| When considering remedial treatment to listed
buildings, special consideration should be given to the recommendations
for work, as there are limitations and legal restrictions
on what work may or may not be carried out, and what materials
may or may not be used. English Heritage (www.english-heritage.org.uk)
has strict guidelines on the remedial treatment of listed
buildings, and this is usually enforced by the local Listed
Building Inspector, or Conservation Officer. It can be a criminal
offence to carry out unauthorised work to a listed building
without the correct consultation on the long term effect of
the work on the property.
 |
 |
Living in a listed building can have its advantages. Inevitably
it will be a unique and interesting building, possibly with
some history (Tracing the history of your house by Nick Barratt).
It has invariably stood the test of time, and the English
weather, and should prove a good investment, as they are always
sought after for their character. It is also possible, when
carrying out alterations (not improvements or maintenance)
to reclaim the VAT on work. It is also possible to obtain
grants for some work, where the property is of particular
interest, although this is unlikely in a Grade II listing.
(Go to www.buildingconservation.com/articles/legislation/legislation.htm
for helpful information on listed properties, or ask pertinent
questions at www.periodproperty.co.uk.)
“How do I consult the list”? With great difficulty,
as this has, at the time of writing, not yet been digitised.
There are currently in the region of 500,000 listed buildings
in England, with over 90% being of Grade II status. A valuable
source of information for the owner of a listed building is
the Listed Property Owners Club, and their excellent periodic
publication ‘Heritage’ (www.lpoc.co.uk Tel: 01795
844939). Your property should also be present on the ‘Images
of England’ website (www.imagesofengland.org.uk), where
a brief description and photograph would normally be found.
Each property will have its own individual UID number. You
may also obtain a copy of the ‘listing’ of your
property by writing to the National Monuments Record Office
(NMRO) (www.english-heritage.org.uk/knowledge/nmr). Unfortunately
the list is not present on their web site. The local area
list should be available for viewing at your local council
offices.
All damp and timber contractors working in this specialised
field should be able to offer an independent underwritten
guarantee to cover their work (www.gptprotection.co.uk),
if they can’t, don’t use them!
DAMPNESS:
When inspecting a listed building for valuation or a full
structural survey, it is not uncommon for professionals to
locate damp readings somewhere in the property. As soon as
even moderate readings are found it has become common practice
to recommend the installation of a remedial chemical damp-proof
course, to what may be completely inappropriate masonry, or
where the insertion of a chemical damp-proof course will have
no, or very limited, effect.
With any damp treatment it is important that the render applied
to the wall is to a waterproof specification, and this will
inevitably be cement based. The quality of the render has
as much bearing on the relief of dampness as the presence
and effectiveness of a damp proof course (DPC). However, in
listed buildings this is not normally permitted, and the use
of cementitious based products is usually prohibited. English
Heritage recommends the use of a range of lime based renders
(heritage renders), which allow the wall to breathe (and dry)
naturally, as they were originally intended. However the presence
of lime within a render mix will inevitably reduce the waterproof
properties of the mixture, and will not form a waterproof
or vapour barrier, nor prevent the migration of hygroscopic
salts from the masonry to the internal wall surface.
Should there be particular problem areas of dampness in a
listed building, there are acceptable modern alternatives
which do not involve the use of cementitious based products,
in particular the industry considers the use of breathable
‘airgap’ membranes (cavity drain membranes) to
be a particular asset in the armoury against dampness in buildings.
Of course this will not suit all eventualities and it may
well be that the use of lime based render needs to be considered.
However it should be borne in mind that as this is not a vapour
barrier, on the completion of work, it would not be unusual
to find the likes of hygroscopic salt deposits forming where
the masonry is drying. Should it be felt that the use of modern
cementitious waterproof render is the only sensible alternative,
then listed building consent can be sought, and if approval
is given, the product may be used. Alternatively you may simply
approach your local conservation officer for his personal
approval.
In some instances it may also be possible to reclaim VAT
charged for work retrospectively from HM Inland Revenue &
Customs, but only when official listed building consent has
been granted. More information on this can be obtained from
The Listed Property Owners Club, and H.M. Inland Revenue &
Customs.
In summary, the presence of high damp readings in a listed
building, or a building of special interest, should not be
viewed as unusual, and certainly blanket treatment, using
modern waterproof products, should not be considered as a
matter of course. The property will usually require sympathetic
treatment, or even no treatment whatsoever, with a view to
long term management of any moisture ingress, combined with
adequate ventilation and heating.
It is worth mentioning that chimney breasts, and in particular
inglenook fireplaces and/or sandstone surrounds, will virtually
always give high readings to modern sensitive moisture meters.
This is usually due to the presence of hygroscopic salts which
have been deposited within the masonry from the burning of
fossil fuels over a long period. Again the installation of
a chemical DPC will have little or no effect. Should effervescence
persist and become unsightly, salt neutralising solutions
are available and are easily applied.
All cases of lateral penetrating dampness MUST be addressed
at the source of the moisture in the first instance, and where
possible allow the internal wall surfaces the opportunity
to dry naturally.
It is worth noting that on the Wealden District Council web
site (www.wealden.gov.uk/planning),
“damp proofing” is amongst the list of items which
require ‘listed building planning consent’. The
assumption is that they refer to ‘none reversible’
damp proofing, which should not include the use of ‘airgap’
membranes, which are classed as ‘fully reversible’.
Invariably surveys on timbers of listed buildings will result
in the requirement for a remedial timber inspection via a
BWPDA registered specialist (www.bwpda.co.uk), (now the Property
Care Association (PCA)). Listed buildings will likely be constructed
with a combination of both hard and soft woods, or in some
instances completely of hardwoods (this refers to the structural
timbers of the property). The timbers used in period properties
were often reclaimed timber, which had been used in previous
construction, timber taken from redundant horse drawn vehicles,
or commonly timbers reclaimed from ship building, particularly
near coastal areas.
