Can tile work on cracked floor due to sittin on clay deposit? [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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08-17-2009, 07:22 PM
Hi Everyone,
I am a brand new newbie and need some advice. I really, really want ceramic on my kitchen floor but we are on a clay deposit so as the soil gets wet it expands and as it dries it settles. I have cracks in the floor & some say yes you can use a membrane to stop the new tile from cracking while others say no way. We have another problem this is a very old house (1952) and our heat pump/ac is in a closet in the kitchen. We originally added a plywood over the cement and used vinyl products as recommended. We have replaced the wood floor and used vinyl products 4 times over a 20 year period due to leaks of some sort in the AC (mainly thought to be freezing up), water gets UNDER the plywood & by the time we realize we have a problem again the floor is soft and messed up so I thought that THIS TIME I would have the plywood ripped up and just do the ceramic right on the cement floor. I am sick to death of spending money on floors and would truly appreciate your advice on how best to solve this problem.
Thanks in advance!

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08-17-2009, 08:54 PM
Hi Anita

If you have cracks in your slab and there are no height differences in the slab on either side of the crack you could tile it. You do make it sound as if this slab moves quite a bit and regularly. Is that so? Ever notice any up and down or vertical displacement between the cracked slabs? If that is so you shouldn't tile it.

I think the isolation membranes do a good job. I think a cleavage membrane, wire and 1 1/4 in of well packed deck mud would be very nice. It would be a new floor over the old slab but independent of it. The slab below could move side to side, but no up and down. :)

08-17-2009, 10:01 PM
Anita - have you looked at the drainage around the house? A lot of times just getting the water away from the house when it rains will go a long way to reducing this kind of movement. I also saw an interesting post by cx that took the opposite tack - actually watering the slab to keep things from drying out. Bottom line is that you want to minimize drastic seasonal changes in moisture under your slab.

08-18-2009, 05:39 AM
possibly quite important - have you figured out what is causing the periodic flooding condition from the HVAC unit?? If that's expected to happen ever again, one might question putting that cart ahead of the flooring horse. :suspect:

08-18-2009, 06:15 AM
This is something we have been trying to get resolved for years and years.
I can't even START to tell you how many different HVAC people we have had come out, how much money we have spent & STILL we have the problem. The last guy said there is only two things that will cause the ac to freeze and that is either a freon leak or not enough air flow. Do any of you know if this is true? If it is then I need to change something about the slatted doors in the closet where it is located. There was an oil furnace in that space when we bought the house 32 years ago and this is our third heat pump.

Even if we can not stop the ac water wouldn't it make more sense to get rid of the wood floor? Right now, if you walk across th floor in front of the ac closet you can see and feel the mush the wood has become.

Now about watering our house, the University of Fl engineering dept sent some guys out about 30 years ago and they bored a hole to the clay deposit for us to water the clay and keep it as consistent as possible. Unfortunately over the years it has stopped up and we can no longer do that so should we just water around the foundation of the house?

Thank you, thank you, thank you all very much for your input and suggestions!

08-18-2009, 06:52 AM
Yes - restricted airflow CAN cause icing, but that by no means is a definitive diagnosis. If your filters are all clean, and the system is operating normally, it should never happen. (I haven't heard of freon leaks causing icing, but what I haven't heard of could fill the Library of Congress, I reckon)

At a minimum, I'm curious why you can't place a plastic or sheetmetal catch-pan under the whole thing, with a drain piped outdoors. if it's gonna make wet, then at least figure a way to make the wet stop impacting your floor.

Is the mushy floor wet to the touch now? Or just mushed / rotten from past incidents?

As to your foundation issues - call a foundation specialist in your area. There are irrigation-type systems that can be installed - some even with automated float-switch actuators - to provide consistent moisture levels to the soils around your foundation, and eliminate those fluctuations (and the subsequent movement they induce). Might be more common in sandy areas like Texas I think, but see about your area, too.

