Prolam I Joists

The flanges are made up from ultrasonically graded LVL15, making them the stiffest I joists available in New Zealand, bonded with exterior adhesive for more load bearing capacity.

The webs being Orientated Strand Board (OSB) are known for their superior strength and consistant performance. 

Prolam I Joists are more uniform than solid sawn joists. They stay straighter and are manufactured with no camber, so there is no chance of crown down or upside down installation. They resist shrinking, twisting, warping and splitting for squeak resistant floors and quality roofs and ceilings.

Holes may be easily cut in the web according to the tables on page 22, allowing ducts and utilities to be run through the joists. Pre-punched 40 mm knockout holes are provided in the web for small diameter services or wiring.


Save Time and Money: Because they weigh less than solid sawn joists, Prolam I Joists are easier to install, saving construction time and cost. Their greater load carrying capacity allows you to space them further apart, so it takes fewer to build the average floor or roof. And with five (4) depths from 200 to 360, you will never have to compromise your design. So whether your plans call for cantilever beams in balconies, cathedral roofs or high pitched roof slopes, SmartJoists are the perfect choice.

An Environmentally Sound Choice: In addition to being cost effective, SmartJoists are also an environmentally sound choice because they are made of a renewable resource - wood. So they are a better choice for building.


Prolam structural laminated timber beams can be used in any form of construction where the structure relies on AS/NZS 1170: 2002 and NZ 3603 1993.

Limitations of use

Prolam I Joists are to be used in dry interior environments only, fully enclosed from exposure to exterior moisture. Prolam I Joists are suitable for subfloor applications provided that the subfloor space is ventilated as per the BCA requirements. This means that Prolam I Joists must not be exposed to environments where the equilibrium moisture content of the joist will exceed 18%. Prolam will not guarantee Prolam I Joists that have been left exposed to the weather either prior to or during construction for more than 90 days.

Detailing such as cladding or lining must be used in moisture laden environments (commercial kitchens, bathrooms, wet industrial areas, saunas, swimming pool and spa rooms etc.) And constructed in such a way as to prevent exposure of the Prolam I Joists to moisture.

Prolam I Joists may be used in applications which are often exposed externally (gable ends, eaves, floor joists applications in elevated houses, cantilevered joists etc.) But must be sufficiently enclosed with a suitable cladding, lining etc. To completely prevent the exposure of the Prolam I Joists to moisture.

Building code statement of compliance

Prolam structural laminated timber installed in accordance with the Prolam installation requiements, will comply with the below performance clauses of the New Zealand building code.

  • Structure B1/AS1: meets the requirements of B1.3.1 B1.3.2 B1.3.3 (a, b, f, j, m, q) B1.3.4 (a, b, c, d, e); AS1170:2002 for engineering span tables, AS/NZS 1328:1998 and AS5068 for building element
  • Durability B2/AS1: meets the requirements of B2.3.1(a) B2.3.2. All timber is treated in accordance with NZS3640. Prolam treats it’s own timber, and is third party audited to ensure compliance to the New Zealand treatment standard.
  • Hazardous Building Materials F2/AS1: meets the requirements of F2.3.1. Timber treatment suppliers meet NZS3640, which includes flash-off requirements.

NZBC designed to comply



Protection from Fire

Hazardous Building Materials

Features & Benefits

Cost Effectiveness

High weight-to-strength ratio of Prolam allows for maximum loads over large spans with the smallest possible end sections.

Product Quality

Prolam manufactured in accordance with AS/NZS 1328 Glue Laminated Structural Timber standard.

Fire Safety

Extensive fire test data shows that Prolam beams maintain structural load support for measurable periods of time in fire situations.

Design Flexibility

Prolam can be curved to virtually any radii without loss of strength and manufactured specifically to the designer’s needs.

Renewable Resource

Made from renewable New Zealand plantation timber, Prolam uses14 times less energy to produce compared to the equivalent steel beam.

Chemical Resistance

Prolam works well in harsh environments as it does not rust and the glues used are service class 3 certified.

Why Choose Prolam

Engineered Structural Timber Solutions

Specify with certainty