A tide mark about a metre up an internal wall, traced to its cause.
Penetrating damp
A patch that is worse after heavy rain, fixed outside first.
Condensation and mould
Black mould in corners, which is usually ventilation, not a damp course.
Not sure which one you have? We can tell you on the visit. We work on flats, terraces, semis, detached and period houses, new builds and commercial premises.
How it works
01
Tell us about the job
Ring, message or send the form. A rough idea of the rooms is enough to start.
02
One of the team comes and looks
A free visit at a time that suits you. Nothing is signed and nothing is owed.
03
A written price
You get a written price after a look at the job, itemised, with no obligation.
04
Agree a date
If the price is right, the work is booked in and the site is left tidy each day.
No charge for the visit, and no obligation after it.
The same wall at every stage
Before, during and after
Back door pier, stripped back, rendered and skimmed
Stripped backRenderedSkimmed
Kitchen damp proofing, rendering and skim
Stripped backRenderedSkimmed
Kitchen pier, stripped back, rendered and skimmed
Stripped backRenderedSkimmed
What will my damp proofing cost?
The price depends on which of the three you actually have, what is causing it outside, and how much wall has to be replastered afterwards. We visit first, then you get a written price after a look at the job.
Which one it is
Three different problems, and only one of them is a damp course.
Fixing the cause
Guttering, ground levels and pointing come before any treatment.
Replastering after
A salt-retardant mix on the affected wall, once it has dried out.
CoveringBromley, South East London, Kent and Central London
Damp proofing on site
A closer look at the preparation and the work behind the finish.
Damp on a wall is a symptom and it has several different causes, and the treatments for them have almost nothing in common. Rising damp, penetrating damp and condensation all show up as a stain on a wall and all three get sold the same chemical injection by somebody, which is why so many houses have a damp course fitted and a wall that is still wet.
So the first visit is a look rather than a price. Where is it on the wall, how high does it go, is there a tide mark, what is outside that bit of the wall, what is the ground level doing, and is it worse in winter. Those answers decide the job, and sometimes the answer is that no damp proofing is needed at all.
Kitchen window wall skimmed, afterCChristopherGoogle...The work is immaculate.Damp door corner rendered, afterRRosieGoogle...their work is seamless.Damp proof course injection outside wall, duringGGeoffGoogle...the finish was perfect.Kitchen units wall rendered, afterPPhilGoogle...Great finish looks really good.Back door pier skimmed angle, afterAAndrewGoogle...done a perfect job.Kitchen window corner skimmed, afterJJohnGoogle...they turned up on time everyday.Back door and window wall skimmed, afterSSuminGoogle...left our place clean and tidy.Damp door corner stripped, beforeFFrancescaGoogle...Perfectly done.Damp corner DPC injected, duringJJemmaGoogle...extremely helpful and knowledgable.Kitchen units wall stripped, beforeSStephenGoogle...done at a high standard.Damp door corner rendered wide, afterDamp door corner stripped wide, beforeDamp door edge stripped, beforeDoor pier by bench skimmed, afterDoor pier skimmed and feathered in, after
“Good honest business, we called SMB after we had a bad experience with previous contractors. ... The work is immaculate (we had our house skimmed), the detail, care and attention is spot on.”
“Frank and Steve did a fantastic job on my hallway! Really professional team and their work is seamless. I was really impressed, and they even fixed my skirting board and put it back on for me, a very appreciated extra! Would highly recommend.”
“They did a great job. I had an awkward hallway area and a large ceiling to skim. I thought they'd finished earlier in the day as it looked great to me then, but they went over the whole area to make sure that the finish was perfect.”
“Excellent work! Scott plastered our living room including some tricky details around fireplace and bay window. Great finish looks really good, all the work was tidy and well communicated all done on time. Would highly recommend.”
“Frank completed a wall for me that needed plastering, he was on time, very polite and nothing seemed an issue. ... Although only a small job, kept my house tidy, even outside the house, cleaned up after he finished and done a perfect job, highly recommended from myself.”
“Hi, Had the team in plastering for a week. What a joy. There were no problems they turned up on time everyday and very polite. Would recommend them to anyone. Thanks very much guys.”
“I don't often leave reviews, but Frank was so helpful and pleasant to work with that he deserves 5 stars. Very responsive and professional. He did a great job and left our place clean and tidy. Thanks again Frank!”
“Frank very kindly stopped by to plaster a chipped wall. Perfectly done and really helpful and kind guy. 100% calling if I ever need any more plastering done!”
“Although we didn't require any work, Frank was extremely helpful and knowledgable on his visit to inspect our issue. He was prompt and on time and responded quickly.”
