I have a house off the ground, will I be able to pour cement over the wood to strengthen the floors before laying ceramic tiles?

Hey ziztozag...

If your floor is out of level then you may want to try a self leveling compound to level the floor... BUT

If just installing ceramic tile onto new floor you really want to install a CEMENT BACKER BOARD.. such as 1/4" or 1/2" hardibacker... check out this link:

James Hardie: HardieBacker 1/4'' backerboard (http://www.jameshardie.com/homeowner/products_backerboard_quarterInch.shtml?openTab=jsn avLink4)

Review the FLOOR INSTALLATION section... and also note that they have an installation video online for you to watch if you want, too.

This cement board needs to be set over a minimum 5/8" subfloor (3/4" minimum is better... thicker is even better) then installed in a bed of thinset mortar or modified thinset and screwed down to floor using alkali resistant screws (buy hardibacker screws). Also need to stagger the boards and tape the seams.

Read up on this stuff and let us know if need more information or if I missed this one by a country mile and this is not what you needed to know... ;)

Let us know what you think... MARK


Other types of cement boards are DUROCK or WONDERBOARD... same rules apply for installing!

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Maybe I don't understand the circumstances right but if the wood is suspended between supports, the concrete will just put more load on the wood supports. I would add more under the joists before putting more weight on top of them. I assume by off the ground you mean over a crawl space?

If you put too much weight on the floor, you may get bounce and cracked tile.

Cement Backer Board as mentioned above is best if you have adequate support for it.

Gee thanks guys

Yes it is suspended by wood supports --what can I do to strength and even the floor?

Put in cement backerboard as Massplumber recommended so long as you have adequate support as mass specified. You should be able to even out irregularities with the thinset.

If you need support below the floor you need to find out what type of supports are acceptable to meet code in your area. If you put in the wrong type and later decide to sell the house and its not to code you will have a tricky (and expensive) problem on your hands.

I used screws jacks but it was in an area where they didn't worry about building codes much.

I agree that a cement backerboard will help but the Hardibacker, glued and screwed, will help way more. Hardibacker is has more strength and the screws will not taer the backer material if there is a stress in the floor, like movement. MASS gave you a good link worth reading. Hardibacker comes in 1/4" and 1/2", 1/4" is enough for flooring unless you need more heighten, then go 1/2".