How to "frame" a shower niche? [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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07-20-2011, 08:15 PM
I have a few situations where I need to frame out a recessed "nitch" inside the shower. The nitch will be something like 12"W X 18"H X 3"D.

In one case, the wall is an exterior wall with concrete blocks. So what I did was chiseled out a recessed area, then I shimmed and fastened several pieces of 1x pressure treated wood to the back and sides of the chiseled out area with Tapcon, to create a level and square recessed box. My intention is when I put up Durock in the shower area I will also attach Durock to all interior surfaces of the recessed box, and they will be screwed into the PT 1x wood. Is this the correct way to do it? Or should I just attach the Durock directly to the hollowed out concrete surfaces, which are not straight and smooth.

In another case, the wall is a standard interior wall with 2x4 wood studs. The other side of the wall will have standard 1/2" sheet rock. So when I frame out the box with just 2x4s, what do I do with the back side? I am not sure it is a good idea to attach Durock to the back of sheet rock. I assume I need some sort of sturdy wood backing? My thinking is instead of using 2x4s to frame the recessed area from the 2x4 studs, use 2x3s instead and frame them flushed on the shower side. This will leave a little room on the back, just enough to put in a piece of 1x plywood and nailed to the back of the 2x3s. The 1x plywood and 2x3 will add up perfectly to take up the 2x4 space. The Durock will then be attached to the ply in the back and 2x3s on the side.

Thanks in advance for any comments and advice.

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Brad Denny
07-20-2011, 08:51 PM
Hello M,
Was the block you chiseled out an exterior wall?
What type of waterproofing/vapor barrier are you using on your walls?

I probably would have used a surface applied membrane to waterproof and SAM'ed over the block rather than chopping it out. Same for the backside of the drywall. You could laminate a piece of Durock to the drywall with thinset, then waterproof over.

07-20-2011, 08:53 PM
Hi there. Please put a first name in your signature line for us, won't you? Thanks. :)

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Is this shower part of either of your previous threads? Looks kinda similar. :)

How are these walls being waterproofed or moisture-proofed? Can you post some photos of the concrete block chiseled out area?

This your house? :)

07-20-2011, 09:12 PM
I don't have any pictures right now but I will snap some tomorrow.

The questions I am asking is a general one because my remodel include four bathrooms, each with their own unique set of requirements. As of right now, I have not done any Durock or sheetrock yet.

The concrete wall is an exterior wall. That particular wall is 12" thick, with an 8" concrete hollow block and a 4" concrete hollow block. I chiseled to about six inches deep but the back side is not perfectly straight - impossible to do with a chisel. When you say "how is the wall waterproofed" do you mean how it will be waterproof in the shower area? or what is currently in place for waterproofing on the outside of the wall? I am somewhat confused by the question as how that pertains to this stage of the process. The location of my house is in Miami, Florida, the outside of the block has stucco and paint. The inside of the wall, is now bare block. I intend to attach PT furring strips, then attach Durock in the shower area including the recessed nitches, then I will probably use the Schluter membrane (not sure yet).

Brad Denny
07-20-2011, 09:17 PM
You got it MC, trying to figure out what route you were going to take to manage the water inside the shower. In your climate, I kinda think that truing up the block with thinset and using Kerdi would suffice, but don't hold me to it. Wait for others to comment. :)

07-20-2011, 09:20 PM
If you're building a shower with niches, then the waterproofing or moisture-proofing of the niches needs to be sorted out. I'd not use pt wood in any shower with tile, there's just no need IMO. Like Brad mentioned above, a surface applied membrane is a good idea, something like Kerdi would work fine. You need to figure that out before getting a whole lot farther, as the niche waterproofing needs to tie into the rest of the shower waterproofing... ;)

Without seeing photos, I'd probably say you'd want to use mortar inside the CMU wall to straighten out the chiseled area, not backer board. :)

07-20-2011, 09:29 PM
Brad, I won't be able to apply the membrane directly on the concrete because there are electrical conduits, copper pipes etc running on the surface as well as shower valves that controls the final surface depth. So I will need to build out with PT lumber. But my build out will be 3", I want my recessed nitch to be at least 4" deep, that's why I did the chiseling.

I got super unlucky as I started to chisel, I found out that area of the wall, the hollowed blocks were NOT hollow, all the cells were filled with solid concrete, so I bite the bullet and did it anyways.

This is one picture I have but it is old, it does not look like this anymore as I have reconfigured things a bit.


07-20-2011, 09:38 PM
OK thanks for the advice so far.

As far as the block wall, the fact that it is "block" is immaterial. Reason is the wall is being build out with wood to the proper depth due to pipes and other variables anyways.

So for that nitch I have about 3" of depth in "front" of the block surface after the build out, AND 6" of depth into the block. A total of 9" which is more than I would need. I chiseled out more than I need because I want to leave room to level and smooth out the back of the uneven nitch with "something".

Eventually I will attach Durock to all surfaces inside the shower, including the nitch. The water proofing goes over the Durock. Then tile.

Therefore the PT 1x I applied to the edge and back of the nitch is not to attach tiles, it is for the purpose of creating a smooth and level surface for the Durock to screw on to. As I can't think of another way to make a perfectly rectangular hole.

I have seen some place that sells those plastic boxes for this purpose. However they are of fixed sizes and I want mine a specific size.

