Description
Moisture Guard MG320 is the heavier of the MJS floating floor underlays, a 3 millimetre acoustic IXPE foam carrying a 200 micron polyethylene film. The thicker film is the point: it is a considerably more substantial vapour layer than the 60 micron film on the 2mm product.
It suits all laminate and timber floating floors, and it tolerates a damper slab, with concrete readings accepted below 90 percent relative humidity rather than the 80 percent the thinner product requires.
Technical Specifications
| Product type | 3mm acoustic IXPE foam with 200 micron PE film |
|---|---|
| Structure | Polyolefin foam, closed cell |
| Thickness | 3.0mm plus 200 micron PE |
| Suitable for | All laminate and timber floating floors |
| Concrete subfloor limit | Below 90% relative humidity to ASTM F2170, or 4.5% by impedance meter |
| Timber subfloor limit | Below 14% moisture content |
| Moisture layer | Vapour barrier film, not a waterproof membrane |
| Standard | Moisture testing per AS 1884 Appendix A |
Which Underlay for Which Slab
The two MJS floating floor underlays differ in the polyethylene film more than in the foam. Sound Block at 2 millimetres carries a 60 micron film and accepts concrete up to 80 percent relative humidity. Moisture Guard at 3 millimetres carries a 200 micron film and accepts up to 90 percent.
That ten-point difference decides which product a slab can take. Test first, then choose, because an underlay specified below the slab’s actual reading is not protecting the floor above it no matter how thick the foam is.
Where to Use
- Under laminate and timber floating floors
- Concrete slabs carrying higher residual moisture
- Apartments and upper storeys needing impact sound reduction
- Installations where a heavier vapour film is specified
How to Apply
- Test the subfloor — Moisture test to AS 1884 Appendix A. Concrete below 90 percent relative humidity, timber below 14 percent.
- Roll out — Lay the underlay with the film side up, running rolls in the same direction.
- Seal the overlap — Join adjoining runs so the vapour layer is continuous.
- Lay the floor — Install the floating floor over the top, keeping perimeter expansion gaps.
Important Notes
- The film is a vapour barrier, not a waterproof membrane. It is not intended to protect against excessive or abnormal subfloor moisture.
- Where readings exceed the stated limits, resolve the moisture at the slab rather than relying on the underlay.
- Film side up. Laid inverted the vapour layer does nothing.
