Water pooling between insulation blanket and ply flooring

[CalBung]

Hi All,

I am undergoing an extension to my home (60 sqm) and have been concerned to find water spots appearing on the plywood flooring (in random positions).

The flooring is as follows:

15mm plywood on steel purloins. The purloins are on brick piers which are approximately 800mm tall. In between the flooring and the purloins is an insulation blanket (aircell type which looks like bubble wrap covered in a reflective foil).

The room was "locked up" in January and I thought that any rain that had been absorbed into the ply would have well and truly dried by now.

I had a look under the floor this morning and noticed that there are several large pools of water "water bladders" (accumulated water, possibly up to a litre of water in each) which have formed between the subfloor insulation and the plywood.

I had a look at the photographs of the day the insulation and ply flooring were laid (November last year) and noted that it was installed on a wet day and exposed to rain for a week or so afterwards. - it appears that rainwater has been trapped between the subfloor insulation and the plywood.

What are the implications for my ply? - it has been in contact with water for 6 months - I am worried that rot may have set into the ply. I am planning on laying timber flooring but am concerned about what is happening to the ply underneath.



Your ideas would be greatly appreciated!

[DJ’s Timber]

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