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Building Defects. Lesson 8. Learning Outcomes. Recognise the main symptoms of common defects in buildings. Distinguish between minor and serious building defects. Identify the proper diagnosis and prognosis of typical building failures.
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Building Defects Lesson 8
Learning Outcomes • Recognise the main symptoms of common defects in buildings. • Distinguish between minor and serious building defects. • Identify the proper diagnosis and prognosis of typical building failures. • Prescribe the appropriate methods of repair for common building defects.
Introduction To introduce a wide range of common defects which affect the following elements: • Walls • Flat roofs • Floors • Finishes • Components • Materials
Common Building Defects STRUCTURAL RELATED Cracking • Assessing cracking: • Does the crack follow joints or does it pass through the masonry unit? • How wide is the crack? • Does it appear new or old? • Is the crack of consistent width or does it widen? • Are the cracks vertical or horizontal? • To be monitored over a period of time whether this movement varies with change in temperature, moisture content or variation in loading.
Common Building Defects STRUCTURAL RELATED Bowing / Leaning • bowing, leaning or bulging walls • serious building defects • caused by :- • Failure of a structural tie or restraint. • Overloading. • Vibration from traffic or enclosed machinery. • Chemical (sulphate) attack within masonry joints.
Common Building Defects STRUCTURAL RELATED Bowing / Leaning • Surveyor need to consider the specific causes: • The thickness: height ratio of the wall • Method of structural tying or restraint. • The extent that the wall is bulging or out of plumb. • The extent, size and location of cracking. • The number, size and position of openings in the wall.
Common Building Defects STRUCTURAL RELATED Wall Tie Failure • galvanised wall ties produced prior to 1981 may have insufficient protection when used with mortars where calcium chloride additives or where black ash mortars have been used. • Poorly protected wall ties can rust when exposed to moist • aggressive environment resulting in separate independent movement of a 2 leafs cavity wall.
Common Building Defects STRUCTURAL RELATED Wall Tie Failure • Typical wall tie failure :- • Horizontal cracking approx. 5-12mm wide • Rust formation and staining on the external face at tie locations – rusting expands the affected mortar joints. • Bulging of the outer leaf. Confirmation of wall tie failure done by intrusive inspection of the cavity either by brick removal or use of a fibre optic probe.
Common Building Defects STRUCTURAL RELATED Joint Failure • arise due to chemical reactions; overloading or structural movement. • The effectiveness of a wall depends upon these mortar joints • Defect or failure has serious implications for structural integrity of the wall.
Common Building Defects Chemical / Moisture RELATED Staining / Soiling • Arises from :- • Chemical (sulphate) attack. • Rising or penetrating moisture. • Defective or contamination masonry units or mortar materials. • External contamination (atmospheric soot or dirt). • Internal contamination (from internal processes). • Condensation. • Moulds, algae or fungus. • affect a buildings’ aesthetics • an indicator of a more serious, underlying defect • care will be needed to identify the causes.
Common Building Defects Moisture RELATED Dampness & Thermal Bridging • moisture can affect a wall either as penetrating rain or as condensation at thermal bridges. • Defective cavity walls can cause condensation at thermal bridges. • Penetrating moisture and condensation occurs as damp patches on the external wall • Remedial works often requires extensive and intrusive re-construction of large areas of the external wall.
Common Building Defects Moisture Related Spalling / Crumbing • arises due to wetting and subsequent frost attack • or due to chemical reaction (moisture driven) within the brick resulting in expansion and spalling.
Common Building Defects Moisture Related Spalling / Crumbing • Remedial actions require • the removal and replacement of the defective bricks or • the application of a render or • a rain-screen cladding to protect the brickwork and mask the physical damage. • It will be a serious structural issue when a large proportion of the brickwork has eroded most of the way through its thickness.
Common Building Defects Flat roofs Flat roof waterproofing • built-up bituminous membranes • mastic asphalt • metals (lead, copper, aluminium, coated steel) • liquid applied coating.
Common Building Defects Flat roofs Rainwater penetration • failure of • waterproof covering • the detailing at upstands • flashing • Due • low slope • standing water penetrate open joints in the waterproofing or at lapped or standing seam joints by capillary action. • Diagnosis - close inspection of the roof detailing / check if its condensation. • Remedy • repair damaged waterproofing • resealing of defective joints and upstands detailing • reinstatement of water bars or sealant at lapped joints.
Common Building Defects Flat roofs Ponding • ineffective falls on flat or low pitch roofs. • if the waterproof covering is intact, there is no risks for water penetration.
Common Building Defects Flat roofs Blistering/cracking of felts • entrapped moisture (or air) below the outer waterproofing layers. • due to : • Water penetration or condensation. • ageing felt i.e. elastic properties of the felt have deteriorated /unable to accommodate temperature induced movement.
Common Building Defects Flat roofs Blistering/cracking of felts • Remedy blisters can be split, drained and resealed, however the source of moisture will need to be eliminated. Cracking felt is approaching the end of its service life and should be replaced or overlaid.
Common Building Defects Flat roofs Degradation of surface finish • solar/UV degradation Abrasion due to • wind action on mineral or gravel finish • traffic (maintenance or service personnel walking and dragging equipment across a flat roof can degrade the waterproof covering) • Solvents, surfactants or oil based contaminants used in maintaining roof equipments can have a abrasive effect.
Common Building Defects Flat roofs Remedy • localised repairs, improved surface protection (granite chippings), the application of a liquid applied coating or the provision of designated walk-ways.
Common Building Defects Flat roofs Chocked rainwater outlets • routine maintenance problem. • can result in gutters backing up and flooding into the building. • leading to overloading of the roof structure (for large choking). Remedyis regular gutter and outlet cleaning, introduction of over-flow pipes for discharge to ground especially for close proximity of trees.
