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BUILDING SURVEYING IN CONSTRUCTION�

Dr Adewale Abimbola, FHEA, GMICE.

www.edulibrary.co.uk

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Aim & Objectives

  1. Identify common defects in ground floors, upper floors, stairs, and walls.
  2. Analyse the causes of these defects and their impact on building integrity.
  3. Evaluate appropriate repair and prevention strategies for external envelope defects.

At the end of the lesson, the students should be able to:�

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Defects to Internal Envelope

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DEFECTS TO INTERNAL ENVELOPE

Introduction

  • Properties require repairs for various reasons, and building surveyors play a crucial role in this process.
  • Understanding the need for repairs and the surveyor's responsibilities is essential for maintaining the built environment.

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Reasons for property repairs:

  • Natural wear and tear over time
  • Weather-related damage, Structural issues or subsidence
  • Outdated building materials or systems
  • Changes in building regulations or safety standards
  • Improving energy efficiency and sustainability
  • Enhancing property value or marketability

Roles of the building surveyor:

  • Conducting thorough property inspections
  • Identifying defects and potential issues
  • Preparing detailed condition reports
  • Recommending appropriate repair strategies
  • Estimating repair costs and timelines
  • Advising on compliance with building regulations
  • Overseeing repair works and quality control
  • Providing expert witness services in legal disputes

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Ground floors

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CAUSES OF DEFECTS – SOLID CONCRETE FLOORS

SULPHATE ATTACK

• Presence of sulphates in sub-base materials (e.g. red shale, industrial slags)

• Moisture allowing sulphates to migrate into concrete

• Lack of damp-proof membrane between sub-base and concrete

  • Absence or failure of damp-proof course
  • High water table or poor site drainage
  • Cracks in concrete allowing moisture penetration

POOR DETAILING/

CONSTRUCTION

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  • Deterioration of damp-proof membrane over time
  • Improper installation or damage during construction
  • Use of inadequate materials for membrane

MEMBRANE FAILURE

DAMP INGRESS

  • Inadequate concrete mix design
  • Insufficient curing time or poorly compacted concrete
  • Improper reinforcement placement or lack of insulation resulting in cold floors.

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CAUSES OF DEFECTS – SOLID CONCRETE FLOORS

SETTLEMENT

• Poor compaction of sub-base material/hardcore

• Inadequate foundation depth

• Changes in soil moisture content

• Cracking of unreinforced floor

  • Incorrect mix proportions
  • Premature drying of screed
  • Poor bonding to concrete substrate

EXCESSIVE SPANS

FOR PRECAST CONCRETE

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  • Expansive soil beneath the slab leading to movement and cracking
  • Chemical reactions in sub-base materials
  • Frost action in susceptible soils

HEAVE

SCREED FAILURE

  • Underestimation of load requirements may lead to the cracking of screed
  • Insufficient reinforcement
  • Inadequate support structure may lead to excessive deflection experienced in bouncing floors

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SOLUTIONS TO DEFECTS - SOLID CONCRETE FLOORS

SULPHATE ATTACK

  • Install effective damp-proof membrane
  • Replace affected concrete and sub-base material
  • Use sulphate-resistant cement in new construction
  • Install or repair damp-proof course
  • Improve site drainage
  • Apply waterproof coatings to concrete surface

POOR DETAILING/

CONSTRUCTION

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  • Install new damp-proof membrane where possible
  • Apply surface-applied tanking systems
  • Improve drainage around the building

MEMBRANE FAILURE

DAMP INGRESS

  • Remedial work to address specific defects
  • Overlay with properly designed concrete topping
  • In severe cases, complete replacement of affected areas

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SOLUTIONS TO DEFECTS - SOLID CONCRETE FLOORS

SETTLEMENT

  • Underpinning of foundations where necessary
  • Grouting to fill voids in sub-base
  • Installation of piled foundations in problematic soils
  • Removal and replacement of failed screed
  • Application of self-levelling compounds
  • Use of proprietary repair mortars for localised defects