“Very, very happy with Franks work finishing off kitchen walls after having been let down by a builder. It was a tricky job as the granite worktops ect had already been installed but I couldn't be happier with the result.”
“Really happy with the work. Great finish and very professional. Turned up on time, kept things tidy, and did a top-quality job. Would definitely recommend.”
“very pleasant experience in communication and the level of service provided. tradesman was very polite. He came around for a diagnosis before outlining the job in details with cost and what needs doing.”
“Just had Scott round, Arrived on time started straight away and just got on with the job. Pleasant at all times clean & tidy worker will definitely use again. Work looks good and he stuck to his price. Thanks Scott was was good to meet you.”
“Very professional, was very clear on what exactly will be done. Agreed a price and kept me update all the way through. Happy with the work completed and after care as well. Very helpful and highly recommended.”
“Scott called me before booking a date to come and do work. He reasured me about somethings i was worried about. He come in time he said he would and helped me with another job as well. Very helpful and happy with service”
“Great job by Scott plastering the small room, he managed to sort out the uneven ceiling and walls. Will be using Scott again to sort out a couple of other rooms.”
SMB Plastering and Sons is based in Bromley and covers Beckenham, Orpington, Sidcup and the towns around them. Send a postcode and we will tell you whether the job is one we can get to.
It stops at a level, usually about a metre, and often leaves a tide mark of salts. If the patch is patchy, higher up, or worse after rain, it is far more likely to be coming through from outside.
Often not. A lot of what gets treated as rising damp is a blocked gutter, a raised ground level or condensation. The first visit is a look, and if the answer is that no damp proofing is needed, that is what gets said.
After a new damp course, months rather than weeks on a solid wall that has been wet a long time. Replastering a wall that is still drying is the commonest reason the same wall fails again.
Because the salts left in the wall travel through ordinary plaster and come out on the paint as a white bloom. A salt retardant backing coat holds them back, and it has to be kept clear of the floor so it is not bridged.
Rising damp comes up from the ground through the wall and stops at a level, usually about a metre, often with a tide mark of salts where the water has been evaporating. It is much rarer than the number of houses treated for it suggests.
Penetrating damp comes through from outside at the point where something has failed: a cracked render, a blocked gutter running down a wall, failed pointing, a ground level that has been raised above the damp course by a new patio. It is worse after rain and it is usually patchy rather than level. Condensation appears on cold surfaces, in corners and behind furniture, is worst in winter, and comes with black mould rather than salts. Treating the third one with an injected damp course achieves nothing at all.
Fixing the cause before treating the wall
Where it is penetrating damp, the work is outside and it is often cheap: clear the gutter, repoint the section, cut the render back off the damp course, drop the ground level away from the wall. Do that and the wall dries on its own, and the only internal work is replastering once it has.
Where it is condensation, the answer is ventilation and heat rather than a chemical. Extract that actually vents outside, trickle vents that are open, and enough background warmth that the wall is not the coldest surface in the room. It gets said plainly even though it is not work anybody is being paid for, because selling a damp course for condensation is the oldest trick in the trade.
Damp courses and tanking, where they are right
A genuine failed or absent damp course gets a new one, injected as a cream into a drilled course of mortar at the right height. It is a day's work on a normal wall and it does nothing on its own: the wall above it is still full of water and salts and has to be taken back and replastered before anything is decorated.
Tanking is the other answer, and it is what a cellar or a below ground room needs, because there is no damp course that will hold back water under pressure from the surrounding ground. That is a membrane or a cementitious system, taken up the wall and across the floor junction, and it is a bigger job with a different price.
Damp proof course injection outside wall, during
Replastering, and why the mix matters
The wall gets hacked back, usually to a course above the highest sign of damp, and left to dry. How long depends on the wall, and it is months rather than weeks on a solid wall that has been wet for years. Rushing that is the commonest reason a treated wall fails again.
Then it is a salt retardant backing coat rather than an ordinary one, kept off the floor at the bottom so it is not bridging, and the finish over that. Salts left in a wall come straight through ordinary plaster and show on the paint as a white bloom within months, and at that point the only fix is to take it off and do it again properly.
When to get it looked at
A tide mark about a metre up an internal wall
A patch that is worse after heavy rain
Black mould in corners and behind furniture
A patio or path built up above the damp course
White bloom coming through paint on a treated wall
A cellar or below ground room being brought into use
City & Guilds Level 2 Diploma in PlasteringFrank McBride, College of North West London, 2021Federation of Damp: Damp Proofing Technician trainingFrank McBride, January 2026be Accredited health and safety trainingAsbestos awareness, abrasive wheels, confined space, accident and incident, environmental awareness