It's just me, but seems you'd be throwing good money after bad until you get those two issues fixed right and final.

08-18-2009, 07:33 AM
I'm going to get this started today! I didn't realize this was an option but I should have if I had really thought it through.
It is piped outside and I have tried the aluminum pan but that's a real pain to get out without spilling water everywhere

08-18-2009, 07:35 AM
I got my own interest level up on the freon leak thing. DEFINITELY something to think about - either a chronic leak somewhere, or some part of the system being mismatched in its original design.

Found this page very informative:

Good luck!

08-18-2009, 08:10 AM
Welcome, Anita. :)

Gettin' lots of good advice here, seems like.We have replaced the wood floor and used vinyl products 4 times over a 20 year period due to leaks of some sort in the AC (mainly thought to be freezing up),It is piped outside and I have tried the aluminum pan but that's a real pain to get out without spilling water everywhere I think it may be common for you not to have a pan and secondary drain under the unit in your type of installation. If you don't have one, I'd recommend a modification to add one. This doesn't involve removing or dumping anything, it should have a drain just like your primary condensate drain I think you're describing above. And both should be checked at least annually for proper operation. putting an air hose into the drain lines once a year, or having your AC guy do so, is likely less costly and disruptive than replacing the floor every five years, no? :)

There is no reason to be having that flooding problem. I've installed HVAC units in attic spaces as a matter of course for years and haven't lost a ceiling yet. Little good planning and design, little customer education, little periodic inspection and maintenance, is usually all that's required.Now about watering our house, the University of Fl engineering dept sent some guys out about 30 years ago and they bored a hole to the clay deposit for us to water the clay and keep it as consistent as possible. Unfortunately over the years it has stopped up and we can no longer do that so should we just water around the foundation of the house?Sounds like some knowledgeable folks have helped you identify some of the cause of your foundation cracks, too. I think it would be a very good investment to invite whomever it was who came "out about 30 years ago and they bored a hole to the clay deposit for us to water the clay" and have them re-open or clean out or whatever to make that system useful again. Periodic watering of the perimeter might be sufficient, but if you had something in place that worked, I'd sure recommend you reinstate it and use it.

Matt (matman) above has you pretty well covered on the issue of tiling, I think. :)

My opinion; worth price charged.

08-18-2009, 11:15 AM
did I see that this AC system is over 20 years old? If so the solution might be as "simple" as a new system installed by a reputable contractor in your area. I'm betting that you can even get some of that free guvmint money because you are replacing your 'clunker' of an AC system. :nod:

08-18-2009, 11:56 AM
Are you sure that the problem is not a clogged primary A/C drain? I used to live in Florida (Tampa) and had regular problems with the primary a/c drain clogging up with algae and causing periodic flooding. There should be a line from the A/C to a plumbing drain or to the outside. (most probably to the outside of the house). (It was actually a heat pump unit)

When the A/C is on, there should be a flow of water from the drain. The higher the humidity outside, the more water should be flowing from the drain. The A/C pulls water out of the warm, humid air passing over the fins and drains it out as the air is cooled.

I ended up using compressed air to blow out the line, and then pouring a dilute bleach solution into the line. Once I got that routine down on a regular basis, the flooding stopped. From then on it was once a month with the bleach solution to solve the problem.

I think if you had a freon leak, by now you would have no cooling at all. Eventually it would all leak out. If it's an older unit, the cost of Freon would have you asking the service person to find the leak. If your filters are clean and the fins are not damaged or clogged there should be no airflow problem. Check the ducts to be sure that one is not collapsed though.

08-18-2009, 12:28 PM
Anita, I hesitate to offer my solution due to the number of HVAC you've had looking at your problem but I will anyway on the outside chance they're overlooking something simple.

