Framing a tub deck/surround

mongoctJanuary 15, 2008

There are different ways to skin this cat. Here's one way.

I don't have a decent step-by-step set of pictures, these pics are a byproduct of another shoot.

I always set non-cast iron tubs in a mortar bed. If your floor is not level, this allows you to level the tub. If your floor is level, then you can either set the tub, feet and all, in a thick bed or you can set the tub in a mortar bed and displace enough mortar so the feet of the tub touch the subfloor. Or you don't have to use mortar. Your choice.

ABOVE: Your tub will have a specified distance from the bottom of its rim to the bottom of its feet. In my example I used 19". Assuming I use a 1" (1" thick after the tub is set and mortar displaced) bed of mortar under the tub, my finished deck needs to be 20" off the floor or above the platform.


1) Tile plus thinset = 3/8" thick

2) 1/2" cement board plus thinset = 5/8" thick

3) 3/4" CDX ply = 3/4" thick

Add those three together to get 1-3/4". Subtract that from 20" and I want my framing for the tub deck to be 18-1/4" tall.

Using 2x4 material, the top and bottom plates (framing pieces with an "X" on them) will be 1-1/2" thick (maybe 1-3/8, measure your wood), so my cripple studs will be 18-1/4" - 3" = 15-1/4" tall.

ABOVE: The above pic is not a great example, because in this case the Lady of the House wasn't certain how high she wanted the tub to be. So I built the frame for the deck, stuffed it in place, and elevated it with the small pieces of 2x4 you see up against the walls. This allowed my to raise it or lower it as needed. Once the height was settled upon, the deck frame was leveled and screwed into the wall studs (do NOT use drywall screws!) and it was then under-filled with cripple studs to properly support it. Get the deck level.

ABOVE: I'm including this pic as it shows what a proper mortar bed looks like after the tub is set. You can see this tub had full support. You won't get that with canned foam.

ABOVE: Instead of a tiled tub deck, this one is teak. This shows the deck after it was epoxied up in place.

ABOVE: Three coats of a good urethane. Shiny because it's wet.

ABOVE: After the third coat, a nice satin finish. You can see that the teak deck doesn't reach all the way to the window wall. Later I installed a raised teak window sill that was about 7 or 8" deep.

Above: Here's the raised teak window sill. It hasn't been urethaned yet. The tub deck is 8/4 teak, the window sill 4/4.

ABOVE: A drawing of how I built this apron. What I like about this apron is that any of the three panels can be lifted and rotated out to gain access under the tub. Or the entire face frame that holds the three panels can also be lifted up and rotated out to gain access to the entire front of the tub. No tools required.

ABOVE: One panel removed.

ABOVE: Then whole face frame removed.

ABOVE: Everything in place.

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I wished you lived in the DFW area...My current tub was marbled in with no access to the faucet pipes.. super fun when you need to replace a 30 year old faucet. So to find a person like you to replace my tub, where do I start looking? The GC I have spoken with all want to completely redo the bathroom and the tub job is too small. Any advice. Your work looks awesome. Lucky lady.

    Bookmark   January 16, 2008 at 9:55AM
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thanks Mongo - this is great! i love the teak

a couple questions...

1. my acrylic tub has a board attached to the bottom of it, which has the electrical stuff & some air tubes attached to it. then under that are 4 wooden legs. the mfr says you can do a mortar bed or shim the legs. initially i was going to do a mortar bed, but after looking at everything, the mortar won't touch the tub at all - it would only touch the wooden legs & the wood platform the tub is sitting on. would that really add anything that correct shimming wouldn't add?

2. what are those mesh panels made out of on the sides of the apron?


    Bookmark   January 16, 2008 at 10:37AM
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Above you stated that you temporarily put the deck frame in place so that you could play with the height until the owner was satisfied..however, the owner could only have the deck as low as the tub was deep, correct? So was the owner wanting (or debating)just going higher? If she went higher than the depth of the tub, would you first have to build a support to raise the floor for the tub to rest on or would the tub solely rest on the decking?