Common Building Defects Flat roofs Interstitial condensation • Arises from flat roof coverings being an effective vapour barrier to moist air • high risk of condensation forming either on the underside of the roof covering or within the fabric of the roof build-up. • IMPACT - reduces the thermal performance of the roof and can reduce the service life of the roof components.
Common Building Defects Flat roofs Interstitial condensation Remedy • complete refurbishment of the defective roof construction. • Or ensure that there is an effective vapour barrier on the warm side of the construction should reduce the risk of such defect.
Common Building Defects Floors Cracking • occurs in solid ground bearing floors as result of thermal, moisture or ground induced movement • may be related to sagging, arching or uneven surfaces. Sagging • occurs in solid ground bearing floors where the underlying ground compacts or is eroded by ground water resulting in reduced support to the overlying floor. • suspended timber floor - sagging can occur due to overloading of the floor or when the span of the joists exceeds the recommended effective load bearing span for the timber section Remedy treatment requires extensive refurbishment of the structural aspects of the floor.
Common Building Defects Floors Arching/bowing • in solid ground bearing floors - following water or chemical induced expansion of the underlying ground. • happens in old buildings which have been constructed using green timbers which have dried or seasoned in a ‘hog’ shape. Remedy- removing the ground bearing floors.
Common Building Defects Floors Uneven/sloping surface • occurs in both solid ground bearing and suspended floors • differential settlement or subsidence over the building area resulting in modified floor levels. Remedyrequires extensive reconstruction and ground stabilisation.
Common Building Defects Floors Cracking of coverings/screeds • due to drying out of the screed causing detachment, curling and cracking. Surface Erosion • due to trafficking of the floor abrading the applied finish.
Common Building Defects Floors Dampness/sweating • moisture entrapped within the sub-floor or screed tends to dry towards the warmer internal environment and can result in moisture forming behind impervious floor coverings. Remedyis by introducing a vapour impermeable membrane or DPC to reduce the risk of moisture migration.
Common Building Defects Finishes • Bossing- wet applied renders or plasters and adhesive fixed tiles can become boss where there are areas of detachment or void adhesion. Boss area produce a hollow sound. • Spalling- areas of detachment of clay, gypsum or cement based materials as the result of wetting and frost action causing in partial delamination. Spalled materials will be obvious by localised areas of detachment, typically crudely circular in shape.
Common Building Defects Finishes • Staining- can arise due to a raft of reasons and results in discolouration of the surface finish. • Lifting- delamination or detachment due to moisture or rapid drying action.
Common Building Defects Finishes • Peeling-curling of surface finish due to shrinkage (typically ageing) and delamination from substance. • Crazing/cracking- surface effect resulting from drying shrinkage movement. Can also be the result of chemical reaction. • Blistering- localised surface detachment or distortion as the result of permeating moisture becoming trapped behind impervious finish. Blistering often terminates in splitting, curling and peeling.
Common Building Defects Finishes • Mould growth- bacterial staining on finishes as the result of moist conditions. A food source, e.g. wall paper paste, adhesive. • Pattern staining- differential surface staining resulting from dirt deposition as a result of variation in moisture content or temperature across a surface. Occurrence on masonry walls where the mortar joints are highlighted.
Common Building Defects Components • Decay- deterioration or rot resulting from the action of bacteria or fungi. Affects organic materials, e.g. timber and stone, and usually arises due to increased moisture content. • Corrosion- the breakdown of, typically, metal components, by chemical action with the presence of oxygen and water, however salts or acidic compounds in solution can accelerate the process. Rusting, pitting and cracking can occur.
Common Building Defects Components • Inadequate fit- this can result from poor initial workmanship or can arise during the service life of a component due to expansion or contraction of the component or the surrounding structure.
Common Building Defects Components • Lack of weathering- this can arise due to lack of applied protection, e.g. painting or staining; ineffective water proofing, e.g. drips, water bars or seals; can arise due to poor architectural protection e.g. ineffective overhangs at eaves or narrow cavities. • Insufficient fire resistance- building regulations require some building elements and components to attain a recommended fire resistance. This will require specialist advise or detailed specification information. Fire escape routes should meet the fire rating requirements.
Common Building Defects Components • Inadequate security - poorly fitting doors and windows; ineffective ironmongery and poor workmanship can lead to deficient security. Unoccupied buildings under refurbishment should also be free form theft and losses. • Inadequate safety- the components utilised within a building need to be fit for purpose and safe to use. The building user should not be at risk from unsafe products or systems.
Common Building Defects Components • Squeaking stairs/floors - timber components , e.g. joists, bearers, floor boards, dry and shrink resulting in small gaps and clearance between the individual components. The squeaking occurs as the components rub against each other and the nail fixings. Remedy is by packing below the joists to reduce gaps and by re-fixing the floor boards to accommodate the re-sized components.
Common Building Defects Issues with materials • Incompatibility- arises when materials react aggressively with each other leading to deterioration or rotting. • Deleterious materials- • Definition: materials or components which can cause harm or damage to health or may cause deteriorate affecting performance. • Problems: many traditional building materials have subsequently been identified as being hazardous to health.
Common Building Defects Issues with materials • Deleterious materials- • Assessment- any works to building requires to have a detailed risk assessment of the perceived risks and a method statement which identifies a safe procedure for undertaking these works. • Main types- asbestos; glass fibre insulation; high alumina cement; urea formaldehyde foam; lead; galvanised steel.
Common Building Defects Issues with materials - Incompatibility • Incompatibility of materials
Conclusion • To identify the main defects; discusses their possible causes and proposes remedial actions. • In practice defects and issues identified on site will not be as quite as easy as the text book. There may be a number of causes and it is only with experience that a surveyor can prioritise and diagnose effectively.
