I own a slabed home and i’m going to be renivating the bath soon. The house was built in the early 50’s. no thermal break or vapor berrior underneath the slab. an suggestions, use a water proofer on the slab before i renevate or another product?? would this hurt the integrity of the concrete over long term?? thnks for your time
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Do you have a moisture problem now? If you are tiling, thinset an isolation membrane, preferably Ditra or Protega, which are both plastic sheet products, to the slab. Taped at the seams, these products will provide you with a VB. No harm should come to the slab in the renovation of your bathroom. I'm not a big fan of the liquid VB or retarders. The vapor pressure from the concrete eventually causes them to fail, mind you that might not happen for 30 years or so which may be acceptable to you.
thanks for the info, do you think it would also work under hardwood or carpet????
No you would not want to use Ditra (Made and sold by Shluter) or Protega underneath those materials. They are sold for the purposes of an isolation barrier for ceramic, porcelain, and other types of tiles. There great for bathrooms because water that is splashed on the floor from the tub or shower also can't penetrate to the substrate underneath. In order to glue hardwood down to the slab you need to determine if any moisture is present. Loosely tape a piece of plastic 12" x 12" to the slab (Tightly sealed on the edges); Wait 24 Hrs and see if moisture accumulates underneath. If moisture is present you can not put hardwood or carpet down over that. You will need a vapour barrier (VB). This test should be done in the spring when the water tables are rising and your slab is breathing in or taking moisture from the ground underneath and discharging it into the house. During certain times of the year the concrete in the slab is either getting rid of moisture from the house by transmitting it to the dryer ground underneath or accepting it from the wet ground etc etc. This occurs at different times in different types of climates. If your water table is always high then you can do this test at any time.
i didn't do that test, its funny you say that because i have a real problem with moisture in this house. I thought it was the way my front yard was dumping water against the frost walls . but i put in a curtain drain, didnt help much. this is becoming a serious problem. that is making me think twice on keeping this house.
thanks for the info
You don't have to get rid of the house just yet. You can treat the humidity condition with a Heat Recovery Ventilator (HRV). Do you have such a beast or even just a whole house air exchanger? These machines remove moisture from your house by exchanging the drier outside air for the moist humid air in your home. The HRV has a heat exchanger core that recovers "some" of the the heat from the exhaust air stream. The curtain drain was a fine idea but what did you do with the drain tile from around the footings. Is it terminating in a dry well further away from the house and or is it going into the storm drainage lateral (If you have one of these)? If the water from the curtain drain has nowhere to go it will saturate the ground underneath you slab and migrate from there into the house. If you like the home don't throw it away yet. In either case, if you sell the home you will want to fix the problem for the next homeowner or at the very least disclose the condition to them. Not fixing it could lead you to lose money on the sale, and goodwill from those whom you sell to.
I have the curtain drain ran to a dry well, down slope behind the house. I've inetrgrated a french drain in there also. I don't have the option of daylighting the drain pipe,(what i would perferre to do.) I have not heard of a hrv system. i would assume it would work in conjunction with a forced hot air sysem. I have a cicr. hot water system. Can one of these systems be retrofited for my application, knowing my heating system???
You can not integrate an HRV with Hot Water Baseboard (HWBB) An HRV can be installed stand alone, but it involves duct work, drywall/plaster work etc. A good contractor can minimize disturbed areas but not all. You can use closets, attics (Though not recommended) , and other less used areas to run the ductwork. It is a pain with your HWBB and may not be a viable option for you. If you like cool air in the summer though, you could probably integrate some of the ductwork from a air to air Heat Pump to do double duty using damper valves etc. You would get two birds with one stone there. Talk to a reputable HVAC contractor in your area and get your options.
Edited 11/25/2008 8:11 pm ET by losh
Is it possible you have a leaking water pipe under the slab? Slab foundations are installed after the rough plumbing has been routed. Penetrations through the slab should be wrapped and under ideal conditions, pipes should be insulated, especially hot loops. If your home is from the fifties, maybe you've got a leak under the slab that's hidden.. One post here suggests using 12 x 12 inch plastic taped to the floor over night. That works very well for indicating subsurface moisture coming up through the slab. If you've got a true moisture problem, it can be solved but it may take some time find the source or sources of your problem.
One option that I found works, or seems to, is mixing latex admix to your dry thin set prior to putting down tile flooring. Suggestion: Acryl 60, acrylic admixture solution. This is used to water proof pools and it really keeps the water at bay but it's usefulness is limited to just the area under the tile floor. If your not going to install tile then that suggestion isn't going to work. Beware, slab floors always have a crack or two that develops over time which will defeat the above thin set suggestion somewhat.
I thought that was the problem when i first bought the house. one of the plumbers from the job site recamended putting a gauge on the hot water line from the boiler that checked out ok. I cant tell you how fusterating this problem is. I heard if i put a pressure gauge on the washer fill line and shut the main off for a period of time that should also show a leak. does anyone have a suggestion on diagonosing a leak in the hot water baseboard system???? thanks for everyones info,
another thing that i know for a fact is that there is no vapor barrier under the slab at all.
I also have a stream that is across the street that disopears under the street and the culvert that the city has installed doesn't daylight on the other side, to be honest i don't know where it goes. if for some reason the stream goes under my house. do you think that there is some kind of legal action that i could do if alll my problems are related to the stream that the city neglacted to redirect properly???