Moisture surfacing through concrete slab flooring

Hi Shibumi

I few questions for clarity.

What is the type of soil and underlying formations?

Do you have a slope in your stand?

Are you at the foot of a hill?

Do you know what the natural water table is?

Are there any drainage restricting structures next to your house?

What type of roof do you have?

Is there any water dripping of the ceiling? (or water stain)

The wet spot surrounded by a soggy spot remind me of a case. The pressure vale on the geyser had a leak and a thin stream of water landed on the ceiling and formed a dam. The water then found a weak spot and dripped onto the carpet. The place where the water landed were wet and it drained away to the side.

Not entirely sure of soil content but I do believe the soil may have a fair amount of clay in it. I only say this because when I was out digging in one of the flower beds in the yard I pulled quite a bit of clay out. My land plot is pretty flat and we are not at the bottom of any hills . Not sure about the natural water table but we are within a few miles of the bay. No structures that I can think of that would interferior with drainage? The roof is ceramic tile (mexican style). My first thought was also water from the ceiling so thats where I started, it's bone dry.

Is the slab in question above or below ground level?

The slab is above the ground level

It's a little difficult to believe that a slab above ground would pass that much moisture. Not that its impossible but the ground would have to be pretty saturated for a while and the concrete laying directly on it with no drain field at all. Just a thought to look at other sources. Condensation against the cold concrete from the high humidity over the rainy week? Broken water line under slab flooding the drain field mite not have been a problem until the rain? Kids spilled something? Then there are the pets? Just thoughts.

I live in california and it's been raining quite a bit in the last week or two. I suspect the groud has absorbed what it can. As far as I know all my water lines are up in my attic. I'd certainly hope none are beneath the concrete. I'm sure I'm seeing the water now due to all the wet weather. But it rains a lot in this area during the Winter/Spring with March and April being the worst months. House is in Newark, CA and was built in 1987? I think. I only mention this in case someone out there knows of the common building materials used at that time.

One way to find out dig a hole down out side the house see if you hit water that will tell you if the ground that saturated. Of course unless it's still raining.

The main water line is under ground into the house. Comes up some where in the wall to get to the attic. Where's your hot water heater mostly comes in close to it.

Hot water heater location is a bit odd in this house. It's actually outside, at the end of my driveway, next to the garage door. It's got it's own "closet".

After looking at the photo's may want to check your tub may have a leak there. They don't pour the slabs perfect just close. May be depression in which the leak is run to. Check the dampness of the carpet in that direction. May be pull it up along the wall.

Could be drip from the drain or leak from the plumbing.

Hello shibumi

You don't give your location, but try Google Search Terms: waterstop paint

That should give you an idea of local suppliers for a cement-rich paint to seal the concrete.

You need to totally lift the carpet, of course, apply paint coats, allowing to dry for a few hours between coats, until no further water comes through.

Waterstop paint works because the cement included in the paint (Stir well before and during application), penetrates and sets in the concrete pores, until they are all blocked off = no further moisture can "wick" through.

This above product is safe for home use.

We used to do a faster sealing job using 2-pot industrial resin, but that needs to have the concrete dry, and has explosive/toxic vapours while in use from the Xylene solvent, so not really practical for the home user..

If the leak is not sealed, what happens is the moisture evaporates from the carpet, and further moisture is pulled through the porous concrete via capilliary action, your carpet will rot out, along with the underlay.

If possible, dig around the foundation, paint the foundation below ground level with waterstop paint too, and backfill with gravel/shingle, hopefully with an included pierced drainpipe which can drain away water before it arrives at the foundation.

It does appear the builder of your house has cheated by not placing an impermeable barrier before pouring the top of the slab.

Let's know your state of progress, please.

Kind Regards....

Thanks, that's good info. If anyone else has suggestions please jump in.

Hi Shibumi,

If your water lines run over head its a pretty safe bet that your water meter is under

ground (often in a box marked as such). Locate it and see if the line runs any place near your wet spot. Also the moisture barrier is installed under the slab prior to pouring.

