Rising Damp and Penetrating Damp
Rising Damp
Rising damp is caused as a result of water migrating through the capillaries of the materials with which most buildings in this country are made. This will be either stone or brick, as well as the materials which are used to bond these substrates together, i.e. mortar, which can be of varying types of mix including sand and cement, ash and various other materials which have been used through centuries. Water can travel through these capillaries to a height of which will be determined by the narrowness of the tube, the narrower the capillary tube the greater the height reached.
To overcome this problem in new construction, a physical damp proof membrane will be installed at 150mm up from the external ground level; this prevents the rise of water within the wall by breaking the continuity of the capillary action. In some cases it is totally missing, allowing water to rise up the wall i.e. rising damp. Rising damp causes damage to interior plaster work and decorations and shows itself by causing wallpaper to peel and paint to blister.
These problems are often made worse by salts efflorescing on the surface of the wall, these salts if deliquescent or hygroscopic, can make matters worse as they will attract extract moisture from the air adding to the problem of surface dampness. The obvious physical deterioration caused by rising damp and the costs involved in putting it right are problems enough but we should also bear in mind that a cold damp house is an unhealthy environment to live in, and it is expensive to heat. These problems can be aggravated still further as rising damp’s often the cause of both and wet rot and dry rot
Penetrating damp
Penetrating damp can be attributable to a wide variety of causes, such building defects as cracked defective external rendering, damaged and defective water goods, i.e. down pipes and guttering, leaking roof covering, high external ground levels, badly fitted or rotten joinery etc.
Penetration of water to the external walls at low level can often be confused with rising damp and care must be taken during an inspection to accurately identify all building defects that may be contributing to dampness within the building. Again, wet and dry rot attack are often instigated by external building defects, allowing water to penetrate and it is an essential part of any inspection to accurately identify all these problems.
Rising Damp evident in internal wall. Notice the discolouration and bulging of the plaster work.
Electro Osmosis
This is the theory that moisture rises from the earth by capillary and osmotic action, causing an electrical potential to develop between the wall and the earth, the introduction of an electric current interferes with the mechanics of this moisture flow.
The system introduces a very small and perfectly safe electrical current into the wall just above ground level. Its effect is to repel the rising moisture molecules down the walls and harmlessly back into the ground.
Description
This system comes in 25 meter rolls of 2mm pure titanium wire coated in a platinum group element interconnected at intervals with anodes. The limits of the anodes are indicated by two distinctive colour bands.
The titanium wire, though tough can be cut with a pliers and a join made using titanium crimps ensuring a mechanically powerful and virtually indestructible joint
Preparation for work
This system carries little preparation for work as such; it can be fitted on the outside or inside of any premises. However if salting is evident in the inside walls then the plaster must be removed if it is being placed inside before work can commence.
A series of 12mm holes are drilled at 1 meter intervals, the anodes are folded back on themselves and inserted in the holes previously drilled.
Holes are back filled with cement to secure the wire. Once the circuit is complete, a one meter copper coated earth bar is driven into the ground (this acts as a neutral for the system) which is connected in to the power unit which is plugged into a standard socket and services the system. This power unit has the same running cost as a standard door bell so is virtually inexpensive to run. The main advantage of this system is that it is a passive system meaning it is constantly on and working. This system is more suited for rubble filled walls as opposed to chemical injection.
Wiring anodes in operation in a wall.
Chemical injection
Chemical injection is a unique silicone emulsion cream for injection into brickwork etc. for the control of rising dampness. This can be used in all types of masonry without the use of high pressure equipment. The cream is delivered by hand pressure only from a simple displacement pump and injector lance into a series of holes drilled into the mortar course. From here it migrates rapidly into the masonry pores where the injection cream reverts to a liquid phase and
polysiloxanes are formed in situ. During the curing period a low molecular-weight silane vapour is also produced givig excellent migration through the wall. Curing of the DPC starts immediately with the final cure taking 2 - 6 weeks depending on wall thickness.
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