The floor of our project will be made of compressed bamboo boards made by Style Plantations. These boards are 12mm thick and are glued to a substrate floor. We had allowed 25mm to so we can adjust floor levels to ensure that there is an even surface between rooms and at doors to the outdoors. This will mean that there are no obstacles to stop free egress for wheel chairs. So we needed to get about 100 square metres of 12 mm “packing” to bring the level up for the compressed bamboo to sit on. The question was what would we use. The alternatives that we thought of were MDF (medium density fibreboard) or plywood. Talking with John the builder we settled on MDF as the surface was very smooth and we could pick up 100m2 at around $7.75 per metre. I had checked in with Ian a close friend who worked at Carter Holt Harvey to get his opinion on MDF. He got back to me pretty quick to say that MDF was probably not a wise choice , but he would get George his engineer to drop me a note. This was his reply;
With regards to using mdf underlay, I am no expert on the matter but am under the impression that it should only be used under moisture resilient surfaces such as vinyl. The mdf needs to be of a moisture resistant variety, but even so if any moisture gets through the board edges and becomes trapped there is the possibility of mdf expansion and blowout, or mdf rot leaving hollows under the floor. Plywood does not have the tendency to do this at the level that mdf does, and as such is recommended as an underlay.
I’m not trying to alarm you or warn you out of using it; I just want to make sure that the product you use will give you a good result for the life of the building.
Well this did alarm me as the compressed bamboo flooring that was going over the packing was going to cost about $16,000. The last thing that I needed was to save a couple of hundred dollars on underlay only to destroy twenty times that amount if the floor had to be replaced.
So even though we had ordered and taken delivery of the MDF it would have to be ply, so the order has gone in and I now have 100 square metres of 12mm MDF to sell.
If you are interested in the specifications of ply download the technical details put together by carter Holt Harvey here.