CSSBI SSF 18-10: Sheet Steel Products and Pressure Treated Wood

Introduction

Sheet Steel Roong and Siding

Lightweight Steel Framing

Isolate the Steel and Wood Components

Avoid Use of Pressure Treated Wood

Fasteners

Many buildings will include wood members in applications

such as sill plates, splash boards, strapping, purlins, door or

window bucks, and posts. In some of these end-uses it is a

requirement that the wood be chemically treated (pressure

treated) to extend the service life.

Designers and builders need to be aware that changes in the

available wood perservatives may impact the durability of

any connected steel components or fasteners.

Eective January 1, 2004 the Environmental Protection

Agency (EPA) banned the use of Chromated Copper

Arsenate (CCA) as a preservative in treated lumber for

residential construction. This was done in an eort to reduce

the use of chromate and arsenic thereby mitigating the

potential health and environmental problems. The wood

preservative industry has been switching to alternative

waterborne compounds including Sodium Borate (SBX),

Alkaline Copper Quat (ACQ), Copper Azole (CBA-A and CA-B),

and Ammoniacal Copper Zinc Arsenate (ACZA).

Unfortunately, research has indicated that ACQ, CBA-A, CA-B

and ACZA, the new generation copper-based products, are

more corrosive to galvanized steel than the former CCA.

Since ACQ is becoming the predominant preservative in use,

the discussions in this paper will refer to it exclusively.

The purpose of this Fact Sheet is to convey the recommendations of the sheet steel industry for the application of steel

products with ACQ pressure treated wood.