Cold single leaf wall

How to improve solid walls

Property Repair Systems - 01626 331351 - where you can speak to real wall people

Click for Home Page





Cold Single Leaf Wall problems

Defects to check and eliminate before replastering or lining with an Air Gap Membrane.

A surface thermometer and a 'damp meter' (see are useful tools for this diagnosis - if not available use the back of your hand to assess the relative warmth of one affected area to another unaffected area.

Penetrating dampness

Penetrating dampness, due to poor 'pointing' (mortar in the joints between bricks or blocks), crumbling or cracked brick faces (spalling) or cracked or hollow render. Dampness that comes through the wall may bring 'salts' to the surface of the plaster and these 'salts' attract more moisture from the air.

Remedy - rake out the joints and re-point with a soft mortar mix (6:1:1 - sand/cement/lime) with a plasticiser additive in the mix (Renderproof) or hack off and re-render, again with a soft mix, but using BondAcryl to bond the new render to the wall and the edges of the old render. Scratch well between coats and damp the wall well before and after rendering, to slow the drying process (reduces the risk of cracking).

For help with penetrating damp and how to eliminate it call our experts on 01626 331351.


Condensation: this forms on the coldest surfaces in a room and often grows 'black mould'.

Remedy - hack off all the plaster and fit an Air Gap Membrane, plus insulation (see

For help with mould and how to eliminate it call our experts on 01626 331351.

Bridging of the damp proof course

Damp course 'bridged' or covered by high ground, pathway, garden or abutting new structure, (e.g. conservatory, steps): the damp proof course must be a minimum of 6 inches (150mm) above outside ground level, in order to avoid rainwater splash up causing penetrating dampness.

Remedy - remove the obstruction or inject a new damp proof course at the proper level (see Damp Proof Injection)

For help with 'bridging' problems and how to eliminate them call our experts on 01626 331351.


Service fixing, pipe or wire penetrates the wall: pipes, wires, bolts and other fixtures that pass into the wall can carry moisture inside, which may emerge at that level or drip down and show elsewhere.

Remedy - remove the obstruction, or carefully seal the entry point. Pipes and wires should always be routed to climb up the wall immediately before entering the duct or hole, to avoid channeling the water by gravity.

For help with services leaks and how to eliminate them call our experts on 01626 331351.

Pipe Leaks inside the walls

Water pipes concealed inside the wall: usually heating or mains water, but can also be boxed in foul water pipes or cistern overflows in modified houses.

Remedy - remove the boxing or a brick or block from the wall to expose the defect..

For help with water leaks and how to eliminate them call our experts on 01626 331351.

What do the symptoms look like?

Symptom - white, fluffy salts, plaster possibly 'blowing' off the wall - 'efflorescence' - you have a water source which needs to be found and eliminated. Use our Water Leak Checklist (click here).

Answer - Salt Neutraliser might work if you can find and stop the leak, or the plaster may be too damaged and need replacement to our Specification. Either replaster to our Renderproof Specification or line the walls with our Mesh Membrane - both act as barriers to the passage of damp and salts, but the Mesh Membrane also provides insulation and is foolproof.

For help with 'salts' and how to eliminate them call our experts on 01626 331351.

Fluffy white salts on a chimney breast wall, showing rusty angle bead.

Close up of fluffy white salts on a chimney breast.

Symptom - damp patches on the ground floor - at low level, right down to the skirting board - that come and go - you have 'hygroscopic' salts that are attracting moisture from the air.

Answer - you may have Rising Dampness, or your damp proof course may be 'bridged' by high outside ground, plaster on the inside or debris in the cavity (cavity walls only). Rectify any defects and if necessary inject Quick Cream at the correct level to form a new Damp Proof Course. The plaster will need replacement to our Specification.

For help with 'hygroscopic salts' and how to eliminate them call our experts on 01626 331351.

Hygroscopic salts causing wallpaper to peel - can be sticky

Peeling wallpaper on hygroscopic salts

Symptom - damp patches on or around chimney breasts - sometimes showing yellow or brown stains in wallpaper or paint - you have 'hygroscopic' chimney salts that are attracting moisture from the air, which may include tars and other chemicals from burning wood or coal.

Answer - these 'salts' are very difficult to hold back in the wall, even with the replastering to our Specification carried out to perfection. We recommend using Mesh Membrane - a type of dry lining - to allow you to replaster using normal, lightweight plaster, with no risk of further 'salting'.

For help with 'hygroscopic salts' and staining and how to eliminate them call our experts on 01626 331351.

Damp patches on a chimney breast

Patches of both hygroscopic damp

and penetrating damp.

Products mentioned above:

Salt Neutraliser - a clear liquid used to neutralise 'salts' in render, plaster or masonry, either to attempt to save otherwise sound plaster or as a preparation prior to re-plastering to our Specification. Apply two coats, wetting in between with fresh water.

Salt Neutraliser

Renderproof - a blue concentrated additive for sand and cement, designed to be dissolved in water. It waterproofs the render mix and acts as a plasticiser and salt inhibitor.

Render additive concentrate - Renderproof

Click here for the Replastering Specification Data Sheet

Mesh Membrane - easy to install dimpled plastic 'air gap' dry lining membrane, supplied in rolls like wallpaper. Designed to cover damp or salty walls and provide a fresh surface for replastering with a modern lightweight plaster (usually 'bonding').

Mesh Membrane - with air gap insulation on dimples

Go straight to our Shop

Learn from the UK's top Expert: become your own expert - save money.

Quick DIY Master Class in Dampness and Condensation - become your own Expert in 1 hour! Buy our "Dampness in Buildings" reprinted book by the great expert Graham Coleman. A great read, short and to the point.

Click here to buy the reprint.

Home | Damp | Plastering | Membrane | Damp Meters | Anti-Mould Additives

| Privacy Policy | Returns Policy | Contact

Use any of our Shopping Pages to place goods in your Shopping Basket - they all use the same Shopping Cart system.

Click to view your Shopping Basket

or continue shopping by clicking on one of our Shops below.


Property Repair Systems

T: 01626 331351

F: 01626 331143

E: Mail us

Site written by: David Moore

David Moore, B.A. (Hons.), C.T.I.S., C.R.D.S. Technical Author


Other Property Repair Systems Sites: - how to use Boron based insecticides/fungicides to treat timber rots and insect attack - how to treat patio decks and yacht decks - how to kill Dry Rot in buildings - membranes for lining damp walls, floors, basements and cellars - resins for repairing and sealing all types of masonry - upgrade doors to 30 minutes fire resistance - how to quickly repair joists and beams of any size - our Home Site - treat steel with Intumescent Paint to provide fire protection - systems of repair, with step by step methods - how to repair timber beams - how to kill and prevent woodworm and death watch beetle - all your questions and our answers about woodworm treatment DIY