A recent inspection of a 1930’s mid terraced house in Wiltshire exposed a farcical series of events due to the incompetence of the Chartered Surveyor undertaking the Home Buyers Survey and also the damp proofing specialist who (on the recommendation of the Surveyor) followed him.
This traditional cavity brick built, mid-terraced house was subjected to a Home Buyers Survey, which identified dampness within the front living room and rear dining room walls, as a consequence of which recommendations where made to instruct a Specialist Damp Proofing Co to undertake a full survey (standard recommendation) and carry out any remedial works.
After an investigation by a local damp proofing company, rising damp was identified and recommendations put forward for a chemical injection damp proof course and re-plastering to the value of £1800 + Vat.
No visual evidence of dampness to the front bay window
Apparently happy with this quote, the prospective purchaser’s builder expressed his concerns with the diagnosis, as the property had (what appeared to be) a perfectly good slate damp proof course (as was installed at the time of construction) visible to both the front bay and rear dining room external facing walls.
A second opinion was sought and Premier Heritage were invited to undertake a survey of the property for Structural Dampness which found the following;-
- No obvious external defects or sources of moisture
- No apparent internal decorative spoiling (other than badly applied wall paper)
- No obvious plaster deterioration
- No surface mould growth
- No significant levels of moisture within the skirtings or adjacent timbers
- However, high and consistent damp readings to ceiling height on both walls.
Question………What type of dampness would cause this?
Answer………. The Metal foil backed paper type of dampness.
Lifting the wall paper expose’s the metal foil paper responsible for the damp readings!
Wrong Diagnosis
The damp problem had been incorrectly diagnosed, as it was metal foil paper (under the wallpaper) that was interfering with the damp meter, causing it to give the readings. The user should however (if he had known what he was doing) been ‘put on notice’ to the fact that the readings were consistent throughout the walls height (unusual) and that there was no obvious spoiling of decorations / plasterwork etc.
This should have at the very least, made him suspicious and he should have looked beyond the damp meter readings. More importantly is the fact that the property had a fully effective physical damp proof course.
The Outcome
The survey and investigation of dampness in an occupied house can sometimes be restricted as destructive investigation cannot always be carried out or approved. The misdiagnosis of dampness in buildings generally results from the misuse of the ‘moisture meter’ as in this case, but one should not rely on the moisture meter alone and should depend on the surveyors experience, eyes and common sense, all of which will tell him far more than the moisture meter alone. But such instruments are there to support and aid in the diagnosis of dampness (if used correctly) and as such their importance should not be overlooked.
We were somewhat surprised that the Chartered Surveyor had failed to identify the problem and far too quickly ‘passed the buck’ to the damp proofing company. We were however not too surprised with the damp-proofing surveyors findings as he was not only inexperienced, but also held no formal qualifications in damp surveying.
The foil backed paper had been applied to the walls due to the colonisation of mould during the winter months, the mould clearly a symptom of a seasonal condensation.
The foil paper, marketed as an aid to ‘damp control’, was naively applied by the Vendor in an innocent attempt to eradicate the mould, which clearly was never going to happen.
Premier Heritage identified that no structural dampness existed within this property and therefore no works were needed. Following the removal of the foil backed paper and redecoration they all lived happily ever after, apart from the surveyor and the damp-company who were asked to contribute towards Premier Heritages costs, which could have been avoided had they looked beyond the end of their noses!
When the owners of a farm house suffering with damp problems needed a damp proofing solution Premier Heritage were on hand to assist with a traditional solution to damp.
This detached, stone built former Devon Farmhouse was refurbished by its previous owners in the 1970’s and unfortunately like many properties of this age was stripped of much of its original fabric, including its lime plasterwork, renders and pointing mortar.
Farmhouse prior to traditional form of damp proofing taking place
In early 2008 Premier Heritage received instructions from its new owners to undertake a full survey of the property for dampness and associated defects and to put forward a specification for remedial works to deal with the dampness present and any associated defects.
Drying out the dampness in the property
The main areas of concern identified by our investigation confirmed the presence of rising and penetrating dampness affecting various walls, although the latter mainly affecting the weather prevailing elevations and most noticeably the front sitting room, rear drawing room and stair area. No structural dampness was identified at first floor level.
As a consequence of the longstanding dampness to the lower sections of the south and western walls, several timber lintels were also showing signs of decay (some having already been replaced) and also death watch beetle activity.
Lintels showing signs of death watch beetle activity and fungal decay
The structural timbers supporting the half landing were also affected by wet rot where bearing into the wall as were numerous skirting and window boards.
To the western wall there was also the added complication of raised external ground levels sloping towards the house and also an obvious, insufficient overhang of the thatched roofing, increasing moisture at ground level and within the walls.
Replaced timbers
It was established that the conditions affecting this property had resulted as a consequence of the building’s past refurbishment and the removal of the original permeable mortars and renders used in the buildings original construction (i.e. the lime plaster, bedding and pointing mortar etc). Subsequent replacement with modern cement, being less permeable has resulted in dampness becoming trapped within the fabric of the wall ‘due to its inability to breathe’. This problem has built up over many years being further compounded by the numerous layers of masonry paint applied to the walls over the past 30 years or so!
