Hi All,
Location is Central Florida.
I'm currently rebuilding a tub surround.
2 walls are concrete block , 1 is wood .
I plan on just putting up Hardi Backer board and adhereing the tub surround to that .
Do I need to put a Vapor barrier ,, AND foam board insulation ,, behind the hardi board ?
Or should I just secure furring strips to the concrete blocks and then screw hardi backer board
to the strips and adhere the tub surround ?
Do I need a vapor barrier ?
again, location is Florida.
THANKS in advance for the help .
KZ

Beeginner:

My experience with tub surrounds is that they're quite reliable for not allowing water leakage through them into the wall, and if you do suspect a leak, there are only a few joints to check, so they're easy to find leaks and repair them IF they occur. If there is a leak, it'll typically be around the holes you make in the front panel for the faucet knob(s) and spout (and possibly for the shower arm). So, if you didn't have insulation in that wall before, and cost is an issue, I wouldn't install it now just because you're installing a tub surround.

However, if I did choose to insulate, I would insulate with EXTRUDED polystyrene foam insulation above the tub lip. Polystyrene foam insulation will be either blue or pink in colour. Blue is made by Dow and pink is made by Owens Corning. I'd choose this kind of insulation because it's "closed cell", which means that the blowing gas bubbles in it don't intersect, and therefore it's not permeable to air or water. That, in turn, means that it doesn't need a vapour barrier on either side of it. So, by using extruded polystyrene insulation (like "RoofMate"), you completely sidestep the question of whether or not to use a vapour barrier and what side of the insulation it should be on because you don't need a vapour barrier at all using extruded polystyrene insulation. Just fit it between your strapping and then inject expanding foam insulation into the gaps between the strapping and the insulation to hold it in place. Then cut any excess expanding foam off with the strapping using a hand saw or razor knife once it's fully cured.

As long as you leave the bottom of the insulation 1/4 inch (or so) above the lip of your tub then you're not trapping water between the tub surround and the polystyrene foam because any water that does get between there can drip down to the floor under the tub and evaporate out the front and back walls of your tub enclosure.

So, if you didn't have insulation before, and you weren't uncomfortly cold having a bath or shower, then I wouldn't bother putting insulation in. But if you did, I'd insulate now with EXTRUDED polystyrene foam insulation instead of what you had before.

Also, reconsider using Hardibacker. Consider using a product called "Dens-Shield" made by the Georgia-Pacific Company instead. Dens-Shield is a gypsum core board, but the gypsum has been chemically treated so that it permanently repels water. I had a piece of Dens-Shield submerged in water for a week before I decided to use it to replace the drywall in my sister's basement after a flood. Dens-Shield is more than water resistant enough for your needs, and it's VERY much easier to work with. It cuts and installs just like drywall and weighs very much less than Hardibacker board. It's not as strong as Hardibacker board, but in my time on this 3rd rock from the Sun, I have never leaned against the wall while showering. I was always sober enough to remain upright during a shower, and had no need to lean against a wall to keep me upright.

If I wuz doing this work in my own home, I'd probably install EXTRUDED polystyrene foam insulation between my strapping and drywall screw Dens-Shield to my strapping to form the tub enclosure. Then glue the tub surround to that. My understanding is that some tub surrounds nail or screw on, but I don't have any experience with that kind of tub surround. If you screw the tub surround on, I'd use stainless steel screws for the few dollars extra they might cost, cuz this is a wet area.

This message has been edited. Last edited by: Nestor,

Thanks Nestor ,
What do you mean by strapping ?
Are you refering to the furring strips on the 2 cement block walls ?
the 3rd , last wall , is a inside wall ,,, just studs .
Would you cut and Glue the insulated board to the cement block walls in between
the furring strips ?
Or should I eliminate the furring strips on the cement block walls ? ,,,, as the surround
I will be using just glues in place ,,, no screws used.
If so ,, Would you use liquid nail as the glue ?
THANKS AGAIN for the help ,, KZ

Beeginner -- thank you for letting us know you are from Florida. There are different ways to build in different areas. As I am from California, I will not give advice in your case, as you people on the east coast do things differently than the west coast. And I'd be willing to bet you do things different than Nestor because he is from Canada. Its up to you, but I'd wait until someone closer to your home adds in, then you'll get the best advice from someone knowledgeable on how to build in Florida.