Polesaver/Postsaver

Global business. Personal services 

Call us on : +44 (0)1452 849322


                                                                                                

postsaver

POSTSAVER

Prevents Ground Rot in Timber Fence Posts

Click Here

polesaver

POLESAVER

Prevents Ground Rot in Timber Utility Poles

Click Here

shop

BUY ONLINE

Purchase Pole & Post Saver products online

Click Here

Polesaver News

rss

All the latest news from Polesaver


Core rot: what causes it? and how to prevent it
Core rot: what causes it? and how to prevent it
  • Summary

    Wood Preservative provides no protection against core rot

    Air or insect borne brown rot fungal spores enter the unprotected core of the pole through cracks that bypass the outer preservative treated sapwood shell of the pole. 

    Moisture from the soil travels up the core from the ground ensuring high moisture content in the core of the pole just above ground level. 

    This allows the spores to germinate and attack the un protected core wood and destroy the core of the pole.

    Typically accounts for around 60 to 70% of pole failures.

    Core rot  can occur at any time in the poles life and can cause early pole failures.

    Applying a a composite sleeve seals the surface of the pole and lowers the entry point for moisture

    This "drops" the moisture profile typically ensuring that the moisture content in the upper part of the sleeve is too low for core rot to occur

     

  • Whilst ground rot attacking the outer part of the pole is well understood by the vast majority  of utilities the causes of core rot are often not so well understood. We are regularly asked what causes core rot and if Polesaver will be effective against this problem.

    Core or brown rot typically accounts for around 60% of pole failures and occurs within the core or central part of the pole. Wood preservatives do not prevent this form of pole rot and this is why.

    The outer part of a pole is made up of sapwood, the living part of the tree when it was felled. The sapwood is permeable to liquids making it receptive to treatment with wood preservatives.The wood preservative provides protection from soil borne soft rot attack.

    By contrast the heartwood is made up of relatively "closed" cells and is relatively impermeable to liquids making it commercially very difficult to treat with wood preservatives.. 

    This leaves the inner core of the pole relatively unprotected from wood decay and rot.

    Above ground the pole is exposed to natural airflow, weathering and sunlight. Over time this results in drying and shrinkage of the wood  which causes the pole to crack vertically.Often these cracks will run right through in to the unprotected core of the pole as shown in the photograph above.

The majority of wood decaying organisms are fungi that exist in the upper soil level and attack fallen organic matter such as wood and leaves. As part of there reproductive process some of these wood decaying fungi emit millions of microscopic spores that are carried on the wind.It is these spores that  literally get blown in to the above ground cracks in utility poles and straight in to the unprotected core.  

For wood decay to occur a moisture content greater than 25% is necessary. On a normal pole the moisture content of the core close to ground level will be relatively high and typically well above the 25% threshold at which decay can start to occur as shown in red in the diagram above. This high moisture content occurs because water moves in to and up the pole from the ground. This effect is known as  "wicking" and  occurs because of the difference in water vapour pressure between the in ground and above sections of the pole. In practical terms this means that the moisture content of the inner part of the pole 5 to 10 cm above ground level will typically range from 50 to 150% or more. This combined with elevated temperatures, unprotected wood and oxygen create ideal conditions for the brown rot spores to germinate and form wood decaying fungi that slowly but surely eat down in to the core of the pole rendering the pole defective. 

Unlike ground rot or soft rot, brown or core rot can occur at any time in a poles life and is relatively unaffected by the type of wood preservative that is used. Core rot is a major cause of failure in poles treated with Creosote, C.C.A. and Pentachlorophenol

The use of a Polesaver sleeve provides a simple but effective means of dramatically reducing the likelihood of core rot and this is how.

The sleeve produces a watertight seal on the surface of the pole and this lowers the entry point for moisture from the soil. This has the effect of "dropping" the moisture profile in the pole by 60cm or so as shown in red in the diagram above. In practice this means the moisture content in the upper part of the sleeved section and above ground section is held at a low level. This is typically below that at which decaying organisms can thrive thus ensuring that brown rot spores that enter the pole via cracks and splits are unable to germinate and attack the core of the pole.