Property Repair Systems

Waterproofing Guide

This project is sponsored by Property Repair Systems

Summary: Checklist, tips and information on how to waterproof buildings

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There are many effective ways of Waterproofing buildings, but firstly you need to be sure that you have a dampness problem that requires such treatment. Many dampness problems do not require waterproofing at all – they arise from plumbing leaks, and poor roof, gutter and downpipe maintenance.

First you need to correctly diagnose the problem (see our diagnosing and analysing damp project), then you may need to refer to our finding water leaks project

If you need any help with diagnosis or leak detection call the Property Repair Systems experts for free help on 01626 336180, or you might like to increase your own diagnostic abilities by purchasing a Damp Meter and Dampness in Buildings Book. This little book is the perfect companion for the DIY enthusiast and Professional Surveyor – a real ‘Masterclass’ in damp diagnosis.

Waterproofing – Common Defects and Solutions

We will take some of the major defects that genuinely require some form of waterproofing from the top of a typical building down to the foundations,

Problem

Chimney Stack Damp – water penetrating the masonry of the stack itself, usually visible in the loft space or even in the ceilings below (stains).

Eliminate Building Faults

Lack of a ventilated capping, poor pointing, rotted ‘spalling’ bricks, birds nesting.

Waterproofing Options

  1. Render the stack – use a Primer and then sand and cement, incorporating a waterproofer. Thorough cleaning and priming are essential because old stacks are heavily contaminated with soot, salts and resins.
  2. Apply a water repellent – this must be a product that is suitable for high levels of salts. A standard silicone based product in solvent is not usually sufficient.
  3. Apply a waterproofing coating – cement based Tanking slurry or Bitumen based products can work, but will probably not adhere long term.

Suggested Products

BondAcryl – Primer for render and as part of the render mix.

Enviroseal Plus – a high build, silicone cream based water repellent. This gives up to 15 years protection.

Technoseal – a bitumised coating, in black or white.

Problem

2. External Wall Damp – penetrating damp above damp proof course.

Eliminate Building Faults

Poor brickwork, poor pointing, lack of window cill ‘throats’ or ‘drips’, blocked cavities in cavity walls, cavity wall ‘trays’ or ‘weeps’ missing, wires or pipes entering, poor mastic or mortar around apertures.

Waterproofing Options

1. Render the walls – use a primer and then sand and cement, incorporating a waterproofer. Thorough cleaning and priming are essential because old masonry can be heavily contaminated with ‘salts’ and other chemicals.
2. Apply a water repellent – this must be a product that is suitable for high levels of salts. A standard silicone based product in solvent is not usually sufficient.
3. Apply a waterproofing coating – cement based Tanking slurry or a Bitumen based product.
4. Slate hang the walls – a favourite in Conservation Areas, to satisfy Planning Regulations.
5. Air Gap Membrane – fix this plastic dimpled material with plastic plugs and then render with sand and cement.
6. Masonry Paint – use an algae resistant masonry emulsion.

Suggested Products

BondAcryl – a Primer for render and as part of the render mix.

Enviroseal Plus Water Repellent, for up to 15 years protection.

Technoseal – a bitumised coating, in black or white.

Mesh Membrane – dimpled plastic sheets, for indoor or outdoor fixing. Direct render or plaster onto the mesh surface.

Algaecheck Masonry Paint – high density masonry paint with added slime and mould inhibitors, for extra long life.

Problem

3. External Wall Damp – penetrating below Damp Proof Course level. Bear in mind that walls are always damp below the damp proof course to some extent, but only from naturally rising dampness. Visible wetness should be treated with suspicion.

Eliminate Building Faults

High ground levels – garden, path, road. Materials or objects up against the wall – piles of soil, debris, building sand, garden walls or posts. Poor drainage – blocked gullies, soakaways, surface drains, drives sloping down towards the building.

Waterproofing Options

1. Render the walls – use a primer and then sand and cement, incorporating a waterproofer. Thorough cleaning and priming are essential because old masonry can be heavily contaminated with salts.
2. Apply a waterproofing coating – cement based Tanking slurry or a Bitumen based product.
3. Air Gap Membrane – fix this plastic dimpled material with plastic plugs and take down to foundation level, to meet a French Drain (perforated pipe).
6. Masonry Paint – use an algae resistant masonry emulsion.

Suggested Products

BondAcryl – a Primer for render and as part of the render mix.

Technoseal – a bitumised coating, in black or white.

Geotextile Membrane – dimpled plastic sheeting fitted with a bonded layer of textile as a filter, for external fixing below the damp proof course. Use with Technoseal and a French Drain.

Algaecheck Masonry Paint – high density masonry paint with added slime and mould inhibitors, for extra long life.

Problem

4. Damp internal Plaster - above the damp proof course.

Eliminate Building Faults

Chimney Leaks (see Section 1. above). Penetrating dampness (see Section 2. above). Bridged damp proof course (see Section 3. above). Hidden water leaks – old Mains Water supply Pipes, buried Central Heating Pipes. Neighbour’s concrete floor laid above the damp proof course – common fault on Party Walls when timber floors are replaced.

