Wooden Isolation Joints

[gloughman]

Concerning joints for flat concrete work such as an isolation joint where a patio pour abuts the foundation of a house, it is my understanding that wood should not be used for this purpose. I am assuming that this is because the wood can attract termites. My question is are there other reasons for not using wood for this purpose and are my assumptions correct?

[rwand1]

It swells when wet, thus causing the concrete to crack?

[Richard A. Hetzel]

Usually one would use a compressible joint filler that will absorb any change in the concrete dimension due to temperature variation. If wood is used, it can behave as the previous poster mentioned, or if the concrete contracts, the wood will not expand to keep the joint full.

[afrost]

i've seen cedar used as joint material. it was at disney, orlando.

i can't think of any structural reasons why a rot resistant wood should not be used as a joint material for a concrete slab. it is used, i think, for aesthetic reasons since cedar is about $1.40/lf for 1 x 4 and compressable filler is about $.15/lf