Introduction: Decay and deterioration can happen in a building for any number of reasons.The first being poor repair and maintenance of the building over its life by users or those responsible for its maintenance such as a landlord etc.It can also mean that there were original problems with the building that impair its ability to function as intended, these may not have been uncovered during the snagging process at the end of the construction stage.
These building problems are referred to as defects, depending on the type of contact most contracts have a 12 month defect period, this enables the users (and funders) to live in the building through the different seasons and see if any problems occur.
A latent defect is after the 12 month defect period has lapsed and the new building shows signs of problems that are so significant that they can stop its functionality (a latent defect period can last up to 12 years on some contracts). Please find below some common reasons for defects: * Design Issues
Design professionals (such as architects or engineers) could perhaps specify material or equipment that cannot perform as intended. For example: a geological survey that does not cover enough areas on a site could mean that the subsoil is not consistent across the site and therefore could eventually cause subsidence in the building. The architect’s motivation for the design may be with the building form, function or aesthetics but the completed design could result as a defect as any cost considerations or value engineering if not well planned, managed and coordinated could result in a defects.
The use of inferior building materials can cause problems such as windows that leak or fail to perform and function adequately, even when properly installed. Leaking windows are a common defect and prevention requires good workmanship. * Site supervision during construction period Poor supervision during the construction period can result in poor quality and sub standard workmanship. For example: this can often manifest in water infiltration through some portion of the building structure (cracks in oundations, floor slabs, walls, dry rotting of wood or other building materials), electrical and mechanical problems, plumbing leaks and back-ups, lack of appropriate sound insulation and fire-resistive construction between adjacent housing units, etc. The above can prevented with a good Quality Assurance process in place that ensures that all trades are well supervised on site, accurate records are kept on workmanship (this can include pictorial evidence) and guidance is given to all staff on the quality expectations that have to be achieved on site.
The traditional role of Clerk of Works should also be used to ensure that all measures are met on site level. * Maintenance No building lasts forever. Day to day planned maintenance of a building is required to ensure that it prevents any problems in the future. Poor planned maintence can cause defects to occur in buildings that would have performed well had they been cared for properly. For example: a master plan for the buildings mechanical and electrical (M&E) equipment to be replaced (such as Boiler replacements, lighting upgrades, ICT Category cabling upgrades etc. also phased window or roof replacement schedule to ensure that all that entire building envelope is protected to protect from the elements. If maintenance of buildings are not kept up to date then in some contracts ‘latent defects’ would not be honoured as the users have not maintained the works that were carried out in line with the contract therefore the contractors would not be obligated to rectify any defective works. * Service installation
Some equipment requires regular servicing under the terms of its guarantee. For example: If a boiler that has been installed with a 10 year warranty is not annually serviced then the manufacture can advise that the user did not meet their obligations and therefore any replacement in the 10 year period would fall to the user to fund. Common Defects found in Low-Rise Housing: Please see below mock defects sheets in relation to the defects outlined in ‘Common Defects in Low-Rise Housing’.
These outline the defect, the cause of the defect, the remedy required to rectify the defect and finally any supporting building regulations/guidelines that support this process. STAGE:A| WORKS/JOB SHEET NO. 6| LOCATION:South Wall| DATE:26th May 2010| BRE REF NO. Defect Action Sheet 116| DEFECT: Insufficient wall ties below Damp-proof Level | CAUSE: Poor design and specification | FUNCTION:A wall tie is a small piece of metal generally made of steel that is installed between a cavity wall void or between two adjoining walls. The purpose of this is to keep both walls together at all times.
A wall tie allows slight movement for expansion but if correctly fitted stops each wall acting independently of one another so therefore keeps the building strong and stable. | DEFECTIVE AREA: * Corroded and show signs of de-laminating (this is when the metal starts to peel and splinter) * Corroded due to water egress (decaying of the tie means loss of strength) * Corroded show signs of ferrous oxide (this is when the metal bubbles and expands) this can cause lifting and cracking the brickwork * Cavity walling that is blocked with decayed mortar that bridged the DPC. Poorly fitted wall ties (this means that it does not function as originally intended) * Incorrect wall ties used (there are 4 different types of wall ties – each tie has its own best area for use)| DEFECTIVE CORRECTION REQUIRED: * Ties should be placed at 900mm centres horizontally and 450mm vertically * Sufficient lap of Damp proof course is required all round * Wall ties to be of a minimum size 5/m2 * Ensure that ties are as specified and are of the correct type * Use BS or BBA Certificated ties of length and type suitable for cavity width and purpose * Space ties in accordance with BS 5628: Pt 3: 2001.
