Back Prime Siding

Types of paint to use.

Back prime siding.

It simply means coating the backside of wood siding with one coat of naturecolor base coat or natureone before putting the siding up. The back side is better left unpainted. First of all lets explain what is back priming. He says that when panels are primed in the factory some primer ends up on the back of the boards as they pass over the rollers but this isn t a half hearted attempt at priming the backs.

It occurs either when heated or air conditioned air from the house radiates out and meets the cold or hot outside air. All siding takes on seasonal moisture from sources as diverse as direct rain wicking and vapor diffusion through the wall assembly. Frequently today s homes are wrapped with a vapor barrier i e. While back priming has proven to be useful to control tannin staining with some types of solid wood siding trim and some composite sidings lp smartside products are not intended to be back primed.

When back priming be sure to prime the ends of each piece after it has been cut to fit since end grain will absorb the most moisture. Not only does back priming prevent rot it prevents bowing cupping. Therefore do not prime the back side of the siding or trim. Back priming helps prevent paint from peeling by reducing the amount of water vapor that passes through the wood.

For best results fresh siding should be pre primed on all six sides with a stain blocking primer and top coated with 100 percent acrylic latex paint. Where is the trapped moisture coming from. Importance of back priming when installing wood siding. Tyvek or foiled faced insulation which does not allow large moisture droplets to flow through.

Back priming consists of applying a coat of primer to the reverse side and edges of boards before installing. Alkyd oil primers are recommended but one may choose a high quality latex primer as long as it contains stain blockers.