Whitt

It is still not clear to me whether or not the slab sits on the ground. You state in your comment #4 that the slab is above ground, so that means there is space between the slab and the ground? Please clarify.

Opps, sorry. The slab is on the ground. There is no space between it and the ground.

Suggest you trench around the circumference of your structure. Then place perforated drain pipe at the bottom of the trench, draining to a cistern. Backfill the trench with gravel. Perhaps, the downspouts should empty into the drain pipes. This method is often used to prevent water from seeping into basements, so it should work in your case, too. If you can't perform the trenching, etc., you'll have to find a contractor.

If you can prove the slab had water seeping problems prior to your purchasing the house, and the problem was not revealed to you before you signed the papers, you have a good case against the seller(s) for reparations.

Just out of curiosity : did the seller, agent or neighbours mention any underlying water problems?

Clay has the nasty habit of swelling in wet periods and the weight of the slab may act as a plunger and create enough pressure when the escape route of the water has been close off.

Did the puddle became less now that the rain is gone?

Built in 1987, Foundation errors must have shown up by now therefore the source of the water need to be found.

I am not sure but I thought I saw California somewhere above. A tremor may have caused a pipe to crack or disturbed the joint and dripping water will flow horizontally on the slab and accumulate at a low point.

You may have to start testing for leaks.

Water supply : Close all the outlets (not even a drip) take the water meter reading (the position of the floe indicator as well) wait a while and do again. any unaccountable movement will indicate a leak.

Shibumi:

You might want to check around the house next time it rains for puddles that form against the foundation. You should always have a slope away from the house near the foundation and, if feasible, you might consider backfilling to create drainage slopes. If your land is completely flat, that may require some trenching and pumping to move the water away from the house.

Eaves and downspouts should also be designed to move water away from the foundation. You do not want conditions that support mold growth in the house. Good luck.

DickL

It might be best to wait with trenching until you are sure of the cause, Trenching while the clay is that wet may allow the clay to move to the sides and then leave a void underneath the slab when it dries out.

Random trenching might also weaken your case in the event of a claim in connection with non disclosure.

If all other possibilities of causes has been ruled out it will be in your interest to get professional help (engineering and legal).

I had a similar problem once, I did not have any water spots in the ceiling and my roof appeared to be in good shape, no sign of leaks. I found that my air-conditioner pan was full and water was running along a wood beam and once it came to the split where the wall was it decide to head south. It appeared in the room as if the floor was just getting wet because I saw no sign of dripping or other tells of a leak.

my point: if the wet spot is near a wall check the attic above it and look for leaks not just directly above the spot but all over because water can run in a little bitty space, a long way, virtually unoticed.

Good luck (hope its not a cracked foundation allowing the oversaturated (and swollen) ground push water up and through.....a little leak is much easier to fix.

Hi shibumi,

As Hendrick says, clay can cause nasty problems. I wonder if at some point the clay has shrunk during a dry period and caused a tension crack on the underside of the slab (One that has not quite reached the visible surface) - even with the wet weather swelling things back to 'normal', the route for water ingress is still there. You have a very specific location where it starts ( the 2" spot). Maybe one of the others can advice you on the risk/possibility of taking a core out at that spot so you can inspect the integrity of the slab ? You'd have to be clear on any hazards, and check on the usefulness of any information gained. It sounds very much like you need a qualified Geotech on site to assess this.

Best of luck.

Dear Sir,

It appears that the vapor barriers that should be installed beneath a concrete slab on grade floor were not installed or have failed. While placing a vapor barrier between the concrete slab and the carpet (using a thick HDPE or other plastic barrier so that it can withstand the wear and tear of shifting carpet on concrete) would provide you immediate protection, I am concerned that, having wetness trapped between the slab and this new barrier is an open invitation for mold and anerobic conditions that may prove to be unhealthy in the long run.

