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.

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


Use a solvent based sealer or sealer primer as then apply further coats as per your chosen manufacturers system.

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

Some common products available in NZ are:  Resene Wood Primer (general purpose wood primer – exterior – solventborne), Dulux 1Step® Oil Based Primer, Sealer & Undercoat (Oil based)

Penetrating Oils

An excellent choice if you wish to see the natural grains and features of the laminated timber.  These products migrate into the timber providing a depth of protection against moisture ingress.  Using the manufacturers stain options adds UV protection .

Some common products available in NZ are:  CD50, Drydens Wood Oil, Resene Woodsman Wood Oil Stain (solvent)


These provide envelope protection much like a paint system and require multiple coats for effective use.  The natural features of the timber can be highlighted using the many colours available while also providing UV and moisture protection.

Some common products available in NZ are:  Sikkens Cetol system

All protection systems require maintenance to ensure their integrity.  If any checking appears in the timber, dry the member out, fill with epoxy or exterior wood filler, sand back and reapply the protection system.  Please follow the coating manufacturers recommendations for frequency of maintenance and care.

Laminated Beams Ltd does not take responsibility for any of the coating systems mentioned.  They are cited mearly as products that we have had success with in service. 

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.