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How much does it cost to damp proof the walls of a house? What is considered a fair and reasonable price to pay for this type of work? And exactly how is this process carried out?
We’ve Done The Legwork…
As with all the price guides on our website, we have done extensive research into the costs charged by tradesmen and companies. This involved getting dozens of written quotes and then calculating an average price which we have displayed in a table further down the page.
One of our team members here at Quotation Check has experience in wall damp proofing and plastering/rendering so we picked his brains about the do’s and don’ts of this work.
You can find more information about how we gathered our quotes by visiting our Meet the Team page.
What You Get For Your Money
Here is a brief summary of the work that is involved with damp proofing a wall:
- Full inspection of walls with damp meter.
- Visual inspection of walls and any existing damp course.
- Removal of skirting boards and plaster to internal wall (1.5m up from floor).
- Injection of waterproof liquid into walls, both internal and external.
- Waterproof render applied to internal wall and then finished off with plaster.
How is the Waterproof DPC Inserted Into the Wall?
Because the wall is already built it would be extremely difficult and costly to try and insert a plastic sheet between the bricks. A more common method is to drill 12mm holes every 100mm along the chosen course and then inject a chemical waterproofer into the wall. The porous bricks and cement will soak up this liquid and when it sets it will provide a waterproof layer, any moisture below this new DPC cannot rise above that course.
The internal side of the wall will also have to be treated, this will involve removing the plaster which if damp will be damaged and soft anyway.
There are several different ways to insert the chemical into the wall. Some companies use a high pressure system, others use a drip-feed system that allows the bricks to soak up the liquid over a 48 hour period. Newer systems involve creams that are squeezed into the pre-drilled 12mm holes.
Common Causes of Damp Walls
In many cases a damp course need not be replaced, it could be that the existing damp course is sufficient but has been bridged.
This is when moisture is allowed to come into contact with the bricks above the damp course. The most common causes of this are:
- Raising flower beds so moist soil is above the damp proof course.
- Laying a patio or concrete floor above the damp proof course.
- Discharging rainwater from gutters near the wall so it frequently splashes the brickwork above the DPC.
- Having the external wall poorly rendered so the cement “bridges” the DPC.
In all of the four examples above, the solution isn’t to install a new DPC but to take other actions; dig out the raised flower beds, lower the patio or put in a drainage channel next to the wall so water is channeled away from the wall. Make sure rainwater discharged from guttering cannot splash onto the wall above the DPC. Remove any external render that has bridged the DPC.
Cost to Damp Proof a Wall
Below are two examples of what you can expect to pay for common damp proofing work:
1) New DPC to Typical Three Bedroom Semi-Detached Property
This work will involve new DPC inserted into both internal and external walls, rendering and plastering internal walls.
As you can see from our table below, the average cost to damp proof a property is £2900.00. This is based on our research into costs charged by UK companies.
|Location||Small Business||Larger Business (5+ employees)|
|Need a Custom Price? >|
|South, SW and Midlands||£2500.00||£3000.00|
|Outer Region and North||£2500.00||£2500.00|
2) Inserting Drainage Channel
This quote is to insert a channel around one side of the building on a semi-detached house so rainwater is channelled away from the walls and cannot come into contact with the bricks. We assume that there is a patio, tarmac or concrete that has been laid too high and has compromised the existing DPC. The channel will be filled with large stones and connected into an existing soakaway which is probably located close to a rainwater downpipe.
This type of work can be done by a general builder, a landscape gardening firm (hard landscaping) or by a patio specialist.
|Location||Small Business||Larger Business (5+ employees)|
|Need a Custom Price? >|
|South, SW and Midlands||£700.00||N/A|
|Outer Region and North||£550.00||N/A|
Looking For a Fixed Damp Proof Quote Instead of a Rough Guide?
Try These Prices for Comparison
See how much it typically costs to render a wall.
Average plastering costs can be seen here.
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Don’t Get Conned – Get Independent Advice
The best advice we can give you is to have your damp walls inspected by an independent surveyor. It will cost more initially but they can give you independent advice, if you don’t need a new expensive DPC then they will advise you of that.
If you get a damp proofing specialist to inspect your walls, chances are they will try to sell you a damp proof course. That is after all what they do and this type of work is very profitable.
The damp proofing industry has a bad reputation in the United Kingdom. There is wide spread mis-selling of unnecessary wall treatments when the main cause of the damp is the existing DPC being bridged.
Why is Damp Proofing so Costly?
The wall injection itself isn’t time consuming or costly, but the plastering and making good of the walls certainly is. It’s also a very messy job and you will probably want to move out of the house for a few days first.
Don’t Leave it Too Late
Whatever the cause of your damp walls, it’s always best to act quickly and tackle the issue as soon as possible. Damp can spread quickly, especially through porous bricks and plaster which can then disintegrate. It can rot timber floor joists, skirting boards and other woodwork.
There is also a health hazard – living in a property that is damp for long periods of time is bad for the respiratory system.
The DIY Option
It is certainly possible for anyone with basic DIY skills to insert a waterproof DPC into an external wall. 12mm holes are drilled 3/4 of the way through the brick course above the existing DPC at 100mm intervals. A cream is then squeezed into the holes via a mastic application gun. A small dollop of cement is then used to plug the gap.
The difficult part is the internal walls. The plaster really does need to be removed to gain access to the bricks behind.
If finances are a real issue, a homeowner could try and seal only the outer wall, then wait and see the results. If the internal plaster isn’t too badly damaged then it may dry out.
The video below explains how a damp proof course is inserted into a wall:
Avoid Doing This:
If you are on a tight budget you might be tempted to paint the interior walls with a waterproof paint/sealant to mask any signs of damp.
This work should never be carried out – if there is still a damp issue then it will eat away at the cement, bricks and plaster behind the wall. This can lead to serious issues which will lead to further expense in the future.
A wall should only be painted with a waterproof if you are 100% certain that there is no damp rising from the ground below, otherwise you are just masking the issue.
Feedback For Our Guide to Damp Proof Costs
Have you received quotes from tradespeople and companies for wall damp proofing? What costs are they charging for this type of work?
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