Also, how much support is needed under a tub? We're going to be remodling a 1950's bathroom and expanding into an adjacent bedroom...We'll be ripping up the floor and will be putting in a jetted tub of some sort and a walk in shower and are wondering if we'll need additional support.

Also, you say you allow of 1 inch thickness of mortar but then say you push the tub down into the mortar until the feet rest on the subfloor...if so then how is the mortar raising the tub by 1 " if the tubs feet rest on the subfloor?


    Bookmark   January 16, 2008 at 1:38PM
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needsleepmommy-- What you might do is go into John Bridge's forum, and look for a guy that goes by the name of "Davey" (Davey Stevens). He's a custom tile contractor in your area. He, his brother, and his father do nothing but high end construction, and I'm sure he could give you a name.

    Bookmark   January 16, 2008 at 5:18PM
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Thanks Bill..where do I find John forum? Also does high end construction mean they only do big jobs? I have trouble when I say I only want the bathtub replaced. I am not very savvy at this...many thanks again

    Bookmark   January 16, 2008 at 8:29PM
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Post in the Pros Hangout:

Or you could just go directly to his website and email him from there:

Here is a link that might be useful: Davy Stevens website

    Bookmark   January 16, 2008 at 8:39PM
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Just emailed him...thanks a bunch...I feel like I am closer to getting my bathroom done....yeah!!

    Bookmark   January 16, 2008 at 9:02PM
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Sorry for the late replies, I went to FL for a couple of days.

needsleepmommy, looks like Bill came to your rescue.


1) If the only contact your wood platform has with the tub is through the legs, then it doesn't sound like a full support mortar bed under that wood platform would provide much benefit. Shims and PL construction adhesive (or whatever the manufacturer recommends) to keep things from moving should do you fine.

2) The grate is a diamond-grid patterned piece of sheet metal, I think it might actually have been purchased at home depot. The original sheets were large, maybe 3' square or so? I use them whenever I need an open ventilation grate of some sort, and where the look will suffice.

I cut the metal down to size, sanded it with a random orbita sander to get down to bare metal, then sprayed it with black paint. Let the paint dry, then sanded by hand in one direction with sandpaper to take away some of the paint and lighten the color. It has a "brushed metal" look due to the sanding.

That grate, as well as the toe kick under the closet to the right of the tub, allow free air to get under the tub. A bit of ventilation.


The original height of the tub was indeed specified, and I set it at that height. That's the height of the original platform (6-1/4" high) that you can see in the first photo. I always felt that it was a couple of inches too low, we went back and forth over it.

So I set the tub and had her climb in. She agreed it was indeed too low and that we should raise it a few inches. So I ripped the tub out, that's why I have the picture of the mortar bed in picture #2.

To raise the tub I then built a mini-platform on top of the first platform. You can get a glimpse of the mini-platform in the second-to-last photo, the one that shows the entire face frame removed.

Drop-in tubs should not be supported by the rim. The weight needs to be supported by the base of the tub, with the rim just touching the deck.

Your tub will have a specified operating volume, most are around 80 gallons. Water weighs a little over 8 lb/gallon, so you're looking at 640lbs for the water. Using my tub above, the water weight is transfered to the footprint of the platform which is 8' long by 4-plus feet wide. 32 sqft. That's a live load of only 20 pounds per sqft on the bathroom floor. Even add two bathers and you're up to 30 lb/sqft. Common code today is to build for a minimum 40 lb live load.

Most bathrooms, even vintage 50's construction, have floor spans that can handle a modern tub. But you can have your joist span, joist spacing, and joist sizing checked to confirm that just in case. the platform not only raises the tub, but it spreads the tubs load over a wider area.

Don't forget that the load is a live load, it's temporary, it's only there while the tub is full of water.

Best to all,

    Bookmark   January 18, 2008 at 3:29AM
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Re: tub secure the surround to the wall studs as well as to the platform? Any photos instructions on building the platform and the support decking? I see your platform, but it is covered by the plywood.

