Live your life. Create your destiny. Housing in South Africa - What DID the 3 little pigs teach us in 2010

Transcription

1 Live your life. Create your destiny. Housing in South Africa - What DID the 3 little pigs teach us in 2010

2 Fred S Crofts (Pr Eng) Consulting Engineers CC MASONRY CONSULTANTS Property Valuers erect@iburst.co.za

3 Overview of paper? Introduction What DID the three pigs know Standards & legislation Cost of walls Sustainable Design Alternative Building Materials (2 Pigs) Traditional Masonry (1 st Pig) Swot analysis Conclude

4 What DID the pigs know NBR (National Building Regulations) SANS Application of the NBR, Part K - Walls A wall must comply to 4 criteria (Simplified): Structural integrity K1 Keep water out K2 Keep roof down K3 Keep fire out K4 NBR does not prescribe material K5 Deem-to-satisfy requirements: - K1, K2, K3, K4 = > Building limitations for empirical rules NBR - Simplified rules for masonry

5 What DID the pigs know (cont) Not compliant with the NBR deem-to-satisfy rules => non conventional building system: Problems - plan approval with Local Authority Problems mortgage lending approval Market value of dwelling Social resistance Address non compliance with the NBR?: => Rational design by a competent person => Agrément certification (innovative or non-standardized building systems) Time and Cost?

6 What DID the pigs know (cont) JSD of the SAICE (Joint Structural Division of the South African Institution of Civil Engineering) Assessment of the performance of housing units in South Africa. Johannesburg, June It is generally accepted that where minimum structural performance criteria for housing have been established, structural engineers can design in a more cost efficient manner. In the absence of such criteria, there is a marked tendency to over-design structurally with wasteful expenditure or to overlook local materials with unknown performance characteristics (JSD, 2000).

7 What DID the pigs know (cont) JSD, 2000 Contents? Two-user performance levels are recognised: User performance level 1: basic shelter/starter units low initial cost short maintenance cycles mortgage lending finance is not involved limited moisture penetration User performance level 2: Focus is on producing a durable house infrequent maintenance mortgage lending finance limited moisture penetration

8 What DID the pigs know (cont) JSD, 2000 Contents? Structural performance criteria: Sub-structure requirements: Minor movement at foundation level Superstructure requirements: Structural strength & stability: => ground movements => winds (50-year recurrence interval) => thunderstorms Robustness (walls): => resistance to impact (daily use) => localised blows (furniture) => door slamming/support fixtures => hail resistant

9 What DID the pigs know (cont) JSD, 2000 Contents? User performance level 1 & 2: Soft body impact: Impact resistance in Joules (appreciable cracking & collapse)

10 What DID the pigs know (cont) JSD, 2000 Contents? User performance level 2: Hard body impact: Resistance in Joules

11 What DID the pigs know (cont) Cost case study: Cost of masonry walling expressed as total building cost (2006) Courtesy NTS vd Walt (QS). Dwelling unit = 267 m 2 (double storey) Footprint = 151 m 2. Total cost = R 1,048m Case 1: Face brick (FBA) and mortar: Face brick = R ,00 Mortar = R ,00 Walling = 18 % of total cost Mortar = 4,3 % Case 2: Stock brick (NFP) and mortar: Stock brick = R ,00 Mortar = R ,00 Walling = 17 % of total cost Mortar = 6,4 % => Masonry envelope is not the bulk of the cost

12 Sustainable Design Emphasizes has shifted: Energy, efficient buildings and systems Renewable, recycled & non-toxic & abundant resources Reduce energy consumption & environmental impact Green buildings Life cycle costing/life cycle assessment of buildings are terms that have become commonplace with economic decisions for selection of building materials and to compare the economics of different building alternatives

13 Alternative building materials Straw bale houses (and other) 1 st Pig Courtesy: Chistiaan Van Zyl (Orania) Alternative to traditional building materials Straw bales are very renewable as a resource Cut down on energy consumption Down side of the use of this material?

14 Alternative building materials Timber houses (2 nd Pig) Alternative to traditional building materials NBR Compliant: Rational design: SANS 1082 Timber Buildings Accepted by Local Authorities & Mortgage Lenders Maintenance, sound insulation & fire

15 Traditional masonry Masonry house (3 rd Pig) House complies with the requirements in NBR Auxiliary building products are available and affordable Building details are proven and tested

16 Traditional masonry SWOT Analysis (Courtesy John Lane) Strengths Traditional building material Well established masonry units (fired clay & concrete) SANS Standards & specs on all aspects of design, construction & materials Associations: Concrete Manufacturers Association made available technical and trade literature => build with confidence

17 Traditional masonry SWOT Analysis (Courtesy Curtain et all) Strengths (Continued) Speed of erection Aesthetics Durability Sound insulation Thermal insulation Fire resistance Repair and maintenance Ease of combination with other materials Availability of material and labour?

18 Traditional masonry SWOT Analysis (Courtesy J Lane) Weaknesses Poor workmanship & detailing Apprenticeship no longer exists Skill training of limited value Lack of education at tertiary institutions Backyard manufacturers lack of manufacturing knowledge Sub-standard buildings arising from poor materials & workmanship (serviceability) Inadequate reference to application of good building practice despite SANS documents & CMA literature

19 Traditional masonry SWOT Analysis (Courtesy J Lane) Threats Losing masonry wall market to high maintenance wall materials viz, plastic, board Losing masonry wall market due to inadequate technical information viz material properties, ease of defect repair Dropping appropriate standards of manufacture, design & construction due to political (& other) pressures Image of industry (after economic boom) OhsAct Increased regulations

20 Traditional masonry SWOT Analysis (Courtesy J Lane) Opportunities To market the advantages of masonry over other materials, value for money, strengths & durability To market life-cycle costing of masonry buildings Exploiting thermal properties of masonry dispense with a/c To market low operating cost of masonry buildings Collection of meaningful statistics and to predict trends costing, etc. Assist new/small manufacturers

21 Traditional masonry SWOT Analysis (Courtesy J Lane) Opportunities (Continued) For clay & concrete masonry industries to combine on joint projects & to promote masonry, technical literature & provide combined leadership To research aspects of masonry where weaknesses exist To unify existing standards (Eurocode 6) To create new users of masonry To provide training to building professionals on design detailing, specifications, con= struction & supervision and testing

22 Traditional masonry SWOT Analysis (Courtesy J Lane) Opportunities (Continued) To liaise with allied industries masonry accessories To disseminate technical information to professionals => quicker designs To address material shortages when demand exceeds supply

23 Conclusion In the famous parable, two of the three little pigs constructed their houses in a non-durable manner, albeit with renewable, green, sus= tainable materials (Courtesy Olson, et all) Only the masonry house had qualities enabling it to serve its intended purpose to endure The wall component in a house is a small % of the total cost Masonry is still the preferred material for the provision of housing by consumers, mortgage lenders and complies with the NBR Based on a swot analysis of the masonry industry in South Africa it has the potential to improve the delivery of future housing

24 Conclusion Concrete masonry => sustainable material - manufactured from waste material If the behaviour of masonry materials is well understood: => defects will be reduced => life-cycle & operating costs of a building will be reduced => durable construction

25 Conclusion Based on the scientific folk wisdom of the three pigs.. masonry is here to stay