Article - basement waterproofing method

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In this article - basement water proofing - how to install membrane to wet walls and damp floors

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Summary: basement waterproofing and cellar conversion.

Damp walls are very prone to Condensation and Black Spot Mould. If the walls are made of a single brick or block 'skin', or have no cavity, or are below the damp proof course, or partially below ground, or 'earth retaining', they will always be cold. Traditionally the way around this problem was to cover up with wooden paneling, but this tends to rot. So, 'dry lining' was invented and from this has evolved the 'Air Gap' or 'Cavity Drain' Membrane, a dimpled, plastic sheet which, because of the dimples, allows air to freely circulate. This prevents moisture from being trapped (as in conventional 'tanking') which can drive dampness sideways and upwards.

Lining Walls - choice of methods

The three main methods are;

1. Board on battens - directly nailed or screwed to brickwork, stone, block or render - likely to decay on old, damp salty masonry, and at risk from Dry and Wet rots unless efficiently treated and ventilated.

2. Inner walls - block walls built inside the building, with an air gap or insulation. Often used in Barn Conversions, where wall thickness and lost internal space is not an issue. Not a vapour barrier, so damp and 'salts' from the unventilated cavity can eventually reach the inner wall decorations.

3. Air gap membranes - a modern, vapour proof barrier lining - it is a dimpled plastic sheet fixed onto brick, stone, block or render with plastic plugs to form an air gap cavity. These Membranes can have a plain surface, for battening, or a Mesh surface for direct plastering or plaster boarding. Ideal for cold, single leaf walls and for lining rooms with cold solid walls.

Air Gap Membranes - how to install

1. Remove all gypsum plaster (solid sand and cement render can stay), wooden plugs and bonding timbers.

2. Check whether you have any 'active' water weeping from the wall, or if the area has ever suffered from flooding. If there has been any activity you will need to install a drainage method - either a traditional drain or a sump and pump. (Ring for help on 01626 872886 ).

3. Choose your wall finishing method - battens and nailed plaster board (with or without insulation between the battens) or direct plastering with Bonding Plaster, or Plaster Board on adhesive 'dabs'.

4. Battens and nailed plaster board - use Kontract Membrane - the plug heads have pre-formed holes ready for No.10 or No. 12 self tapping screws, to fix the battens.

5. Plastering or Plaster board dab fixed - Mesh Membrane - the welded-on mesh supports the plaster or the adhesive.

6. The floor may also need to be covered with Kontract Membrane - a 'floating' (not screwed, nail or glued down) tongued and grooved chipboard or concrete screeded floor (3 inch/75mm thick) can then be laid. Where liquid water is involved this floor Membrane has to be joined to the wall Membrane - this is called the 'sealed system' and must incorporate a drain or a sump and pump. Floor insulation can also be inserted.

Salt Neutraliser - a clear liquid used to neutralise 'salts' in render, plaster or masonry, either in an 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').

UltraCure DPC Cream

A 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.

If you need any help with lining damp walls or 'tanking' products, Property Repair Systems staff will be pleased to give you completely free, no obligation advice on 01626 872886 .

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Other Property Repair Systems Sites: - epoxy resins for repairing wood, concrete, brick and stone - 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

Site written by: David Moore

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