7 Step Guide to Waterproofing Your Home

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 as they arise from plumbing leaks or poor roof, gutter and downpipe maintenance.

Waterproofing – Common Defects and Solutions

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.

We will take some of the major defects that genuinely require some form of urgent waterproofing from the top of a typical building down to the foundations, they are as follows:

1. 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 on the chimney stack
• Poor pointing
• Rotted ‘spalling’ bricks
• Birds nesting

Waterproofing Options and Procedures

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

• SBR for render and as part of the render mix. This is mixed in with a sand and cement render mix and provides an additional bond to existing concrete or render. It can also allow the laying of thinner screeds and also waterproofs a sand and cement mix
• Enviroseal Plus Ultraproof / Everbuild Waterseal – a high build, silicone cream based water repellent. This gives long lasting protection, is water based and provides a water repellent protective layer for stone and brick walls, concrete floors, render and plaster
• Technoseal / Black Jack DPM – a bitumised coating, in black or white. Tough and strong rubber membrane than can be applied internally or externally that is applied with a brush

If you are looking for more help and advice on how to deal with damp issues on and around chimney breasts see our project here.

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 the property
• Poor mastic or mortar around apertures

Waterproofing Options and Procedures

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

• SBR for render and as part of the render mix. Mixed in with sand and cement render and helps bonding to existing concrete or render surfaces
• Enviroseal Plus Water Repellent / Everbuild Waterseal, for up to 15 years protection. Gives surfaces a water repellent and protective layer. For brick, stone, plaster or render
• Technoseal / Black Jack DPM – a bitumised coating, in black or white. Can be brushed on to surfaces and once cured provides a tough and protective rubber membrane
• Mesh Membrane / Damp Proof Membrane – dimpled plastic sheets, for indoor or outdoor fixing. Direct render or plaster onto the mesh surface

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 and investigated further.

Eliminate Building Faults

• High ground levels – garden, path or 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 and Procedures

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)
4. Masonry Paint – use an algae resistant masonry emulsion

Suggested Products

• SBR for render and as part of the render mix. Once mixed with the render mix, this provides a bonding agent that helps with joining to existing concrete and render surfaces
• Technoseal / Everbuild Waterseal – a bitumised coating, in black or white. This product can be applied by brush to a surface and once dried forms a protective rubber membrane
• 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.

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 and Procedures

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 into other areas
3. Air Gap Membrane – fix this plastic dimpled material with plastic plugs and then plaster with Bonding Plaster

Suggested Products

• SBR for render and as part of the render mix – 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 / Damp Proof Membrane – dimpled plastic sheets, for direct plastering with Carlite Bonding, or ‘dot and dab’ fixing of plasterboard

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 and Procedures

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

• Tanking Slurry Powder / Tanking Solution – apply this cement based tanking slurry, then render with sand and cement. This is a powder based product that is mixed with water to form a think paint like substance that is then brushed on to the wall to provide a water resistant barrier
• Mesh Membrane / Damp Proof 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. Comes in a powder form that is mixed with water to form a stiff mortar

6. Damp Solid Floor

When concrete, brick, slab, slate or quarry tiled floors are in a sound and otherwise decent condition but feature areas of 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

• Tanking Slurry Powder / Tanking Solution – 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

7. Damp Basement or Cellar

As in the above point where brick, slab, concrete, slate or quarry tiled floors are damp but still in a good condition and also surrounding wall surfaces feature damp brickwork or stonework and where there is also liquid water ingress present.

Eliminate Building Faults

• Hidden water leaks – old mains water supply pipes, buried central heating pipes
• Water table issues such as naturally occurring springs or wells
• Adjoining cellars or basement areas that are suffering from 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

• Tanking Slurry Powder / Tanking Solution – 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

Water and moisture ingress can be a real pain to diagnose and resolve as some issues can seem like they’re caused by one thing when in fact they’re not, so by using our waterproofing guide above you can get to the bottom of your problems and find out how to fix them.

Although the above checklist will help you to narrow down issues and suggest a fix, sometimes it’s also best to get a second opinion from a trade professional if you are in any doubt.