EXCESSIVE SPANS

FOR PRECAST CONCRETE

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  • Excavation and replacement of expansive soils
  • Installation of heave-resistant membranes
  • Design of flexible floor systems to accommodate movement

HEAVE

SCREED FAILURE

  • Installation of additional support beams
  • Strengthening with carbon fibre reinforcement
  • In extreme cases, replacement with properly designed system

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CAUSES OF DEFECTS – SUSPENDED TIMBER FLOORS

ROTTING

• Excess moisture due to poor drainage or leaks

• High humidity in subfloor space

• Timber or wall plates in contact with damp masonry

  • Failure of damp-proof course
  • Rising damp from ground
  • Penetrating damp through walls

EXCESSIVE SPANS

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  • Blocked or insufficient air bricks causing fungal attack
  • High external ground levels restricting airflow
  • Poor cross-ventilation in subfloor void

LACK OF SUBFLOOR VENTILATION

DAMP INGRESS

  • Undersized joists for the load and span causing bounce
  • Removal of load-bearing walls below
  • Increased loading due to change in use

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CAUSES OF DEFECTS – SUSPENDED TIMBER FLOORS

INSECT ATTACK

• Presence of wood-boring beetles

• High moisture content in timber

• Lack of treatment to prevent infestation

  • Incorrect joist sizing or spacing
  • Improper bearing of joists on walls
  • Use of unsuitable timber species

END OF FLOOR JOIST TOUCHING INSIDE SKIN BELOW DPC

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  • Omission of herringbone or solid strutting
  • Inadequate lateral support for floor joists
  • Poor workmanship during installation

LACK OF STRUTTING

POOR DETAILING/CONSTRUCTION

  • Incorrect installation allowing moisture transfer
  • Settlement of building causing joist movement
  • Absence of proper joist hangers or support

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SOLUTIONS TO DEFECTS – SUSPENDED TIMBER FLOORS

ROTTING

• Identify and rectify sources of moisture

• Replace affected timber with treated wood

• Improve subfloor ventilation

  • Install or repair damp-proof course
  • Improve site drainage
  • Apply waterproof treatments to affected areas

EXCESSIVE SPANS

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  • Install additional air bricks
  • Lower external ground levels
  • Fit mechanical ventilation systems if necessary

LACK OF SUBFLOOR VENTILATION

DAMP INGRESS

  • Install additional support beams
  • Strengthen existing joists with flitch plates
  • Reduce loading or redistribute load paths

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SOLUTIONS TO DEFECTS – SUSPENDED TIMBER FLOORS

INSECT ATTACK

• Treat timber with appropriate insecticides

• Replace severely affected timber

• Ensure ongoing monitoring and treatment

  • Rectify specific defects as identified
  • Reinforce joints and connections
  • Replace unsuitable materials with appropriate alternatives

END OF FLOOR JOIST TOUCHING INSIDE SKIN BELOW DPC

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  • Retrofit herringbone or solid strutting
  • Install steel straps for lateral support
  • Reinforce joists at mid-span

LACK OF STRUTTING

POOR DETAILING/CONSTRUCTION

  • Install proper joist hangers
  • Create air gap between joist end and wall
  • Apply localised damp-proofing measures

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Self-assessment Task

1a) How do ground floor defects affect a building?

1b) Research the symptoms that a surveyor is likely to see that indicate the need for remedial works.

