Hi Tim
You have stated that a plastic or felt vapor barrier should lap inside a
bathtub (over the bathtub lip) and caulked. If a bathtub runs along an
exterior wall, how should a vapor barrier be installed over the insulation
on an exterior wall space that extends below the tub lip to the floor?
Thanks!!
Waterproofing Tile Installations
Summary: Waterproofing tile installation means making sure water that leaks through the grout is diverted back into the tub or shower basin. Although straightforward, it is not always so simple. Here are some tips to make your tile area waterproof.
Tubs
Standard bathtubs have a lip on three sides of the tub to capture water. The fourth side is of course the long side that you pass over getting into and out of the tub. Porcelain coated steel tubs have a much higher lip than cast iron tubs. Cast iron tubs have a very slight rise that will capture and divert water back into the tub, however, you must make sure the tub is installed level in both directions.
Capillary Attraction
Have you ever noticed that water can travel up a paper towel or rag that you suspend into a bowl of water? This is caused by capillary attraction. The same thing can happen with cement board or water resistant drywall that is allowed to 'sit' in a puddle of water along a tub edge.
When you install ceramic tile board around a tub you do NOT want it to contact the surface of the tub. I recommend a 1/4 to 3/8 inch space between the bottom of the board and the tub or shower surface. You can caulk this crack if you like with pure silicone caulk.
Tar Paper or Vapor Barriers
What happens if water somehow gets past your cement backer board? You can stop it cold in its tracks and divert it back to the tub or shower basin if you install tar paper or a plastic vapor barrier on the wall studs before you install your ceramic tile backer board. You must make sure that the vapor barrier or tar paper laps into the tub. If you use tar paper make sure that different layers overlap one another like roofing shingles. You don't want water running behind a sheet of tar paper. Don't trim off the excess material until after you have installed the ceramic backer board. Then carefully cut it back so that it is flush with the outer surface of the ceramic backer board. When the tile is installed, the vapor barrier or tar paper will be recessed 1/4 inch from the finished edge.
Caulk ALL Seams BEFORE Tilework
As you install each sheet of ceramic tile backer board, leave a 3/16 or 1/4 inch space between sheets. These cracks will be caulked with 100 percent pure silicone caulk BEFORE you begin to install ceramic tile. I have had great success doing this. If you then decide to tape the joints with thinset and fiberglass tape, you can do so AFTER you have caulked.
If you do tape with thinset, you must be careful NOT to create a hump at the taped seam. Ceramic tile is very unforgiving. The tile will not sit evenly as it crosses the humped area. Add to this the high gloss surface of most ceramic tile and you have a recipe for disaster. The high gloss surface will visually transmit the defect.
Grout is NOT Waterproof
Contrary to popular belief, grout is not waterproof. Water can travel through grout and especially past the contact point between the grout and the ceramic tile.
The joint between the tub and shower must never be filled with grout. This joint should be filled with silicone caulk only. I always grout the tub or shower areas and dig the grout out of this crack while it is still soft. It is very hard to try not to grout it. Caulking the crack before grouting is a huge mistake.
After grout has cured for approximately one week it is a great idea to seal it with a silicone sealant or better yet a silane-siloxane water repellent. Silicone is a film forming sealant that cannot breathe. You can get a great silane-siloxane water repellent from Saver Systems.
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Comments:
mark 20 Mar 2008, 07:50
AsktheBuilder 21 Mar 2008, 13:57
Mark,
Great question! You need two. The first one goes over the entire wall plate to plate. The second one goes from the top plate to the tub lip.
Tom 26 Mar 2008, 20:16
Hi Tim You state the obvious in that cast iron tubs have a milder lip than
steel. I am doing a remodel that I am using a cast iron tub. We are using
Dens shield tile backer as a membrane. Since the lip is very low I am not
sure if I should use wood lath furring to thicken the wall so my den shield
jumps the curb lip or butt the backer to the lip. Its a 1/4 inch high
before we even tile. The void is siliconed either way right? Also would you
silicone inside corners and backer/tub transitions as you go before tile
then again after tile? This would be like control joints.
Thanks Tom
AsktheBuilder 28 Mar 2008, 15:48
Tom,
No need for lath. Keep the backerboard off the tub ledge 1/4 inch. Caulk the gap and all corners with clear silicone. Tile and caulk that horizontal joint as well. No grout.
Troy Ensor 07 Apr 2008, 15:47
Tim,
I have a situation where the lip on my tub is 1/4 inch away from the studs on one side and 1\2 inch away on the other. I am planning on using concrete backer, but there is almost no way to get over the lip without shimming the studs. I really do not want to do that because it would make connecting to the walls I did not remove very difficult and ugly. Any ideas? thanks, Troy
AsktheBuilder 12 Apr 2008, 06:28
Troy,
I can't see how shimming the walls would make it look *worse* than what it will if you don't. What am I missing here? You must not be telling me everything.
E Burns 24 May 2008, 08:19
Hi,
i have a problem with my tub. Obviously none of the above were done when it was installed because the tub is not level and the shower water splashs back into the corner and goes through the grout and ends up in the ceiling of the room below. We have reacaulked and recaulked with no luck. We now have a towel soaking up the water, but it is not a practical solution and the water also goes through the towel. Is there something I can buy to divert the water back in to the tub and not down my wall? Thanks.
Steven Hobbs 19 Jun 2008, 10:04
I have an issue similar to Troy Enser's with the concrete backer
(Hardibacker) not fitting inside the lip of the bathtub, because the
framing around the bathtub is almost half an inch too wide on one side. If
I bend the Hardibacker to fit inside the rim, I get a half inch vertical
offset between the Hardibacker and the surrounding drywall, which the bull
nose tile won't cover. The solution that I'm considering is to run the
Hardibacker flush to the top of the bathtub lip, which would leave about a
3/4 inch vertical gap between the top of the bathtub rim and the bottom
edge of the Hardibacker. I could probably still caulk the
Hardibacker/bathtub intersection and run a waterproof membrane behind the
Hardibacker and over the lip to make the water seal tight. But, I'm
honestly not too worried about water because I live in a very dry part of
colorado. The previous tile was on regular drywall and had no water
issues.
But, here is my question: Is there a problem with not running the Hardibacker to the inside of the bathtub lip? I'm wondering if the tile grout will stick to the bathtub lip at the vertical section where the tile hangs over the lip and does not have Hardibacker behind it. If the grout sticks today, will it work it's way out down the road because it's resting on a porous backerboard type of material? Any thoughts? Thanks!
Steven Hobbs 19 Jun 2008, 10:27
Correction to the last sentence of my above inquiry. It should read,
"...because it's NOT resting on a porous backerboard type of material?"
Thanks!
Ivor Davies 31 Aug 2008, 12:57
Hi Tim, replacing bathtub tile as exisiting lifting on outside wall about
2-3 inches from tub. Replace section only: rip-out old, denshield (or aqua
board) 3' up silicone all joins to exisiting. Original installation does
not sit on, or slightly above bathtub lip as you suggest. How high is this
lip? Need to know for tile pattern (1" mosaic) sheets 12" X 12")if I am to
do this replacement succesfully.
Thanks View all comments |
