Do I need to use End Seal?

by | Jun 2, 2014 | Blog


There has been much written and debated in online forums around whether or not it is necessary to use an End Seal product with your treated timber. Unfortunately, a lot of this debate is based on out-dated, or just plain inaccurate information. Let’s take a second to re-cap…

What is treated timber?

In any Vacuum/Pressure treatment process, a preservative chemical is forced into the timber to provide a seal of protection. Due to the large number of variables involved in any given piece of timber (species, permeability, moisture content etc.), there is no way of knowing exactly how much penetration the treatment process will deliver. Modern treatment processes are not designed to completely permeate each piece of timber, rather, a layer of concentrated chemical is forced into the timber, and provides a seal, which protects the inner parts of the timber from decay. What this means is that if this seal is broken, then there is potential for insects and fungicidal growth to breach the treatment barrier and expose the timber.

What does this mean?

In practical terms, what this means is that the best process to follow is to have timber machined up to specification prior to undergoing the treatment process – this isn’t so bad for fence posts and other standard size pieces, but for any other timber product which it’s impossible to size prior to fitting (e.g decking), there is going to be some inevitable exposure of the untreated core of the timber. In these scenarios it is imperative that an end-seal product is used to repair the broken protection seal of the treated timber, maximising the longevity of the product.

What are my options?

There are a number of end-seal products out there, and at Glenavon we stock End Seal produced by Osmose, which is a product designed to complement the Osmose Naturewood treatment chemical used in the pressure treatment process. You can pick this up from our Keynsham branch.

Prices are £6 per 1 litre can, £12 per 2.5 litre can. (+VAT).

More information.

This article makes a good analysis of the need for endcoat.