Premier Heritage’s specification for remedial works concentrated on the removal of the cement materials (both inside and out) to allow the walls to dry down, along with subsequent repairs to structural and joinery timbers. The main contractor was appointed and the works were project managed by Premier Heritage.
The first task was to remove the external paintwork and cement pointing which was impermeable and trapping moisture / dampness within the wall’s, increasing the levels of dampness and internal damage to the building’s fabric. Having removed all external coatings and cement mortar (including that to the interior of the sitting room) the walls started to dry down.
New oak lintels were introduced, where existing were structurally unsound and timber repairs were completed to the interior staircase and landing etc.
Ground levels to the western wall were also reduced, with improved drainage and a vertical slate barrier fitted to the lower sections of the wall to minimise damp penetration.
Following the drying period re-pointing commenced to the exposed stone walls and this was undertaken using a lime based (permeable / breathable) mortar, after which the building was re-thatched and finally redecorated throughout.
The building has now been restored to its former condition and is dry and comfortable as well as looking great!
The finished farmhouse free of damp
This 1976 brick built Dorset bungalow retained blown fibre insulation introduced in the late 1990’s.
Wall showing rain penetration
Saturated perp end joint
Saturated motar between the brick work
Moisture squeezed from the insulation material
Cavity Wall Insulation
(What are the benefits? …..…..DAMP)
From October 2008 all domestic buildings (being built, rented or sold) were required ‘by Law’ to have an Energy Performance Certificate (EPC) to help improve the energy efficiency of the building. The EPC provides an ‘A’ to ‘G’ rating for the building, ‘A’ being the most efficient and ‘G’ the least and to-date a ‘D’ rating is currently being banded as the average.
It is claimed that around a third of heat loss in a house is through its roof and walls and currently there is a government drive (supported by television advertising and the offer of Home Improvement Insulation Grants) to encourage home owners to increase loft insulation and also to fit cavity wall insulation, as it is claimed this can save on average around £180 per annum on heating costs!
However were you aware that by installing cavity wall insulation, whilst you may well be saving some money on fuel costs, you could also be creating a major expense for the future……..damp!
Example of cavity wall insulation
The cavity wall (as we know it) dates back to the early 1900’s and is commonly found in the coastal areas around Britain, used to reduce the risk of rain penetration. In the 1920’s, local building by-laws encouraged the construction of the cavity wall and by the 1940’s it had become the Industry Standard. The familiar cavity wall (as we know it) is two leaves of brickwork, forming a 60mm cavity and tied together with metal wall ties.
Even back in the good old 1970’s concerns were being expressed over Energy Conservation and home owners were then being encouraged to introduce loft insulation and it wasn’t long after that cavity wall insulation was also being recommended.
Fill your cavities with foam, polystyrene, mineral wool or any other material you can introduce through a small hole in the wall and you will save energy and loads of money. Sounds good, but what if by introducing this insulation you increased the risk of damp to your property, which in turn would cause internal decorative spoiling, plaster damage, fungal decay to structural and joinery timbers and also accelerate the risk of corrosion to the metal wall ties.
Could that really happen? Well the answer is yes and it is.
Paul Carter, the principal of Premier Heritage, has investigated hundreds of buildings over the past 20 years of so, where damp has affected internal decorations etc and found that the damp present was due to bridging of the cavity by the earlier installed insulation materials. Whilst some of these cases were wrongly diagnosed by others as rising damp, most of these buildings (if not all) retained a physical damp proof course, the newest being a 1980’s brick built bungalow in Hampshire.
Ok, lets put this into perspective, there have been thousands of cavity built houses within the UK that have been insulated and a good majority of these don’t currently have nor will ever have a problem with damp. But there are a great number that have and no doubt more will be affected in the years to come!
Increased rainfall in past years has resulted in a noticeable increase in damp problems affecting conventional cavity-constructed housing, due to moisture penetrating / bridging the cavities and in particular on the weather prevailing elevations and this isn’t a problem relating to current rainfall, but a gradual build of damp over many years.
Rainwater driving into the masonry of a building can penetrate the outer leaf brickwork leading to the wetting of the insulation materials, increased damp penetration and a reduced thermal performance of the material. Poor construction methods, mortar and perp joints, debris within the cavities, dirty wall ties and poor installation procedures by installers all contribute to the overall problem, which generally will result in the need to remove the insulation, which is not only expensive, but will almost certainly cosmetically scar the building when finished. Unfortunately it doesn’t come out through the same hole through which it went in!
So how do you avoid this problem? Well there’s no easy answer to this other than to look carefully at the building’s construction (porosity of building materials) and its exposure to the prevailing weather conditions. If having then decided to proceed, ensure that the chosen contractor / installer, during the survey, checks the cavities and cavity trays for debris and dirty wall ties, but more importantly offers a system and material that guarantees (preferably insurance backed) that the materials being installed will not transmit / bridge moisture through and into the internal wall!
Alternatively, if you’re still unsure then don’t install.
Examples of Cavity Wall Insulation causing damp:
Cavity Foam Insulation
1970’s block constructed bugalow with poorly installed cavity foam insulation and debris bridging moisture via wall ties, cost around £800 to remove and rectify internal damage caused.
Polystyrene bead cavity insulation
Polystyrene bead cavity insulation 2
