Bonding Cement Board to Wood

Elmer's Glue. Hot melt glue. Construction adhesive. Epoxy. Etc. etc.

The choices are limitless, until we really know what you are trying to do. Building a house, bridge, fence, shed???

You might also try the two product's web sites.

I want to bond cement board to a wooden shower kerb. I want the joint to be resistant to water.

I will also screw the cement board to the wood.

Then I will tile on top of the cement board.

Any thoughts?

Angus

Sounds like a job for silicone rubber. It's a great water resistant sealer, but not too strong. So, if you use screws you should be fine.

Google waterproof sealers.

I am sealing yes, but I am also trying to get the 2 porous surfaces to adhere so I doubt if a sealer will work. I think the option from Australia is better. Ther is a construction adhesive which does not dry completly hard in Home Depot. When it dries it still has some elasticity: it is not completely rigid. I am thinking to try that on a piece of wood and and piece of cement board as an experiment.

Angus

Angus, maybe I am missing something here... Can you help a guy out?

A shower curb... for your shower... in your house?

Like this:

A 4" high by 5" wide x 3 feet or so rise above the floor, to help keep the water inside the stall?

Is this what we are discussing?

Yes; it is a kerb: it is made of wood. This was done by the previous owner; the tiles came loose and I investigated. THey were slack so I removed them all. I cleaned the wood, scraped it and samded it.

Now I intend to attach cement board first and then tile. First I must stick the board to the wood with an adhesive with moisture resistance on the inside I have Loctite PL 375 and I am doing an experiment with it right now to evaluate it. The ideai is to minimize on water wicking to wood. The kerb 31/2" on the outside and ~21/4 on the inside and about 21/8" thick.

I guess you didn't think much of what I did.............that worked, and continues to work.

Indoor/outdoor carpet adhesive for the concrete board to wood.

After using thinset with the mesh tape to fill the joints in the board, I also used the adhesive to set the tiles. Grouted the joints, allowed to dry, thorough cleaning, followed by grout sealer.

Keep experimenting, you'll get there.

Hi Angus

The picture tells me were you are at. I would Fiberglas the whole bottom part and start again with tiling. If the curb is one tile high even better. The build up of one tile around the basin could look decorative, maybe black?

Ask the Missus about that choice and I can see a brownie point coming.

Fiberglas, definitely Fiberglas. It would give you a solid start and stop water for sure. That's what I would do anyway.

Good luck, Ky.

I do not know what is immediately below that piece of wood. But I do think that water is reaching it from the inside. The water is probably coming from the cement below the tile or from water gettign through the grout where the tile terminates. The question arises if that piece of kerb wood should be removed with a view to inspection what is underneath the wood prior to any action step.

Any thoughst?

Emil teh chemist

there is no continuous membrane stretching out over the kerb: this was not done so we have an imperfect situation. I think below the shower tile there is concrete that sits on a plastic tray that extends thoughout the shower. THat is waht was used (I think) so that plays the role of the liner.

So the question arises how to fix this. How about remving the piece of kerb wood and then what .........///

To properly fix this, it will be a fair amount of work. None of it is difficult, but there will be many steps.

If you try the two links in my previous post, there are many suggested methods to install new. That is what you should do, remove the floor tile, the base... everything down to the concrete. And then start over, doing it correctly.

Or, you can do like the last guy... glue a curb form in, caulk it real good, tile 'er over, and sell the house before it leaks again.

Thanks: this is an upstairs shower. It is not really leaking hugely. My forensic examination arises, since some of the tiles were a little slack. Examinaion shows that water is slowly permeating into the wood of the kerb (since it is wet and there is some mould).

Upstairs does not have concrete so the start from scratch procedure would involve a huge amount of work.

(a) removal of kerb and shower tile (there are 2 layers of tile).

(b) Removal of all walls of shower

(b) removal of shower floor pan (originally thinset) cement.

(c) replacement of plywood below.

Then start from scratch along the lines of your post. I understand the fundamental problem well.

But how to find a way around this: this is the nature of my thinking. How to creatively block the water permeation; that is my thinking. Previously there was no cement board used on the kerb.

Hence my raising the issues of cement board waterproofing then tile with grout. Fit an additional tile ledge around the bottom of the shower with grout. That way it makes it difficult for the water to escape to get at the wood.

Any thoughts?

You said "That way it makes it difficult for the water to escape to get at the wood."

That is the point exactly. For an effective, long lasting fix you do not want to make it difficult for the water to escape...

Two layers of tile? So at least two previous attempts to stop the water (doing it incorrectly), and here we are today.

