Nemesis
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Also, a DPC could cause damage not easily reversed, and that's not a great idea.
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Does painting beams need LBC?
- Thread starter robson2205
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Nemesis
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Andrew's DAMP letter:
Dear Sirs
Re: Installation of a Chemical Damp Proof Course and associated works at *********************Norfolk
I write in response to the report prepared by *********** Preservation Services dated 30th November 2005 regarding the treatment of timber/damp at ******************Norfolk, as required by paragraph 609 of the ***********special condition mortgage offer.
In my opinion, in order to repair or remedy a building one needs to fully understand the building’s primary construction and the causes of its decay mechanisms. ‘Modern’ buildings tend to rely on an impervious outer layer or a system of barriers to prevent moisture penetrating or rising within the walls, whereas ‘traditional’ solid walled structures generally rely on allowing any absorbed moisture to evaporate freely from its overall surface area.
Unfortunately, many believe that water at the base of a wall indicates rising damp and that any solid walled building will be prone to rising damp unless a damp proof course is installed; this problem is not assisted by the incautious use of damp meters.
The British Standard Code of Practise for the installation of damp proof courses (BS 6576: 1985) states in section 3.1 that it is essential to ‘confirm whether the property has rising damp, or has suffered from rising damp’ before installing a D.P.C. Section 3.2.2 of the same document also states that surface measurements alone cannot confirm the presence of rising damp, although they can, when moisture meters are used correctly, confirm the presence of dampness.
This is perhaps an oversimplification as a series of meter readings taken up a wall may suggest rising damp but they cannot show the severity of the problem. A major difficulty is that moisture meters are actually measuring the electrical properties of the material tested and any salts that have been mobilised or carried into the test area by water movement strongly influence these electrical properties. Salts may well produce extremely high meter readings in a wall that is in fact virtually dry. This can be particularly the case in conversion works of farm buildings. As a result, the use of a moisture meter will not diagnose rising damp with any degree of reliable accuracy. Moisture levels can only ever be accurately tested in laboratory conditions following the extraction of core samples from the walling in question.
In addition, where an injection D.P.C is installed in such solid walling, together with re-rendering and re-plastering in water and salt proof mixtures, it is extremely probable that moisture will be prevented from evaporating from permeable materials resulting in the build-up of moisture or even damper conditions in localised areas.
Therefore, in my opinion, the provision of chemical D.P.C.'s and associated renders, plasters, damp proof membranes and concrete floors can be of great detriment to ‘traditional’ buildings and must be strongly avoided – such fabric must be able to breathe freely rather than encapsulate moisture – a view shared by numerous other conservation bodies.
I have yet to witness a situation where such remedial interventions have proved to be effective without detriment to historic fabric. One has to ask why, if an injection D.P.C is so effective why are impermeable renders and plasters a conditional provision? Impervious renders and plasters and modern concrete floors all result, in my opinion, in dampness being encapsulated; the best solution is to ensure that dampness is released via the provision of new permeable surfaces rather than via the proviso of ‘quick fix’ systems that do not address basic problems.
I shall respond to the contents of the *****************Preservation Services report in the order of their presentation.
Walls
The walling to ***************Street, as is the vast majority of walling to the other listed properties on the street, is a mixture of knapped flint, chalk block and gault brick. Although the walling can be described as being solid or ‘traditional’ in its construction, the walling has two distinct leaves or skins which are butt jointed vertically; chalk block is used to form the inner load bearing leaf or skin whilst knapped flint forms the outer leaf or skin and gault bricks are used to form dressings to corners and openings.
From an internal visual inspection I did not witness any extant visible signs of dampness; as previously mentioned, the use of hand held damp meters is questionable in the diagnosis of dampness in building fabric.
Flint itself is 98% silica and consequently virtually impermeable; this in itself is unusual as the vast majority of other materials used in solid or ‘traditional’ walling is permeable. In this instance it is therefore imperative that the mortar used to bed the flints is as permeable as possible i.e. a pure non-hydraulic lime and sand mortar only.
