Treating Rising Damp in a Lower Ground Floor Flat, Thame OX9
A full damp-proofing treatment to the entrance hallway of a lower ground floor flat, addressing an isolated area of DPC failure identified during survey, with hack off, chemical DPC injection, waterproof render and skim.
Project at a Glance
The Brief
We were asked to attend a lower ground floor flat at Park Court in Thame to investigate damp ingress the client had noticed at the front of the property, along a low level section of the exterior wall. The concern had shown up as staining low down in the entrance hallway, close to the front door and the stairs leading up from it.
A damp survey was carried out by our surveyor, Lionel Sewell FODCS, to establish the cause before any treatment was proposed. Rising damp can look similar to several other issues at first glance, so identifying the actual source correctly is what determines whether a repair actually lasts.
What the Survey Found
The findings from the external inspection showed that the building was in good condition overall. There were no cracks, holes, or other defects on the external walls and rendering capable of allowing moisture to get into the building, nor were there any signs of moisture stains and water tracking on the bricks. A damp proof course was evident in the property. Minor weathering and surface erosion were observed on the isolated mortar joints, and this was expected due to the age of the building.
In reality, however, the matter was somewhat different. In the entrance hallway, isolated wet stains were noted, and they were connected with the penetrating moisture and high humidity level. The presence of damp and musty smell was not observed, and the atmosphere inside was clean.
To test for moisture levels, a Protimeter pin-type moisture meter was used, as it takes readings of moisture levels in the material without a surface pad, which can give false results due to surface humidity and condensation. Readings confirmed isolated rising damp up to the second step on the party wall to the right of the front door.
Because every external element inspected- the walls, the rendering, the visible DPC- was found to be in good condition, the surveyor concluded this was most likely an isolated area of DPC failure specific to this section of wall, rather than a wider problem with the building’s damp proofing. No signs of timber decay were found in any of the accessible areas inspected.
Since the damage was done in an area that is adjacent to the party wall which separates the two buildings, the survey further indicated that there should be a Party Wall Agreement prior to carrying out any work, as required by the Party Wall etc. Act 1996.
The Treatment Strategy
Based on the survey findings, we recommended a full damp-proofing treatment to the affected section of the entrance hallway, covering an area of approximately 3.5 sq.m. All these steps included the removal of the contaminated plaster, installation of a chemical damp proof course, application of waterproof rendering, and finally the plastering process.
Each step here tackles a different aspect of the problem. Hacking off the existing plaster removes material that has become contaminated with hygroscopic salts carried up by the rising damp, salts which would otherwise continue drawing in moisture from the air even after the source is treated. Injecting a new chemical DPC re-establishes the damp proof barrier at the isolated point of failure identified in the survey. The waterproof render also provides an additional protective layer between the brickwork and the plastered surface to ensure that there will be no migration of any salts or moisture from the wall back to the surface. The plaster skim serves to provide a smooth and decoratable surface after the rendering.
Overall, this combination is the best treatment method that can be used for such isolated cases of rising dampness, providing permanent protection against it
The Treatment
Our contractor, Brandon Halson, carried out the treatment over two days on site. The scope of works followed the recommendation from the survey:
- Hacking off the contaminated plaster from the affected section of the entrance hallway wall.
- Injecting a new chemical damp proof course at the isolated point of failure.
- Applying a waterproof render to the treated area.
- Finishing with a new plaster skim ready for redecoration.
As part of the works, the old skirting board was removed at the client’s request, and the handrail was taken down and left safely outside for reinstatement. No unexpected issues were encountered on site, and the job was completed to the full scope agreed, with no additional variations required.
The photographs below show the finished render and skim to the entrance hallway wall, ready for the client’s decorators to complete redecoration once the recommended curing period has passed.
The Result
The isolated area of rising damp identified on the party wall of the entrance hallway has been fully treated, with a new chemical DPC, waterproof render and plaster skim now in place. The work area was left safe and tidy, and the scope of works was completed exactly as agreed with the client.
As with all our damp-proofing treatments, redecoration of the treated area should not take place for 5 to 6 weeks, to allow the render and plaster to cure fully. An interior paint that allows breathing needs to be applied, and any drilling through the treated wall needs to be plugged using silicone before installing wall plugs to prevent damage to the newly installed. The completion was done on-site, and it was observed that the work done was according to what had been discussed and done safely.
the right way of dealing with rising damp is through the identification of where the problem is coming from.
In this case, the DPC failure can be isolated to a particular part of the wall through survey and moisture readings.
Rising Damp FAQs
What are the reasons for rising damp in the property?
It occurs due to the absorption of groundwater in the wall by capillary action owing to the failure of the damp proof course, bridging of the DPC or non-installation of DPC. It usually appears in the form of discoloration, staining, or crumbling plaster towards the bottom of walls, along with contamination of the plaster with salts.
How can you identify that the problem is due to rising damp and not other kinds of damp?
A proper damp survey takes into account both visual examination and moisture readings, generally done using a moisture meter with pins to differentiate rising damp from penetrating damp or condensation. Moisture pattern, height of moisture, and condition of the external fabric of the building can help ascertain the cause before proposing treatment.
What is involved in a complete damp-proofing treatment?
The standard treatment method usually involves chiseling away the damaged plaster, injecting a new damp proof course chemically, putting on waterproof rendering, and topping it off with a plaster skim. Through this process, it is ensured that the rising damp is prevented at its source, along with preventing the salts from entering again in the decorative layers.
How long will it take for my damp proofing to dry?
It is advisable that one should allow a period of around 5-6 weeks after the process of rendering and skimming to complete the decoration process. A breathable paint should be used once redecoration goes ahead.
Do you carry out damp surveys and treatment across Oxfordshire?
Yes. We carry out damp surveys and remedial damp-proofing treatment across Oxfordshire and the wider South East. You can read more on our damp proofing page.
Planning a damp survey or dealing with a damp problem?
Our surveyors diagnose the real cause of damp before recommending treatment, using moisture readings rather than guesswork. The survey fee is deducted from the cost of work if you go ahead.
Book a Damp SurveySurvey carried out by Lionel Sewell FODCS, damp surveyor at Advanced Damp. Treatment completed by Brandon Halson. Project completed at Park Court, Thame, OX9.
Sam Fitzgerald is the founder of Advanced Damp and a working damp and structural waterproofing surveyor with over 12 years of experience diagnosing and treating moisture problems in residential and commercial properties across London and the South East. He is FODCS certified (a Federation of Damp Certified Surveyor) and a member of the Federation of Damp. His hands-on work covers rising damp, penetrating damp, condensation, basement waterproofing to BS 8102, and thermal imaging surveys, and he has personally completed over 400 damp surveys across properties of every type and age. Everything he writes draws directly from jobs he has carried out. He does not write about treatments, products or causes he has not dealt with first-hand in the field.
