7/25/2019 Damp in Traditional Buildings
1/25
DAMP IN TRADITIONAL BUILDINGS
Prepared for discussion with students
Dr.Phani Sree Vagvala
7/25/2019 Damp in Traditional Buildings
2/25
Diagnosis
Causes of damp
There are four main causes of damp in historic buildings:
Penetration of water.
. Condensation.
Hygroscopic salts (usually resulting from rising
damp).
7/25/2019 Damp in Traditional Buildings
3/25
Diagnosis
Locating the source
The source may be remote from the symptom. A case of damp may have more than one cause.
A long term assessment may be necessary as.
Leaks from concealed plumbing can be mistaken forwater penetration.
The source of damp must be located before considering
specific treatment. Building defects are the most common source and
professional advice is recommended.
7/25/2019 Damp in Traditional Buildings
4/25
Diagnosis and investigation
Visual inspection of the fabric A systematic
inspection of the roof, roof space, walls andrainwater system should be carried out.
Ground levels around the buildin should be
checked.
Visually assess the extent and properties of the
damp and its effect on materials.
Dampness due to rainwater penetration differs from
rising damp
7/25/2019 Damp in Traditional Buildings
5/25
Treatment of damp
Keep up regular maintenance of external fabric.
Defects must be remedied using compatible
materials.
.
Maintain or increase levels of ventilation to aid
evaporation.
Reduce water vapor and increase surfacetemperatures.
7/25/2019 Damp in Traditional Buildings
6/25
Rainwater Penetration
1. Debris, leaves and moss in parapet and centre
gutters.
2. Damaged lead or asphalt gutters.
3. Mortar joints in ridge tiles.
4. Displaced or damaged slates.
5. Lea as ings at a utments, c imney stac s an
parapets.
6. Mortar joints on top surfaces of coping stones and
parapets.
7. Open joints in brickwork.
8. Structural movement e.g. opening of mortar joints.9. Damaged rainwater gutters and downpipes.
10. Hairline cracks in render.
11. Missing render.
12. Vegetable growth and debris ingulleys.13. High ground level.
7/25/2019 Damp in Traditional Buildings
7/25
Rainwater Penetration - walls
External Conditions
Some walls can be more susceptible to waterpenetration. The degree of penetration will depend
artl on the followin :
Thickness of wall.
Degree of exposure.
Porosity of material. Type of construction.
7/25/2019 Damp in Traditional Buildings
8/25
Rainwater PenetrationRoof and wall defects are the most common source of
rainwater penetration. Lack of routine maintenance is a major cause of
building faults resulting in rain penetration.
enera a ure o ma er a s o e ex erna a r c walso cause water penetration, for instance:
Structural movement eg opening of mortar joints.
.Decay or failure of materials.
Incorrect earlier repairs such as impervious externalcoatings and cement rich mortar pointing.
7/25/2019 Damp in Traditional Buildings
9/25
Rainwater Penetration - Roof level
Roof leaks not attended when the fault is hidden, remote or
inaccessible causing dampness and sometimes structuraldecay.
Tile and similar roof finishes
Re-fix displaced tiles and renew those broken in a
matching tile.
Renew mortar joints in ridge tiles where damaged, and
rebed any found to be loose. Ensure correct weathering
details
7/25/2019 Damp in Traditional Buildings
10/25
Rainwater Penetration - Roof level Abutments and parapets
Renew fractured or missing lead flashings and soakersat abutments, and parapets
Renew cracked or missing mortar fillet at chimneys ac s. ep ac ng e e w ea as ng spreferred where possible.
Re-point mortar joints on top surfaces of coping stonesat parapets.
A lead DPC below the coping may be required if waterpenetration is serious.
7/25/2019 Damp in Traditional Buildings
11/25
Rainwater Penetration - Roof level
Parapet gutters
Remove debris, leaves and moss and clearoverflows.
gutters. Do not line lead gutters with asphalt or
bitumen.
7/25/2019 Damp in Traditional Buildings
12/25
Rainwater Penetration - wallsDefects in rainwater systems and external wall finishes can cause
damp in solid walls.
Defective rainwater goods
Leaks from damaged rainwater gutters and downpipes are normally apparenton the surface of the adjacent wall. (Evidence may be obscured where for instance square downpipesare flush with the wall surface or where exposed gutters are recessed into elaborate fascias.)
Replace cracked or damaged cast iron gutter and downpipe sections. Usethe identical section and material as the original.
Dismantle gutters and downpipes where joints have failed and reassemblewith a yam and red lead joint.
Repair cast iron hopper heads and all lead rainwater goods if defective,
do not replace them. Splits in lead downpipes should be patched notsoldered.
Remove all vegetable growth and debris from the discharge point ofdownpipes at gulley's.
Realign gutters if necessary to falls.
7/25/2019 Damp in Traditional Buildings
13/25
Rainwater Penetration - walls Defective external wall Rainwater will penetrate walls
more readily where mortar joints have been washed out orwhere original render has cracked or blown.
Re-point open joints in brickwork in a mortar to match theoriginal pointing where the mortar is absent or extremely
.
Specialist advice should be sought where joints haveopened due to movement in the wall.
Hairline cracks in render should be widened sufficiently torepair. Render for the repair should be of a similar mix to
the original. DO NOT use waterproof membranes such as bitumen,
silicone water repellants or oil paint to remedy.