It is quite likely that moisture will continue to get to the floor due to capillary action, even if your floor is higher than the immediate grade.

I cannot tell if the source of the moisture is a temporary rise in the water table due to more moisture infiltrating down or if surface water is finding its way to beneath your slab. Unfortunately, short of visiting the site, you may have to make this determination yourself. If surface water ponds near your house, you may want to construct a cutoff trench with drain tile around the perimeter of your house. This trench should be constructed similar to a french drain. It is better for you to discharge the runoff by gravity to the surface, but you indicated that the land was flat around your house. So you may have to connect it to a sump pump. Whereever you discharge this water, make sure you put a valve in the line to prevent backflow (water coming back up the pipe).

However, if the water is rising ground water and there is not sand already beneath your slab, you will have a constant problem every time there is a "rainy season".

Another solution, though more expensive, may be to install a very shallow well near your hose to draw the ground water down. This would be somewhat similar to the sump pump, but at a deeper depth (say 5 to 15 feet deep). If the sub-grade soil is truly clay, this may not be very effective. This solution would probably require that an exploratory hole be dug to ascertain the soil conditions before paying to install a well that may not be functional.

Sealing the concrete will provide a temporary solution. In addition, injecting urethane in any concrete cracks will stop the flow of moisture. But the concrete will crack again some day which will providea new path for water to seep through. Plus, you would have to tear up your carpet to seal the concrete. You should investigate the other solutions because they would provide a permanent solution without disrupting your life. But they do require money and a fair amount of effort. You may be better off just sealing the concrete and injecting urethane in cracks everytime the problem arises. Who knows, you may seal and inject once and be good for ten years. Incidently, the urethane has to be inected while there is wetness. This is because moisture causes the urethane to swell and then plug the cracks.

I think you should consider hiring a professional, because as you can see, there are a lot of items to consider in determining the best solution for you.

Thanks again for all the advice. You guys are a great think-tank!

I've posted some photos of the exterior perimeter of the house to give everyone an idea of what I'm dealing with.

http://members.aol.com/littlehoss/house/house.html

From the looks of the stains on the concrete walkway, alongside the bedroom and between the next building, it appears that there is rain runoff that falls from the roof edge onto the walk. Apparently, there is no rain gutter along this roof edge, or the downspout is plugged, so all of the rain dumps between the two buildings? This certainly needs attention, and may be the root of your problem. The first thing I would do would be to place a run of gutter along this roof edge to dispose of the water appropriately.

Can't actually see a gutter on this roof edge in any of your photos. Am I correct in assuming there is no gutter?

I believe there the gutters are all in place but a good cleaning certainly can't hurt. That's a good and easy "Step 1".

This is just observation, but might be of help;

If you draw a line from the centre of your bath, thru the bedroom damp spot, it appears to meet the external down pipe (on the walk way). Next look at the distance from bedroom damp patch to external down pipe - it appears to be the same as the distance from downpipe to damp patch at front of patio. Is a common drain being used ? I ask because the lengths appear equal and at 90^o to each other. The dampness around the down pipe (picture 3) might indicate that the pipe jointing was l done wrong throughout the property.

In all likelihood, you should have some water and sewer lines under your concrete slab, this is a common practice in northern california. Given the amount of water you are talking about and the localized nature, I would suspect a leak in a line (assuming you have eliminated other common things like people and pets). You should have a plastic vapor barrier under the sand bedding underlying the concrete slab. However, I have seen Plumbers come in at the last minute and break through the barrier to make repairs/modifications before a pour. Also, concrete guys sometimes penetrate the barrier with shovels (time is money for these guys, and no one really sees it. Depending on elevation, in the SF bay area, groundwater can be quite shallow (e.g. with in 10ths below surface at Moffett Field and parts of Santa Clara/ Fremont/ San Jose/ and Newark). What can happen is the water table rises, the fine silty clay bay muds have a high capillary rise (maybe a foot or two), the perimeter around the building is saturated from rain, and there is no where for the water leak to drain off too. Near the east side of Newark, you are near the hills of the coast range, and could see seasonal artesian effects during periods of heavy rains, also. the Bay mud tends to be deposits of clayey silts and sandy silts, with stringer of medium to fine sand running through it. So ground water moves similar to fractured rock patterns, just slower.