The outer walling to the property has unfortunately been repointed in the past with a strong impermeable cement based mortar. This will have undoubtedly contributed to the saturation of the walling as both internal condensation builds up in the body of the walling and where penetrating water enters the exterior of the walling - via the fine cracking which will invariably form between the flint and the inflexible mortar - due to capillary action.
I would suggest that the previous treatment of the outer walling has resulted in the current condition of the walling and not the absence of a D.P.C; the overall situation may well be exacerbated by the possible internal replastering of the walling in an unsuitable gypsum based product which, although to a lesser degree when compared to cement based mortars, will also be impermeable.
I would therefore recommend that the most vulnerable lower section of outer walling, say to the underside of the cill level, be carefully repointed in a pure lime mortar to reintroduce permeability and to allow the walling to breathe and remain dry as opposed to continuing to saturate; the importance of this cannot be understated due to the unconfirmed treatment of the internal surface.
Cellar
The walling to the cellar is a mixture of lime washed chalk block and brick. One has to appreciate that cellars in buildings of this age are invariably visibly damp due to the very nature of the construction and the placement of such walling in a subterranean environment. Internal tanking or vertical damp proofing works in cellars, unless a ventilated and sumped system is used, will cause significant damage, as the saturation of the walling will become far greater. Historically, cellars benefited from ventilation via a coal hole/chute and the ‘airing’ of the space due to daily access to bring coal into the upper levels of the building for heating and cooking.
Unfortunately, the coal hole/chute has been blocked in as a result of the 20th Century rear extension, and the new trap door to the living room is inadequately ventilated.
I would therefore recommend that the walling is left as is, and that appropriate external ventilation is provided on the opposing side of the blocked coal hole/chute to the front of the property and that the existing access hatch is provided with an increased level of ventilation holes/slits.
It was noted that a section of the timberwork to the cellar space had an area of fruiting body (approx 150mm, 2 max). Dry rot spores (Serpula Lacrymans), which exist virtually everywhere, will thrive in a humid environment where the timber is allowed to maintain a moisture content of 20% and above.
Increased ventilation will reduce overall humidity and subsequently the moisture content of the timber which should witness a cessation of the rot.
I would recommend that the extant fruiting body be removed and the affected area be treated locally with a ‘neat’ proprietary disinfectant or bleach.
I would confirm that D.P.C injection and associated replastering would, in my opinion, require the benefit of Listed Building Consent; an application for Listed Building Consent to undertake such work will not receive support for approval at Officer level.
I have had previous involvement with building societies (Kensington Mortgage Company, 200 Aldersgate Street, London, EC1A 4JJ, Nationwide Mortgage Company, 17-21 Queensway, Stevenage, Herts, SG1 1DA and Virgin, Discovery House, Whitling Road, Norfolk, NR4 6EJ, amongst others) and have successfully achieved the removal of such associated retentions from mortgages and respectfully request that you give full consideration to allowing your client to follow my recommendations as opposed to those contained within the above named report.
Yours sincerely
Andrew Gayton
Dear Sirs
Re: Installation of a Chemical Damp Proof Course and associated works at *********************Norfolk
I write in response to the report prepared by *********** Preservation Services dated 30th November 2005 regarding the treatment of timber/damp at ******************Norfolk, as required by paragraph 609 of the ***********special condition mortgage offer.
In my opinion, in order to repair or remedy a building one needs to fully understand the building’s primary construction and the causes of its decay mechanisms. ‘Modern’ buildings tend to rely on an impervious outer layer or a system of barriers to prevent moisture penetrating or rising within the walls, whereas ‘traditional’ solid walled structures generally rely on allowing any absorbed moisture to evaporate freely from its overall surface area.
Unfortunately, many believe that water at the base of a wall indicates rising damp and that any solid walled building will be prone to rising damp unless a damp proof course is installed; this problem is not assisted by the incautious use of damp meters.