Your A/C problem sounds identical to my problem several years ago in a 1960 house in Palm Springs, CA--both hot climates and plenty of A/C use in the summers. My problem turned out to be a plugged condensation discharge line from the A/C unit in the closet to the outside of the house. Plugged line equals no place for the condensation to go, condensation pan overflows, result is water on (in your case under) the floor. My condensation pan overflowed to the rear of the unit (not visible from the front), down the wall, ruining the carpet in an adjacent bedroom.

As CX mentioned above, the solution is to unplug the condensation discharge line leading to the house exterior so the condensation can exit the residence. Newer homes have discharge lines plumbed (downward slope)through an interior wall to the outside so this is no longer a problem.

My situation was the discharge line under the condensation pan that traveled down through the concrete slab, under the slab past an outside wall, then up above the ground. Picture the letter "U". The bottom of the U will plug with debris in the condensation.

I tried what CX recommended, blowing out the line with air, but found I had better luck with blowing out the debris with water. Air would cure the problem for a month of A/C use but with water, the cure lasted for 3 months.

To cure, I simply cut my discharge line (in my case 3/4" copper) below the condensation pan, converted to PVC, added a PVC ball valve, below that a PVC T, then converted back to copper above the slab. On the T fitting, I added a female threaded fitting to accept a water hose.

Every couple of months of A/C use, I attached a garden hose to the T fitting, CLOSED the ball valve above the T (to prevent water from traveling up to the condensation pan and all over your house), and SLOWLY turned on the hose. After checking to make sure the hose was not leaking at the fitting, I then turned the water all the way on. I was amazed at the amount of debris that came out of the discharge line. When done, simply turn water off and remove the hose, then OPEN the ball valve so future condensation can drain.

The secret is to frequently unplug your discharge line. Also, make sure the outside end of the line is unobstructed so the discharge condensation has somewhere to go. If it ends below ground rather than above ground, I would buy a valve box to put over the end of the line so it can drip freely into the dirt rather than being buried in the dirt. I would further add a hose fitting to the end of the line and when you blow out the system, attach another hose to the end to direct the water where you want it.

I hope the above is the solution for your wet floors and happy tiling.

08-18-2009, 12:44 PM
yikes! that reminds me - time to check my AC drain line! :D

yes, I have seen the drain problem. The funny thing on mine is that it actually has an inline sensor to detect water backing up and shut down the system until it drains. Problem is that the discharge just empties into an open standpipe in the furnace closet. It's impossible for the safety to detect a backup! :bang:

08-18-2009, 04:39 PM
Last month we had the coil replaced in this one and it doesn't seem to be freezing anymore however condensation gathers on the pipe to the point that it drips down. He did this spray on insulation on the pipe but it is still wet each morning. Tonight I'm going to leave the door open to the closet and see if it is wet in the morning.

Back to the tile.....even if we can't stop the water wouldn't it be better to rip out the wood floor and put it on the slab like Matt said? If I discover the cracks ARE uneven and I should not use ceramic, what should I do? I'm going to wait until I'm pretty sure the water problem is settled.

Thanks to everyone for all the incredible advice! I already know a great deal more than I did when I started.

08-18-2009, 09:50 PM
I don't think you can afford to let "can't stop the water" be an option.

But at the same time, yes - you should do something w/ your flooring if it's all rotten and decayed.

If you're hellbent on having ceramic on the floor, you COULD (hopefully I don't get vilified for this) consider something like DuPont's floating/click laminate floor, which is offered in many ceramic tile-looking finishes.

I used an early version of this flooring about 4 years ago in a kitchen, and it was very well received, plus easy to install.

But I wouldn't even think of putting a laminate floor down if there's a real potential for water to drip onto or run underneath it. You gotta find a way for everything that generates condensation to run into a catch pan, and then that pan needs to have a free and clear drain to the outdoors.

Or find a way for the errant condensation(s) to stop in the first place.

08-18-2009, 10:06 PM
two heat pumps and you didn't think maybe you should try something else the 3rd time? I'm not a big fan of heat pumps, but don't know much about them. Prolly cuz I've mostly lived where it's either real cold in winter or real hot in summer - neither good for pumps.