When I lived in Northern California, I had several friends (3 people) whose homes had leaks like you describe. MID 1980's to 1990's tract homes. (All looked alike) They were all near a bathroom (One wall away) and was caused by a broken water line under the slab floor. One was actually in the slab and when the house settled and the slab cracked, so did the pipe. That one was easy to figure out because the puddle was actually warm since it was coming from the hot water line. They had to tear up the carpeting and cut and break up the concrete slab to fix the leak.

Another thing that others have mentioned. Water can be very tricky. A roof leak on one side of your house can show up as a puddle on the other side, depending on how it found it's path down.

If it is neither of these things and is just dampness from below, look into Krystol by Kryton. It is a crystalline waterproofing compound that actually gets better over time, as the presence of moisture will "grow" the crystals deeper into the concrete. It can be painted on either side of the concrete. A relative used it on his leaky basement and had fantastic results. It lasts as long as the concrete.

http://www.kryton.com/support/tds/K210_220.php

As said before, the idea that the water is wicking up from under the slab is not that likely even in N. California at this time of year. From your description I observe that you have not removed the carpet (and flooring, if any) to inspect the concrete area of the slab. It is possible that the water is coming not from below, but from the side or even from above...and flowing (possibly along a visible or unseen crack) to a point of concentration (lowest point) where you first noticed the carpet wet spot. If water is migrating to a low spot, that would be why the problem persists even after rains cease.

Your area has had a supernormal amount of both rain and very high winds this winter. It might be a good idea to check the roof for shingle blow-off and felt damage/nail holes were water could be entering. Also inspect the attic space very carefully looking for wet insulation and for dark, wet tracks running down rafters and other members. Water might have found a hidden path in a wall cavity, down to the floor from which it could migrate to the carpet wet spot.

You stated that you have overhead plumbing in your aging house--that could be a source of water running down as well. But also, you say you don't think there is plumbing in the slab; I find that curious since that would have been the standard construction practice for "slab" houses at about the time your house was built. Is it possible that the overhead plumbing was a retro-fit...to replace problem plumbing in the slab which was abandoned...and which might be providing a conduit for ground moisture into your foundation? Or might even have a connection (thought to be cut off) to your water supply? (If there is a problem now, it's always possible that the same problem could have led to a plumbing retrofit long ago. Because Calif has hot dry summers and the thin soil layer becomes parched, it could be a problem that could escape notice for long periods until very wet years like this one.)

In short, I would say a very thorough inspection is in order--beginning with looking under that carpet before things dry out...and also trying to eliminate roof and attic space as the pathways of water intrusion.

I'll be cleaning the gutters and checking attic space very thoroughly. I'll let you all know what I find, if anything. Additionally I will check roof tiles and get a peek under the carpet to see what's really going on. Stay tuned!

Oh, I forgot to mention: be sure to check the ceiling...in case water is falling on the carpet and spreading from there--the wettest spot. With the peculiar weather pattern this winter in Calif. (with predominant nighttime as opposed to daytime rain), it is indeed possible for dripping from a ceiling to go unnoticed for indefinite periods (during nocturnal or no-one-home rain events, ceiling area becomes saturated; water finds opening or dissolves through finish paint, water drips unheard onto carpet and soaks down and spreads; ceiling stops dripping after rain lets up...people with shoes/slippers fail to notice in low traffic area....etc). It can even be difficult to tell that a ceiling has dripped. One way is direct flashlight beam held close to ceiling in such a way that it propagates (preferably) perpendicular to ceiling joists and "lands" at the joint between ceiling and the opposite wall. That joint should be visibly and clearly illuminated across the width of the wall; however, as tile/rock soaking will generally cause (albeit not always easily perceptible) sagging (which typically remains even after drying), such sagging will cast a shadow on the distant wall that occludes "sharp" viewing of the ceiling-wall joint. If such sagging were to be detected in proximity to the ceiling over-head of your wet spot, you might have found your problem source; and eliminated water sources/paths below the carpet. Go to attic and feel for wetness (or insulation darkening/compaction) in the suspected area.

