Inground H5 Laminated Posts

FAQ Categories

Can H5 Laminated posts be used in ground?

Under the Sale of Goods Act 1908 and where the end use is known, a warranty is implied that the product is fit for purpose.  Consistent with these legal obligations, Prowood stands behind the use of its H5 glulaminated posts for in-ground structural use.  Our confidence is based on the following:

  • Timber laminates are treated in accordance with NZS3640 to H5
  • Glulaminated posts are manufacture in accordance with AS 1328.1:1998, and
  • Installation requires the below-ground part of the post be fully encased in concrete, and
  • The supply H5 glulaminated posts for in-ground structural use for over 15 years without any evidence of failure – systemic or episodic.
  • We have confirmation from our glue manufacturer that the finished laminated product remains durable when in ground contact situations.
  • We have confirmation from Mick Hedley (Then Project Leader, Wood Preservation Scion Wood and Biofibre Technologies) that the only reason why AS/NZS 1604.5 does not include H5 treatment was because nobody on the standards committee believed any company was (or would be) treating glue laminated products to an H5 specification.

Also some have correctly identified, the key issue is not only the treatment of the timber per se, but the integrity of the adhesive used in the manufacture of the timber, of which we have confirmation from the manuafacturer that the glue remains durable when in ground contact situations. 

Prowood stands behind the performance of our H5 glulaminated timber posts  However, there is no evidence that glulaminated timber fails when used in ground and there is good evidence that these engineered wood products provide better structural performance than solid timber.

Are H5 laminated posts certified for in ground use?

Prolam H5 posts meet the penetration requirements that comply with NZS3602 and the NZ Building Code B2. (see producer statements under Technical Tab / Code of Compliance). We are currently working with the standards committee in acquiring this official product quality certification.