We have recently begun to import American red oak and I was pleased to see that red oak is listed on the table of species that have been tested and a Fire Group number given (Fire Hazard Properties Specification S7C4 Wall and Ceiling Linings [2019: Spec C1.10: 4]), however on looking into the report from Warrington Fire (RIR 45908.10), they have listed the species as Quercus Alba (actually, they say Quercus Abla), not Quercus Rubra. We all know it will be Group 3, but could you confirm which species was actually tested, and whether the resulting group number can be applied to Quercus Rubra without further testing?
American red oak was not included in Warringtonfire's tests on wall and ceiling linings, only American white oak as per our Regulatory Information Report RIR 45980.10. However, red oak has been confirmed as a Group 3 material in a separate report which we will send direct to your email.
Timber is relatively unaffected in a salt-laden environment, hence the number of structures in coastal areas which are traditionally made from timber (jetties, boardwalks, steps down to the beach, etc.) One type of degradation that has been observed in coastal areas is "defibration", explained in a US Forest Products data sheet that can be accessed via this link https://www.fpl.fs.usda.gov/documnts/techline/Techline_06-2011-001.pdf. Defibration has been observed adjacent to Sydney beaches in unsarked roof spaces where salt-laden air can enter, becoming absorbed by uncoated softwoods such as oregon. However, it progresses very slowly, and simply causes a woolly, stringy surface. Presumably your sub-floor timbers will be hardwood, which is not affected due to its greater density. No doubt the external cladding and decking will have some kind of coating eg. decking oil. Internal timber framing is unlikely to be affected in any way. Framing for external decking could be hardwood, or treated softwood with a coat of decking oil. Note that many coastal boardwalks are built from treated pine with satisfactory results, and the defibration issue should not be over-emphasised. All metal fasteners, or course, need to be corrosion resistant, preferably stainless steel.
What is the standard or recommended tongue thickness for 19 mm Tasmanian Oak floorboards?
According to Australian Standard 2796, Timber-Hardwood-Sawn and milled products, Part 1: Product Specification, the tongue thickness for 19 mm hardwood strip flooring should be 6.0 mm for face nailed, double-dressed, off-centre milled boards, or 6.5 mm for face nailed, double-dressed, centre milled boards. The corresponding groove dimension should be 0.5 mm greater to allow entry of the tongue.