The only thing I can think of is a fan that blows air across that area. The moving air might carry moisture away before it can turn into water and drop on the floor. :idea:

08-18-2009, 10:10 PM
Naaaa, heat pump isn't the problem, Art. And today's heat pumps are even more of a non-problem than they were not a problem ten years ago. :)

Sounds like there may be some sort of design problem there in the AC system, along with a design problem in the condensate drain.

A good HVAC contractor should be able to put an end to every bit of her problems in short order, seems to me.

08-19-2009, 09:02 PM
Back to the tile.....even if we can't stop the water wouldn't it be better to rip out the wood floor and put it on the slab

I'm no AC guy Anita but I think someone should be able to stop that water or at least contain it if its only condensation

If you can determine that the slab is suitable for tile then yes, the wood on the floor is coming out.

08-21-2009, 05:15 AM
With all the money I have spent and "supposedly very good" HVAC people working on it, you really would think the problem would have been solved YEARS ago. We have been here over 30 years and have probably spent at least $15 or 20,000 on this problem and STILL it exists. I even called a couple of HVAC engineering firms but they will NOT be bothered. I think I'll try the UF again and see if they have a graduate student that may be interested. What do you think????

08-31-2009, 05:56 AM
In fact I love the floor I have down now which is a laminate. I'm just sick and tired of having to put in a new wood floor plus whatever is on top of it time after time. I can't even begin to thank you guys for all the help & suggestions and at this point STILL do not have the water stopped. The drain to outside is flowing free, the (what I suppose is the drain in the unit) flows freely into the outside but STILL water comes out the bottom. Any suggestions as to what I should look for in a HVAC person??? I will NOT give up until this is solved.
Have a great week!

Brian in San Diego
08-31-2009, 03:32 PM

I'm going to ask some questions, offer a couple of suggestions and see if we can't solve where this water is coming from. Does the condensate line leave the evaporator coil and enter the slab? How is the condensate line piped? Is there a trap in the line? Is it vented? How many tons is the heat pump? Where are the return air grills located? Does the indoor unit sit on a platform with the return air grills cut into the walls below the level of the platform? What are the dimensions of the return air grills? Have you ever run the unit for let's say an hour and shut it off and then opened the unit where the filter is to see if water is on the floor in the return air chamber? Can you take some photographs of the unit and post them?

I have two suspicions. The condensate line is piped incorrectly and water is not flowing as freely as it should be or the line runs through the slab and it's cracked. My second suspicion is that there may not be enough return air surface and your coil may be icing up and when it melts it's dripping down through the indoor unit and saturating the floor in the R/A area. Either of these two problems should have been discovered by someone long before this. Even if it's neither I am having trouble this hasn't been resolved after all these years.


08-31-2009, 09:27 PM
Had a guy in today & he said there were large openings in the ceiling of the closet where the unit is located. He said when he opened up the AC every single part that was metal had condensation and was driping. He said everything is draining properly but felt that with the air return (it's in the closet under the AC) located there, a big part of the air the unit was pulling was from the attic. Said he thought the unit was pulling in all that humid, hot air from the crawl space/attic & that was the problem. I didn't realize there were open spaces up there so that will be done tomorrow and HOPEFULLY this time it will be right!!! What do you think? Does this make sense to you or is this something else that won't work? Should the return perhaps be in the hall which is just on the other side of the wall where the unit is? I'll get pictures and send them tomorrow. Will keep you all informed as to what happens.
Thanks so much for your patience.

Brian in San Diego
08-31-2009, 10:36 PM

I think I need pictures. If the unit is sitting on a platform and the air is being drawn from under that platform through a return air grill how could an open ceiling have anything to do with it? Are the plenums properly insulated? How about the duct work? Although condensation everywhere is not a good thing because the condensation has to find it's way to the condensate pan for it to drain properly I'm not sure I can buy the explanation. My furnace sits in a garage so it's completely open all around it but it doesn't draw air from that space because it sits on a platform that draws air from inside the house through a return air grill. If your system isn't similarly designed (where it draws air from inside the conditioned space) then you have a problem and probably electric bills to prove it.


