CMT3212 Chapter 4

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CMT3212 Measurement of Construction Works I KIST Level 2/1

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4.0 Measurement of Substructure

4.1 Introduction

Substructure is a term used to indicate all

supporting building work in the groundbelow a specific demarcation line, usually the

damp proof course.

The substructure therefore includes the

following trades or work sections.

1. SITE PREPARATION.2. EXCAVATION.3. DISPOSAL OF WATER.4. PLANKING AND STRUTTING.5. HARDCORE FILLING.6. PLAIN CONCRETE AND

REINFORCED CONCRETE.

7. REINFORCEMENT.8. FORMWORK.9. PRECAST CONCRETE UNITS.10.WALLING.11.DPC.

The above follow the order in which the

items of work appear in the SMM.

4.2 Site Preparation

Site preparation is one of the first operations

carried out on a site. SMM clauses D2, D3

and D4 provide the rules for measurement of

anti-termite treatment, preservation of

vegetable soil and removal of trees, hedges,

bushes and scrub and tree stumps.

(1)Anti-termite treatment to sub-soil orfilling is measured in square metres

(SMM D2 (a)). The removal of termite

nests shall be given as an item and the

method of destruction of the termites

stated.

(2)Oversite excavation is measured tothe extreme dimensions of the

building including the splash apron.

Excavating vegetable soil which is to

be preserved shall be measured insquare metres stating the average

thickness (SMM D3). If there is no top

soil (vegetable soil) or if the vegetable

soil is not preserved then the

resultant excavation is measured as

reduce level excavation either in m2

or m3 as per SMM D6.

The oversite excavation must be

completed before the measurement

of excavation of trenches or pits of

which the depth is calculated from

this reduced level (also known as the

commencing level of excavation).

(3)Clearing the site of vegetation such astrees, bushes and scrub or hedges is

measured in either square meters,

enumerated or in linear metresdepending on the convenient unit of

measurement. Trees over 600 mm

girth, and tree stumps (stating thegirth) shall be enumerated. The girth

is measured at a height of 1m from

the ground (SMM D4 (a), (c), (d) and

(e). Cutting down hedges is measured

in linear metres (SMM D4 (b) while

clearing the site of bushes is measured

in square metres (SMM D4 (c).

4.3 Excavation

In the measurement of excavations, it should

be noted that the quantities are measured

nett without addition or allowance for

bulking and shrinking (SMM D5 (a)), and

working space (SMM D5 (g)).

Excavation is therefore measured to the

shape shown on the drawings. Any working

space required and any bulking of the soil will

be included in the unit rate of theexcavations by the estimators.

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Picture showing an excavated trench for

foundation.

Excavating trenches to receive foundations is

measured in cubic metres (SMM D9) stating

the starting level and the depth in 1.5 mstages (SMM D5 (f).

Excavating pits to receive bases shall be

measured in cubic metres (SMM D10) stating

the starting level and the depth as

aforementioned.

Earth backfilling and Surplus spoil shall each

be given in cubic metres (SMM D15 (c) and

(f) respectively.

4.4 Disposal of Water

Keeping excavations free from water (i.e all

water except spring or running water) shall

be given as an item (SMM D18 (a).

4.5 Planking and Strutting

Picture showing upholding the surfaces ofexcavations.

Planking and strutting to uphold the sides of

excavations shall be measured as an item(SMM D19).

4.5 Hardcore Filling

Hardcore is either measured in m2 or m3

depending on whether or not it is more than

300 mm thick. Hardcore is measured as

equal to the void to be filled (i.e between the

walls).

Picture showing hardcore filling. Notice thehardcore is placed between the walls.

Hardcore less 300 mm thick is measured in

m2 stating the thickness (SMM D20).

4.6 Plain and Reinforced Concrete

Picture showing pouring of concrete infoundations in trenches.

Plain in-situ concrete shall be given under an

appropriate heading (SMM F2 (a)). Reinforcedconcrete shall be given under an appropriate

heading (SMM F2 (b)).

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Generally for Concrete the following shall be

included in the description SMM F1.

(i) Kind and quality of materials forconcrete.

(ii) Any tests of the material.(iii) Any tests of the finished work.(iv) Composition and mix (or strength

requirements) of the concrete.

(v) Any additives e.g. accelerators,retarders, waterproofing agents

and the like.

Concrete works are measured as follows:-

Item Unit

Foundations to columns,piers etc m3 Ground beams m3 Machine bases m3 Beds over 300 mm thick m3 Beds less than 300 mm thick m2 Walls over 300 mm thick m3 Walls less than 300 mm

thickm2

Suspended floors and roofs m2 Beams and columns m3 Steps and staircases m3

Concrete required to be consolidated by aparticular method (e.g. mechanically tamped,

vibrated) shall be so described.

Picture showing formwork to columns andedges of slab and a complete surface bed.

Concrete in foundations is measured to the

exact dimensions shown on the drawings.

4.7 Reinforcement

Bar reinforcement (measured as executed)

including links, stirrups, binders, special

spacers shall be measured in kg. Bends,

hooks, tying wire, distance blocks and

ordinary spacers shall be given in the

description. In addition twisted bars or high-

tensile steel bars shall be so described (SMM

F16).

Picture showing mesh fabric reinforcement and damp

proof membrane before poring of surface concrete.

Fabric reinforced shall be measured as to the

area covered without giving allowance for

laps. For fabric reinforcement, the mesh, the

weight per 1 square metres and the minimum

extent of side and end laps shall be described(SMM F17).

4.8 Formwork

Formwork shall be measured as the actual

surfaces of the finished structure which

require to be supported during thedisposition of the concrete.

Generally, formwork is measured in square

metres except to the following surfaces:-

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Edges and risers Edges of beds,roads, footpaths, suspended floors,

landings, roof, risers of staircases etc

shall be measured in linear metres in

stages of 75 mm.

Formwork to bands and cornices ismeasured in linear metres (SMM F22). Formwork to chases, mouldings etc

((SMM F23).

4.9 Precast Concrete Units.

Generally, the following shall be given in the

description (SMM F25).

(i) Kind, quality and size ofreinforcement.

(ii) Shape of cross-section of unit.(iii) Nature and extent of surface

finish.

(iv) Composition and mix of joiningand bedding materials.

(v) Method of fixing.4.10 Walling

Walling shall consist of bricks/blocks/stone

laid in mortar e.g.

Solid concrete blockwork. Hollow concrete blockwork. Natural stone. Brickwork

Walling shall be measured in square metres

stating the thickness (SMM G4).

Particulars of the following shall be given:-

Material, kind, type, finish and size ofthe blocks or blocks.

Any requirements as to the stone andthe quarry.

Type of bond of the brickwork:-o English bond,o Stretcher bond,o English Garden bondo Header bondo Flemish bond etc.

Composition and mix of mortar forbedding and joining:-

1:3 Cement: sand

1:4 Cement: sand

1:5 Cement: sand

1:6 Cement: sand

1:1:6 Cement: lime: sand1:2:9 Cement: lime: sand

4.11 DPC.

Particulars of the following shall be given

(SMM G96):

(i) Kind and quality of the damp-proof materials.

(ii) Gauge, thickness or substance(e.g. weight per square metre) ofsheet material.

(iii) Number of layers.(iv) Composition and mix of bedding

material.

Examples of Descriptions are shown on

Plate 3

Documents

CMT3212 Chapter 4