There is a commercial product available, I'm not sure of the name, but I seen it at Lowe's. Its a type of sub floor made to go over a concrete slab to prevent moisture from wicking up into the carpet. Its and interlocking 3/4"x24"x24" wood panel glued to a black plastic backing thats has 1"x1" raised areas so as to make minimal contact with the concrete floor. This is not a very inexpensive fix but you may want to at least look into it as it may be a more permanent fix. This would require lifting the carpet replacing or cleaning any damaged carpet and install this product, then you'll have the option to reinstall carpet or install just about any other flooring you would like (such as that faux wood laminated flooring they have out now). There are many other ways of correcting the moisture problem, but this one just came to mind first.

Good luck BigEd Professional Woodworker

Ok, I cleaned out the gutters today and they definitely needed it. Theres no way they were draining properly. The front gutters were worse than the back ones by the bedroom but they were all filled with varying levels of mud and debris. We called the guy who installed the carpet and he said absolutely DO NOT cut the carpet. He said pull it up with a pair of pliers from a corner and pull it back. To lay it back down he said use a large bladed kitchen knife and shoe-horn it back under the baseboards. Anyway, I've pulled the carpet back to get a look. The cement itself looks good. No cracks at all, not even small ones. I don't see any puddling water under there but it's definitely damp. Some of the wood used for the carpet strips was pretty wet and thats a good distance from wet spot on the carpet and against the wall so I'm headed into the attic next to look for leaks. The spot on the carpet is beginning to take on a brown tinge and when you run your hand over it, the carpet fibers are stiff.

Hello,

I am a full time basement waterproofer from Boston MA.

Though I am not confident enough to fully diagnose your problem with out looking at it I can say this. 1) Concrete is a porous material and it is constantly wicking moisture into EVERYONE'S home. To the tune of 15 gallons a day on average. A vapor barrier should be installed under the carpet. If you are worried about mold remember this. Mold needs moisture, food, and air to survive. There should be no food and little air under your vapor barrier. 2) Hydrostatic pressure can build and send water ANYWHERE. Even though you are above grade you may need a drainage system and a sump pump. 3) I have seen thousands of houses, more than half have tried to use sealers before calling me. None of them have ever been effective.

I hope I helped some. Good luck.

generally this indicates a lack of a damproof membrane beneath the slab. if the house is old this could be true. One test to see if there is excessive moisture/ water is to cut a piece of black plastic polythene sheet say 400mm x 400mm or so, tape it (tape all the way around) to the floor and leave it overnight, if it is wet underneth, you have a problem. In most cases applying a good epoxy coating of approx 3 coats will prevent moisture coming up through the floor or you can use a cement modified slurry material (such as penetron) on the floor also.

this is not an uncommon problem on old floors where a damproof membrane was not used. basically the water is attracted to the warmer side of the slab (unfortunately your room). I suspect the problem has always been there but has not been noticed before. It probably did not show itself when it was just a concrete floor as the moisture would dissapate quickly in the open, however when you put a barrier in place like carpet (which is also warm) the moisture is attracted to the warmer side. It could also be that there is a tear or hole in the damp proof membrane at the point where you see the moisture/ water. In which case an isolated repair may be possible. I live in New Zealand and deal with this sort of problem from time to time. It generally (as long as it is only water) does not present to many difficulties to fix.

if you need any other help (albeit from thousands of miles away!!) please feel free to email me karl@equus.co.nz I do not know what obligation the carpeters had, but it can be fixed which is the main thing

I'm anxious to know what the problem was? Is there any update or fix?