The British Standard Code of Practise for the installation of damp proof courses (BS 6576: 1985) states in section 3.1 that it is essential to ‘confirm whether the property has rising damp, or has suffered from rising damp’ before installing a D.P.C. Section 3.2.2 of the same document also states that surface measurements alone cannot confirm the presence of rising damp, although they can, when moisture meters are used correctly, confirm the presence of dampness.
This is perhaps an oversimplification as a series of meter readings taken up a wall may suggest rising damp but they cannot show the severity of the problem. A major difficulty is that moisture meters are actually measuring the electrical properties of the material tested and any salts that have been mobilised or carried into the test area by water movement strongly influence these electrical properties. Salts may well produce extremely high meter readings in a wall that is in fact virtually dry. This can be particularly the case in conversion works of farm buildings. As a result, the use of a moisture meter will not diagnose rising damp with any degree of reliable accuracy. Moisture levels can only ever be accurately tested in laboratory conditions following the extraction of core samples from the walling in question.
In addition, where an injection D.P.C is installed in such solid walling, together with re-rendering and re-plastering in water and salt proof mixtures, it is extremely probable that moisture will be prevented from evaporating from permeable materials resulting in the build-up of moisture or even damper conditions in localised areas.
Therefore, in my opinion, the provision of chemical D.P.C.'s and associated renders, plasters, damp proof membranes and concrete floors can be of great detriment to ‘traditional’ buildings and must be strongly avoided – such fabric must be able to breathe freely rather than encapsulate moisture – a view shared by numerous other conservation bodies.
I have yet to witness a situation where such remedial interventions have proved to be effective without detriment to historic fabric. One has to ask why, if an injection D.P.C is so effective why are impermeable renders and plasters a conditional provision? Impervious renders and plasters and modern concrete floors all result, in my opinion, in dampness being encapsulated; the best solution is to ensure that dampness is released via the provision of new permeable surfaces rather than via the proviso of ‘quick fix’ systems that do not address basic problems.
I shall respond to the contents of the *****************Preservation Services report in the order of their presentation.
Walls
The walling to ***************Street, as is the vast majority of walling to the other listed properties on the street, is a mixture of knapped flint, chalk block and gault brick. Although the walling can be described as being solid or ‘traditional’ in its construction, the walling has two distinct leaves or skins which are butt jointed vertically; chalk block is used to form the inner load bearing leaf or skin whilst knapped flint forms the outer leaf or skin and gault bricks are used to form dressings to corners and openings.
From an internal visual inspection I did not witness any extant visible signs of dampness; as previously mentioned, the use of hand held damp meters is questionable in the diagnosis of dampness in building fabric.
Flint itself is 98% silica and consequently virtually impermeable; this in itself is unusual as the vast majority of other materials used in solid or ‘traditional’ walling is permeable. In this instance it is therefore imperative that the mortar used to bed the flints is as permeable as possible i.e. a pure non-hydraulic lime and sand mortar only.
The outer walling to the property has unfortunately been repointed in the past with a strong impermeable cement based mortar. This will have undoubtedly contributed to the saturation of the walling as both internal condensation builds up in the body of the walling and where penetrating water enters the exterior of the walling - via the fine cracking which will invariably form between the flint and the inflexible mortar - due to capillary action.
I would suggest that the previous treatment of the outer walling has resulted in the current condition of the walling and not the absence of a D.P.C; the overall situation may well be exacerbated by the possible internal replastering of the walling in an unsuitable gypsum based product which, although to a lesser degree when compared to cement based mortars, will also be impermeable.
I would therefore recommend that the most vulnerable lower section of outer walling, say to the underside of the cill level, be carefully repointed in a pure lime mortar to reintroduce permeability and to allow the walling to breathe and remain dry as opposed to continuing to saturate; the importance of this cannot be understated due to the unconfirmed treatment of the internal surface.