I think I will remove the wooden kerb and look at what is immediaetly underneath this wood. I am concerned that below it is plywood that may have rotted somewhat. It seesm to me that the problem is that water is permeating from the concrete outwards to the wood kerb. I do not think that the secodn tiling woudl have helped the water pemeation problem.

Any thought on the best way to remove the wooden kerb?

The problem is that over a long period of time ( >5 years) the wooden kerb becomes damp on account of slow wicking to the wood : there is no leak per se. If I can remove the wooden kerb and replace it with a brick kerb and tile over the brick then it will stop the wicking process.

I stress the problem is not acute not at all. On close inspection of the kerb there is no standing water under the kerb nor has there been standing water leaking out at any time.

Depending on how it's fasten to the structure, I use a reciprocating saw (sawzall), a large pry (crow) bar and a good hammer.

Doorman: it is a significant amount of work to redo the entire shower. PLease can you elaborate somewhat. I can see how the walls can be removed along with the tiles scured to it.

I cannot see how the concrete can be removed. I envisage that a moulded plastic pan or tray was used. The concrete sits in the tray. Also how do you deal with the drain to make sure it remains undamaged (intact) and can be used again.

Please can you comment on this

aer you saying you saw the concrete with this tool? surely not. Can you articulate and give more step by step details.

Doorman: please see my post above: I am not like the last guy. I am a different kind of guy. I am a professional scientist with experience in coatings, fillers including polyurethane, epoxy resinns.

Doorman is correct in that there needs to be a waterproof membrane under the entire show stall......it should also extend up the walls if they have ceramic tiles and Wonderboard underlayment as well.

I suggest that you install some poly plastic sheets on to exposed face of the cement board with adequate laps. Make sure to use a plastic sealing tape on the seams. I've used clear packing tape and have had no problems of leakage ever since we reconstructed the bathrooms. BTW, the cement board is somewhat porous and will allow transmittance of water vapor and water through it. You must protect your wood framing (floor and walls) as well as your plywood (?) subfloor sheathing!

I would not use any type of adhesive to secure the Wonderboard to the floor or the walls, as it'll be almost impossible to remove the cement board later on for maintenance or reconstruction purposes. Just use a high quality silicone sealant for the joints. The Wonderboard cement board screws will be enough for your project, and they can be backed-off at a future date if they're not rusted too badly.

Aside and possibly OT (but it depicts what is needed to protect the wooden structural elements): We're currently in the process of totally reconstructing our Kitchen/Dining Room (combined 400 SF) due to severe water intrusion due to the bad winter weather we experienced with huge ice dams on the eaves and tremendous amount of alternating snow and ice layers on the remaining portion of the roof)....over $50K of damages occurred in the kitchen/dining room , guest bathroom, living room, and master bedroom. I'm even replacing the T&G plywood, Wonderboard and very expensive Italian porcelain floor tiles (only 9 years old!).....even the solid oak cabinetry and granite tile countertops have to go! ACKKK!!! The new plywood sheathing is being protected by a coating of bituminous paint flooring by the installation of a 6-mil poly plastic sheet membrane prior to the installation of the James Hardie Backerboard and the new Italian granite tile (which ain't cheap either @ $95/10 SF). Now I'll not have to worry about spilled water from the kids or the dogs getting through the finished flooring systems and attacking the plywood subfloor.

i would suggest you look for shower pan construction details. Waterproofing is the key here, you might want to use a liner. Here is a link that pictures the steps of installation hope this helps http://www.ontariotile.com/preslope.html

Where are you Angus?

Go to your local hardware store and ask them about "construction adhesives". They will point you at a selection of caulking tubes and tools.

You will need to select one that is "Wet area approved" for the porous materials that you nominated. (Fullerprene 303 is what I used in Aus bathroom rennovation.) Choose one that cures "rubbery" rather than hard. This allown for differential expansion of the house frame to the panel without cracking.

When you screw or nail the sheeting, remember to NOT nail through your adhesive, since that stops the ability for movement. The nails/screws are only to hold the material in place while the adhesive cures, so don't go overboard. (Think about it, if you use enough nails why does anyone even bother about the adhesive? It's because the adhesive is the fastener!)

Hello Cobber: then from your comment I should use the adhesive and clamp it in place with a series of clamps along the 48 " of the shower kerb: it will then set in place securely....yes? do not use scres or nails at all. Surely that is more logical.

Angus

I used indoor/outdoor carpet adhesive. You want to use one of those trowels with the little square cutouts along the edge to spread it, giving you ridges. Apply it to the wall, slap your board up, and screw it in. If your cement board is dusty, clean it off first for maximum adhesion.

