Page 202 - The Building Conservation Directory 2013

2 0 2 t h e b u i l d i n g c o n s e r vat i o n d i r e c t o r y 2 0 1 3 T w e n t i e t h a N N i v e r s a r y e d i t i o n
6
Useful Information
Number ❹
Lighting in the Victorian Home
Jonathan Taylor, BCD 2000
The majority of Directory articles focus
either on the on-site, practical end of
conservation or on the science, technology
or ethics that underpin it. A handful, like
this one, provide concise historical overviews
of a kind and quality that you would be
hard pushed to find elsewhere. ‘Lighting in
the Victorian Home’ takes the reader from
candles to the advent of electric lighting in
a concise and accessible article. An earlier
article looked at light fittings in Georgian
and early Victorian homes. Both provide a
useful insight into restoration approaches.
Number ❸
Structural Movement: Is it really a
problem? Clive Richardson, BCD 1996
The words ‘structural movement’ can strike
terror into the heart of any homeowner and
may have an even more alarming effect on
the owners and managers of precious historic
buildings. Clive Richardson’s article pointed
out that old buildings do move, and that
not all cracks are significant. Indeed, some
remedial treatment can actually be counter-
productive. This rational and well-reasoned
article will doubtless have ‘stabilised’ some
over-anxious readers.
Number ❷
Chimneys and Flues
Russell Taylor, BCD 1999
Russell Taylor’s illuminating article follows
a tried and tested pattern. Having outlined
the historical development of chimneys
and the construction methods and
materials associated with different stages
of that development, the article goes on to
identify common defects and the remedial
alternatives. Using this simple structure,
the article manages to pack a wealth of
historical and technical information into just
three pages, still finding room for a handy
list of recommended technical guides and
regulations.
And at Number ❶ …
Rising Damp TimHutton, BCD 1998
Given the remedial treatment industry’s
influence, it is perhaps not surprising to
learn that thousands of anxious homeowners
have been busy Googling ‘rising damp’. The
fact that Tim Hutton’s eminently sensible
article has generated the highest hit rate
of any of our online articles is a perfect
demonstration of the value of both the
Directory and Buildingconservation.com.
This article explains how often rising damp
is misdiagnosed and, as a result, how often
inappropriate and potentially damaging
‘treatments’ are specified. Hopefully it has
helped many readers to avoid unnecessary
damage and expense.
Need-to-know information
These articles provide just a glimpse of
the range of topics covered by technical
and advisory articles in The Building
Conservation Directory and BCD Special
Reports Historic Churches and Historic
Gardens. Key topics such as listed building
legislation are regularly covered from one
edition to another, so the website provides
only the most recent articles on some
subjects. However, most articles that we
publish provide entirely new information, and
there are always fresh subjects to investigate.
For example, in this current edition of
the Directory you will find a number of
subjects covered that we have not previously
looked at in isolation. These include:
• scheduled monument consents (page 15)
• corrugated iron (page 35)
• enabling development (page 43)
• traditional slate roof details (page 77)
• sandstone geology and
characteristics (page 94)
• sandstone conservation (page 106)
• cleaning stained glass (page 124)
• steam in masonry cleaning (page 148)
• harling and traditional roughcast
render (page 156)
• 19th-century heating systems (page 173)
• scagliola (page 182).
Over the years we have been fortunate
to have had the support of many of the
leading authorities in their field, and we are
extremely grateful that they have been so
generous with their time and expertise as
authors and advisors.
Who reads BCD articles online?
When it was first launched in 1997,
Buildingconservation.com was one of
very few online providers of conservation
information. It now welcomes around 50,000
unique visitors per month, most of whom
are regular visitors. Unsurprisingly, articles
are particularly popular with conservation
course tutors and their students.
According to statistics provided by our
host Clara.net, 70 per cent of the traffic
comes direct to the website without being
referred from other sites, and most of the
remaining 30 per cent of traffic comes via
internet search engines such as Google.
What’s more, most of these visits are
made by people who have bookmarked
the site or added it to their favourites.
The website is well known and
respected throughout an international
community of conservation professionals
and historic building owners who are
repeat users of the site, regularly consulting
it for information and advice. Recent
statistics indicate that the website is
particularly popular in North America.