Also, on a side note..any instructions installing a kerdi shower but with a preformed shower pan? I did download the Kerdi book and just started to go through it. But I really don't want a tiled floor, but do want a waterproof if we go with a preformed pan of some sort (would have to be custom as our size/shape isn't "standard") can we still integrate kerdi system?

Also, I read on another post someone got a tub, but doesn't have a big enough water heater to fill it...does that happen often? I never even considered that possibility?


    Bookmark   January 18, 2008 at 9:24AM
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"Re: tub secure the surround to the wall studs as well as to the platform? Yes.

Any photos instructions on building the platform and the support decking? I see your platform, but it is covered by the plywood. No pictures of that. Frame it like a mini-floor. 2-by framing members spaced 16" on center. I usually run the platform "joists" perpendicular to the direction that the floor joists are running. Do mark out a the area where your tub's drain and trap will run, box that out accordingly so the platforms' joists don't interfere with the plumbing. Then cover the platform with 3/4" CDX plywood.

Also, on a side note..any instructions installing a kerdi shower but with a preformed shower pan? That might have been discussed in the "Kerdi Shower" thread. If it wasn't covered specifically, the detail for joining the wall Kerdi to the preformed shower pan flange is essentially the same as joining the Kerdi to a tub flange.

I drew a couple of sketches regarding that detail in the KS thread. Should be towards the end. There should be one drawing showing the cement board being held above the flange and the tile hanging over to cover the flange. There should be a second drawing showing furring strips added to the faces of the wall stud, with the cement board then hanging down past the tub flange and the tile no the cement board. The latter would be a better when using small mosaic tiles.

Also, I read on another post someone got a tub, but doesn't have a big enough water heater to fill it...does that happen often? That could happen. There is usually a minimum quantity of water that needs to be in a tub for a jetted tub to operate. That volume will put the water level above the jets, preventing the pump from cavitating. Some folks on the forum with smallish water heaters have mentioned that they fill the tub as much as they can, climb in and soak while the water heater is recharging, then fill it more while bathing. Remember, your body will displace water as well, raising the water level. So the answer? Yes, it could be a factor. How much of a factor depends on your water heater's volume and recycle time. That's not a question I'd be able to answer.


    Bookmark   January 18, 2008 at 10:49AM
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There was a thread a couple months back asking about DIY tub framing. Link below.

Our tub came attached to 2x4s. We just shimmed them level and screwed the 2x4s into the subfloor so the tub wont move.

    Bookmark   January 18, 2008 at 5:08PM
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Hi Mango,

Your post is really really helpful!!

We are planning to add new bathroom to our sun lite basement, and would like to ask your advice on tub framing/installation...

We would like to install our tub raised up about 1 foot from the floor, so we can look out from the window easily and enjoy the japanese garden just outside of the window.

What would be the best way to build the solid base for the raised tub?

Our bathroom is located in unfinished basement (= floor is concrete). The tub height is 20'', so the finished raised tub height will be 30'' - 32''. It has factory-installed alcove tile flange, so we won't need to build a tub deck I believe (just attach 2x4 along the wall studs to hold the edge of tub).

Hope I explain my questions w/enough information.


    Bookmark   February 2, 2008 at 2:35AM
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needsleepmommy...I live in Fort Worth & would love to piggy back on your discovery. I need to build a shower.
Thanks so much

    Bookmark   January 7, 2009 at 9:20PM
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Where did you get the piece of teak wood? Was it more a veneer?

    Bookmark   July 29, 2011 at 3:22AM
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    Bookmark   February 11, 2012 at 2:54PM
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I want to build a platform for a 66x32" tub, but my bathroom is small and I don't have any room for a platform that is any larger than the tub's dimensions. Since the tub's weight is resting on the floor and the tub lip just rests on the top of the platform, can't I make the platform the same size or AT MOST 1" wider than the lip of the tub?

    Bookmark   May 4, 2012 at 9:26PM
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