Should Tyvek Be Used for Cedar Siding Over the Original Siding?

Function

• Tyvek is a non-woven paper-like material used since the 1980s as a replacement for rosin paper, a waterproof paper used to protect house sheathing from moisture, or building felt, an older material. Tear-resistant and rot-proof, Tyvek products shed water but are vapor permeable, allowing moisture trapped behind them to escape. DuPont, which makes Tyvek, and the Western Red Cedar Lumber Association both recommend Tyvek as a backing paper for cedar. DrainWrap paper is specifically recommended for use behind cedar by DuPont because of its moisture channeling properties.

Layering

• House wrap is an essential part of a system of layers that protects the wood and other natural components of a building. It covers the sheathing or sheathing plus foam board that covers the framework of the house. If new siding is added to existing siding, house wraps such as Tyvek add a layer that replaces original felt or rosin paper that might have deteriorated. Old siding, and the layer of air between it and the new siding, forms added insulation for the house.

Considerations

• Some original siding must be removed before new cedar siding is applied. Rotted siding compromises the skin of the house and vinyl must move to function correctly. Once the siding is removed, underlying house wrap, whether felt, rosin paper or Tyvek, is full of nail holes and must also be removed. After repairing defects in the sheathing, a new wrap with Tyvek DrainWrap seals the house against infiltration.

Preparation

• Wood is more porous than other siding materials, so cedar should be treated before use. Storing clapboards from five to 30 days, depending on their variety, allows them to acclimatize and minimize shrinkage. The Western Red Cedar Lumber Association recommends priming clapboards on the backs and edges as well as face with natural or alkyd oil before use. The primed surface and Tyvek combine to channel moisture down behind the siding.