Using 280 Over Concrete Board

Many of you ask how to use the 280 system over Hardy board for use in various areas. Here is a step by step instruction on how to put this system together accompanied with an illustration:

1. You should screw the Hardy board down with SS Screws every 6-12 inches on center. Make sure to countersink your screws.

2. Apply a coat of 280 over the joints where the Hardy board or DuroRock meet. You should dab some over the screw heads as well.

3. Apply drywall fiber mesh tape over the joints on the 280 waterproofing membrane.

4. A second coat of 280 is applied to the joints and troweled smooth.

5. Once steps 1-4 have been performed, the system should be allowed to dry for 24 hours. Then sand or rub brick to help smooth out and feather the edges.

6. The CTI System is now applied as usual over the top.

The CTI concrete board system is used for going over interior subfloors, countertops, walls (interior and exterior) and has been used to make custom signs.

NOTE: You need to make sure that what you’re going over does not have too much movement or flex to it. This is one of the reasons we screw the concrete board 6-12 inches on center so as to help ridge up the floor, counter, etc. If there is too much movement, the seams (joints) will telegraph or show a hairline crack at the surface.