It's better than liquid nails, etc., because it gives you a continuous water repellant, rubbery coating behind the board.

I screwed it down tight.

If you really want to go overboard, apply a coat of water based primer to the mating surfaces first and allow to dry before hanging.

OSI construction adhesive.

Stay away from silicone sealants they do not bone two non porous materials well.

I am puzzled by your comment, since both of these materials (wood and cement board) are porous. I am bonding strips of cement board (2" to 48") to the wooden kerb that is the shower kerb.

Angus

Not sure I would introduce silicone to the area for a lot of reasons. But, the biggest is trying to Bond other materials once the silicone is on any surface in the area. Causes bonding issues you can then never correct.

Good comments about going to sales outlet for construction materials in your area and ask for some help. You also might call the manufacture of the cement board and ask their take on this issue.

There are many grades of paintable silicone adhesive sealants that will not cause reticulation/cratering/fisheyeing or adhesion problems.

Silicone greases are notorious for migrating, but that's another story.

I also take exception to the comment about bonding to pourous surfaces, if properly applied.

I do agree that he should go to the local "experts" and see what's hot these days.

Per the USG DUROCK^® Installation Guide:

Use Type 1 organic adhesive, and secure with screws or nails 8" on center.

There. Was that so hard?

I looked into this: I took this up with manufacturers of Type 1 organic adhesive. They told me their product is water based and did not recommend it where water exposure was an issue. So I do not favour this option. I am thinking of an adhesive which is based on organic water insoluble material as mentioned above or epoxy.

Type I organic adhesive: Test is conducted using 6" by 6" birch laminates glued together to make three-ply plywood.

Type I testing involves cutting the 6" by 6" assemblies into 1" by 3" specimens, boiling them for 4 hours, then baking the specimens in a 145°F oven for 20 hours. They are boiled for an additional 4 hours, then immediately cooled using running water. The specimens are sheared while wet, and the bonds must pass certain strength and wood failure requirements to pass the Type I specification.

Sounds to me like it might work... I dunno, continue your quest. You are the chemist, and the end user. See ya later.

thanks: the issue here is sticking the wood to cement board in a most environment.

If your trying to glue to moist wood, your battling an up-hill battle. All wood and backer board needs to be dry for proper adhesiveness of any adhesive. Besides liquid nails there's another adhesive that comes to mind is PL1300L, waterproof and will bond most anything.

Wouldn't mastic be the proper product? It is used to bond cement board to wood floor and for bonding tiles to the cement board. Use the proper screws for that purpose too.

Following on from most thoughts in this string. One a patch job and sell or two rip her out and do it right. Water is such a tricky little bastard and will get in.

Actually you may not have to rip everthing out - you may be able to pick up a hob that can sit in place. Once the hob is in place or your own 'solution' then a water proof membrane painted on; then your ready to tile. Any reasonble tiling shop should have a water proof membrane.

If you want to stay with your step why not fabricate a new one out cement and or bricks and tile over it?

I have done several of both, new installs and replacement of shower stalls. But you keep feeding us bits and pieces about your project. And trying to take short cuts. You said in one of your later posts that this has been a problem for 5 years, If, you've had this going on for that length of time, you need to check the soundness of the substrate and floor joists for dry-rot. Without a sound foundation, your wasting your time and money. The two links that Doorman posted (#21) give pretty good instructions of the steps needed to DIY. Kramarat also has a good suggestion (#5) outdoor carpet adhesive. I prefer liquid Nails myself, for gluing backer board

I can only add two things you DO NOT do, (1) cut miters in the membrane corners or penetrate the membrane, no closer than 4" above the finished height of the shower floor, I, myself prefer no less than 6" above. (2) Do Not Block or Plug the weep holes!

This is a Back Breaking job and not for the faint of heart, so do yourself a favor and do not take short cuts unless you plan on selling right away. And if you do, let us know where your at, so we know where not to buy. DJ

Thanks for your advice!

I have in fact done this jop before in the basement. I converted a plastic cabinet shower into a proper one with tiles. I removed the cabinet and replaced everything. I used a liner nailed to the studs prior to installing 1/2" Durock board and laying the shower floor. I had an instructional DVD. So it is teh easiest thing in the world to take the position replace everything. The question arises if it is appropriate to take that position with this project. I do know the size and nature of such a project. I did it one step at a time. I did an additional step by waterproofing the surface of the Durock board with Redguard prior to tiling. From a theory standpoint I am not a novice, but from a technical standpoint I need advice.

