Formwork deduction rules is 1200 part 5 shuttering measurement for engineers

Introduction

Formwork  ( Centering & shuttering work ) is one of the  most common activities in constructions. Proper measurement of shuttering work is important for accurate billing and quantity verification.
In this article, we will understand the Mode of Measurement of Formwork as per IS 1200 (Part-5)  including measurement rules, deduction provisions, and materials used in formwork

What is Formwork ( Centering & Shuttering work )

Formwork is the complete temporary mould system used to give shape and size as per given drawing to fresh concrete.

It Includes:
Plywood / steel plates
Battens / Studs
Props / Adjustable jacks
Tie Rod / Pin patti
Welding support
Supports & Bracing
and scaffolding as required.
Formwork is a Entire temporary structure used to support and shape, size to concrete until it gains strength.

Basic rules of formwork measurement

1.      All Dimension measured in square metre
Formwork measured actual surface touch with the concrete or any other material.
Dimensions measured to the nearest 0.01M
Area measured to the nearest 0.01M
No deduction shall be made for opening upto 0.4M².
If slab thickness upto 200MM measure norm
If slab thickness above 200MM measure separately.
Extra Height where exceeding 3.5 metre height in one floor shall be measured
and paid for separately.

Measurement  of Slope area

Sloping Surface (More than 30°)

If slope is more than 30°, shuttering may be required on both sides.
But measurement is taken only for the underside area.
Even if shuttering is done on top and bottom, only bottom area is measured.
Arches
Measured separately based on span:
Up to 6 m span
Above 6 m span
Bigger arches are measured separately because they need more support.

If slope is more than 30°, shuttering may be required on both sides.
But measurement is taken only for the underside area.
Even if shuttering is done on top and bottom, only bottom area is measured.

Arches
Measured separately based on span:
Up to 6 m span
Above 6 m span
Bigger arches are measured separately because they need more support.

Cylindrical Shells (Curved Structures)
Only underside area is measured.
Classified by radius:
Radius less than 3 m
Radius more than 3 m
Small curve and large curve are measured separately.

    Measurement in stages

     Below ground level
     Above ground level 

    Work to be measured separately

    work executed under special conditions must be measured separately
    work in or under water
    work in  liquid mode
    work in or under foul positions
    work in interrupt by tides.
    These conditions make execution difficult, so the work is measured separately and usually paid   at           different rates.

  Types of formwork

1.    Wrought formwork :-  Planed or smooth timber surface.
Tongued & grooved board sheathing :- Interlocking wooden boards.
Plywood lined sheathing :- Plywood surface for better finish.
Special lining :- For extra smooth, textured, or architectural finish.
Steel sheeting or tubing :- Steel formwork systems.
Slip form technique :- Continuous extrusion method (used in tall structures like silos, cores, chimneys).

1             Formwork Deduction rules
  Is 1200 part-5 clause 6

       Example
       Opening size = 0.35 m²
→   Deduction = No deduction
       Opening size = 0.60 m²
→   Deduction = Deduction allowed

Shuttering work  Deduction Rules
IS 1200 PART-5
Is 1200 part-5 Clause 6 Mode of measurement
Clause 6.1 shuttering work in measured in square metres  as the actual surfaces to touch with fresh concrete or any other material
Clause 6.4 No deduction shall be made for opening upto 0.4M².
Clause 6.5 Ranking or circular cutting and rounded and moulded edge shall be measured in running metres.
Clause 6.6  Measure secondary beam shuttering only up to the side of the main beam. Measure main beam shuttering only up to the side of the column Do not deduct anything from the beam in the main beam.
Deduction Table
Sr. no.	Opening area	Deduction Action	Side addition
1	Area upto 0.4 m²,	No deduction	No Addition
2	Area more than 0.4 m²	Deduct surface area from slab	add side touch with concrete surface
3	Secondary beam measured  main beam to main beam
4	Main Beam measured no deduction of secondary beam rest area.
5	If the slab thickness upto 200MM measured in normally.
6	If the slab thickness above 200MM measured separately.
7	Extra Height where exceeding 3.5 metre height in one floor shall be measured and paid for separately.

