Acorn Information

treatments, products and services


Wood Rotting Fungi: show or hide content

Wood Rotting Fungi
All rots are Wet Rots, with the exception of the brown true Dry Rot (surpula lacrymans). All wood rotting fungi obtain their food by breaking down wood cells, causing loss of strength. The fundamental principle for the control of all fungal decay such as Dry Rot and Wet Rot is the control of water; a fundamental consideration for timber preservation is that timbers should not be left in a position where they might become or remain damp. Wood rotting fungi can be categorised in two groups: brown rot and white rot. Brown rots tend to darken the timber, causing cracking along and across the grain. White rots lighten the timber, but cause no cracking.

True Dry Rot: show or hide content

True Dry Rot
There is only one species of Dry Rot. It occurs when excess moisture penetrates the fabric of the building, raising the adjacent timber moisture content to above 20% of the oven-dry weight. Dry Rot has the ability to travel through brick walls and concrete floors well away from the source of moisture in search of additional timber. Dry Rot can be serious and expensive, and immediate action should be taken to arrest the problem and minimise further damage.

Wet Rot: show or hide content

Wet Rot
All Wet Rot occurs when poor ventilation and high levels of moisture content (above 50%) have been allowed to penetrate the fabric of the building, enabling the Wet Rot fungi to cause the structural break down of timbers. Unlike dry rot, wet rot will remain near the source of moisture. There are many species of Wet Rot, but it is not necessary to identify them as the treatments required are the same for all of them.

Condensation: show or hide content

Condensation
Condensation is a common problem in many properties and is responsible for most types of visible mould/ mildew growth on wall surfaces, often affecting stored items in wardrobes, particularly clothes, shoes etc., affecting walls and the corners of the ceiling. Condensation is caused due to the moisture produced by cooking, cleaning and occupants etc, being unable to disperse from the property due to the lack of adequate ventilation. A typical family of four is likely to produce around 10-15 litres of water vapour each day, through breathing washing and cooking. A sleeping adult will exhale up to 1 litre of moisture per night. Whilst the air in the property is warm, moisture is retained in the atmosphere. Once the air temperature cools the airborne moisture condenses on to the wall surfaces and results in mould/ mildew growth. Modern living conditions have resulted in many properties having much smaller rooms and air circulation has been reduced. Many properties remain empty during the daytime. Combined with energy saving measures such as reduced ventilation and double glazing this provides the ideal environment to sustain condensation on cold unventilated surfaces such as external walls, within wardrobes and behind furniture etc

Rising Damp: show or hide content

Rising Damp
There are many sources of dampness that affect our properties. The most common forms of dampness tend to be Rising Damp, Penetrating Damp, Condensation, and leaking rain water. It is important to identify the correct cause in order to treat the problem and not spend cash unnecessarily. What is Rising Damp? Rising Damp is the transfer of moisture from the soil to the foundations of a wall. The absorption continues into the bricks via Capillary Action. The Rising Damp carries natural ground salts such as nitrates, chlorides and sulphur, which can sometimes be seen on the surface of the plaster as white crystals. What is capillary action? Bricks are generally full of tiny fissures, some are narrow and some are wide. The water gets into these fissures and the surface tension created allows the water to rise. The more narrow the fissure the higher the rise of dampness. How high will damp travel up a wall ? There is a common misconception that Rising Damp only travels 1 metre high. In fact the height that damp can travel depends on many factors such as the density of the brick (as stated above, narrow fissures result in water rising higher) or whether the evaporation of the water is only possible from one side. A good indication of how high Rising Damp has travelled is the white salt band that can some times be seen because the salts are carried with the water. Why do I have to change my wall plaster? The ground salts carried up via the Rising Damp contaminate the wall plaster. As the damp evaporates, the salt migrates to the surface of the plaster and can some times leave a salt band. These salts are sulphates, nitrates and chlorides. The nitrates and chlorides are hygroscopic, which means they have the ability to absorb moisture from the atmosphere, where it will condense to form water. The wall plaster will always appear damp, although the bricks under the plaster may be dry. Sulphates are not hygroscopic but they can attack and break down cement. This is a real problem if sand and cement render has been applied. What treatment is available? The installation of a Chemical Damp Proof Course (DPC) into the base of the wall, supplemented with (a) a Vertical Damp Proof Course, and (b) re-plastering will cure the problem. How does the DPC work? The chemical is installed either as a cream or liquid into the base of the wall. The walls of the fissures are lined with silicone to make them very slippery, reducing the surface tension of the water and stopping its ability to rise.

