Cost of having your House Walls Damp Proofed

All you need to know about damp proofing your house walls including costs of materials, costs of labour and time frames.

damp proofing

What the job entails

Damp proofing is a general term that covers all methods and treatments used to prevent damp being absorbed through walls or floors into the interior of a property. Damp and rot can eventually cause structural damage to a property so it is essential to identify and tackle damp as soon as possible to help prevent any further damage. If there is no existing damp proofing or the physical barrier is damaged, it can lead to problems including rising damp, dry and wet rot.

When a property is constructed a preventative damp proof course (DPC) is normally built into the walls, just above ground level. If you hire a professional in to do damp proof your home then damp proofing will normally include a full inspection of walls (visual plus damp meter), checking the existing damp course, the removal of skirting boards and plaster internally 1.5m high, the injection of waterproof liquid, then Waterproof render applied to internal wall and then finish the job off with plaster.

If you are getting this work done, then it makes sense to check the condition of the interior plaster and redecoration. You may need the entire walls plastered, so this would be a good time to redecorate, painting walls and skirting boards.

If you spot any signs of damp then the best thing to do is to have your home inspected by an independent surveyor or a trustworthy damp proofing specialist. Be careful hiring an unknown damp proofing company to inspect your walls as they may try to sell you a damp proof course that is not required. The damp proofing industry has a bad reputation in the UK selling unnecessary wall treatments when the real cause of the damp is often just the existing DPC being bridged.

Damp proofing is a really messy job due to the plaster and skirting boards needing to be removed, so it's best to move out for a couple of days if you can, otherwise try and seal off the area where the plaster is being removed as best as you can. It’s always best to get the damp proofing work done quickly and to tackle any damp issue as soon as possible as damp can spread quickly rotting timber floor joists and skirting boards.

Although the plaster only needs to be removed up to around 1.5 metres from the floor, if the plaster is old and in particularly poor condition, it will probably all need to be removed and re-plastered. Same goes for skirting boards, if they are damp and rotten, they may crumble when being removed so will need to be replaced. Also, once the job is done, there will still be painting or wallpapering required to finish the walls which will not be included in any quotes you get when pricing the job.

Damp Proofing Cost

To damp proof an entire typical 3 bedroom semi-detached house, will cost around £2500. This price will include a new DPC inserted into both internal and external walls, plus the rendering and plastering of the internal walls to finish the job. Other common damp proofing work includes building a drainage channel around one side of the building so rainwater is channelled away from the walls and cannot compromise the existing DPC. The drainage channel is usually filled with stones and connected to the existing soakaway and rainwater downpipe. Drainage channel quotes are typically in the region of around £1000.

Most damp proof specialists don't charge by the day, more so by the size of the job. In terms of the time it takes to complete the job it again depends upon the size of the property. The actual damp proof course itself won't take more than a few hours but the plastering and rendering to make the job look tidy again afterwards could take a couple of days.

Here are a few average costs for hiring someone damp proof your house walls:

House Type Drainage Channel? Avg. Cost Duration
Terraced No £2000 2-3 days
Semi-detached No £2500 3-4 days
Detached No £3000 4-6 days
Terraced Yes £2500 3-4 days
Semi-detached Yes £3000 4-5 days
Detached Yes £3500 6-8 days


Cost Breakdown

Individual costs for hiring a specialist company to damp proof the walls of a 2-storey semi-detached house - Total Cost: £2500

20%

Damp Proofing
£500

30%

Tradesmen
£750

50%

Plastering & Rendering
£1250

FAQ's

When a DPC is inserted into a new building it is normally a rigid plastic board between the brick walls. But this is too difficult for an existing building, the most common method for existing buildings is to drill holes and then inject a chemical waterproof material into the wall. This material is soaked up by the porous bricks and cement and when set it will provide a waterproof layer. The internal side of the wall also should also be treated which will require removing the plaster. There are various commercial high pressure systems available to insert the chemical into the wall, but some use a drip-feed system that slowly introduces the waterproof liquid over a 48 hour period. Some of the newer systems on the market use creams that are squeezed into the holes rather than a liquid.
Rising damp is where a DPC is faulty, damaged or missing; or where the ground level around the house has been raised above the level of the existing DPC. Water will permeate walls which are made of naturally porous materials such as brick, stone and mortar. This water then travels up the walls and not only looks unsightly, it also causes heat loss and timber rot, while also encouraging mould. Not all damp problems are caused by rising damp, penetrating damp and condensation can also cause damp issues.

To prevent penetrating damp, make sure check the guttering is clear of any blockages, ensure there are no cracks in the walls or window frames, or loose roof slates. Condensation can be prevented by adequate ventilation and heating, plus using extractor fans in rooms such as the kitchen and bathroom where there is a lot of water/humidity. Damp caused by rising damp can be identified as the damp patches literally rise up from floor level up to a typical height of around one metre. Damp patches higher than this will likely be condensation or penetrating damp.
Rising damp can occur in any property but is more common in older houses. Rising damp happens when water from the ground penetrates walls which either do not have a DPC, the existing DPC is damaged or missing, or the ground level is raised above the level of the existing DPC. The symptoms include wet or rotting skirting boards, discoloured wallpaper, damp stains on the walls, wet plaster or exterior stains.