10 Residential Under Slab Duct

Normally we suspend duct, but when we place duct in concrete, we have to look at the job differently. In concrete, the duct will be buoyant. Being that it is basically a tube full of air, if the duct is not held down correctly it will float. Slab duct must be secured in place and held in position.

The duct must be made of a material strong enough to withstand the force of the concrete. If it is too thin of gauge, it will collapse under the pressure of the concrete. Using spiral pipe is a good idea because of it’s strength. Stiffeners, ribs, beading should all be considered for slab duct.

The slab duct should also be sealed appropriately and have enough slope to allow moisture to run back to the air handler. This is where any moisture will evaporate the quickest and not sit to cause further problems.