Is backerboard a must in my situation?

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Old 09-13-04, 03:57 PM
nesbitt
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Cool Is backerboard a must in my situation?

I am constructing a countertop which I will tile. The countertop is really out of the way of "traffic". There is no sink in it and there's a very slim chance that liquids will even be used on it or around it. My question is: Do I need to use a cement backerboard on top of the 3/4" plywood if liquids seeping between the tiles is not a concern? Backerboard wasn't used back in "the good old days" so didn't they just tile on top of the plywood? Will the adhesive damage the plywood - is that a concern? I used backerboard when I tiled my bathroom wall and could understand the need for moisture resistance and a good grip but I'm not seeing the need with a dry, horizontal surface. Any advice or input would be greatly appreciated. Thanks much.
 
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Old 09-13-04, 07:11 PM
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Hi

If your cabinets are constructed so that the plywood top is supported well, then you can get away with going on top of the plywood. Putting down a layer of 1/4 inch cement board would be better though.
 
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Old 09-14-04, 10:22 AM
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I used 4" ceramic tiles for the top of the double-sink vanity in my children's bath, spreading the thin-set directly on 3/4" plywood. This was three years ago and you have to see how messy (i.e., water and soap all over the place)my now 5 and 7 year old boys (not tow mention their twin brothers who can't quite yet reach the counter) are with brushing their teeth and washing their hands and faces.

Yet, the tiles look as great as the day I completed the job!

Truth be told, however, I never use backerboard. Didn't use it for any of my 3 different bathroom floor jobs or my kitchen. I have one more tiling job left (for this Winter when it is cold and dark in Boston) and that is my master-bath...and yes, I will NOT use backerboard there either. Of course, this is a definite minority (if not sole) opinion on this board as it seems everyone is quick to include backerboard as a requisite for most tiling jobs. But I can see why they would...after all, it can't hurt to use it (excpet for in the wallet)...but I wonder if most of them can articulate exactly why it is necessary.
 
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Old 09-14-04, 02:03 PM
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I'll give it a try. Wood, will expand and contract with changes in temperature and humidity. When you attach ceramic tile to wood, it has no choice but to move with the wood(if it does move I mean). The result could be cracks in the grout joints, or even the tile cracking over any joint there happens to be in the wood. Cement backer board is more stable than wood, in fact it barely moves at all with changes in temperature and humidity. Now, I know you are going to say " but the backerboard is attached to the wood, so doesn't it move with it?" . The answer is yes, but it is more isolated now, the wood can move underneath the backerboard, without tranfering up through the tile.
 
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Old 09-15-04, 02:01 PM
nesbitt
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Smile Thanks much!

I appreciate all the advice!!
 
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Old 09-18-04, 01:21 PM
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Of course, this is a definite minority (if not sole) opinion on this board as it seems everyone is quick to include backerboard as a requisite for most tiling jobs
Amen brother....I have tiled several floors with no cracks yet, and never used backerboard. I (and I'm ONLY speaking for myself) don't see the need for it. I understand the concern with wood expansion/contraction, I've just never had a problem with it. Luck?..good area of the country?...I dunno, but mine are all crack free, oldest floor is 4 years old and counting.
 
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Old 09-18-04, 05:47 PM
floorman
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i used to set tile over plywood all the time before c.b.u"s came into existance without any problems and still do on occasion but very rare.
There are other reasons for the c.b.u. than floor tile it was also made for the problem of walls as well.Drywall was n't cutting it.
You can set tile on the plywood following certain rules.it needs to be an exterior grade plywood such as c.d.x.You need to leave an 1/8 inch gap where the sheets meet and at the wall line.now here is where the argument comes in,i always have used 8 penny nails and nailed the joists and then used ring shanks to nail the seams and the field,according to the tile council of america though they don't want you to nail into the joists so the 2 layers can move independantly of each other.I nailed every 2 inches on the seams and then every 4 to 6 in the field.You also need a thinset rated for wood substrates, not all are rated for that.Here's another point for argument also,i lay the sheets perpendicular to each other cause i feel it adds to the strength of the subfloor that laying them the same doesn't,soem don't feel that way.
Tile calls for a subfloor of atleast 1 1/8 thick so if the actual subfloor is 3/4 and you need an additional 3/8 oyu can use plywood or c.b.u.Just follow the rules and you will be fine
 
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Old 09-24-04, 02:47 PM
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First, plywood is a a structural material, but it does not hold up against moisture. Tile backer, concrete board, and durrock boards are not structural materials, but they provide that much needed mortar bed tile requires to prevent deflection. A HUGE misconception here is that tile backer or concrete board is a moisture barrier. It's not. That's why showers which are constructed using these types of materials have to be protected by vapor barriers, and water proofing membranes. The moisture will literally pass right through it - thereby being absorbed by the material supporting the board.

Yes, you can get away without using a tile backer, but only in areas where a classic medium-to-thick mortar bed would not be required. The old way of setting tile involved building a box with float strips, laying out a lattice like chicken wire, and using a conventional mortar to float a bed for the tile - even for countertops. The lattice gives the mortar bed strength, while the mortar bed itself gives the tile a strong medium, and all of this prevents damage to the underlying structure over time.

Concrete boards and tile backer boards take the place of this mortar bed. This is solely to provide a medium to both adhere the tile and minimize flex to allow the tile to stay adhered. The only upkeep should be grouting the tile and replacing a damaged tile every once in a while. Not using anyting means your tile will be subjected to any deflection allowed by the material underneath. For countertops and backsplashes that's not generally a problem, but for floors it is. It's usually first evident with the grout. It'll begin to loosen and come apart.

All of this is subjective when talking about dry areas. Even tiling on drywall with mastic is ok in dry areas. However, this argument becomes more critical when talking about wet areas. A mortar bed (or tile backer protected by a water proof membrane) is REQUIRED in these cases. Period. Not because it's over-engineering the job, but it protects the subfloor from long term water damage.

No professional would tile a floor on plywood (especially in a wet area) without a mortar bed. It would be irresponsible to do anything else. It's also simply good practice - but only because good tile jobs are built to last 40+ years. Not 10+ years with resulting damage to the subfloor.

As some examples the countertop in my 1926 craftsman home was set in 1926 using a conventional mortar bed hand made by the builder, and the only thing it needs is new grout after almost 80 years. If no mortar bed was used it might have lasted 10+ years at most and would have had to be replaced. That's the difference, and it matters.

When building my master bath my goal was to restore it to its original tile work, so I screeded the walls and floors to construct a mortar bed for the subway and hex tile. I know this tile job will last several decades, but if I cut corners to save money I'd bet the job wouldn't last, and I would have wasted time and money on a job that wasn't worth it.
 
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