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Upper Floor

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CAUSES OF UPPER FLOOR DEFECTS

LACK OF SUPPORT AND STRUTTING

  • Omission of herringbone or solid strutting
  • Inadequate lateral support for floor joists
  • Poor workmanship during installation
  • Incorrect joist sizing or spacing
  • Improper bearing of joists on walls
  • Use of unsuitable timber species

LACK OF SUPPORT TO JOIST END:

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  • Exceeding design load capacity
  • Changes in room use without structural assessment
  • Addition of heavy furniture or equipment

OVERLOADING

POOR DETAILING/CONSTRUCTION

  • Insufficient bearing area on walls
  • Deterioration of joist hangers
  • Settlement of supporting walls

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CAUSES OF UPPER FLOOR DEFECTS

  • Excessive notching for services
  • Improper placement of holes in joists
  • Unauthorised alterations to floor structure

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ALTERATION AND SERVICE HOLES/NOTCHES INTO TOPS OF JOISTS

FAILURE OF MECHANICAL FIXINGS BETWEEN BOARDS AND JOISTS

  • Corrosion of nails or screws
  • Inadequate number or size of fixings
  • Movement causing fixings to work loose

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INSECT AND FUNGAL ATTACK

  • Presence of wood-boring beetles
  • Dry or wet rot in timber elements
  • High moisture content in floor void

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SOLUTIONS TO DEFECTS - UPPER FLOOR DEFECTS

LACK OF SUPPORT AND STRUTTING

  • Retrofit herringbone or solid strutting
  • Install steel straps for lateral support
  • Reinforce joists at mid-span
  • Rectify specific defects as identified
  • Reinforce joints and connections
  • Replace unsuitable materials with appropriate alternatives

LACK OF SUPPORT TO JOIST END:

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  • Conduct structural assessment and reinforce as needed
  • Redistribute loads or add additional support
  • Educate occupants on floor load limits

OVERLOADING

POOR DETAILING/CONSTRUCTION

  • Install proper joist hangers
  • Increase bearing area on walls
  • Underpin or strengthen supporting walls if necessary

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SOLUTIONS TO DEFECTS - UPPER FLOOR DEFECTS

• Assess structural integrity and reinforce where necessary

• Use steel plates to strengthen weakened areas

• Reroute services to avoid further damage

ALTERATION AND SERVICE HOLES/NOTCHES INTO TOPS OF JOISTS

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FAILURE OF MECHANICAL FIXINGS BETWEEN BOARDS AND JOISTS

  • Replace corroded or damaged fixings
  • Increase number or size of fixings where necessary
  • Use specialist flooring adhesives in conjunction with mechanical fixings

INSECT AND FUNGAL ATTACK

  • Treat timber with appropriate preservatives
  • Replace severely affected timber elements
  • Improve ventilation in floor void to reduce moisture

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Stairs

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CAUSES OF STAIR DEFECTS

STRUCTURAL ISSUES

  • Inadequate support for treads and risers
  • Loose or missing wedges under stairs
  • Broken or worn treads, especially on winders
  • Loose or damaged carpeting on stairs

MATERIAL DETERIORATION

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  • Inconsistent tread width or riser height
  • Inadequate handrail support

POOR CONSTRUCTION

WEAR AND TEAR:

  • Rotting or warping of wooden frames
  • Corrosion of metal components

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CAUSES OF STAIR DEFECTS

Moisture Problems

  • Decay in wooden components due to damp conditions
  • Rising damp affecting lower steps

Safety Hazards

  • Missing or loose handrails
  • Insufficient lighting on stairways

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SOLUTIONS TO DEFECTS - STAIR DEFECTS

STRUCTURAL REINFORCEMENT

  • Install additional support beams where needed
  • Replace or secure loose wedges under stairs
  • Replace broken treads or damaged carpeting
  • Reinforce weak areas with steel plates

REGULAR MAINTENANCE

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  • Improve subfloor ventilation
  • Address sources of damp and install damp-proof courses

MOISTURE CONTROL

REPAIR AND REPLACEMENT

  • Address minor issues promptly
  • Install or repair handrails

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Group-assessment Task

  • Collect at least five photos of internal walls (masonry and timber) defects.
  • Discuss with your group the possible causes of each one.
  • How do you think they can be repaired?

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Bibliography

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