Concrete Bathtubs

Concrete. A natural substance, and one of mankind’s most durable inventions. Handmade and can be formed into jut about any shape you want. It radiates creativity. If you can think of a shape, it can be implemented with concrete.
From ancient times concrete has been used as a construction material. Roman coliseums, senate, and other historical monuments are just some of the examples of the use of concrete in human civilization. There is an increasing trend towards designing in concrete bathtubs over marble ones.

In today’s world also we use concrete in our construction works. We can have concrete that hardens over time, and even produce a concrete that creates an effect like soapstone. Obviously due to this versatile nature, concrete is one of the top choices for home owners.

Here is how one homeowner went about constructing a concrete soaking tub, or Ofuro.

concrete tub formOutside dimensions of the tub are 42"L x 42"W x 36"H The walls are 4" thick rebar reinforced concrete. The seat inside is about 13" high and the back is slightly reclined for comfort. As with any concrete pour, the formwork is what really matters and what takes the most time.

This was my first foray into anything cast concrete, but you'll recall, I've just built a concrete house so I had plenty of opportunities to pay attention in class during the course of that work and I never missed an opportunity to ask questions and learn about the material.

The inner and outer form panels I made using 3/4" melamine. This was basically just an exercise in visualizing negative space and a lot like forming a stoop, although slightly more complex. What required the most thought here was figuring out how to hold all of the panels together, not screw through the inner melamine surface, and still be able to get everything apart and out once the concrete hardened.

I used blocks of scrap melamine screwed together in a lenghtwise "L" and then screwed to the form panels. I also braced the melamine panels with scrap lumber to keep them from bowing and reinforced the corners with plumbing strap. Because the tub needed to have a floor, the inner form needed to be held up higher than the outer form. This was accomplished by basically hanging the inner form from the walls of the outer form, again using scrap lumber and plumbing strap.

concrete bath tub melamine formRegarding the plumbing rough in: I had the drain roughed in slightly lower than the intended height of the tub floor to allow for a pitch of about 1/4"/foot for drainage. The overflow pipe was roughed in so that it ended up within the 4" thickness of the tub wall.

You can see the circular hole in the form wall in the pictures. This is the PVC collar that the chrome overflow trim screws to, and the flange of this PVC piece fits into and extends just slightly into that hole to prevent concrete from filling the overflow.

I had originally planned on getting ready mix for the tub and the concrete counters, and pouring all of this stuff at once. Fortunately, I came to my senses and realized that was going to be WAY too much of a panic to worry about all at once, and I decided it would be better to DIY our mix using bagged materials. I was also concerned about having very tight control over the amount of water in the mix, and I decided that ready mix would be too unpredictable and likely too wet.

I rented a portable, electric concrete mixer for this event which turned out to be not as useful as I had hoped. We found that mixing two bags of material at a time using a wheelbarrow and mason's hoe worked a lot better. Having two great friends there to lend a hand was a huge bonus as well. Here's the form all filled, showing the slanted back and the bracing inside. The cross pieces with the strapping on them are suspending the inside form off the floor.


I used 1/4" rebar. I drilled 1" or so into the floor to place three uprights per side. Then I bent some "L"s and tied these to the uprights to encircle the whole thing in two separate layers. We did have to be careful and make sure to adjust the rebar here and there to keep things from poking through the concrete, but it ended up fine.

If I did it again, I'd epoxy the uprights into the slab first so they couldn't move. This would have made placing the horizontal layers and keeping them in place a lot easier.

It was helpful that we were pouring up against an existing wall, as that was one less side of form to have to brace and worry about keeping square. There was also a temporary wall on the supply side of the tub (built to soothe the plumbers and give them somewhere to place their rough-in), that provided a backer to a second side of the form. The other two sides we braced to the walls of the bathroom, shown here:concrete bath tub bracing Any good concrete guy will tell you you can never go overboard with bracing. A yard or two of wet concrete all over the floor inside the house would have been a huge drag, and while we got a little bowing, the bracing and form reinforcements did their job.

In this regard, our slow process of mixing a few bags of material at a time, by hand, was a boon as it allowed us to keep a sharp eye on the form and make adjustments to the bracing as necessary.

We also made an effort to mix the concrete with as little water as possible, both because of the effect of this on the cured product and because less water equals less pressure on the mold. :concrete bath tub finished Here's a shot of the newly de-molded tub. The concrete is still slightly wet and very green. We've also removed the temporary pony wall here, and you can see the water supply lines.

Decorative Possibilties of Concrete Bathtubs

If anything can single handedly change the decoration of a bathroom, then it is a concrete bathtub. As it is created from such a versatile substance we can get almost any kind of bathtubs designed specially for a particular bathroom. It can be suited in a gothic style bathroom and similarly can look great in a very modern bathroom also. So if delicacy is the prime concern, then the use of concrete bathtubs is inevitable.

These bathtubs can be customized according to customer needs. There is no hassle of choosing from a fixed range of designs available at that particular moment that may not suit well in one’s requirement.

Benefits of Concrete

First of all, it is versatile. Varieties colors and designs are there to choose from. Regular developments on this particular field create more and more possibilities and varieties that enhance its attraction.

Concrete is durable. It is warm to touch and durable than most other popular stones. Due to this reason concrete can be placed in the bathrooms of most delicate life styles with no difficulty at all. Concrete, when piling with some chemical substances can produce extra durable effect that is harder than any conventional rocks used in the construction sector.

It can be made beautiful. Years of researches on this particular field has found ways to make it more presentable to the people. In ancient roman ages concrete pillars were covered with stone for that extra look good effect. On the contrary these days concrete is replacing stone structures in a very rapid rate.

This is happening because concrete can be treated and can be made as beautiful as the requirement may be. It can have colors of different types and natures with vivid architectural designs which are very difficult to carve on stone plates.

photos and construcrion details courtesy of splatgirl. - CreativeCommons Attribution