Looking ahead
Around 30 new articles appear each year
in our in-house publications and the
majority of them are later reproduced on
Buildingconservation.com, so the readers’
top ten will continue to change and
evolve. You can keep an eye on its progress
at buildingconservation.com/articles/
top10articles.htm.
David Boulting is deputy editor of
The Building Conservation Directory.
On the left,awell-paintedwindow, showing reasonable
overpaintingof theglass. Above,a similarexample,buthere the
painterdidnotunderstand thedifferencebetween the frameand
the sash: there isanarbitrary lineacross the topof themuntins
(whichare in the sameplaneas theotherouter linings).Hehas
alsonot returned the frame colour round the lining returns,which
has resulted ina slightly insubstantialappearance.
3.3
STRUCTURE&FABRICMetal,Glass&Wood
thebuildingconservationdirectory 2001 131
SASH WINDOWS : PAINTING
AND DRAUGHT-PROOFING
DAVID WRIGHTSON
The sliding sashwindowhas been
withus for over three centuries and
the operatingprinciplehas remained
almostunchanged throughout that time. Some
of the components, such as the staff bead and
theparting bead can still bebought off the
shelf.Sashwindowsaremade in suchaway that
theycanbe easilydismantled for repairor for
replacingbroken sash cords.Manypeople fail to
realise thiswhen they encounterproblemsand
think that theonly sensibleoption is replacement
– in some cases,withplasticones–which
is simplynot thecase.Some timberwindows
have lasted forcenturiesbecause theyhave
beenproperlymaintainedandpainted regularly.
Plasticwindows (PVCu)by comparison,cannot
bedismantledand repaired so easily,and the
componentscannotbemadebyany competent
joiner.Theyhavenotbeen testedby timeand
therearealready signsof failure.Plasticwindows,
whichusuallycomewithdoubleglazed sealed
unitsaregenerallyonlyguaranteed for ten
yearsandare expensive to replace if they fail.
Furthermore, theyare constructed in sucha
way that they cannot reproduce themouldings
anddetails characteristicof traditional timber
windows.Theyare,almostwithout a single
exception, completelyunsuitable foruse in any
historic context.Theproblemsmost likely tobe
encounteredwith traditional timber sashes are
sticking, failure of joints, failure ofputty,wet
rot, rattling, anddraughts.Thefirst four of
these are the result ofpoormaintenance and
the lack of a goodprotective coat ofpaint.
Rattling anddraughts can bedealtwith in a
number ofways,whichwewill examine later.
MAINTENANCE
You should aim to inspect yourwindows every
year (and, ideally, get a qualifiedprofessional
to inspect thewholehouse every four orfive
years).Typical sashwindowproblems likely to
be encountered include:
• Cracked andflakingpaintwork: the
outside of thewindows should be
repainted at intervals offive to eight years,
normally.
• Stickingwindows:usually the result ofeither careless replacement of staff bead,
following repair or re-cording,which is
easily remedied, or a buildup ofpaint
whichneeds to be removed.
• Failedputty andbroken glasspanes: these
are relatively easy to replace.
• Broken cords: in former timespeople
re-corded their ownwindows– the cords
and sashweightswere available at any
ironmongers (and still are at some).
• Timberdecay,particularly to the bottom
rail:fillers are invaluable forminor
decay and surface imperfectionswhere
the strength of the timber isunaffected;
loose corner joints can be strengthened
bymeans of cornerbracketswhich
can then bepainted over; andmore
significant repairs canbe carried out by
any competent joiner.
David Wrightson’s article at number 6
38 TheBuildingConservationDirectory 1998
RISING
DAMP
Tim HuTTon
Risingdamp iswidelymisdiagnosed
in existing buildings, based on the
incorrect interpretation of visual
evidence and the readings of
moisturemeters.Because of a
highly successful sales campaign over the last
20 yearsby specialist remedial contractors
installing injected ‘chemicaldamp-proof
courses’, thismisdiagnosis of risingdamphas
also become synonymouswith adiagnosis of
a lack of an ‘injected chemicaldamp-proof
course’.Although thishas been very good for
business, ithas often resulted in awaste of the
clients’money and resources; originalplasters
and finisheshave beendestroyed in theprocess
of installation, andunnecessarydamagehas
been caused to original structures by thedrilling
of irrigationholes. In addition,money that
mighthave been spent onmore cost-effective
maintenance or repairworkshas beenwasted.
