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Concrete Bathtub

by Matthew O. Daby last modified Jul 02, 2012 05:35 AM
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Concrete Bathtub

Posted by Matthew O. Daby at June 20. 2005

Hello All,

I am in the middle of a design and really want to do a custom shape spa tub. The budget we are dealing with is very limited. I was thinking of constructing it of concrete. Does anyone have experience in this process? Do you basically build a form out of plywood, lay in rebar? and pour in the crete? (lightweight I assume) shed some light on the subject for me? Is it a pain to fit all the pieces for the spa? leaks? stains from your various grooming products? any other material opinions?

Re: Concrete Bathtub

Posted by Zachary Anderson at June 20. 2005

check out this article:

http://trendsideas.com/us/home-design/bathroom/20/04/cutting-corners/

they used plaster and made it look like crete, eh.

Re: Concrete Bathtub

Posted by ThreeDogKnight at June 20. 2005

This site is a good place to start to learn about concrete in the home:

[url href="http://www.concreteexchange.com/index.jsp"]http://www.concreteexchange.com/index.jsp[/url]

Re: Concrete Bathtub

Posted by Splatgirl at June 20. 2005

I am getting ready to cast a ofuro (soaking) tub from concrete in our master bathroom. Mine will be of standard concrete and sits on a rebar reinforced concrete slab that is our finish floor. I added extra rebar to the floor under where the tub will go to accomodate the extra weight, and yes, I basically plan to build a form and pour it in place. I'll be sure and take lots of pics.

There are a few issues that I am aware of:

It's a bad idea to embed plumbing valves directly in concrete, as replacing/repairing them later would be impossible without major headache and destruction. I'm doing a soaking tub, not jetted, so I overcame this by locating the fixture in a wood framed wall that butts up to one of the tub walls. An alternative to this would be sleeving the pipes and valves in the concrete, but then you have a problem with attatching and stablilizing the sleeved valve and fixture on the deck surface. Presumably, this would be an even bigger issue with a jetted tub where you've got multiple outlets and pipes that you will eventually need access to. And then where to put the mechanical stuff (pump) that typically goes inside the skirt part of a commercially made tub?

Problem two is the trap and drain, as these need to sit below the level of the bottom of the tub. Since our tub sits on a poured slab, I had to box out space for this stuff and leave what amounts to a big hole in the slab that will be covered by the tub once it's placed. I don't know how this would work in a wood framed floor but it might be easier.

You'd get the best advice on all of this by explaining what you want to do to a very smart plumber, or a few very smart plumbers, because you're probably going to find resistance to anything outside the box from most of them. I found out that it's not as simple as I expected and honestly, I'm still not sure how it's going to work but I'll find out shortly.

I'm not sure if lightweight concrete would be suitable as a casting and finish material for such an item. All of the cast concrete stuff (including tubs and sinks) I've seen or read about has been done in regular concrete as far as I know, which makes me wonder if there's something about lightweight that makes it unsuitable. I'd put the question to as many concrete experts as you can find, see how many different answers you get and then research the crap out of it on your own before you try it.

Good luck and let us know what happens.

Re: Concrete Bathtub

Posted by aaron coates at June 21. 2005

Concrete is cold. If this is a new construction project, and you are using radiant heat, its a good idea to run some tubing through the tub to keep it at a comfortable temp.

Re: Concrete Bathtub

Posted by Brandon J. Gore at June 30. 2005

Concrete tubs can be challenging. I would recommend talking to someone in your area who does pre-cast to advise you on bracing your forms. A blow-out on a poured in place tub would be catastrophic to say the least.

Secondly, are you planning on pouring your tub in levels (i.e. the floor first and then the walls)? If not you will need to drill holes in the form that will be the tub floor to allow trapped air to escape.

The form construction is key to a good tub. The next most important factor is vibration. To reduce the entrained air you will need to use a portable concrete vibrator. Makita makes a good one, or you can rent one from a local tool rental center.

Let me know if you have any other questions I could help you with.

Good Luck,

Brandon Gore
brandon@goredesignco.com

Re: Concrete Bathtub

Posted by Splatgirl at July 03. 2005

Hi Brandon. I'm glad you showed up on this thread.

How would you address the cold joint between the floor and walls in a tub poured in two parts? (Assuming I will topically seal but not apply a secondary finish like tile, etc.)

Do you use ready-mix or site mix your own mud for large cast pieces of this nature?