Inevitably these timbers will be of unusual shapes and may
have completely unrelated joints, shakes, and crevices. It
is also inevitable that these timbers will have been infected
by some form of wood borer during its lifetime, and particularly
evident is Wharf borer and Marine borer beetle, found in decayed
timbers, or extremely damp hardwood and softwood timber. The
insect flight holes present in the timbers are commonly mistaken
for active infestation by Death watch beetle (Xestobium rufovillosum),
or Common furniture beetle (Anobium punctatum), when in fact
the timber can be solid and the infestation long standing
and inactive. When dry, these hardwood timbers become extremely
dense and it can be difficult to insert fixings, such as screws
or nails. Insect bore dust from legitimate previous infestation
can remain in the timber for many years after introduction
into the property, and may be dislodged by redesign of the
interior of the property, resulting in falling bore dust which
is mistaken for new active infestation.
Again the infestation of these old, and in some instances
extremely old timbers should, as a rule, be viewed as normal.
It would be our opinion that blanket treatment of hardwood
timbers within any building, should not be carried out as
a matter of course. Apart from softwoods found in roof spaces,
which are readily accessible, the use of modern timber treatment
products should be limited to actual areas of proven active
infestation. This can usually be limited to softwood, or hardwoods
where they abut softwoods, or where the hardwood contains
an amount of moisture, and in particular where timber is embedded
within masonry, without the provision of a damp proof membrane
or DPC.
Some species of wood borers do not actually require any treatment.
The Wood-boring weevil (Euophryum confine) is one such case.
The simple removal of the moisture source will result in removal
of the infestation without the need to resort to chemical
treatment. Bark borer beetle (Ernobius mollis) is also regularly
mistaken for an active infestation requiring chemical treatment,
when in fact it will usually be longstanding and inactive,
and, if active, only requires the removal of the bark (its
food source) to eliminate the infestation.
Active infestation by wood boring beetle can and is found
in older properties. When this is the case, it is prudent
to isolate the area of the outbreak and treat accordingly,
with regular monitoring, possibly on an annual basis, during
the active season (currently March to early August). Thatched
roofs may be treated, but whenever possible, none flammable
materials should be used.
In England the Death watch beetle is one of the major enemies
of historic buildings, and its favourite food is oak, and
it is extremely difficult to eradicate. Generally the infestation
will be in timber with some decay or moisture content. As
an infestation can only be detected by the presence of insect
‘flight’ holes, the beetle will usually be well
established before being detected. The cycle from lava to
adult insect can be as little as 5 years, but 10 years is
considered normal, however a 20 year cycle has been known
(but much depends on the type of timber and its moisture content).
Therefore, eradication may take a similar period and emergence
of adult insects should be anticipated for several years prior
to complete eradication (the ‘fly out’ period
– although they do not actually fly).
“Death Watch beetle is extremely rare in Scotland, and
has only been recorded twice in Ireland. There is no recorded
infestation within a property constructed entirely of coniferous
timber, which seems to confirm the opinion that attacks originate
only in hardwood.”
Outbreaks of wet rot may only require the removal of the
moisture source to result in the removal of the fungus. Dry
rot (Serpula lacrymans) however, should be treated with extreme
caution and specialists will be required to eradicate the
outbreak thoroughly, for which you should always obtain a
long term and underwritten guarantee from a BWPDA or PCA registered
company. This particular fungus is a ‘cancer’
to buildings and can spread rapidly causing major structural
defects. Evidence of such rot should be treated urgently.
The presence of Wet rot fungus is again commonly mistaken
for Dry rot. Look out for large cubed cracking, and the timber
will crumble to dust when rubbed between the fingers.
“The ‘management’ of listed buildings is
felt more desirable than the application and installation
of radical modern building products, which can be unsympathetic
to the original construction of the building.”
CONDENSATION:
Experience has shown that condensation within listed properties
is not particularly common. However in modern construction,
including ‘new build’, it is extremely prevalent
(primarily due to a lack of ventilation). Condensation is
usually a consequence of modern living and will be a balance
between heating, ventilation, security and cost. Mould spots
on cold walls are the common feature, and these may be black,
green, brown or blue mould. They will usually be found on
cold external surfaces, although the actual source of the
moisture may be some distance away. Mould spores on clothing
and shoes, particularly when stored in cupboards against cold
walls, is very common. One of the reasons for the lack of
condensation in listed buildings will be the presence of single,
rather than double, glazing, and of course, draft’s.
Should condensation persist, there are unobtrusive ‘Forced
Air’ units which may be placed within the roof void
which are easily installed and relieve condensation throughout
the complete property. The installation of a ‘Forced
Air’ ventilation system may also assist in the heating
(and cooling) values of the property.
 |
 |
A significant proportion of both Wet and Dry rots found in
listed buildings are due to condensation. If a building is
left empty, particularly over the winter months, localised
condensation can produce the ideal environment for the germination
of rot to timber.
We trust the above guide may be of some assistance to those
involved with, or purchasing a listed property. The foregoing
is certainly not exhaustive, however the list of useful web
site addresses should answer any further queries on this subject.
For first hand advice on listed buildings see also English
Heritage web page: www.english-heritage.org.uk/server/show/nav.001002004002005
As they say on the BBC’s ‘Crimewatch’ programme,
“Don’t have nightmares” – You can
bet your Grade II Listed Property will outlast many of the
modern ‘New Builds’, and it will certainly be
far more rewarding and fun!
|
