tiling over osb board

[Unregistered]

What is the proper way to tile over osb. I am finishing a lower level of a house and the subfloor is osb. Is thin set mortar ok to use or does something else need to go down before the thinset. thanks

[mdshunk]

Concrete backer board on top of the OSB, then thinset to adhere the tile to the backer board. Anything less, and you'll have grout cracks out the wazoo.

[Unregistered]

can I use the thinest concrete backer board I can find or is there a minimum thickness I need to cover the osb.

[mdshunk]

Probably without realizing it, you've opened up a big contraversial topic with respect to tiling over OSB. The very first thing you need to do is make sure that the joist stucture is stiff enough to support a tile job. A floor can be 100% structurally sound, and still have enough deflection to ruin a tile job. Check out this super easy to use deflection calculator (http://www.johnbridge.com/vbulletin/deflecto.pl) to resolve this issue first and foremost.

Secondly, the most current ANSI standards for tile installation (A108 - 1999) specifically exclude tiling on OSB. This is not to say that tile cannot be installed reliably over an OSB subfloor - however, there is significant debate in the tile industry regarding the conditions necessary for a long-lasting successful installation. The allowable ambient moisture level, extent of moisture related swelling before tiling, blocking and bracing and many other issues are still being debated. Each installation materials manufacturer has their own criteria and proprietary methods and requirements. Some backerboard companies will warrant installations using their products over OSB - however, their specific methods must be followed.You need to get on the net and research the backer board product you intend to use over the OSB. The backerboard is normally used to ensure that the tiles is bonded well to the floor. In installation over OSB, it takes on an additional semi-structural role. Note, thinset manufacturers do not recommend installing ceramic tile directly to OSB.

That's about all I know about tiling over OSB. Use care, do your deflection calculations, and research your backer board.

[Unregistered]

Probably without realizing it, you've opened up a big contraversial topic with respect to tiling over OSB. The very first thing you need to do is make sure that the joist stucture is stiff enough to support a tile job. A floor can be 100% structurally sound, and still have enough deflection to ruin a tile job. Check out this super easy to use deflection calculator (http://www.johnbridge.com/vbulletin/deflecto.pl) to resolve this issue first and foremost.

Secondly, the most current ANSI standards for tile installation (A108 - 1999) specifically exclude tiling on OSB. This is not to say that tile cannot be installed reliably over an OSB subfloor - however, there is significant debate in the tile industry regarding the conditions necessary for a long-lasting successful installation. The allowable ambient moisture level, extent of moisture related swelling before tiling, blocking and bracing and many other issues are still being debated. Each installation materials manufacturer has their own criteria and proprietary methods and requirements. Some backerboard companies will warrant installations using their products over OSB - however, their specific methods must be followed.You need to get on the net and research the backer board product you intend to use over the OSB. The backerboard is normally used to ensure that the tiles is bonded well to the floor. In installation over OSB, it takes on an additional semi-structural role. Note, thinset manufacturers do not recommend installing ceramic tile directly to OSB.

That's about all I know about tiling over OSB. Use care, do your deflection calculations, and research your backer board.

Wow, guess I did open a can of worms. I will try to do some more homework. Thanks Md, you always come through.