I am preparing to lay a solid tallow wood floor over a yellow tongue structural floor on timber joists. It is 130x19 mm feature grade. My question is - what are my options for managing the expansion of the floor? The space I am concerned about is a wedge shape- the widest part is 12 m wide and the narrow end is about 9.0m I am hoping there is a technique that will avoid the traditional expansion joint every 6m. A project I worked on in the past used sheet metal packers to create small gaps every 4 boards to allow a wider floor without noticeable expansion joints. Thoughts or advice would be much appreciated.
Our Technical Design Guide number 9 provides detailed guidance on the installation of timber floors. A copy can be downloaded free of charge from our website via this link https://www.woodsolutions.com.au/publications. Whether you need an expansion gap at all depends on a number of factors, including initial moisture content of the flooring, local climate, etc. Note the advice in our Guide to the effect that floors are generally more prone to shrinkage in cities with drier internal environments (e.g. Adelaide and Canberra) and more prone to some swelling in warmer more humid cities (e.g. Brisbane) - p. 23. If local experience shows that an expansion gap is warranted, using a metal spacer to leave small gaps is one way to allow for swelling. Perhaps a neater technique is to use cork which compresses if the flooring swells. This topic is also covered in our Guide (p. 37) and cork products are available from specialist suppliers eg. here https://www.ecocork.com.au/other-cork-products/expansion-cork/.
The Baigents were a prominent timber industry family in New Zealand for over a century, operating as H.E. Baigent & Sons until they were bought out by Carter Holt Harvey in the late 1980's. The stamp "BAIGENT 'S' MSG AS1748 90 x 35" identifies the sawmiller (Baigents), the 'S' indicates that the timber was seasoned, MSG confirms it was machine stress graded, and AS 1748 is the Australian Standard to which it was graded, but oddly enough the actual stress grade is not specified. The stress grade, or strength rating, is perhaps the most important piece of information and it is a requirement of AS 1748 that it is included in the brand. In any event, we feel it is most unlikely that the timber was treated against termite activity, although we cannot positively confirm this either way. Of course, some form of termite protection may have been put in place after construction.
My home is 47 years old and constructed of 2 storey in-ground tallowwood timber poles surrounded by a concrete slab on the interior with open access to the exterior. Having read your product guide for the preservation and treatment of timbers against fungal infiltration, thus sapwood decay and termite infestations can you please advise what might be suitable in my situation. As my situation is not straight forward, a conversation may be required to clarify past treatments etc.
Tallowwood is rated Class 1 Durability in-ground (the highest durability rating) according to Australian Standard 5604:2022, Timber - Natural durability ratings, meaning the heartwood is resistant to termite attack and fungal decay. While the lifespan of timber in the ground varies according to site conditions (damp site v. dry site, tropical climate v. dry climate, etc) it would seem that if the poles have survived for 47 years without any problems there is no immediate cause for concern. Presumably the poles around the perimeter of the house are the most exposed to the weather, and in-ground moisture, while the internal poles are in dry ground and at less risk of decay. While tallowwood is resistant to termites and decay it is not immune, particularly if sapwood is present. Consequently you could consider installing boron preservative sticks, as used by some utility companies to maintain their timber poles. You will find information about this type of preservative by clicking on this link https://preschem.com/products/wood-pole-preservatives/polesaver-rods/.
