Question:

We are project/construction managers based in China. A client has asked us to assist them complete a private members club (construction stopped over one year ago due to contract disputes). Much of the work has been completed, including the subfloors and approximately 45% of the imported hardwood floor system (South American wood, I believe). I have several concerns:

1. There is a large ballroom with hardwood floors. The base substrate is concrete, with wood battens and then 9mm standard plywood on top. The imported hardwood boards (parquet type) has been glued (glue material not known) to the plywood.

The hardwood floor boards are 25mm thick, approximately 75mm wide, and unfinished.

2. I am not convinced the 9mm standard plywood is sufficient for a long lasting ballroom dance floor.

What type of subfloor do you recommend?

3. I am concerned about the type of glue that may have been used.

What type of glue (or nailing?) to you recommend in this situation?

4. Central coastal China has extremely high humidity in the summer, and though this club facility will be airconditioned, I am concerned about checking and shrinkage. Most of the hardwood floor materials have been sitting in a basement level for at least 1-2 years in high humidity.

Should the hardwood floor strips be installed as they are now, or should they be stored in an air conditioned environment that approximates the club's future conditions?

Any advise and help is greatly appreciated.

Yours sincerely,

James

Answer:

Dear James

You have many reasons to be concerned. First the plywood sub floor is much too thin too provide any long lasting support. It should be at least 18mm and in a tongue and grove configuration on it's edges so that there are no weak areas. Glue for parquet in such a hard used area should always be a rubber based mastic. Here in North America a popular brand is Dri-Tac made in New York.Their phone number is 718-497-5462, they may be able to provide you a local supplier. You can tell a rubber based glue by it's tan colour and flexability. The directions on the label will tell you to spread the material and then let it flash off for about one half hour. This glue works so well I have had my completed jobs go through 3 accidental floods and the laminated floor only sustained partial damage on the third flood.

The floor was a laminated 5 ply aok plank and is a very durable and stable material, being plywood it will not shrink or expand and is the only type of wood floor that should be inslalled below grade. You can get these floors with special commercial duty finishes already on them.

You will have to get yourself an electronic moisture meter and certainly get that wood out of the basement now. No flooring material should be installed until it's miosture content is about the same as the subfloor's. And in an air conditioned environment it will eventually go down to 6-8%. Don't install that floor until it does or it will shrink the rest of the way on its own leaving gaps all over.

There is one more issue, just what is the species of wood you're using? Some of the South American hardwood imbuya wood and many others have such a high oil content in them they will eventually reject any finish you put on them, and may also reject the glue it's held with. Do some research and find out what this material is and it's suitability for flooring.

As always your Most humble servant, Joseph, the Wood Floor Doctor.

You may also find these articles helpful:

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4. Custom Staining Wood Floors Without The Blotchy Effect

5. How To Take Care Of Your Health And Safety when Installing, Finishing, Repairing or Cleaning your wood floors

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