BUILDING PATHOLOGY & DILAPIDATION Unit 2 Property Surveys

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Wilfrid Harmon
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1 BUILDING PATHOLOGY & DILAPIDATION Unit 2 Property Surveys

2 2.1 Learning Objectives Understand the two main types of property surveys Differentiate the different property surveys and describe their purpose and objectives Explain the degradation model of a building and using the model to understand Building Pathology and Dilapidation 2

3 2.1 Synchronic Assessments Provide an assessment of a building or a comparison of a group of buildings and their performance or condition at a particular moment or period in time. Typically preferred by building surveyors, planners and architects interested in comparing current condition or looking for current design specifications and fashion. Building surveys, condition surveys and dilapidation surveys are typical examples of synchronic assessments. 3

4 2.1 Diachronic Assessment Provides an indication of how buildings change or evolve over time. Typically the process deployed by architectural historians and building maintenance surveyors who wish to appraise condition or performance over a measured period of time. Maintenance surveys, heritage or conservation plan inspections and historical surveys of older properties are typical methods of diachronic assessments. 4

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6 2.2 Types of Property Surveys The main types of survey are classified according to their function as follows: Acquisition- involves a survey and valuation of the property on behalf of the prospective purchaser. Records general conditions. Identify and record issues which are likely to have an impact on current or future value of the acquisition. Lease-related- schedules of dilapidations or repair schedules can be prepared for landlords or tenants. Highlight the need for repair or reinstatement of elements at salient points in the lease. 6

7 2.2 Types of Property Surveys Investigation- typically a highly specialized and focused investigation, concern failure or defect. Can also include remedial actions and costs to remedial works by specialist, e.g. structural engineer. Record- undertaken, typically to provide information on the condition of a number or stock of buildings at a specific moment in time. Measured surveys are also used to provide accurate dimensioned information on buildings prior to more detailed surveys or refurbishment. Reinstatement- typically undertaken on behalf of insurance companies to determine the extent and costs of reinstatement works, to determine risks associated with, damage to the building. 7

8 2.2 Classifications of survey Surveys can be classified by level as the following: Scheme 1- The Mortgage Valuation, prepared for the lender not for the borrower. A brief superficial inspection of the property. Scheme 2- Homebuyer Survey and Valuation is based on RICS and provide prospective purchaser information on:- The general condition of the property, Any significant factors likely to affect materially the value of the property, The value of the property in the open market, The value for insurance purposes. Scheme 3- Building or Structural Survey is a detailed inspection lasting typically 2-4 hours. Then inspections includes the exterior and interior of the building, service installation, drainage, grounds and outbuildings. Report includes guidance on maintenance and remedial works and detailed comment on individual defects as well as comments on possible improvements (if required). 8

9 2.3 Degradation Model Deterioration begins as soon as a building is completed and begins the incipient stage. The rate of this incipient stage depends on the inherent properties of the material, the quality of detailing and construction and the aggressiveness of the environment. The end of the incipient stage may be as early as 15 years or as long as 50 years. Accelerating stages begins after the incipient stage with the failure of the first major sub system and extends to a point of zero utility. This ultimately leads to the overall failure of all the building systems. Decelerating stage is that state of the building whereby all functions fail and is left for ruins. 9

10 2.3 Degradation Model Examine the life stages of a building by examining the effective life span of its building elements, systems and materials. 10

11 2.4 Deterioration mechanisms The performance of fabric of a building is reduced or undermined by two primary influences: Climatic agencies (environmental influences) - external influences, e.g. rain, snow and wind which can impact critically on the internal environment and fabric. User activities (functional influences) internal influences, e.g. misuse or poor maintenance, which can also have an adverse effect on the external building fabric. 11

12 The following list highlights the key deterioration mechanisms: Chemical- juxtaposition(combination) of incompatible materials or contamination close to building. Solar radiation - absorption of infra-red radiation results in surface temperature increase resulting to movement of material leading tom cracking and crazing. Mechanical - impact in surface resulting to wear and tear and extreme cases cracking and deformation of wearing surfaces. Biological - attack by moulds, fungi and insects to timber products due to damp and stagnant conditions. 12

13 The following list highlights the key deterioration mechanisms: Hygro-thermal - moisture and temperature work together to create an aggressive environment, e.g. condensation. Freezing of water causes expansion in building materials once temperature drop below zero. Stress - material movement that are restraint due to shrinkage or expansion, the stresses can result to serious disruption e.g. cracking, splitting, bending or deflection. Stress from dead and live loads within buildings could affect the structural elements. Use - natural wear and tear and lack of regular maintenance will result in deterioration and reduce life span. 13

