Standard FireCrunch is a water resistant product before sealed, in that it does not retain water; if unsealed in warm weather it will release any moisture.

This means that an “unsealed board will absorb some moisture in damp or wet areas” if left unsealed. You should not expect the board to hold it’s integrity if submerged in water or exposed to multiple wet/dry processes, before use, particularly without the adequate primer sealing— our recommended primer and recommended top coatings applied to finish water proofing.

Use special MgSO₄  recommended primer. (The Recommended Warranty Primer is available at major hardware stores (Bunnings, Mitre10) – see Recommended Products).

FireCrunch MUST NOT be left out in the rain before sealing/priming. PRIME THE BOARDS UNDERCOVER BEFORE ANY EXTERNAL INSTALLATION. HYDROMETER CHECK 10% OR LESS (Warranty – See Recommended Products).

Because FireCrunch is a breathing permeable board it will hydrate when not sealed. However, if inadvertently left in the wet or in exterior weather, move it to a dry environment with separated sheets. FireCrunch will dry out quickly without swelling or warping and hold its strength and integrity.

FireCrunch that has been installed externally and not pre-sealed could crack at fixtures due to residual moisture in the board being removed in the drying process, especially when exposed to multiple wet/dry processes.

Best practice:

• Store undercover on delivery to site before use. Do not attempt to paint if board wet or over 10% hydro.
• Allow to dry completely before sealing painting or rendering, hydroscopic level under 10% (Warranty).
• FireCrunch board called (Type K) is sold in 10mm K-Clad SE 10mm and TE 10mm sizes 2.4/1.2, 2.7/1.2 and 3.0/1.2.
• For flooring, K-Floor 19mm TG Tongue and Groove. Fire separation walls to FRL 120 minutes K Fire 19 2.7/0.6.
• For exterior walls or in a bushfire area, K-Clad flat finish or K-Wall, a timber appearance groove/weatherboard TS12 2700×1200 x12mm.
• Decking 16mm K-Deck TG decking groove boards for exterior decking. 2.7 x 0.6.
• TG 19mm K-Roof  2.7×0.6 is also used for bushfire roofing substrate eliminating expensive 15mm marine ply (which is actually combustible 
and does not now have a AS 1530.1 certificate) NCC 2022 and so should now never be used in bushfire areas (NCC 2022 revisions) combustible material.
• 16mm FireCrunch is designed for internal/external use and is the best choice for decking and external applications.
• Pre-seal FireCrunch boards with MgSO₄ recommended primer (See Recommended Products).

Link: Recommended Products