Cellar
The walling to the cellar is a mixture of lime washed chalk block and brick. One has to appreciate that cellars in buildings of this age are invariably visibly damp due to the very nature of the construction and the placement of such walling in a subterranean environment. Internal tanking or vertical damp proofing works in cellars, unless a ventilated and sumped system is used, will cause significant damage, as the saturation of the walling will become far greater. Historically, cellars benefited from ventilation via a coal hole/chute and the ‘airing’ of the space due to daily access to bring coal into the upper levels of the building for heating and cooking.
Unfortunately, the coal hole/chute has been blocked in as a result of the 20th Century rear extension, and the new trap door to the living room is inadequately ventilated.
I would therefore recommend that the walling is left as is, and that appropriate external ventilation is provided on the opposing side of the blocked coal hole/chute to the front of the property and that the existing access hatch is provided with an increased level of ventilation holes/slits.
It was noted that a section of the timberwork to the cellar space had an area of fruiting body (approx 150mm, 2 max). Dry rot spores (Serpula Lacrymans), which exist virtually everywhere, will thrive in a humid environment where the timber is allowed to maintain a moisture content of 20% and above.
Increased ventilation will reduce overall humidity and subsequently the moisture content of the timber which should witness a cessation of the rot.
I would recommend that the extant fruiting body be removed and the affected area be treated locally with a ‘neat’ proprietary disinfectant or bleach.
I would confirm that D.P.C injection and associated replastering would, in my opinion, require the benefit of Listed Building Consent; an application for Listed Building Consent to undertake such work will not receive support for approval at Officer level.
I have had previous involvement with building societies (Kensington Mortgage Company, 200 Aldersgate Street, London, EC1A 4JJ, Nationwide Mortgage Company, 17-21 Queensway, Stevenage, Herts, SG1 1DA and Virgin, Discovery House, Whitling Road, Norfolk, NR4 6EJ, amongst others) and have successfully achieved the removal of such associated retentions from mortgages and respectfully request that you give full consideration to allowing your client to follow my recommendations as opposed to those contained within the above named report.
Yours sincerely
Andrew Gayton
Gareth Hughes
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Pford75 said:1. Airbrick(s) inserted in front elevation at ground level
2. Floorboards stripped and made good (they've already been badly sanded by a previous owner and stained again)
3. Demolition of a 1950's garage in the rear garden (it has an asbestos roof)
4. Installation of a gas supply
5. Installation of gas central heating
6. Insertion of a DPC at ground level (I don't want to do this but the mortgage lender won't accept anything else)
1. Possibly
2. Unlikely - others will disagree..but I can't imagine any CO requesting LBC
3. Yes, almost certainly
4. Depends where and how...if it is non destructive, no.
5. Again..if non destructive no. However, if there is no CH at present and you require and get LBC...you can reclaim the VAT on the work
6. Yes
Sorry to disagree, but
5. No - if it's freestanding and dates entirely from after 1 July 1948, it is not considered to be a curtilage listed building.
Nemesis
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Think that's number 3 not 5!
Curtilage is a messy situation though, and many legal judgments have muddied the waters.
http://www.stedmundsbury.gov.uk/sebc/live/Listed-Buildings.cfm
http://www.ihbc.co.uk/context_archive/66/mynors/curtilage.html
http://www.buildingconservation.com/articles/legislation/legislation.htm
However, if it's in a conservation area and considered to make a positive contribution it could require conservation area consent.
Unlikely to be that lovely I appreciate but...
Curtilage is a messy situation though, and many legal judgments have muddied the waters.
http://www.stedmundsbury.gov.uk/sebc/live/Listed-Buildings.cfm
http://www.ihbc.co.uk/context_archive/66/mynors/curtilage.html
http://www.buildingconservation.com/articles/legislation/legislation.htm
However, if it's in a conservation area and considered to make a positive contribution it could require conservation area consent.
Unlikely to be that lovely I appreciate but...