WELCOME TO OUR Damp in a cavity wall PROJECT
This project is presented by Property Repair Systems
Summary: How to check and remedy damp in a cavity wall.
If you need any help with any type of Damp in a cavity wall, timber repair or maintenance problems, Property Repair Systems will be pleased to give you completely free, no obligation advice on 01626 331351. The information you need may be in the project below, if not, call them.
One of the most effective ways of stopping damp travelling through the walls of a property is to build with a cavity but sometimes the cavity can actually cause the damp problems. Below is a list of ways a cavity can be compromised and allow damp through to the inside.
If you believe you have damp walls, check first with a meter available from www.dampness-info.co.uk/meters_diydoc.htm. The back of your hand will also give you a good indication of damp within a wall. You can also click on the images below.
Problem: Damp course could be '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, although even in this case a clear cavity should prevent transfer of dampness to the inside wall.
Remedy: Remove the obstruction or inject a new damp proof course at the proper level (see Damp Proof Injection - small jobs Project)
Problem: Cavity 'bridged' or filled with debris: usually brick ends, sand and mortar, all dropped by the 'Brickies' during construction, or sand gradually falling from soft mortar joints.
Remedy - remove a brick or block from the wall and clean out the cavity.
Problem: Wall ties dirty: can cause damp spots to appear on the inside plaster, sometimes with 'salt' or black mould.
Remedy - use a metal detector to locate the ties on the outside, examine with a borescope and remove a brick or block from the wall and clean the ties.
Problem: Wall ties rusting: can cause damp spots to appear on the inside plaster, sometimes with 'salt' or black mould.
Remedy - use a metal detector to locate the ties on the outside, examine with a borescope and if necessary fit replacement ties before isolating or removing the old ones, (see Check Wall Ties Project).
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Problem: Poor cavity insulation job: can cause cold spots on the inside plaster, sometimes with 'salt' or black mould.
Remedy - Try re-injection first, but if this is not successful remove a brick or block from the wall and check the cavity insulation.
Problem: Service fixing, pipe or wire penetrates the cavity: pipes, wires, bolts and other fixtures that pass into the cavity 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 channelling the water by gravity.
Problem: Water pipes concealed inside the cavity: usually heating or mains water, but can also be boxed in foul water pipes or cistern overflows in more modern houses.
Remedy - examine with a borescope and remove a brick or block from the wall to expose the defect.
Indoor Walls - ground floor, a quick summary checklist:
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
Remedy - 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.
Symptom - damp patches (at low level, right down to the skirting board) that come and go - you have 'hygroscopic' salts that are attracting moisture from the air.
Remedy- 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.
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.
Remedy - 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'.
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.
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').
Quick Cream - new, easy to install, cream damp proofing product - no pump required, no mess, no smell - includes injection nozzle extension. Designed to gently diffuse into the wall to form a water repellent layer - a 'damp proof course' (DPC). It is approved by the British Board of Agrèment - BBA Test Certificate No: 02/3961 - as used by the professionals. The BBA is a Government Approved organisation which has been testing building materials for over 30 years. Note - not all damp proofing materials have passed these tests - beware of cheap imitations).
click here for a check list if you want to diagnose your damp
click here if you would like to read a genuine testimonial
Go straight to Price List and Order Form
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