Protection against moisture

Surface coatings used on face, edge and end grain repel moisture penetration and are designed to provide temporary protection for a limited time during erection. They fall into two categories:

1) Translucent sealers having low solid content provide protection for a limited time. These are suitable when the final finish is clear or stained. Where stains are used on exterior members dark colours should be avoided.

2) Primers and non-penetrating sealers have a higher solid content (minimum 25%) and provide protection by sealing the surfaces of the glulam. These surface coatings should be maintained to prevent deterioration or fractures of the film, which would allow the ingress of moisture.

Care should be taken to ensure that sealers are compatible with the final finishing stain, sealer or paint. Sealers as specified in (1) and (2) above should be specified subject to the anticipated period of on-site exposure.

Do not paint under a Light Reflectance Value (LRV) of 45% as these attract heat and can cause the timber to dry out excessively resulting in splitting, resin bleeding, distortion and cracking.


Must be coated with a turps based film forming sealer once product is received.

Do not coat with any water based product.

Also see Can Glulam beams be used in exterior situations” located under FAQs


Protective Options

Metalex Wood Protector

Is a unique resin product, designed to encapsulate the timber structure to protect it from UV degradation, moisture ingress along with protection from insect and bacterial/fungal attack. It is a solvent based product. Once applied it cannot be painted over, and even after several years, and should you wish to change the colour of the timber, you will need to completely remove the Metalex Wood Protector from the surface of the timber.

Metalex Timber Preservative “Clear”

Metalex Timber Preservative meets the requirements of the New Zealand Building code for the provision of a supplementary “Envelope Treatment”. This is based on the use of zinc combined with naphthante salts (referred to as Zinc Naphthenate) to produce a solvent based penetrative product that surrounds the wood fibres as it penetrates to provide a barrier to UV degradation, moisture ingress along with protection from insect and bacterial/fungal attack. With the Zinc Naphthanate applied, especially to the cut ends (we tend to describe this as “cut ends, scarfs, notches & holes, to cover all bases), when applied in two coats, the water/moisture repelling properties is extremely high, although two coats are not generally required, we recommend it as to cover off the chance of the applicator missing as area on the first coating.

Laminated Beams Ltd does not take responsibility for the Metalex range of products. Extra care & research should be conducted before accepting any advice.


Protection against ultraviolet light and heat

Where members are exposed to direct sunlight care should be taken in specifying a surface coating with suitable ultraviolet resisting properties. The use of reflective colours in stains and paints will assist in this regard. Glulam members should not be exposed to extreme heat in storage where the moisture content would be reduced to a level considerably lower than the service moisture content.


Surface protection – Wrapping

Glulam members may be individually wrapped using heavy kraft paper. Impervious wrapping (plastic film) should not be used. The wrapping should be applied in such a manner as not to trap rain water and should be secured to the members by any method that does not damage exposed surfaces. Seams of the wrapping should inhibit moisture penetration.


Where individual wrapping is not required glulam members may be bundle wrapped as above.