What is a gum vein, and how does this affect your decking boards?

gum veinWe have all seen gum veins in decks, even though we may not have known what they were. Gum veins are the white or lighter parts of the decking board.  A gum vein is the build-up of resin or tree sap and can be identified by the vast difference in colour on the same board as shown in the photo.  At their centre gum veins are white in colour and have very few timber fibres in them. As you move towards the edges of the gum vein they become darker in colour.  The white part of the vein at the centre is very soft (you can indent the white vein with your fingernail).  As you move towards the edge of the vein, it becomes harder on account of the increasing amount of timber fibres.

So what does this mean for your decking boards?  Gum veins are a defect in the timber, a weak point.  With regards to decking, the strength of the timber is not as much of a concern when compared to a vein being in a structural timber beam, for example.  However the durability (ability to resist rot and wear and tear) of the decking becomes a concern as the gum veins are susceptible to rot.

When laying your decking boards:

  • Always cut out the white/centre part of the gum vein even if by doing so that means you need to throw away a full length of decking board.
  •  Whenever possible avoid using decking boards that have an outer edge of a gum vein in them.

By following these suggestions you will have a great looking deck that will last the distance.

For more information of on installing decking boards have a look at our “Installing Decking Boards” guide which is available from the Resource Shop.

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