Waterproofing Options

1. Render the walls – use sand and cement, incorporating a salt inhibitor/waterproofer. Plaster finish with a skim coat of Multifinish. Thorough removal of old plaster is essential. DO NOT use any type of Bonding or Browning plaster on the walls, or as ‘dabs’ to secure beads.
2. DO NOT apply a waterproofing coating –Tanking Slurry, Bitumen based products or Unibond – used above the DPC these will simply drive the moisture upwards and outwards.
3. Air Gap Membrane – fix this plastic dimpled material with plastic plugs and then plaster with Bonding Plaster.

Suggested Products

Renderproof – as part of the render mix (mix with the water in the sand and cement) to prevent damp and ‘salts’ from emerging onto the plaster finished surface and spoiling the decorations.

Mesh Membrane– dimpled plastic sheets, for direct plastering with Carlite Bonding, or ‘dot and dab’ fixing of Plasterboard.

Problem

5. Damp internal Plaster - below the damp proof course.

Eliminate Building Faults

Plaster taken down to the solid floor, wicking moisture from a non waterproof wall surface or an unsealed floor to wall joint. Raised external ground levels. Blocked cavities in cavity walls.

Waterproofing Options

1. Apply a waterproofing coating – cement based Tanking, then render and plaster skim.
2. Air Gap Membrane – fix this plastic dimpled material with plastic plugs and then plaster with Carlite Bonding.
3. Floor to wall Joint Seal – cut out the gap to at least 25mm x 25mm and fill with a waterproof mortar.

Suggested Products

Ultra Tanking Slurry Powder – apply this cement based tanking slurry, then render with sand and cement.

Mesh Membrane – dimpled plastic sheets, for direct plastering with Carlite Bonding, or ‘dot and dab’ fixing of Plasterboard.

Fillet Seal – a flexible cement based mortar for filling floor to wall joints, and cracks and joints in solid floors.

Problem

Damp Solid Floor – concrete, brick, slab, slate or quarry tiled floors, sound but damp.

Eliminate Building Faults
Hidden water leaks – old Mains Water supply Pipes, buried Central Heating Pipes. High external ground levels. Lack of a damp proof membrane.

Waterproofing Options

1. Apply a waterproofing coating – cement based Tanking. NOT a full vapour barrier. Can be screeded over with sand and cement.
2. Apply a vapour proof coating – Epoxy based paint, two part system. Ideal for new wood floor protection. Can be screeded over with sand and cement.
3. Air Gap Membrane – lay this plastic dimpled material dimple face down and cover with tongued and grooved boards (chipboard or MDF), or a sand and cement screed.
4. Floor to wall Joint Seal – cut out the gap to at least 25mm x 25mm and fill with a waterproof mortar. This should be carried out in conjunction with Items 1-3 above, to eliminate vapour at the floor edge.

Suggested Products

Ultra Tanking Slurry Powder – apply this cement based tanking slurry, then render with sand and cement.

Air Gap Membrane – dimpled plastic sheets, for direct laying over the floor. Can then be covered with a screed or wooden flooring.

Fillet Seal – a flexible cement based mortar for filling floor to wall joints, and cracks and joints in solid floors.

Problem

Damp Basement or Cellar – concrete, brick, slab, slate or quarry tiled floors, sound but damp. Damp brick or stone walls. With or without liquid water ingress.

Eliminate Building Faults
Hidden water leaks – old Mains Water supply Pipes, buried Central Heating Pipes. Springs, wells and adjacent cellars or basements with water ingress.

Waterproofing Options

1. Apply a waterproofing coating – Floors and Walls: cement based Tanking. NOT a full vapour barrier. Can be screeded over with sand and cement.
2. Air Gap Membrane – Floors: lay this plastic dimpled material dimple face down and cover with tongued and grooved boards (chipboard or MDF), or a sand and cement screed. Walls: fix either Mesh or standard Membrane, then either plaster or plasterboard. Ventilate at the wall base and ceiling if no risk of liquid water ingress, or seal and fit a sump and pump if water ingress is likely.
3. Floor to wall Joint Seal – cut out the gap to at least 25mm x 25mm and fill with a waterproof mortar. This should be carried out in conjunction with Items 1-2 above, to eliminate vapour at the floor edge.
4. Pumped Drainage – fit a sump and pump system to ensure that water cannot spoil the contents and finishes.

Suggested Products

Ultra Tanking Slurry Powder – apply this cement based Tanking Slurry and then render with sand and cement, or screed the floor.

Air Gap Membrane – dimpled plastic sheets, for direct laying over the floor. Can then be covered with a screed or wooden flooring. On walls use Mesh or standard Membrane. These can be directly plastered, plaster boarded or insulated and lined with any board material.

Fillet Seal – a flexible cement based mortar for filling floor to wall joints, and cracks and joints in solid floors.

Sump and Pump, plus perimeter drainage – a must where occasional flooding is remotely possible. Fitted under the Membrane System.

Property Repair Systems can provide telephone advice and support for all the above forms of Waterproofing – call 01626 336180.

Damp Meters, Technical Books and the products mentioned above can be sourced via www.PropertyRepairSystems.co.uk

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