A good, sturdy form I think I can manage...it can't be too much more dicey than a 10 x 12 cap stoop form, right? Other than being inside instead of outside, that is :)

Re: Concrete Bathtub

Posted by Steve Rankin at July 05. 2005

My only recommendations (I have have not made a concrete bathtub but have worked with concrete many many times before) are to:

1. Reinforce your floor if there's a crawlspace or basement, or if it's on a second floor.

2. As mentioned by someone in an earlier posting on this forum, be careful with embedding pipes and/or anything breakable in the concrete; you may have to destroy part of the tub to replace them should they fail.

3. Concrete can be/is somewhat porous, so make sure there's some kind of sealant or water barrier installed/added during construction.

4. Look at some books on concrete to figure out what kind of and the amount of reinforcing (rebar, etc.) you should use.

5. A book I found useful for working with concrete in general is a book on concrete countertops by Fu-Teng Cheng via Amazon: http://www.amazon.com/exec/obidos/ASIN/1561584843/102-1955678-4384916). He has written other books on concrete use that may be helpful.

That's all I got...
Good luck!

Re: Concrete Bathtub

Posted by Kevin Cotton at December 28. 2010

Previously Matthew O. Daby wrote:

Hello All,

I am in the middle of a design and really want to do a custom shape spa tub. The budget we are dealing with is very limited. I was thinking of constructing it of concrete. Does anyone have experience in this process? Do you basically build a form out of plywood, lay in rebar? and pour in the crete? (lightweight I assume) shed some light on the subject for me? Is it a pain to fit all the pieces for the spa? leaks? stains from your various grooming products? any other material opinions?


Are you still out there Matt? I'm in the middle of building a Concrete Bath Tub and I have a few question ????  How did you water proof it? Did you use a membrane in between the croncrete? how thick is the walls? How thick is the Floor? What kind of mix did you use?  kevincotton@cox.net

Re: Concrete Bathtub

Posted by Kevin Cotton at December 28. 2010

Previously Brandon J. Gore wrote:

Concrete tubs can be challenging. I would recommend talking to someone in your area who does pre-cast to advise you on bracing your forms. A blow-out on a poured in place tub would be catastrophic to say the least.

Secondly, are you planning on pouring your tub in levels (i.e. the floor first and then the walls)? If not you will need to drill holes in the form that will be the tub floor to allow trapped air to escape.

The form construction is key to a good tub. The next most important factor is vibration. To reduce the entrained air you will need to use a portable concrete vibrator. Makita makes a good one, or you can rent one from a local tool rental center.

Let me know if you have any other questions I could help you with.

Good Luck,

Brandon Gore
brandon@goredesignco.com


Are you still out there Brandon / Matt? I'm in the middle of building a Concrete Bath Tub and I have a few question ????  How did you water proof it? Did you use a membrane in between the croncrete? how thick is the walls? How thick is the Floor? What kind of mix did you use?  kevincotton@cox.net

Re: Concrete Bathtub

Posted by Lou De Lorca at February 04. 2012
Previously Kevin Cotton wrote:

Previously Brandon J. Gore wrote:

Concrete tubs can be challenging. I would recommend talking to someone in your area who does pre-cast to advise you on bracing your forms. A blow-out on a poured in place tub would be catastrophic to say the least.

Secondly, are you planning on pouring your tub in levels (i.e. the floor first and then the walls)? If not you will need to drill holes in the form that will be the tub floor to allow trapped air to escape.

The form construction is key to a good tub. The next most important factor is vibration. To reduce the entrained air you will need to use a portable concrete vibrator. Makita makes a good one, or you can rent one from a local tool rental center.

Let me know if you have any other questions I could help you with.

Good Luck,

Brandon Gore
brandon@goredesignco.com


Are you still out there Brandon / Matt? I'm in the middle of building a Concrete Bath Tub and I have a few question ????  How did you water proof it? Did you use a membrane in between the croncrete? how thick is the walls? How thick is the Floor? What kind of mix did you use?  kevincotton@cox.net

Re: Concrete Bathtub

Posted by Paul Wilson at July 02. 2012

This thread has gone quiet but I am about to pour my own bath. I am curios to know if pouring the bath in two parts is the best option. If not how do you ensure you get good concrete flow between the inner and out moulds. Thanks. 

Re: Concrete Bathtub

Posted by Paul Wilson at July 02. 2012

This thread has gone quiet but I am about to pour my own bath. I am curios to know if pouring the bath in two parts is the best option. If not how do you ensure you get good concrete flow between the inner and out moulds. Thanks. 

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