14 2.5 Effective Building Life Span Through life issues Durability- is the ability of a material component or building system to resist the effects of deterioration. Changeability of buildings- negate(exclude) the need for large factories, lack of maintenance Service life prediction- service life of material or component Whole life costs- cradle to grave costs & revenues Maintenance cycles- undertaken during service life 14

15 2.5 Through life issues Shearing layers of change- view buildings as a set of components that evolve in different timescales. The layers are as follows: Site- geographical, location, legal plot, boundaries. Structure- the foundations and the frame. Skin- the façade. Services- M&E, HVAC. Space plan- interior layout. Stuff- furniture and fittings. Souls- the occupants. 15

16 2.5 Different types of ageing All materials, products and components age, figure below is a graphical representation of different types of ageing. 1. Ideal performance profile - there is no drop off in performance over the life of the product. However due to natural deterioration, ageing and use this is unobtainable. 2. Abrupt - sudden failure following a period of slow linear deterioration in performance over time. Associated with building services materials and 3. systems. Linear - typical failure of building materials which perform effectively and deteriorate over a fixed period of time. 4. Exponential - this is typified by a slowing up of the rate of deterioration over the service life of the product. 5. Minimum acceptable standard - a level of life expectancy which must be obtained either due to economic, social, 16 environmental or practical

17 2.5.2 Deterioration and time relationships Highlights the deterioration over time relationship for maintained and unmaintained buildings. The points A through D represent the stages of accelerated deterioration. The structures which has been repaired at point A cost less and last longer than the structures left and maintained at B. 17

18 2.5.2 Bath tub failure The bath tub represents the typical service life model for many components or systems (buildings). In the early stages of life there is potentially a high risk of failure which level off, increasing again towards the end of the service life. 18

19 Service life assessments Service life assessment is typically defined as: A methodical approach to predicting the durability of materials and components. PREDICTION A structured, traceable method to manage the risks inherent in construction procurement. RISK MANAGEMENT A mechanism for information management which allows the involved parties to learn from best practice and poor performance. EXPERIENCE A system to demonstrate value for money in construction procurement. VALUE A method to assess the implication of variations during the project and mitigate the impact of such variations. CHANGE 19

20 Types of service life Aesthetic- looks of the building can influence the overall service life. Wear and tear of the building fabric can have detrimental effect on appearance, thereby affecting the user s perception of quality and enjoyment. Physical- as materials, components or systems become defective or require increasing maintenance to remain effective they are considered to be approaching the end of their service life. Economic- commercial or economic decisions can determine the effective life span of the building. Low rise building can be demolish to make way for high rise development. Refurbishment of conservation building could be more costly then re-building new ones. Design- the service life of the building is design to meet clients intended requirements without over or under design and create low operation cost. 20

client s minimum acceptable condition beyond the required service life.

21 The curves shown indicate the results from two design options. Design A clearly deteriorates quicker than Design B, which exceeds the client s minimum acceptable condition beyond the required service life. Design A, unfortunately, falls below the acceptable minimum prior to the required service life. 21

22 Sources of service life data Experience using knowledge and experience to understand various building properties behaviour on their life span. Modelling- using computer mathematical or small scale testing to simulate the prediction performance of the building. Testing- the routine and standard testing of materials and components to obtain typical properties from which service life predictions can be made and compared. 22

23 Methodology for determining service life Identification of key criteria: in order to determine or predict service life, a number of data need to be collected, assessed or considered. There are as follows: Performance characteristics- the requirements of the clients such as materials, quality, performance, life span. Exposure conditions- the environmental conditions which will be experienced over the life of the building. Site examination- the local location; topography; natural exposure; proximity of aggressive environments. 23

24 Methodology for determining service life Tests: the undertaking of routine tests and the collection of standard performance data or data or result which allow the comparison between similar components and exposure regimes and the subsequent prediction of service life. also provides an indication of the limits of performance which enables the designer to provide protection to the building to ensure service life is achieved. 24

25 Methodology for determining service life Diagnosis- by examining current or existing building performance and in particular failures, which highlight limits of performance, the designer can more accurately predict expected performance. Prognosis- the prediction or forecast of a likely course of events. Having gathered data on existing condition or performance the designer is able to make an educated prediction or forecast of future performance. Therapy- the treatment or remedial action proposed to reduce or remove the effects of a disorder or defect. Proposals which may improve or enhance the performance of a component or which may provide a solution to an existing defect or failure. 25

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