Sometimes precast concrete trench drains are used when implementing a drainage system, making the formation onsite unnecessary. However, when a cast-in-place trench drain is needed, there are seven steps to form the perfect concrete trench drain. Following these steps ensures an efficient trench drain that will last for many years.
Determine the Width
After selecting the design and trench drain type, determine the correct width for the trench drain. This is done by first considering the grate seat, which is the area where the grate sits. Accuracy is required for this step, so the grates don’t fall into a trench that’s too wide or end up not fitting into one that’s too narrow. The grate seat is commonly determined by adding a ¼ inch to the actual grate width itself.
Clear the Ditch and Install Rebar
The ditch is the area in which the trench drain is poured. Concrete, dirt, gravel asphalt can be used. Whatever’s in there—whether it’s concrete, dirt, or gravel asphalt—it must be cleared out to create the trench drain. The ditch is excavated according to the thickness of the concrete and the depth of the drain. Once excavated, any required rebar is put into place.
Pour the Footer
Once the rebar is installed, it’s time to pour the footer. Water stops are necessary when the trench drain is inside a building. If a swell stop is chosen for this purpose, install it after the concrete has firmed. Using a trowel, smooth the inside of the concrete after the footer is poured.
Form the Inside
The fourth step is to form the inside of the concrete trench drain. This is done by setting the forms with the smooth side facing the rebar cage and screwing them to the bottom of the concrete trench drain footer. Forms are then cross-braced from the bottom to the top, to each other, and repeated until complete.
Wood is nailed to the form to set the top of the trench drain frames. The wood must be the same width as the frame that’s already in place. It also needs to match the thickness of the grate that will be put in later. This part is essential to avoid added stress to the trench drain and possible failure. The elevation of both sides must be exactly the same so no rocking happens when traffic passes over it.
Outer Edge Forms
Make outer edge forms the same height as the finish grade to ensure better water flow. The outer edge should have a slope of at least 1/8 inch toward the trench drain grates, but 1/4 inch is preferred. Brace the outer edge forms securely so they don’t move.
Pour the Drain
It’s time to pour the drain. It’s tough to fix a mistake once this final step takes place. So, triple-check everything before the concrete is poured. When all measurements are accurate and framing is stable, pour the concrete. After the concrete sets, remove all framework and put the trench drain grates into place.
We hope our seven steps to form the perfect concrete trench drain are helpful in understanding how cast-in-place trench drains are created. At ABT, we hold our trench drain systems to the highest standards and have for over 30 years. Contact us and we’ll answer all your questions about a water drainage channel and all trench drain systems.