For example: the cavity width should be 50 to 300mm, number of ties 2. 5 per m2, 900 mm horizontally 450mm vertically and provide extra ties adjacent to openings * Check that there is a row of ties at every sixth course of bricks * Ties should be staggered and evenly distributed * Check that the horizontal spacing’s have the correct number of specified ties per m2 * Check that ties are at every block course within 225mm of opening | RELEVANT BRITISH STANDARD:| * BS:5628 Pt 3.2001 | | | | | STAGE:A| WORKS/JOB SHEET NO. 1| LOCATION:Rear externals| DATE:26th May 2010| BRE REF NO.
Defect Action Sheet 96| DEFECT: Mature trees too close | CAUSE: Poor design and specification | FUNCTION:Movement where a building is in close proximity of a mature trees. This is a common problem found generally in the following species Oak, Poplar, Ash, Plane, Willow and Elm although any very large mature tree close to a building can spell disaster. These trees require a considerable amount of water to grow much of this is taken up by their root system. For example: a mature poplar can take up to 50,000 litres of water from the sub-soil each year.
The more mature the tree the greater amount of water it requires. The outcome of the site survey and soil investigation should inform the decision on the type of substructure to be used for the proposed buildings in relation to soil type, saturation levels and lay of land e. g. sloping etc. It is recommended that buildings be built at least a distance equivalent to the tree’s height away from that tree to protect both the tree and the building although in some cases of Willow, Poplar and Elm the root radius can be twice that of the tree height. DEFECTIVE AREA: * The trees potential root radius has not been calculated correctly * Poor choice of substructure for the new building| DEFECTIVE CORRECTION REQUIRED: * Repair works require the retrospective installation of a root barrier (see attached diagram). This means detailed surveys are required to identify were the tree roots are. If the tree has a Tree preservation order (TPO) on it then any damage to its roots could mean an appearance in Majesties court and a fine up to ? 20,000| RELEVANT BRITISH STANDARD:| * BS:5837 * Approved Document A & C * Tree Preservation Orders: A Guide to the Law and Good Practice 2000|
STAGE:A| WORKS/JOB SHEET NO. 22| LOCATION:Flank wall| DATE:26th May 2010| BRE REF NO. Defect Action Sheet | DEFECT: Poor Mortars, Bricks, Blocks in sub-structure| CAUSE: Poor design and specification Poor site supervision| FUNCTION:Mortar is used a bonding agent to secure brick and block work. These three elements used together ensure that the building is sound, secure and water tight. | DEFECTIVE AREA: * Poor specification of an inferior brick and blocks that are engineered to support the loadings of the finished building is poor design planning.
A poorly specified mortar could also be the reason that water could ingress the building this could lead to significant problems later for the building. * Poor site supervision of this area could mean that the mortar is poorly laid or not given enough time to set, or could even have been laid in the wrong temperatures such as Frosty weather. | DEFECTIVE CORRECTION REQUIRED: * The building may require additional support. For example: underpinning externally could support the substructure sufficiently enough to take the load away from the problem areas. The best method in this case is to pile and beam. This method stabilises the existing substructure by using piles installed either side of an existing wall. A small excavation is made below the ground level and a reinforced concrete needle beam is used to connect the piles and support the wall. * Reducing the distance between needle beams can accommodate very high loads. | RELEVANT BRITISH STANDARD:| * | STAGE:D| WORKS/JOB SHEET NO. 24| LOCATION:Internal/External various locations| DATE:26th May 2010| BRE REF NO.
Defect Action Sheet | DEFECT: Notches and holes for services mis-positioned and oversized| CAUSE: Poor design Poor site supervision| FUNCTION:The location of holes and notches for services is very important in relation to the functionality and quality of finish to the end building. A misplaced large hole could lead incorrectly fitted lighting, heaters, light switches etc. | DEFECTIVE AREA: * Poor design drawings that are sent to site with the wrong measurements could mean that the location and shape of the holes for services are installed as per the drawing. It is more lightly that this defect would be down to poor site supervision. This could mean that the inappropriate person has been tasked to carry out this work such as a labourer that does not have the skill to read drawings but was asked to install holes for services rather than an electrician or electrician’s mate (i. e. being supervised by the trade lead at all times)| DEFECTIVE CORRECTION REQUIRED: * If caught early enough this should not be a great problem to resolve on site.
However, if this was left to practical completion were the building is being handed over to the user/occupier then the works to rectify could be much greater and could include the following: * Re-routing electrics and mechanical pipe works to suit correct dimensions * Repositioning of all electrical and mechanical equipment * No direct connection to main sewer therefore re routing all connections to bathrooms, kitchens and any sinks etc| RELEVANT BRITISH STANDARD:| * | STAGE:D| WORKS/JOB SHEET NO. 30| LOCATION:Door No. GF32| DATE:26th May 2010| BRE REF NO.
