Wood on Concrete Slab

[Red Stick]

I am looking for an interpretation on a section of the commercial code relating to wood on concrete slabs. The section is 2304.11.2.4 Sleepers and Sills in the 2009 Michigan Building Code. There is a statement referring to "...concrete or masonry slab in direct contact with earth..." Does this refer to a second story slab, or a moisture barrier between the slab and earth, thus preventing moisture to the wood.

Thanks

 

[codeworks]

not in michigan, but i'd say no and no. if it's not in direct contact with earth, it doesn't apply. i do, however, always install pt plates on any concrete, just a matter of course.

 

[Big Mac]

Pressure treated plates are required when in contact with concrete as a mitigating factor against excessive moisture. When there is not an excessive moisture issue (such as elevated slabs or slabs that have some type of moisture proof product to separate the concrete surface from the ground or sorce of moisture) typically pressure treated wood is not required, though it is perhaps a reasonable insurance policy against decay.

Some moisture is almost inevitable on any concrete surface that is colder than the other elements that it comes in contact with for any extended period of time.