09-01-2009, 06:45 AM
Ok, I have the pictures, go to just double click on the picture and they all come up
It's a real mess and a real challenge!

Brian in San Diego
09-01-2009, 11:37 AM

Thanks for posting the pictures. I don't like what I see in regard to how the return air system has been set up. Using a 16x20 filter in front of a plywood box behind some louvered doors is not a very good design IMHO. Generally speaking return air grills are sized at one square foot per ton of A/C. Your louvered doors I believe are offering more restriction that a normal return air grill. Even if you had a normal grill there and it was the same size as the filter then you only have enough return for a 2 1/4 T. system.

Facing the closet is there interior wall to the right side? I think it'd be imporant to find a way to make sure ALL the air returning to the indoor unit is coming from INSIDE the conditioned space. I also think the condensate could be piped a little differently to insure it is flowing freely out the drain. I think I would repipe the drain to have a vent as soon as the PVC was attached to the coil. There is no way you should have all that moisture running down inside the air handling unit. There also shouldn't be any standing water in the drain pan in the evaporator coil section. If condensate lines aren't properly vented water can sometimes "back up" into the coil pan. I have even seen them overflow the pan. A telltale sign is to go look at where the drain terminates outside after the unit has been running an hour or so and look at the flow out of the pipe. Then have someone turn the unit off and see if the flow rate changes. If there is a "surge" of water it is indicative of water getting "backed up" in the coil pan while the system is running.

Another possibility is the coil icing and defrosting as a result of low air flow but I think a competant A/C guy would have discovered that by now. Well, actually I think a competant A/C guy would have mentioned the return air situation by now and I think it should have been remedied long before now (especially in light of the fact that you have had equipment replaced).

I don't think the air coming from an unconditioned space (like your attic) is the only thing at work here.


09-01-2009, 03:52 PM
Had a 86 yr old guy that has a 40 yr old HVAC business that he is ready to sell and retire from. That's what I do...sell businesses. He said just from what I told him that air from the attic wasn't going to cause that much water that there must be something else. Gave me the name of his best guy and told me to have him come out and he would figure it out. I will call him and have him come tomorrow if he can.
The drain works great, it's not slow or anything. I think the fresh air return needs to be put back in the hall personally. I'm beginning to have a little hope again that I may get this fixed, am I wrong? Another thing....we have a 3 T unit in that space.

Don't know if you noticed or not but I had captions under the pictures. Sorry to be so wordy!

09-01-2009, 04:09 PM
Well, I think that even if you aren't getting a lot of air inflow from the attic, it should be closed up better than you have it. You do want to restrict air flow between conditioned and un-conditioned spaces.

I think the old position for the air intake was not the problem. My thermostat is right above the return, and it causes no control problems at all. Certainly not moisture issues.

I'd like to see 2 separate drains, one for the unit, and the other for the pan. The unit should drain adequately and completely, but if it somehow becomes clogged, the pan becomes your drain. You don't want a common mode failure. I would also consider a water alarm in the pan to warn you of a primary drain failure. If you cannot route 2 drains out of the area, consider making the common drain bigger, at least 1-1/2".

Vents and cleanouts are good things, as have been suggested.

09-01-2009, 04:12 PM
He said just from what I told him that air from the attic wasn't going to cause that much water that there must be something else.Old guy say sooth. :)

But it really doesn't matter. Poorly designed installation should still be able to make alla water it wants without a drop of it finding its way onto your floor.. My thermostat is right above the return, and it causes no control problems at all. Injineer Bob say sooth, too. :)

We frequently want the return air intake near the center of the conditioned area. We frequently want the thermostatic control near the center of the conditioned area. The central locations are frequently inna same place, the conditioned areas being the same. Very common.

My opinion; worth price charged.