Defect Action Sheet | DEFECT: Lintels in external walls: missing, damaged, bedding, insulation| CAUSE: Poor design and specificationPoor site supervision| FUNCTION:A Lintel is a piece of steel or concrete that is used as a support in walls. These are generally used above openings (such as windows or doors) in the wall to support the load above. Lintels are usually supplied with load bearing at each end for 100mm openings up to/including 1000mm, 150mm for openings up to/including 3000mm and 200mm for openings over 3000mm. For spans in excess of 1200mm, it is good practice to provide temporary support such as an Acro at every 1200mm point. DEFECTIVE AREA: * Poor design could mean that the location window or door opening is in a difficult position to properly fit the correct size lintel * Poor specification could mean that a concrete lintel is specified when the location requires a small and compact steel lintel * Poor site supervision could mean that the area were the lintel is to be installed in not supported prior to installation and therefore the floor above is already sagging with the load. Also installation of the wring lintel in time will show on the exterior and interior of the building. DEFECTIVE CORRECTION REQUIRED: * Lintels should be carefully bedded on a full mortar joint * Wall ties should be positioned in accordance with current building regulations * A damp proof course should be used for all lintels in external walls, and must be fixed in accordance with building regulations * In cavity construction, it is recommended that both internal and external leaves are taken up uniformly * It is good building practice to insert a flexible joint between the lintel and the top of the frame| RELEVANT BRITISH STANDARD:| * BS:12 * BS:882|
STAGE:E| WORKS/JOB SHEET NO. 20| LOCATION:| DATE:26th May 2010| BRE REF NO. Defect Action Sheet 73 & 74| DEFECT: Floor joist quality and installation: not graded or marked, bowing and twisting, high moisture content and wet rot| CAUSE: Poor specification Poor site supervision| FUNCTION:A floor joist is a beam of wood that stretches from one side of the sub-floor to the other bridging the floor load bearers. They are the essential component to the foundation of each floor level and floor boards are laid onto of them to give a foundation to any floor covering.
Wood should be marked Top/Bottom, be graded (for the load) and have a kite mark or brand number referring to BS: EN 14250. | DEFECTIVE AREA: * Poor specification of a floor joist can mean that the wood used is not the correct grading to support the load. This can mean that the floor in time will show effects of overload bowing and twisting are one of the signs. * Poor site supervision of this area could mean that the wood has not been stored correctly on site meaning that it is now warped and twisted and has high water content. If wet rot occurs it is generally at the bearings of timber joists in external walls.
For example: the sole or head plates rather than in the studs. | DEFECTIVE CORRECTION REQUIRED: * An assessment on if there is any ‘dead air’ within the cavity between the joists and the floor board. If so, then air bricks (to BS:493) can be installed into the external walls to allow air flow. If wet rot is localised in small area then minor repairs can be made * If poor ungraded wood has been installed then the floor will have to be taken up and reinstalled with the correct graded wood to ensure it complies with current building regulations. | RELEVANT BRITISH STANDARD:| * BS:EN 14250 * BS:493|
Area H: Defect| Drains below foundations| Reason for Defect:| * Broken or damaged pipes * Failure to washout subsoil leading to foundation settlement; * Lack of clearance to debris or materials * Lack of flexible joints. * Non compliance with Approved Document H * Non compliance with the Public Health Act revised 1985 * Non compliance with Building regulations C part 2 * Incorrect type and size of pipe used for subsoil drainage * Drainage not laid to correct gradient| Specification Issue:| * Possible poor quality drainage pipes specified| Design Issue: | No|
Site Supervision Issue:| * Compliance with Approved Doc H * Compliance with Public Health Act 1985 * Compliance with Building regulations C part 2 * Correct size and type of pipe use for each type of drainage identified e. g. foul, rainwater, soil type. * Ensure movement joints are in place * Ensure drainage meets the required gradient * Ensure pipes are clear from obstructions * Check pipes are not broken or damaged prior to installation. | Maintenance:| No|
Responsible area:| The above defect is due to poor management on site on manual labour workforce| Image:| Ref: Image taken from NHBC Good Craftsmanship Guide for Drainage| Area H: Defect| Installation of DPC and DPM| Reason for Defect:| * DPC pointed or rendered over * DPCs bridged by mortar droppings * DPM punctured * DPCs and DPMs not lapped * Fill and paving not kept at least 150mm below DPC * DPM should comply with BS CP 102, Section 3, and Building Regulations Approved Document C. | Specification Issue:| No| Design Issue: | No|
Site Supervision Issue: | * Check that edging of DPM projects enough to lap later with the DPC * Sheet should be sealed with adhesive tape and any punctures patched with an overlap of no less than 150mm * Use polyethylene sheet not less than 500 gauge and should carry a BBA certificate or is to the PIFA standard| Maintenance:| No| Responsible area:| The above defect is due to poor management on site on manual labour workforce| Image: | Ref: Image taken from http://www. bricksandbrass. co. uk/images/walls/damp. gif| Area H: Defect| Damp walls |
Reason for Defect:| * No DPC installation in walls * Poorly installation of DPC in walls| Specification Issue:| No| Design Issue: | No| Site Supervision Issue:| * A responsible contractor should understand the importance of DPC within the external walls * If just poorly installed retrospective DPC injections can be used to back fill in areas that require additional waterproofing * If no damp proof course is in place then Electro Osmosis method can be used this is when a low voltage steel stake is placed intermediately around the external walls as long as the unit is on it will keep the damp at bay | Maintenance:| No|
Responsible area:| The above defect is due to poor management on site on manual labour workforce| Image: | Ref: Image taken from www. petercox. co. uk/prevent| Area J: Defect| No lintel above the window and doors | Reason for Defect:| * No installation of lintel above window and door openings| Specification Issues:| * Possible incorrect lintel specified * | Design Issue: | * For an architect to exclude lintels from the design, it means that they have not complied with building regulations.
