Measurment Lecture 2

• The presentation covers SEHS3290, Measurement, Documentation and Estimating.
• The lecture focuses on the Measurement of Excavation and Concrete Works.
• Dr. Joseph Chan is the presenter.

Contents Overview

• Introduction to the format of HKSMM4.
• Measurement of excavation.
• Measurement of foundations.
• The presentation includes an in-class exercise.
• Measurement of concrete works.

Introduction to the Format of HKSMM4

• The lecture references HKSMM4 as its basis.
• HKSMM4 provides information in the form of:
  • Classification table
  • Measurement rules
  • Supplementary rules

General Principles of Measurement

• Bills of Quantities (BoQ) should accurately represent the work with clear descriptions of materials and workmanship.
• Supplementary information defining tolerances, methods, or sequences must be included in the descriptions or elsewhere to clarify the work's nature.
• This Standard Method of Measurement provides uniform units of measurement.
• Discretion is expected in special cases but should remain clear to the estimator.
• More detailed information can be provided for improved accuracy.
• Deviations and qualifications to the standard method shall be stated in the BoQ preambles or item descriptions.
• Measurement methods should apply to both the preparation of BoQ before work and the measurement of finished work.
• Linear measurements are taken to the nearest whole meter.
• If the unit of billing is the metre, quantities are billed to the nearest whole unit; fractions less than half are disregarded.
• Kilograms are billed to the nearest whole unit.
• Dimensions should be given consistently in the sequence of length, width, and height.

Measurement of Excavation

• Site clearance and excavation are part of the first construction procedure.
• Major work items are covered in Section VI of HKSMM4.
• In general, the nature of the soil should be described in the documentation.
• The items covered include site clearance, excavation, earth support, disposal, backfilling, filling, hardcore or granular filling, blinding, and surface treatment.

Site Clearance

• Site must be cleared before construction work begins by removing trees and brushes.
• Stumps and roots must be removed resulting in a level ground surface.
• HKSMM4 P.45 lists to items to be included.
• Refer to Figure 12.1 in the notes for measurement of tree girth.

Excavation

• According to HKSMM4 P. 46, VI (a).C.3 excavation includes excavation in any ground encountered.
• Contractors take on the risk excavating in any encountered ground including rocks.
• The rule applies to surface, trench, and basement excavation work.
• For surface excavation and over site excavation to reduced level, the average depth is less than or equal to 0.20m, measured in square meters.
• Over site excavation to reduced level is more than 0.2m deep.

Excavation for Basements and Foundations

• Refer to VI(a).3.4-3.7 for excavation rules for basements, trenches below basement level, foundations, etc.
• Measurement is done in cubic meters.
• State the commencing level.
• Measure in successive stages of 1.50m.

Working Space

• VI(a)..M2 states that working space needs to be included according to the following.
• Allow 0.25 m working space if formwork does not exceed 0.60m high and the bottom of the formwork does not exceed 0.60m below the starting excavation level.

Measurement of Foundation

• Foundations usually use replacement nature bored piles formed in-situ, using a non-percussion approach.
• Bored piles cast-in-place concrete on the construction site.
• A bored piling machine casts the piles using designed drilling tools, buckets and grabs, to remove soil and rock.
• Drilling can reach depths of 50 meters.
• Reinforcement bar put into bore hole; concrete poured into the bore hole.
• The method produces less vibration and noise.
• Bored piling is often used in construction as a foundation, especially for bridges and tall buildings.

Measurement of Concrete Works

• Refer to Section VII(a).1 Concrete Works.
• Concrete is generally measured in cubic meters, unless otherwise stated.
• Different concrete mixes should be measured separately (e.g., Grade 45/20).
• Formwork is measured to the surface of the finished structure that requires support during casting; refer to VII(d).M1.

Concrete Types and Components

• Reinforced in situ concrete and plain in situ concrete.
• Watertight reinforced concrete.
• Concrete in casing to structural steelwork.
• Precast concrete.
• Prestressed in situ concrete and precast prestressed concrete.
• Lightweight concrete.
• Gun applied reinforced concrete, measured in square meters.
• Common components: Blinding layers, small bases for fencing posts, beds, surface channels, foundations, column bases, pile caps, suspended slabs and roofs , strings, filling, walls, columns, piers, and staircases.

Concrete in Slab and Beam

• Slab dimensions measured across beams and columns

Concrete Walls

• Concrete walls are measured between columns or projections and up to the soffits of beams and slabs.
• If the width of a column is four times greater than its thickness, it is classified as a wall

Measurement of Formwork

• Section VII(d).1 governs formwork.
• Measurement is in square meters unless specified otherwise
• Includes formwork that produces a fair faced finish.
• Left-in, permanent to both faces, and permanent to one face only formwork.
• Includes formwork to different components of the buildings.
• For Soffits refer to Section VII(d) 2-3 and the following steps.
  • Measure overall slab area.
  • Deduct area of beam soffits.
  • Deduct wall and column area on the plan.
  • Adjust for other items (e.g., deductions for openings).
• Main forms include slab soffits and for landing soffits.
• Wall faces can occur in the vertical, sloping and curved orientation.
• Sides of piers, columns and stanchions can occur in different axis.

Formwork to Slab and Beam Soffits

• Heights of the struts are measured from level of the concrete
• Formwork to the side will include formwork to the beam
• Formwork to the edge will include formwork for edge of the beam

Formwork to Walls and Columns

• No formwork to sides of columns or edges of walls shall be measured for the junction between structural walls and columns.
• Section VII(d).5-6 specifies that it is only be measured to each wall requiring support.

Formwork to Beams

• Section VII(d).7: Measure formwork for the sides and the soffits together.
• Do not add any additional formwork for secondary beams where the the main intersect.

Measurement rule for VII(c) Reinforcement

• Reinforcing bars shall be measured separately according the the following points.
• Different types of steel.
• Different bar sizes.
• Fabric reinforcement to BS4466:1989 or BS8666:2005 clear formulae for different bending shapes.

Unit Weight

• Reinforcement shall be measured in kilograms except for the reinforcement mesh as square meters
• Instead of using the drawings measure the weights
• Take the lengths of the rebars and convert to weights

Reinforcement (Rebar)

• Round, indented, and square bars should be accounted for in measurement.
• Fabric must be flat as per the Engineer and designed according to specification.
• Measure the couplers but not the openings
• Use a detail description with detail of weight
• All proprietary should contain manufacturers reference