lingering in your house.
If it’s just for moisture sealing, most hardware stores carry UGL Drylock, which works well for sealing. I’d use a 2-part epoxy on the floor if it’s not going to have any kind of floor covering laid down over the concrete.
drylock sealing paint, with a 2 part epoxy pour over it but only after it’s cured and been through at least 2 full years of seasonal changes.
I am a water damage restoration business owner, and I do mold inspections and testing in homes and businesses.
1. Ground water will travel through concrete.
2. Gravity is the answer... not sealant. Over time, the sealant will fail, and water can still enter through small cracks or pits. The only way to properly seal a concrete basement is on the OUTSIDE of the concrete. not the inside.
3. Contact a basement waterproofing professional. We have one here that uses a method of digging a 4” trough around the perimeter of the area and channeling the water to a sump pump. Water that effervesces through exterior walls travels down to the trough. Water that would otherwise effervesce up through the floor will find it’s way to the sump basin instead.
4. Avoid installing wood based products such as sheetrock in the basement. If you want to use wood finishing materials in the basement, use cedar or other mold resistant materials.
5. Keep a dehumidifier operating in the basement. A good one that moves about 50-75 pints a day can be purchased at Lowes for under $300.00
Stay away from Rustoleum’s “Restore” deck & concrete sealer!
I spent the better part of last summer preparing & painting our 800+ square foot deck with this crap. Very expensive and time consuming. I strictly followed the directions for application and it gave us a non-skid surface that looked great. That lasted until the first freeze and then started coming off in big chunks. The next rain dissolved the paint into a chocolate pudding texture that our new puppy took a liking to.
Called Rustoleum customer service and they issued a full refund ($450.00) without argument. To my surprise, two months later Fed-Ex delivered 25 gallons + rollers at no charge.
The product is total junk and should be pulled from the market. Hopefully I can find an 0bama voter to sell it to!
Reviews from other customers can be found here:
Good luck with your problem....
For researching methods, see articles at buildingscience.com:
Thank you. The floor is about 12 year old. One of the contractors that I checked with is claiming their product ( a water based Epoxy Seal)to be the best and to pretreat and double coat the floor and walls with their product at this link www.moisturesourcesandsolutions.com quoting a 3 grand. The square footage of the floor is about 700. Is that a reasonable quote?
I dont think it was.
Thank you. The floor is about 12 year old. Does $3000 to clean and seal floors and wall for a 700 soft area sound reasonable?( For 2 coats of a water based epoxy seal. )Thanks in advance.
That was helpful. Thank you.
The best concrete sealer is a silane. These coatings react with the concrete chemically. Expensive but the best.
Do NOT use any of the epoxy products sold at Home Depot, Lowes or Sherwin Williams. These are all just surface applications and they will eventually peel. If you want a true epoxy finish, you will have to pay a professional to put it down. Shop around prices vary greatly between companies.
If there was not a vapor barrier, like 6 ml poly, put under the concrete prior to pouring it there is very little you can do to keep the moisture from coming up through the floor. Therefore, you need to remove the moisture that accumulates in the basement with a dehumidifier. The UGL will work on the walls but may peel on the floor.
I am two decades past my experience with that. And my father and I did the work so I cannot judge cost to hire.
I don’t like the idea of a water based product to stop water. It could work fine, but I would search for competitive pricing.
I would spend $300 on a quality dehumidifier first and see if that solves your problem, it I had the basement.
I would follow Thackey’s recommendations with one exception. The other method prep the floor other than acid wash is to rent a diamond tip buffing wheel. It goes on a floor buffer typically used for removing and applying wax. This is what I did prior to having a professional 4 part epoxy applied. The diamond wheel removes about 1/16” of the concrete surface. This gives you the best surface prep so that the epoxy can adhere to the sanded surface. However, it is very messy and a respirator(not a nuisance mask) is a must. It also takes a lot of strength to handle the buffer when it starts across the floor. It was the toughest rental piece of equipment I have ever used, and I’ve used many.
$3.75 to $4.00/square foot sounds about right to apply an epoxy finish. If you are flexible with color it may save you if they have some material left over from a previous job. I had my kennel floor(130 sq ft) done for $500. I used a left over color. I had another bid for $800. Another for $1500. Make sure they put enough grit in the top seal coat so it is not slippery. Most of these companies will bid a two car garage for $2000-2500 to give you an idea. That is the bulk of their homeowner work.
If 30% humidity is as dry as it gets, you’ll never have a problem with the wood cracking.
After 12yrs your floor is about as cured as it's gonna get, and a good etching should suffice. The process would typically involve 3 cycles of > etch/rinse, etch/rinse, etch/rinse.
See the product's directions for acid %s, etc.
I've used the following on my own basement, and have been satisfied with the cost/benefit result.
It's a 1200 SF space, with moderate foot traffic and occasional furniture rearranging.
After etching (i use UGL Drylok Etch) is finished and the floor is *thoroughly* dry:
Two coats of a product called Epoxy-Seal, mfg. by SealKrete .. ~5 gal @ $35/gal
Followed by two coats of Clear-Seal, same mfg .. ~4 gal @ $30/gal (the clear coat goes further)
It's been 7 yrs since mine was applied, and still looks great, imho.
The few times something heavy/sharp has been dropped and caused a ding, I do a light spot sanding and the touchup applies/blends seamlessly.
With occasional ding maintenance, I can't see needing a do-over here for at least another 3ish years, and even that would only be as above: light sanding/color/clear.
A big caveat is that I wouldn't use SealKrete for a garage/shop floor .. there you're looking at a major materials expense for industrial duty epoxy.
