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Question

I am trying to find a design guide or manual for the design and specification of nail laminated timber including:
- reduction factors relating to lamination
- maximum spacing of nails etc.
Do you have any resources that focus on nail lamination?

Do you know of any guides for horizontal lamination for example where the plane of lamination is parallel to the axis of the moment where there maybe shear in the plane/

Woodsolutions Answer +

Vertical lamination:

If you have access to Australian Standards nail lamination is covered in Section 2.4.5 of AS 1720.1, Timber structures, Part 1: Design Methods. Section 2.4.5 is titled Strength sharing between parallel members. The calculation of the modification factor for strength sharing, k9, is given as equation 2.4.5.3. For nail-laminated members AS 1684.2 Residential timber-framed constructionassumes nmem = 1.0 and ncom = number of combined sections in calculating k9. Or to keep it simple just refer to AS 1684.2, Section 2.3 where the recommended nail pattern is shown.

Horizontal lamination:

It is surprising how few resources there are for designing horizontally laminated timber. We haven’t been able to find any guides or tables so designs would have to be calculated from first principles according to the shear capacity of the fasteners (nails, screws or bolts). There is an example calculation here, but since it’s a US site all values are in imperial units: http://hyperion.usc.edu/courses/ame204/Homeworks/HW6.pdf.

Question

What product can be applied to a Tas oak screen (clear finish) that will comply with BCA Fire Property Group 1 (non combustible). Is there a product that will suit our needs?

Woodsolutions Answer +

Various fire retardant coatings delay ignition and/or reduce the contribution to total fire load. However, we are not aware of a fire retardant product that makes timber ‘non-combustible’ according to the Australian Standard non-combustibility test. Non-combustibility is assessed by testing to AS 1530.1 The test is a small-scale fire test involving immersing small samples of a material in a furnace held steady at 750°C.  A material is deemed combustible if the mean duration of sustained flaming lasts for a period of 5 seconds or longer at any time during the test for any of the five samples tested. However, several timber veneer suppliers hold test certificates giving Material Group 1 status to fire retardant treated MDF with a decorative face veneer, so perhaps the proposed screen could be made in this way. Note that Material Group 1 products are not necessarily ‘non-combustible’ in terms of AS 1530.1. Material Group numbers are defined according to ‘time to flashover’.

Question

Our client has specified ROUGH SAWN TIMBER for this project.
We provided a sample board of 1m lengths some lengths have more prominent saw swirl marks than other lengths of timber.
Can saw marks be controlled or are saw swirl marks an unavoidable by-product of specifying that type of timber finish.

Woodsolutions Answer +

It sounds as if the timber in question has been sawn with a circular saw if it is showing ‘swirl marks’. The other type of saw marks are those left by a bandsaw, which are vertical rather than curved. The sharpness of the saw, and the grain and density of the timber, also have an influence on the final result. However, either kind of sawn surface would qualify as ‘rough sawn timber’ in our opinion, unless there was a more detailed specification.

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