07-20-2011, 11:46 PM
Welcome, MC. :)

Therefore the PT 1x I applied to the edge and back of the nitch is not to attach tiles, it is for the purpose of creating a smooth and level surface for the Durock to screw on to.Dana was advising against exactly that, and I agree with him and very strongly recommend against using pressure treated wood in that application.

Unless, of course, you have access to KDAT (Kiln Dried After Treatment) treated wood in your area. If not, use good quality KD lumber in there.

My opinion; worth price charged.

07-21-2011, 12:23 PM
OK here are some pictures I just took. There are two nitches. The situations are similar. The walls will be "built out" by another three inches from the face of the concrete to get to the desired depth needed to clear the valves, pipes and conduits. In addition, each wall is chiseled to be about 5 to 6 inches deep but obviously the back side is not even.

This is the first one. The walls there are hollow concrete blocks filled with concrete and had to be chiseled out. I did the best I can but no way to male it perfectly square and even on the side and back.



This is another one, this one, the block is hollow. In addition, the left side of this block is also hollow "sideways".



07-21-2011, 12:52 PM
Is the reason PT lumber not good as backing for cement board because of it's expansion/contraction issues?

If so, what are other acceptable substitutes?

Brad Denny
07-21-2011, 01:44 PM
I'm sure you are trying to keep everything as close to the wall as possible to save on floor space, but if you can, I'd just build a typical 2x4 wall tight to the block. Can you adjust the plumbing away form the wall enough to do that? if you are wanting to have super deep niches, you can do so in the hole you made in the block or allow the stud wall to be a few inches out from the block. If it were me, I'd fill the holes you have in the block back up. I'd always wonder about creepy crawlers and critters, not to mention the structural integrity. You could put foam board between the plumbing and block, and insulation where you can in the stud wall cavities if you think you need it. Might help on heat/cool transfer and noise.

cx metioned KDAT, which would be best, or KD if KDAT is unavailable for framing lumber. Use your cement board, mud the floor, cover all with SAM waterproofing of your choice.

07-21-2011, 05:17 PM
I have at one time considered building a 2x4 studded wall to the block. Floor space is not really an issue as the shower itself is 6'x7' in size. The two niches are on opposing walls of the shower. The problem is I have too many features (sprays, hand shower, overhead shower, valves, diverters, supply pipes, electric conduits) running along that wall, the 2x4 studded walls cannot be spaced at conventional 16" apart and would have to be terribly notched everywhere for this to work. I eventually gave up on that idea. Furthermore, I would prefer the niche to be a bit deeper to be able to place more than a shampoo bottle.

Insects and critters are a fact of life in Miami so I am not concerned about that, I have basically sealed off all concrete opening with concrete or foam from below. Structurally it is sound and not an issue.

I am not familiar with "KDAT", I will look into it. Thanks.

07-21-2011, 05:25 PM
One related question.

Along the block walls, we have wood furring strips that were basically pressure treated 1x2s from the original construction back in the 70s. We demoed everything but left the furring strips alone.

We would be hanging sheet rock back on the walls by fastening to the furring strips in all areas except the bathrooms. The bathrooms we would use moisture resistant greenboard outside the shower, and inside the shower we use cement boards then membrane over.

Now I am thinking after the comments above, should we remove all PT furring strips from the block walls inside the shower areas and use this KDAT materials instead?

07-21-2011, 06:05 PM
the 2x4 studded walls cannot be spaced at conventional 16" apart and would have to be terribly notched everywhere for this to workNot uncommon in conventionally framed structures, either.Is the reason PT lumber not good as backing for cement board because of it's expansion/contraction issues?Primarily dramatic shrinkage and warpage issues.Now I am thinking after the comments above, should we remove all PT furring strips from the block walls inside the shower areas and use this KDAT materials instead? I would.
I am not familiar with "KDAT", I will look into it. Thanks. Many lumber yards won't be, either. But in your area of the country it should be something that's more available than it might be in other areas. In San Antonio, Texas, a little town of several million, there is exactly one source for that material. In the Pacific Northwest we're told it's a very common item at most real lumber yards. South Florida should know the stuff pretty well.

Take you moisture meter with you when you go to buy it. Our supplier in Houston sometimes seems to forget to complete the KD part of the operation sometimes. :rolleyes:

07-21-2011, 06:53 PM
Hi MC,

Just a housekeeping note - please upload your pics to the forum using the paperclip icon, you can add up to ten images per post and attach them with comments in between. Linking to sites like photobucket with the image tag is not recommended. If you browse back a few years in the forum you'll come across lots of posts with missing pictures because they are no longer hosted at the linked sites. Makes some of those posts darn near useless without the pics.


Houston Remodeler
07-21-2011, 09:44 PM

You need to make friends with the folks at the PT factory on the south loop. They are mighty friendly once they warm up to you and start fetching the good stuff from the back of the oven.

07-21-2011, 10:07 PM
I have a very good, very long-term relationship with the good folks at Allen & Allen in San Antonio, Paul, and Allen & Allen buys a whole lotta that KDAT from your friends in Houston and I'd certainly expect the good folks in Houston to take much better care with the product they deliver to the good folks in San Antonio, eh?

But I'd be disappointed. :( More than once. :(:(