Waterproofing: show or hide content

Basement and Cellar Waterproofing
What is Penetrating Damp? Waterproofing is necessary when Penetrating Damp travels across or down masonry. Where high ground or below ground areas (i.e. your basement / cellar) are affected your surveyor will inform you that these areas require a tanking system. What are tanking systems? There are many methods of tanking and all are designed to deal with lateral penetration of moisture from high and below ground levels. They can be grouped into three categories: - Cement Based Tanking - Cavity Membrane Systems - Slurry Applied Coatings. Cement-based Water Proof Render (Tanking) Water proof renders are one of the oldest methods of water proofing and have been used by the remedial industry for many years. The application of multiple coats of a water proof render (using sand and cement incorporating a quality waterproofer) to a previously prepared surface is designed to stop water entering the tanked area. However there are many disadvantages: • Tanking with this method can cause condensation as the wall surfaces are cold and the ambient air is warm in normal living conditions. • The render is subject to salt attack from sulphates which attacks the cement and breaks it down over a period of time. • It is prone to cracking due to structural movement or even vibrations from heavy traffic in some cases. • It is very difficult to repair should a failure arise. • It is difficult to achieve fixing of skirting and heavier items, as the render can not be pierced and everything must be glued. • It creates water pressure, pushing the water to other areas such as your neighbours' property, and in some cases can cause sheets of render or floor sections to blow if the water pressure is not relieved with sump pumps. Cavity Drained Membrane Systems The Cavity Drained Membrane System is, as the name suggests, a polyethylene studded sheet which is fixed to the walls, floor or ceiling with specially designed plugs with fitted seals. It creates a cavity between damp masonry and a new wall surface. The base of the wall carries a drain channel which normally runs to a sump pump or manhole, thus relieving water pressure. The system can be either dry lined or plastered directly on to achieve a smooth plastered finish. This method of tanking: • eliminates the risk of condensation associated with cement render tanking. • is not affected by structural movement or vibration from traffic. • manages the water pressure by allowing the water to drain away, eliminating the risk of pushing the water elsewhere. • can be repaired fairly easily should it fail. Slurry Systems These are often cement based, two part flexible coatings which come pre-packed in powder form. The surface must be prepared and a salt inhibitor applied. The slurry can then be mixed and applied by brush. The system has the same disadvantages as the Water Proof Render system with the added problems of eroded or perished brick requiring special attention, and the high cost of the materials.

Woodworm: show or hide content

Woodworm Treatment and Control
The term woodworm is an inaccurate one, as 'woodworm' is actually a beetle infestation. The damage caused to the timbers is due to the feeding of beetle larvae. The adult beetle lays its eggs in a crack or crevice within the timber and the larvae hatch soon after. The larvae burrow their way through the timber for many years before emerging as an adult beetle in the warmer summer months, and when they in turn lay new eggs the infestation process begins again. It is important to identify which infestation we are dealing with, as some infestations require no chemical treatment whilst others require more particular attention. The different species of wood boring beetle larvae attack various types of timber. Some larvae live for less than a year while others live up to 11 years before hatching as an adult beetle. The most common infestations are: The common furniture beetle. The common furniture beetle is responsible for around 70% of all infestations and attacks softwood and European hardwoods. The emergence hole is around 2 mm in diameter, and active infestation will often be accompanied with cream coloured bore dust. Severe infestation of timber will result in structural failure. Structurally unsound timber should be replaced and then Micra emulsion insecticide preservative applied via spray treatment. Wood boring weevil. The wood boring weevil will only attack decayed timber that has been attacked by wet rot. The beetle will travel down the grain of the timber forming plough like tracks. The replacement of the decayed timber (isolating it from any further moisture) is sufficient to eradicate this infestation, and no chemical treatment is required. Deathwatch beetle The deathwatch beetle attacks decayed hardwood and sometimes soft woods that are in contact with hardwood. The name derives from the ticking sound (rather like a watch) made by adult beetles tapping their heads against the walls of the emergence holes to attract a mate. This was often heard in coffins made of oak. Deathwatch may be a secondary problem, as fungal decay must be present for an infestation to become established. Extreme damage to bearing end timbers can often be concealed in walls that are prone to dampness. It is critical to identify the correct species of decay and insect to eradicate this problem completely. Other, reasonably rare types of beetle attack can occur, but are rare in domestic situations, especially in the North Home Counties.