Painting Hardiboard and a couple of other questions

[PeteD]

Hi:

Let me give a quick background on my questions, so you know what the overall project entails.

I am redoing the surround on an enameled tub in an apartment that I own. The previous tub surround (mostly demolished already) was lath/horsehair with patches of drywall in some areas against the studs, covered with glued-on masonite fake tile panels (4 by 8 sheets in the entire bath - style disaster, but one problem at a time), capped with a glued-on 5-piece plastic surround. Surprise, surprise, the wall was was not stable (has been unstable for some time) and the caulked joint at the tub would never hold,m allowing some water infiltration. There was no current wetness behind the surround (I have kept up with the caulking), but obviously there was previous of evidence of water and some dried-out mold in the plaster and fake tile. Right now I am seizing the opportunity for a more solid solution to make the surround watertight.

My plan is:
1) Strip everything down to bare studs above the tub, which I am keeping
2) Install 1/2-inch hardiebacker (want to paint above new surround and it seems smoother than Durock) over the studs working from top down in full sheets
3) Seal corner seams (no other seams will be present) and screws holes above level of new 5 piece surround
4) Prime and paint area above new 5-piece surround height
5) Install new heavier-duty 5 piece surround onto hardiebacker

I have the following questions:
1) What do I seal the corner seams and screws holes in the hardiebacker with before painting? (thinset?)
2) What type of primer and paint combo should I use for the hardiebacker?
3) Should I place a vapor barrier behind the hardiebacker? (House is more than 100 years old and walls are "well-ventilated"
)

Being an apartment, I want to avoid tiling and keep everything low maintenance and durable.

Thanks for reading this post.

Pete

[jadnashua]

Put a vapor barrier on the studs, lap it over the tiling flange of the tub. Leave the bottom edge of the cbu about 1/4" above the tub and caulk that gap. Assuming you are going to tile this, use alkali resistant mesh tape and thinset. If there are areas that are just going to be painted, some people like to do a skim coat of drywall mud over the whole thing. You can use regular paper (stronger) or fiberglass tape on the corners prior to painting. Getting the screws set well enough to hide in areas that are going to be painted is a little tricky since the stuff is very dense, but possible if you use the special screws (they have ribs on the bottom of the head to ream out room to allow it to sink in).

[geniescience]

ditto. If you are good with drywall compound or plaster, put a coat or two on the Hardi before painting. That will cover screw holes, corners, tape and rough spots. Also, it will remove the harsh tone that concrete surfaces have. I agree with you that Hardi is better than Durock if you are going to paint it RAW, but once you plaster the surface a little bit, it doesn't matter which product it is, Anything fiber-cementy, even something less expensive than Hardi.

I have done this. We are happy with the solid feel that the room has. Sounds echo differently; the walls don't feel hollow and cheap; the walls "feel" massive although they are thin. If you can add some cheap open-cell styrofoam insulation in the stud cavities, go ahead. It will insulate against sound transmission and heat/cold transmission too.

Vapor barrier, yes. If you are going to put up another surround, i think you don't need to align it to drop into the tub flange.

david

[PeteD]

Thanks guys.

Should use galvanized nails for the tar paper (as opposed to staples that are not corrosion resistant)?

Staples would be easier to use for obvious reasons.

Pete

[dx]

Best is to glue the tar paper or plastic film used as water barrier. ANY fasteners will make it less of a barrier (hint: it's like putting nails through the hull of a boat).

You will already puncture the tar paper plenty when you screw down the Hardi, so you want to avoid making it a total sieve.

If you must use fasteners, use stainless staples.

dx

[lee polowczuk]

I used those roofing nails with the plastic circle for the tar paper vapor barrier.. then i did the durock.

I will use joint compound in a few small areas where paint will cover the durock..

but for the most part....tile will cover the durock.

with joint compound , thin coats are better... i don't sand inbetween, I wet sponge....

[PeteD]

Thanks guys. I can see the light at the end of the tunnel.

I do have a question about caulking an old-fashioned style 3-handle bath/shower faucet. I know how to caulk the tub spout, but how do I caulk the handles?

Do I need to put on the sleeves and fill the gap in the wall around the sleeves with caulk before putting on the finish plates against the wall, or can I just seal the finish plates against the surround with caulk and have the shiny sleeves "float" through the holes in the wall? The old faucet had a 1/4-inch to 3/8-inch inch bead of caulk around each of the 3 sleeves...

Also, if I just need to caulk the three individual plates onto the surround, do I need to caulk them to the shiny sleeves to prevent water infiltration at that joint?

TIA,
Pete