Expert: Dan Griffin - 3/17/2011

Question
Are there often differences in the final sub-floor for piling houses?
We are building a house on pilings which has plywood over the floor joists for its sub-floor.  Areas with tile floor have hardie backer over the plywood sub-floor.  Now at the wood floor install stage (3/4" hard wood t and g nail down)  Installers are not happy with condition (not level) of sub-floor.  The house took a bunch of rain before it was dried in.  Is there often an additional or different step to prep sub-floor for a house on pilings for wood floors?

Answer
Lisa, I can't think of any reason for the floor to be unlevel because of it being on pilings.  I don't know exactly what material was used for the subfloor, but most plywood is not meant to be very wet, some can swell substantially.   If the installer is not happy, ask him for his recommendation to resolve the issue.  It may require some additional nailers being installed  between joists to pull down any humps.  I would make sure that the subfloor was glued and screwed rather than nailed, especially for a hardwood floor.  I would think that the installer would be well prepared to floor stone lows and sand ridges.  He may expect some additional prep money that he did not bid on his original estimate.  I assume you are planning some form of separation sheet between subfloor and hardwood to cut down on squeaks, etc.

I assume you are well under roof now.  Perhaps bringing in air conditioning or some form of dehumidifier will help normalize the plywood.