I do not think I am making it clear what I am saying. This shower is now 20 years old. It has not caused me any problem whatsever. It is when I investigated the tiles on the kerb were loose that I decided to take them off and found that I had damp wood kerb below. There is no membrane overlapping the kerb , which is 31/2" on the outside and 21/2" inside shower). I surmise that over the years we have slow wicking of water from the inside shower to the wooden kerb. There is 1" of a difference in height. Now this water may be coming from the inside below the 2 1/2" height mentioned. By inspection of the drain I think there is moulded plastic tray or pan that surrounds the entire shower and it was there when the house was built ~25 years ago.

I am thinking to remove the wooden kerb to see if I can get more information on that 2 1/2" " as I view from the outside. The only damage I see is to the kerb in so much as it is damp and had some mold (that I scraped off).

It may be possible to seal there with Redguard and use a brick kerb. Use Durock on the brick (Redguard again) prior to tiling.

Any comment?

I can appreciate you wanting to keep this as simple as possible, (KISS to me)

I have to assume this problem is either on the first or second floor of you house? Now to try and keep from doing a lot of extra work. The Question is, have you had water staining on the ceiling below the problem shower? If Yes, more investigation needs to be done. If No, then you need to "water poof" your curb. To do so and keeping it simple, apply liberal amount of either, mastic or thin set, completely covering the wood, set your backer board while the adhesive is wet. Make sure that your fasteners or below the surface of the backer board, then finish with tile.

Now if you need to remove the mortar (concrete) bed, that's fairly easy, you can either use a sludge hammer (gently) or a hand held demolition hammer, you can rent. Fracture the mortar, (I use Duct Tape to protect the drain), I generally stay about 2" away from the drain, then remove the chunks. If, you have to remove the mortar bed, you should also think about removing the walls, starting from scratch, to insure you have a water proof transition between the walls and floor pan, using the membrane method as previously posted.

Good Luck, and let us know how your progressing. DJ

This is easy, except that the wood will usually shrink and swell if not epoxy-sealed all over, or otherwise regulated. Why not just pour a cement kerb?

Why not just pour a cement kerb?

I thought the same but imagined it would be too easy. Maybe it supports something on the other side? Take the bugger out and create a form and fill with concrete.

Then Fiberglas in any case. The whole area is possibly compromised by hidden stuff of all kind.

I might go and have a shower now, because I can .

The form's already there, all he's got to do is take the top off.

After reading all above, it appears to be a total amateur installation - meaning it will just go from bad to worse and any 'yet to be discovered flaw' will null all expense and effort.

Given it is upstairs - I'd demolish it and install one of the prefab versions.

"Now, there are sleek acrylic-and-glass pre-fab models that can be rather sexy. What does make my heart pound fast about pre-fab units is the lack of tile seams, which inhibit cleaning"

Don't know about the sexy and heart pounding part in a shower stall context, but they are dead easy, moisture problem free, a fraction of the structural loading compared to cast and tile the equivalent of a square bath - and you can actually clean them.

If only you wanted to destroy your personal cleaning area & it were just a bit deeper

There would be no end of advice

I would recommend ADEPS ADHESIVE manufactured by Dryvit Systems, Inc. (WWW.DRYVIT.COM)

Use epoxy paste. Get some that is marketed for concrete. Often it will be marketed to bond dowels in concrete. There are several maufactures. Try locating it in some builders supply house. This will be a two part product. Once it is mixed it has a "potlife" the potlife given for the product is usually for 75 degrees. If you are in a Hotter enviroment your pot life will be shorter. Mix it in quantities that you can use before the potlife time expires. Do not contaminate one part with the other. You need one spoon or ladel for each part. Then you need some other trowel or putty knife to mix the two parts. Make sure and get a PASTE. Some epoxies are in a liquid flowing form. You want the paste.

You can get this in a two cartridge unit that comes with static mixing heads (you do not need to measure and mix). These cartridge units are much more expensive per weight than the buckets. You will need to invest about $50.00 in the special caulk gun for these double cartridges. If you have a small volumn of work to do, get the special gun and cartridges. If you have a lot of bonding to do then get the paste in Buckets and mix it yourself.

If I were doing the job, I would put paper backed metal lathe and use thin-set with a polymer additive to a smooth finish. I would the use the same thin-set with a ¼x¼x¼ notched trowel to set the tiles. That's what I would do. It's funny this subject can up cause I'm installing tile over backer board adhered onto plywood with thin-set using roofing nails 12" O.C. for my kitchen countertop.

Now I shall take my two pennies and try to help someone else.