Whilst injected chemicaldamp-proof
coursesmayprovideuseful short tomedium
termprotection for certain types of structure if
properly specified, their general application is
rarely themost cost-effectiveway of controlling
dampproblems in buildings, andmay be
wrongly specified and ineffective.
CAuSEAnDEFFECT
Risingdamp actuallydescribes themovement
ofmoistureupward throughpermeable building
materials by capillary action. It becomes a
problem if themoisturepenetrates vulnerable
materials or finishes,particularly in the
occupiedparts of a building.Thismoisturewill
dissolve soluble salts from the buildingmaterials
such as calcium sulphate, andmay also carry
soluble salts from its source. If themoisture
evaporates through apermeable surface, these
saltswill be left behind and formdeposits on
orwithin the evaporative surface.Where there
is a large evaporative surface, salt crystals are
deposited as aharmless flour-likedusting on the
surface. If evaporation is restricted to localised
areas such asdefects in an impermeablepaint
finish, then saltdeposition is concentrated,
forming thick crystallinedepositswith the
appearance of small flowers;hence the term
‘efflorescence’.When evaporation occurswithin
thematerial, salts canbedepositedwithin
thepores.The expanding salt crystals in these
locationsmay result in fractures forming in the
material and spalling of the surface.This type
ofdecaymaybe seen inporous brickwork or
masonry.
When therehasbeen a long-termproblem
withmoisturepenetration, evaporation at the
edgeof thedamp area leads to adistinctive ‘tide
mark’ as a resultof saltdeposition.Where this
occurs at thebaseof awall, the tidemark isoften
taken as a typicaldiagnostic featureof ‘rising
damp’.However, these salt accumulationsmay
remain evenwhen thewaterpenetration that
originally caused themhas long gone.Similarly,
waterpenetrationmayhaveoccurred from causes
other than ‘risingdamp’.
Themost common source ofmoisture
in the base of thewalls ofbuildings is from
defective ground and surfacedrainage.This is
present to somedegree in almost every building
in the country,due to a combination of such
factors as rising ground levels, the failure of
grounddrainage systems, and the increased
use of concrete or tarmacadam finishes around
buildingswithoutproper consideration of
drainage slopes.
The accumulation of ‘moisture reservoirs’
in the foundationsmay also arise as the result
of chronicplumbing leaks or floods from
catastrophicplumbing ordrainagedefects.Damp conditions at the foot ofwallsmay
be greatly increased by condensation.This
occurswhenwarmmoisture-laden air cools to
duepoint (the temperature atwhichmoisture
condenses) against a cold surface. Such cold
surfaces commonly occurwhen the insulation
value of the externalwall is reduced bywater
penetration, asdescribed above. Intermittent
occupancywith intermittentheatingprovides
the conditions for condensation of furtherwater
on these colddamp surfaces,particularly in
ground floor bedrooms.Thesephenomena are
themain causes ofdamp in the base ofwalls
rather than ‘risingdamp’ alone.
Dampmasonry at the base ofwallsmay
lead to anumber ofproblems:
◆Themoisture content of the structuremay
rise to a level atwhichdecay organisms
may grow, or thematerials themselvesmay
be adversely affected.For example, timber
skirting boards or built-in bonding timbers
along thebase ofwallsmaybecome infected
anddecayed bydry rot,wet rot,weevils or
woodworm.
◆In verydamp conditions, the inorganicmaterials themselvesmay lose their
structural strength.This occursmost
spectacularlywithwallsmade of cob (earth)
soakedwithwater.
DryrotfruitingboDies: (top)at thebaseofadampwall
where tilinghaspreventednaturaldryingand (below)on
distempered stonework.
risingDampatempressplace,singapore:anextremeexampledue topoorgrounddrainageand internally (left)due to the
dry,air-conditionedatmosphere.
Tim Hutton’s article on rising damp from 2008 is
still our most popular article