This is not only a design floor but a dangerous and hazardous way to leave the building| Site Supervision Issue: | No| Maintenance:| No| Responsible area:| The above defect is due to poor design management by the design team and should have been picked up by various professionals along the process including Building Control| Image: | Ref: Image taken from http://www. bancroftcentre. org/images/eco/insulation. bmp|
Area J: Defect| Plaster break up on internal walls and ceilings| Reason for Defect:| * Bond failure between plasterwork and plasterboard due to ‘watering down’ of bonding agent * Plaster itself poor quality or poorly mixed together (plasterer should have a mate to mix for them as plaster can ‘go off’ quickly) * Cracking due to movement * Drying out period hurried and room artificially heated to increase drying time| Specification Issue:| * Poor quality bond or plaster | Design Issue: | No| Site Supervision Issue: | * Remove poor quality plaster, apply a thick oat of Unibond allow to dry and then re-applying a suitably mixed plaster (plasterer should have a mate to mix for them as plaster can ‘go off’ quickly) * Ventilate and allow to naturally dry out| Maintenance:| * Poor maintenance of internal finishing can make plaster work decay and break up * Poor ventilation or extreme weather (if no heating) then plaster can become brittle and break up| Responsible area:| The above defect is due to poor management on site on manual labour workforce and/or poor maintenance by the occupier/users| Image:| Ref: Images taken from Google images ‘plaster work’|
Area J: Defect| Shrinkage to wooden floor joists| Reason for Defect:| * Temperature to install to extreme * Stored poorly on site allowing water to penetrate – Part C of the Building Regulations “Site preparation and resistance to contaminants and moisture” * Area needs better ventilation| Specification Issue:| No| Design Issue: | No|
Site Supervision Issue:| * A responsible contractor should have the knowledge and experience to know at what temperatures they can have to install after the installation * Air bricks may need to be installed in the external walls tp improve under floor ventilation * All materials should be stored off the ground and well covered in accordance with building regulations| Maintenance:| No| Responsible area:| The above defect is due to poor management on site on manual labour workforce| Image:| Ref: Image taken from Google images ‘defective timber joists’|
Area K: Defect| External wall movement| Reason for Defect:| * Incorrect substructure * Restraints missing from wall to floor| Specification Issue:| No| Design Issue: | * Substructure must be designed following an accurate soil survey, bore holes are taken from the proposed site and are inspected in laboratory condition. * The soil samples are tested and categorised in accordance with their load value * Then detailed calculations are erformed by structural engineers to establish the most suitable substructure for the proposed building * Below a ‘tell tale’ is a measuring device that can check how much a crack is moving over a period of time| Site Supervision Issue: | No| Maintenance:| No| Responsible area:| The above defect is due to poor design management by the design team and should have been picked up by various professionals along the process including Building Control| Image:| Ref: Image of a ‘tell-tale’ taken from Google images|
Area K: Defect| External wall movement| Reason for Defect:| * No cavity tray installed to discharge water outwards * No weep hole specified in brickwork at lowest tray * No flashing identified, Lead or a suitable substitute should be installed in accordance with BS 1178 * All roof tiles to Part C of the Building Regulations “Site preparation and resistance to contaminants and moisture”| Specification Issue:| No| Design Issue: | No|
Site Installation & Supervision Issue | * A responsible contractor should install cavity tray to ensure water is discharged correctly * Ensure appropriate weep hole is installed in the brickwork at the lowest tray level * Install appropriate flashings where required * Ensure tiles and drainage is compliant with Building Regulations Part C| Maintenance:| No| Responsible area:| The above defect is due to poor management on site on manual labour workforce| Image:|