7/25/2019 Damp in Traditional Buildings
14/25
Rainwater Penetration - Roofs and walls
7/25/2019 Damp in Traditional Buildings
15/25
Condensation Condensation
Condensation results from a complex relationship between the moisturecontent and temperature of the air and that of the structure. It cannotbe satisfactorily controlled whilst other problems of damp remainuntreated
S m toms
Cool porous surfaces: Condensation will be absorbed. Moulds, normally black in color will occur on the surface of paint or
wallpaper (fig 10). Rising damp however may cause similar growth.
Moisture readings will be uniformly high, unlike those for rising
damp which decrease with height. Cool impervious surfaces: Condensation appears as tiny droplets of water
on cool non-porous surfaces. In extreme cases it forms vertical streamlets.
It can occur for instance on oil paint, metal surfaces and wall tiles.
7/25/2019 Damp in Traditional Buildings
16/25
Condensation-RemediesThe following measures will help reduce condensation:
Reducing water vapor:
Maintain high levels of ventilation to the building, especially inkitchens, bathrooms, stores, cellars and roof voids.
Treat damp in external walls and solid floors caused by rising
Reduce human activities which raise the moisture content of air (eg:clothes drying, cooking etc).
Increasing surface temperatures: Surfaces warmer than dew-pointwill not attract condensation.
Provide continuous low level radiant heating to maintain warmsurfaces. Intermittent heating in old buildings can actually aggravatecondensation.
Insulate roof voids and install a continuous vapor barrier.
7/25/2019 Damp in Traditional Buildings
17/25
Condensation
7/25/2019 Damp in Traditional Buildings
18/25
Ventilation Ventilation is the key to a healthy historic building. It
reduces dampness, combats condensation and preventstimber decay.
The need for ventilation :A well maintained historicbuilding will gradually suffer the problems associated
wit amp w en starve o a venti ation. Natural ventilation is vital:
In vacant buildings. Continuous low-level heating mayalso be required.
To all areas and rooms, especially those with highhumidity.
7/25/2019 Damp in Traditional Buildings
19/25
Ventilation
In cellars and roof spaces. Extra ventilation is necessary
where felt has been installed. Behind timber paneling or dry lining to walls where
there may be a risk of damp.
c mney ues w en ey ave een oc e up.
In stores adjacent to external walls.
Below raised ground floors.
Behind furniture where it is close to the wall in areas ofhigh humidity.
Provide an air gap.
7/25/2019 Damp in Traditional Buildings
20/25
Ventilation
7/25/2019 Damp in Traditional Buildings
21/25
Rising damp
Ground water rises by capillary action and affects mainly masonrywalls and solid floors. Its extent depends on the amount of water in
the ground, the wall's capacity to absorb it, and evaporation levels.Its symptoms differ from those of penetrating rain.
Dampness is always present, even during dry weather but notalways easily detectable. Damp will retreat in prolonged drywea er.
Symptoms
A characteristic 'tide mark' of crystalline salts is often apparent atthe top of the damp.
Salts expand forcing plaster to exfoliate and spall.
When measured dampness reduces with height.
7/25/2019 Damp in Traditional Buildings
22/25
Rising damp
Causes for worsening of rising damp
The effects of rising damp may have worsened as conditionsin and around the building have changed.
External ground levels may have risen, pushing dampnessfurther up the wall.
An impervious floor, floor finish or damp proof membranemay have been installed. This increases rising damp in wallslacking a dpc.
Ventilation may have been restricted to avoid heat loss.
Non-porous surfaces may have been applied or pointingcarried out in cement rich mortar, driving moisture up thewall.
7/25/2019 Damp in Traditional Buildings
23/25
Rising damp -Remedy
Reduce the moisture content of the structure and excessive groundwater, and increase internal evaporation:
Examine underground drains for leaks and repair. Remedy all faults causing penetration of rainwater.
Take measures to reduce condensation.
ncrease eve s o na ura ven a on roug ou e u ng
Use vapor permeable emulsion rather than impervious paints orother impervious finishes.
Timber such as skirting and door linings in contact with the remainingdamp wall must be isolated to prevent fungal attack.
Treat any salts which appear on the surface after drying out.
7/25/2019 Damp in Traditional Buildings
24/25
Rising damp Remedy for Solid floors
Rising damp may affect some valuable historic floors. The type oftreatment should be tailored to avoid disruption of the floor finish.
Porous floor finishes such as stone, brick and some clay tiles whichhave been laid directly onto ground may suffer from rising damp.
Remedy rising dampness mild
Do not apply waterproof sealers. A beeswax and turpentine polishmay be suitable.
Open the joints in a brick or stone floor by removing hard pointing.Create a dry area (see next page)or batter the external ground toa channel to direct water away from the building.
7/25/2019 Damp in Traditional Buildings
25/25
Rising damp Remedy for Solid floors
Remedy Dising Dampness Severe
Relaying the floor on hardcoreWater levels will be lowered by relaying the floor on
sand blinding overhand packed hardcore. The
treatment may however cause movement in thestructure.
Relaying the floor on a damp proof membrane
This concentrates more ground water in the walls. It istherefore only effective if used in conjunction with adpc
Top Related