Brian in San Diego
09-01-2009, 05:53 PM
I read back through the thread and found you just replaced the indoor coil. What was the reason for that? Did you see the old one after they removed it? I suspect some of your earlier problems may have been due to a dirty indoor coil (low air flow). The filter arrangement the way one of the previous installers put it in is just not right for trapping the dust. Eventually the dust finds it's way on to the coil and eventually becomes a blanket of dust that reduces the airflow to the point of freezing the coil or it prevents the water from following the "normal" path down the coil to the pan and it drips wherever it wants. I recommend that the platform be reconfigured so that a return air grill(s) can be installed back in the hallway. The rule of thumb is one square foot per ton of A/C, so you should have about 3 sq.ft. of return air grill surface for your system. I think the louvered doors are restricting the airflow too much. All of this is just conjecture without actually being able to see, hear and touch the system while it's operating. Hopefully the man coming out is a "systems" man and can look at the entire system and determine what's going on. I wish you all the best.


09-04-2009, 07:04 AM
The guy my 86 yr old seller said was the "best" came yesterday. Very nice, put in a trap outside on the drain so "in case" it was backing up & said wait a couple or three days & see it that worked & if not to call him and he would bring their installation guy out. Today there is water again but I'll be patient. He said there was a baffle in the unit and he thinks it could come from the OLD vent where the oil furnace was attached going in a sharp right degree angle and causing the air to back up and cause a baffeling noise. (maybe not exact but something like that) He's the first person that has ever mentioned that. For ages we thought all the water came from the unit freezing up and when it melted running under the wood floor & this did happen fairly often. Since Gary replaced this coil, for the first time since we have had this house, we actually have to lower the unit because it gets so cold in the house. However we still have water consistently now instead of before when it froze, I suspect it was always doing what it's doing now but not sure.

09-04-2009, 11:08 PM
Okay, alla you HVAC guys help me with this. what good is a trap? if water is flowing out, it ain't backin up. is it? how do the trap help?

09-04-2009, 11:45 PM
In the scenario she presented I ain't got no eye-dee why the guy would pewt a trap outside on the condensate drain and think it might help it drain better.

Maybe somebody else can help. :)

Brian in San Diego
09-05-2009, 12:42 AM
I asked if the coil drain was trapped in one of my earlier posts. I just looked at the pictures again and from what I am seeing the coil is a "draw through" coil meaning the blower sits above the coil and draws air through it. If the drain isn't trapped then air gets sucked up the drain preventing proper drainage. I think the guy today should have installed the trap right at the coil because of the secondary drain line teed into the primary. Once condensate water fills the trap then no air can get sucked through the condensate line. Even though the drain may be draining a certain amount of the condensate is may be getting blown out of the pan because of the suction created in the condensate line. The condensate line should be trapped and vented like I stated earlier but I think it needs to be done at the coil. This article ( explains it a little better.


09-05-2009, 08:34 AM
Yeah, I thought we'd decided there was a proper trap on the condensate drain line back when you axed about it, Brian, but I don't see that now. And her photos are gone from that online storage facility, so I can't see anything there.

Still, ain't never heard of adding a trap outside in hopes of improving the drain, or for any other reason, whether the drain is on the high or low pressure side of the air handler.

Wish we could get a good look at this installation. Just doesn't sound like a complicated problem to me. But, then, I ain't there. :)

My opinion; worth price charged.

Brian in San Diego
09-05-2009, 08:48 AM

I can still see the pichers. Here's the one that shows the lack of a trap or vent at the coil. Air can get sucked up the drain line from the opening at the secondary pan. There should be a trap as the PVC exits the coil and it should be vented there as well. The trap the guy put outside is going to be useless because air will get sucked up through the secondary drain opening. There may be other factors at work here but you have to start somewhere...and where and how one starts is important. If the outside trap doesn't work I can see the guy saying "well, that's not the problem." Ah, yeah, it could be the problem because you put the trap in the wrong place.