Rising damp

Rising damp is generally accountable for a small percentage of damp cases in the UK; however, it is grossly over represented due to mis-diagnosis and ill informed homeowners.  As such many homeowners wastefully spend money on incorrect remedial action, which fails to eradicate the source and consequently the effects of damp.

Rising damp, like its namesake is caused by the upward movement of moisture through fine pores in masonry, caused by the process of capillary action, which relies on the surface tension of moisture to draw moisture vertically from the ground.

Dampness may be caused by a variety of factors, and can range from a simple, e.g. misaligned gutter to more complex failure of a roof membrane. Although, the water ingress may be caused by a simply corrected defect, this does not automatically make the task of identifying the damp source an easy task, as many professionals will testify to, this can be a difficult, costly and time consuming process.

Water ingress, through rising or penetrative damp sources if left for a period of time, may result in consequential damage, resulting in rotting timber members, skirting boards and can lead to other issues, such as Wet rot and Woodworm.

There are 3 main causes of dampness in buildings; these are Rising Damp, Penetrative damp and Condensation. This section will explore primarily the issue of Rising damp, with comparatives to penetrative damp sources.

 

What to look out for?

If you suspect you may have an issue with Rising damp, either in a property you are looking to buy, or in your existing home, which may have appeared, over a prolonged period of rainfall, or perhaps following recent work to a garden, it is worth looking out for the key tell tale signs, as noted below:

Tell tale signs

  • Tidal mark and or damp patches or stains at low level (less than 1.2-1.5m)
  • White, floury salts (efflorescence): - in the form of nitrates, chlorides and sulphates on the wall (these are rarely found from other water sources)
  • Fungal decay in skirting boards
  • High progressive moisture readings at low level

Some typical causes, which you should be aware of include:

  • Failure of DPC/ Inadequate or missing
  • Raised external ground levels
  • Splashing from down pipes
  • Render bridging the DPC

 

Is it really Rising Damp?

Contrary to common beliefs, Rising damp does exist, and is present in a number of properties, particularly those from the Victoria era, which often did not include a DPC. However, the presence of Rising damp remains a fairly uncommon occurrence, see article Rising Damp myth

The most typical sign of rising damp is a tidemark at low level, which generally does not extend more than a metre or so above the floor.

Rising damp problems, which have lingered for some time, may be exacerbated by hygroscopic salts, which draws moisture from the air, and can increase the height and extent of damp staining.

There are other causes of damp at low level, which may cause confusion and lead to a mis diagnosis. There may be a leaking down pipe, or overshooting an open surface water gully, which is consequently soaking the external wall, or it may be simply due to an overloaded kitchen sink, resulting in water running down the back of the unit.

Patches of mould growth on the wall are indicative of condensation issues, as the salts, which are usually drawn up in the process of capillary action, inhibit the formation of mould spores.

There are many damp specialists whom are well prepared to advise homeowners, and are quick to establish a cause as due to Rising Damp. This is often due to a vested interest in remedial solutions such as application of an Injected DPC.

Therefore, it is essential that all other aspects be considered, before the cause is attributable to Rising damp.

Rising Damp Treatment

It is generally advised, that, if you suspect Rising Damp in your property, that you undertake an initial assessment/ appraisal of your DPC to check such things as ground levels etc. Further to this, an RICS Chartered Building Surveyor or Structural Engineer should be appointed to undertake a survey.

The cause of action, for dealing with rising damp may include:

Physical DPC Insertion
This is generally the most effective method, although this can be costly, and is not suitable for Rubble walls. If there is a missing or inadequate DPC, an option may be to either saw cut a groove, using a diamond chainsaw, or undertake manual removal of bricks to insert a new DPC.

This may be in the form of a polythene sheet, to provide an impervious layer, combined with a Stainless steel tray, which is filled with an epoxy resin mix. See link below for further specification information.

Chemical Injected DPC
This is often the cheapest and most common form of remedial treatment, although not necessarily the most effective. This can take the form of pressure-injected silicone or a diffusion cream, the latter of which is inserted into the mortar bed. 

Replaster/ Decorations
In addition, it is essential that hygroscopic salts within the wall and plaster area dealt with. Internal plaster and decorations will need to be renewed up to a height of approximately 300mm, using a cement based plaster, which may be applied in co ordination with a salt neutraliser and redecorated with 2 coats waterproof paint.

Further Advice

For further advice and or information, please contact us: Alternatively, you may wish to contact the companies in the resources section.