But for your likely purposes, and assuming no environmental conditions out of the ordinary, it should prove satisfactory.
So for ~700 SF DIY: etching supplies $20, color coat $100, clear coat $100, misc cleaning brushes etc $30 = ~ $250 DIY +/- 20%
A small portable fan somewhere else in the basement, running on low just to keep the air moving, wouldn't hurt either.
Investigate a Wave Ventilation System. I have used this in my very damp Crawl Space with excellent results - I now have it below 55 percent (humidity control) set at 55 percent.
It basically draws air from the living space - draws that air thru the basement space and exhausts it outside.
Ventilation System uses a lot less energy than a Dehumidifier and is quieter.
That was a detailed estimate. Thanks. But Im hiring a contractor. Will the numbers vary drastically if I dont do DIY?
Thank you all very much for taking time on a busy weekday morning to share useful ideas . Very helpful information from my FR(iends) as usual. :)
Do you have any recommendations of a particular model of a quality dehumidifier? Thanks in advance.
As to non-dyi, it'll vary drastically given your geography, urban vs rural, contractor honesty, etc.
Ideally you've friends/acquaintances who've had similar work done and can recommend someone.
Failing that, there's really no quick/easy substitute for having guys in to estimate the job, comparing quotes, then rolling the dice.
The $3K you mentioned earlier is probably barkpark-ish, but it wouldn't surprise me in the least if you're quoted much more than that, esp. if you're urban.
Regardless, good luck with it.
Not much will adhere to an old concrete slab that has a constant supply of water feeding it.
At Home Depot, they will always answer your questions and suggest products, although they usually know nothing, on the rare occasions when I have had to go to one, I will ask them questions, and am usually amazed at the stupid answers, but they are always confidently given.
They never just say, "I don't know".
They’re exactly the same way at Best Buy. Someone can go in there needing a device to achieve some sort of solution or goal, and one of their idiot employees will have them leaving with a $700 cart full of ‘stuff’, while a simple $15 part would have sufficed(I’ve seen that happen MANY times to people I do IT work for).
I suppose that’s a GREAT business model, assuming everyone is ignorant.(more so than the store employees)
What hurts, is when Home Depot employees confidently give advice which is destructive and wrong, on matters that will cost a fortune to repair within just a few years.
As a contractor, I see Home Depot as a business that has had a devastating effect on American home repairs and remodeling over the last 30 years, they trashed the American home.
Note how in my original remarks, I referred to one of their job requirements as having to “give authoritative bullshit answers”. They must SOUND like they know what they’re talking about. Which leads to the scenario you just explained.
>> “As a contractor, I see Home Depot as a business that has had a devastating effect on American home repairs and remodeling over the last 30 years, they trashed the American home.” <<
And they have run off the legitimate operators in most locales.
In the Bay Area, it was Yard Birds that was the good operation, but Home Depot bought them out and shut them down.
Back with more questions. I did get the dehumidifier that you recommended. Moisture level in my basement currently is below 30%. The contractor who came into do some other work feels (looking at the moisture levels and also since there is no visible presence of mold ) epoxy paint might be an overkill especially since Ill be finishing the basement in a year or two. He thinks a couple of coats of concrete paint would work equally good. Appreciate any thoughts or suggestions.
You're going to find that any reputable coating intended for concrete will BLARE AT YOU on the directions the need for etching prior to painting bare concrete.
Granted it's a time-consuming chore, but it's ignored at peril of wasting coating money and applicator's time.
(not to mention voiding any possible warranty claim)
Glad to hear the dehumidifier is working out for ya .. good luck with the floor.
It is dry now because it is exposed to air that is being dried by the humidifier.
When you finish off the basement, I expect you will have some type of barrier, paneling, wallboard, etc that will prevent your dehumidifier from adequately keeping that surface dry.
You have not stopped the moisture intrusions. The dehumidifier is just drying it up as fast as it comes in. As long as the surfaces are exposed, this works fine.
If you are going to cover up that porous block and concrete, preventing the direct drying action on the surface, you should expect mold behind the walls you put up.
Unless that “concrete paint” is a complete moisture barrier, I would not use it.
Thank you for your quick reply. Is it necessary to use a moisture barrier on the walls too? I feel it is because most part of the wall is underground too.
I would think so as well.
The lowest points will have the highest moisture level.
I don’t know your soil and conditions. But you had a problem prior. I would want to be sure the problems was sufficiently protected before I spent money putting other finishing on top of it that would be damaged by mold growth.
All I can do is relate the experience I've had treating the basement in my home and several others.
This place has 140LF of exterior walls and 100LF of interior walls (both sides), so using it as an example:
After proper prep work, I applied 2 coats of DryLok to the exterior walls, taking care to get as many of the pinholes as possible.
After that thoroughly dried, I went over them again with an exterior latex semi-gloss, and did two coats of the same semi-gloss on the interior walls.
I'd agree with thackney re the problems inherent in covering concrete block below grade with other wall materials eg drywall/paneling/etc.
Tho prop prep and DryLok or similar will keep it to a minimum, there'll always be some moisture, hence your shiny new dehumdifier.
I'm not affiliated in any way with either or SealKrete or DryLok other than having used them with good results professionally.
You should still read up on effloresence, but additionally DryLok has a good web page here with a step by step overview of the hows and whys of the process.
I've had zero leaks in ten years, and only this past autumn gave them all a single coat of the semi-gloss latex only.
Tho that was only because I'm out in the country next to a big corn/dairy operation and microdust is a fact of life, weekly vacuuming notwithstanding.
But that's a rant for another day .. lol !
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