A concrete bath tub has many advantages, including a luxurious design and low cost. It can also be poured to fit your space and needs exactly. A concrete tub, since it is made from concrete, can be shaped how you want. It also has a nice surface that makes it ideal for tubs.
Design the tub on AutoCAD software. This way you can accurately break down the number of forms you will need to cut for your concrete tub.
Cut the outer form boards to size from 1/2-inch plywood, for instance for a 2 by 4 foot tub that is 2 feet tall, cut two 2 by 2 foot boards, and two 4 by 2 foot boards.
Set up the forms in the shape of the tub. Fasten them together using 2 by 4 boards and braces. Lay them on a 2 by 4 plywood sheet, and securely fasten with screws and metal braces.
Measure the inner width and length of the tub to cut and install the inside forms in the same manner. These can be fastened together with bracing and 2 by 4 boards as well. This form is to be installed inside the tub.
Install additional 2 by 4 boards across the tops of the two forms as strapping and supports between the two forms.
Mix the concrete and pour it into the mold. Then let dry. Remove the forms to create your tub.