I found it quite amusing this morning when looking for a product online and stumbled across a fencing panel manufactured by the same company offering a 10 year guarantee. The following is taken directly from their website in relation to the guarantee;

“Please note Our garden fences are pre-treated with a water based timber treatment for protection during transit. In order to receive the full 10 year anti-rot guarantee, it is necessary that you treat the garden fence with a high quality, spirit-based, timber preservative prior to or shortly after construction. This will protect the timber from weathering and will need to be repeated accordingly in relation to manufacturer’s instructions. See Terms and Conditions for further information. The fencing arrives in a fixed unit for easy installation”.

So basically they will offer a 10 year anti rot guarantee on their fencing panels if you treat them either prior to or immediately after installation and then each year thereafter with a good quality preservative. Fantastic!

So is it possible to offer a guarantee that doesn’t involve numerous hours preserving panels and the cost of purchasing good quality spirit based preservative?
The short answer to this question is no. Timber is a naturally occurring product displaying many natural characteristics that occur in the tree that it is taken from, even the best quality timber is affected in the same way. Let’s examine a few of the commonly occurring characteristics that will not be covered under guarantee.

1.) Knots – All softwood has these and they are largely due to infant branches being engulfed by the growing tree. Knots are a natural feature of timber and in many cases, enhance the appearance of the wood, however they can have a negative effect on the strength.

2.) Shakes –  Shakes occur during the natural seasoning of timber as the timber moisture content dries out causing shrinkage, this will often lead to distortion also.

Rot – This is a slightly more contentious issue as there are so many factors that could cause the onset of rot. The first of these is obviously the quality of the timber and the treatment it has received prior to manufacture. Tanalising has been the standard treatment for external timber for a number of years now and up until a few years ago manufacturers had the confidence to guarantee that this would give the timber a 15 year life expectancy, without further treatment. However, since the health and safety executive decided that a timber treatment containing arsenic wasn’t the best idea the treatment companies have been working hard to come up with an alternative. As of yet this has not reached the level of effectiveness that the previous treatment was consistently reaching which poses a significant problem for the manufacturers using timber products. Good quality dense timber will resist the onset of rot better than poorer quality less dense timber as standard but without an effective treatment and especially in ground contact this will not add a significant amount of time to the product lifespan.

Thinking about timber in ground contact, namely timber fence posts we can identify a number of factors that would mean that the same post would last for a different period of time that are largely due to positioning e.g. If a post was fitted in soft, well drained soil it would undoubtedly last longer than the same post fitted in heavy soil that retains water and leaves the base of the post constantly wet. Likewise, if a post carrying fencing panels was fitted in a nice sheltered position it would last longer than the same post and panels fitted in a position that is constantly battered by strong winds. As the post gradually rots underground it will reach a point that any load placed on the post will snap the post at ground level. At this point the post under windy conditions would fail where as the one in sheltered conditions will not have the wind load problem and should remain intact for many more years, until the post has rotten enough to mean that the load from the fencing panels alone will snap the post.  Very high gale force winds may snap a timber post in the first weeks after installation, well before any rot in the post has set in.

You can see from the brief examples above the problem fencing companies face when offering guarantees on timber products. Some will offer a 10 or 15 year guarantee but I suspect there will be numerous exclusions that will be cited making the guarantee virtually worthless and any of the above reasons could invalidate any claim made. The only timber that would completely free from any of the above problems would be Cedar wood. A softwood that by its nature is free from knots, warping, and rot. Whilst this type of timber is largely used in entrance gates the cost makes it largely prohibitive in the use for timber fencing products.

We attempt to be as honest as possible to customers when identifying the most suitable products to use when planning their fencing. Panels are not a problem as due to the quality grade of timber that we use we would expect any panel to last between 10 – 15 years as standard without any need for further treatment. The main problem arises with the posts and we would always recommend the use of concrete posts and base panels rather than timber wherever possible as it is guaranteed to last much longer. We do understand people’s reluctance to use concrete for aesthetic reasons but strongly advise that they consider the implications of using timber posts before making their decision.

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