tub installation

My bathroom is stripped to concrete and 2by4s. When installing a new tub, do I first install cement backer boards from floor to ceiling or do I install the new tub first and bring the backer board down to the tub edge? Thanks.

tub

Put the tub in first and then bring the walls down to it. Unless your space is larger than most, if you put the backer boards up first the tub would not fit in the space.

depending on the size of the tile, sometimes it is good to shim the studs above the tub rim out slightly so that the backer board can be brought down over the rim to about 1/4" above the tub surface. Large tile can hang unsupported there, but smaller tile should have the cbu further down. Check out www.johnbridge.com for tiling stuff. Also, put a vapor barrier behind the cbu (cement backer unit). Tar paper or poly works fine, bring it down over the tub flange; cut it off after you get the cbu up. My unprofessional opinion.