There should be a membrane between the backer board and the wood framing. There isn't, correct? I would remove as much as you can reasonably expect to retile, let it dry completley. Cut one piece of membrane (pond liner works fine) to cover all exposed framing. Nail sparingly into framing to hold it in place. Use high quality 100% silicone caulk to seal all membrane edges at joint, and dab on nail heads. There is no adhesion occurring at this layer. Cut backer board carefully, screw backer every 8 inches on all sides, at least 1/2" from edge. Thinly parge surface with modified thinset, with heavy portion of latex additive. Let dry completely. Set tile with Modified thinset, butter tiles completely. let dry at least 24 hours. Grout thoroughly with modified sanded grout. Let dry at least 5 days. Use silicone based grout sealer on all surfaces, especially on the inner curb to shower floor. Enjoy

Well noticed - there is no membrane.

Nuff said - see my previous post.

By now, I'm sure poor old Angus McLean regrets ever coming here. After all of us "experts" have declared that our way is best, bickered among ourselves for supremacy and claimed the all other ways, except our way, sucks I wonder what he will do.

Having owned boats for years, I'm inclined to go along with kramarat on this one.

Good luck.

Had I decided to pursue the option of preventing water wicking to the kerb I would have used a marine epoxy or urethane adhesive seal. I would have replaced the wood kerb with a brick kerb adhered to the side of the shower front. The subfloor outside of the shower (below the brick) would have been cleaned and sealed thoroughly.

On inspection I did not see any sign of water damage at the sides, but I did detect that greenboard had been used for teh walls of this shower. (cement board is to be use since it is impervious to water).(Obviously the pipe hould be clamped). Thes are signs of poor work. I am replacing the shower completely. I am a scientist and it is difficult for me not to intervene and fix this problem. What appears to be good is often not good.

So far what I see is as follows: shower floor comprised one layer of 2"X 2" tiles; a thinset layer and another tiling usign 2X 2" tiles. It has been very easy to prise the floor sandwich up to reveal thinset on the plywood subfloor. There is no plastic moulded tray or pan throughout the shower. The shower drain has the connector part of such a tray or pan. Now this is very bad, since obvioulsy the plywood subfloor needs to be protected from water.

So I am now surgically remvoing the wals: teh tile job is very nice, but some major fundamentals of this work were wrong. It could led to major damage down the road.

Wow, you have done a very thorough investigative job. I would, however, at this point, abandon the surgical removal technique and adopt a new, more American, I dare say, technique.

Get an eight or ten pound sledge hammer, and a large (18") flat pry bar.

Bash repeatedly. Pry repeatedly. Clean up.

Pull all nails. Sweep.

Breathe a sigh of relief, and build a correct shower pan and tile system.

We'll be waiting for your next post.

Thanks; I have a 10 lb hammer and a pry bar ~ 12" long so I will make use of this also. I do not want to damage the wood frame in the background.

At least I know a good bit about the worms in the can. This is quite a large shower about 48" square.

Angus, the peace of mind, is going to be worth the extra work to do the job right. I know it's a bear to demo the old stall, but that will reveal all of the hidden problems. It's strange how easy it is, to open a can of worms (#35), huh?

Good Luck to you, and post some pix when your done! DJ

Do a Google search for waterproof construction adhesive and you will find many products that will bond cement board to wood. Cement board is porous enough and will have no problem bonding with the construction adhesives. There are adhesives that will even bond to wet surfaces if the wood backing is not completely dried out. Be sure to kill the mold with a bleach solution or better yet, completely replace the curb and start fresh. It is best to have a full liner as suggested previously but thin set will work as long as the curb is solid and there is zero movement. Take into account the size of your tiles and you may find you need to make the curb a specific size to avoid extra joints in the tile. Good luck with your project.

You don't have a problem with the bond. You have poor moisture protection for your wood framing. If you want to know how people have been doing this very successfully for many years, look up what is called a mud pan, which in the old days, was constructed of a large quantity of very dry concrete mix packed over some felt, or in modern construction, a smaller amount of concrete mix over a membrane,fitted to a weep drain, which (membrane) covered a wooden curb, then (the curb and walls only)covered with durock, then tiled. You may have noticed that bond is not a part of any of this (except maybe for the tile). It sheds water like you waterproof a house, that is, joints drain to horizontal surfaces sloping away (or in this case toward) your drain.

PL400 construction adhesive should work - it is generally used to cement subfloor materials to joists, but it will stick to just about anything and is very durable. Much better than silicone.

Kerdi to the rescue.

what's a Kerdi.

Ba doop boom

Isn't This a little overkill for a simple job? I mean experimenting with different glues and all? Your not building the Taj Mahal. Thin set over wood or cement board is plenty good it seals and sticks to just about anything, just make sure You cover every part of Your curb.

oilcan13

#35

They should be all over the place by now.