       Formwork Design & Tolerance in Constructions
 CPWD specification clause 5.2.2

Design & Tolerance in Constructions
CPWD Specifications
CPWD Clause 5.2.2 Formwork must be constructed as per drawing, but small size differences are allowed.
Tolerance Table
S.No	Item	Permissible Tolerance	Simple Meaning
1	Columns & Beams (Cross Section)	+10 mm / -5 mm	Can be 10 mm bigger or 5 mm smaller
2	Footing – Plan Dimensions (L & W)	+50 mm / -10 mm	Footing size can slightly vary
3	Footing – Eccentricity in Plan	0.02 × width of footing (Max 50 mm)	Slight shifting allowed but within limit
4	Footing – Thickness	+50 mm OR ±5% of thickness (Whichever is less)	Thickness variation allowed within safe limit
	(Note- These tolerance apply to concrete dimensions only, and not to positioning of vertical steel or dowels).

  Material for formwork supporting

      CPWD specification clause 5.2.3.1
Propping and Centering
All propping and centering should be either of steel tubes with extension pieces or built up sections of rolled steel.

     Centering & Shuttering work

CPWD specification clause 5.2.3.3
shuttering must be strong, properly supported, tight at joints, and clean to prevent leakage and defects. Steel shuttering should generally be used, with waterproof 12MM ply allowed only in small unavoidable areas.

      Extra Height support

      CPWD specification clause 5.2.3.4
Formwork must be designed to safely carry its own weight, reinforcement, fresh concrete, and construction loads (workers, materials, equipment). If the centering height is more than 3.5 m, multi-stage props should be provided for proper support.

      De-shuttering Duration

         CPWD specification clause 5.2.3.7

De-shuttering work
CPWD Specifications
CPWD Clause 5.2.3.7 Removal formwork duration
De-shuttering  Table
S.No	Type of Formwork	OPC 43 Grade	PPC
1	Vertical formwork to columns, walls,	16-24 Hours	24-36 Hours
2	Soffit formwork to slabs (Props refixed immediately after removal)	3 Days	4 Days
3	Soffit formwork to beams (Props refixed immediately after removal)	7 Days	10 Days
4	Props to slabs (Span up to 4.5 m)	7 Days	10 Days
5	Props to slabs (Span over 4.5 m)	14 Days	20 Days
6	Props to beams & arches (Span up to 6 m)	14 Days	20 Days
7	Props to beams & arches (Span over 6 m)	21 Days	30 Days

     Measurement book with example

	PROJECT NAME		Sun Tower Greater Noida
	CLIENT NAME		Onsite XL
	CONTRACTOR NAME		SANGEETA DEVI
	RUNNING BILL No.		RA-01
MEASUREMENT  BOOK
S.No.	Description	Unit	No.	No.	L	B	H	Qty.	Remarks
	EXAMPLE -1
	Footing foundation
	F-1 ( 3000 X 3000 MM ) Height 450MM
	Side	Sqmr	1	2	3		0.45	2.7
	Side	Sqmr	1	2	3		0.45	2.7
	Final quantity								5.4 Sqmr
	EXAMPLE -2
	column
	C-1 ( 500 X 750 MM ) Depth 3000MM - 450MM beam
	side	Sqmr	1	2	0.5		2.55	2.55
	side	Sqmr	1	2	0.75		2.55	3.83
	Final quantity								6.37 Sqmr
	EXAMPLE -3
	Beam
	B-1 ( 230 X 450 MM ) Lenth 3000MM beam depth 450 - 150 slab thickness = 300 depth of beam side
	Bottom	Sqmr	1	1	3	0.23		0.69
	2 side both side same size	Sqmr	1	2	3		0.3	1.80
	Secondary beam :-  measured main beam inner to inner dimension
	Final quantity								2.49 Sqmr
	EXAMPLE -4
	Beam
	B-2 ( 300 X 750 MM ) Lenth 3000MM beam depth 750 - 150 slab thickness = 600 depth of beam side
	Bottom	Sqmr	1	1	3	0.3		0.90
	2 side both side same size	Sqmr	1	2	3		0.6	3.60
	Main beam :-  measured column inner to inner dimension no deduction from secondary beam area
	Final quantity								4.5 Sqmr
	EXAMPLE -5
	Slab
	Ceiling	Sqmr	1	1	3		3	9.00
	shaft area  500 X 500MM	Sqmr	1	1	0.5		0.5
	No deduction area below .4sqmr
	Final quantity								9 Sqmr
	EXAMPLE -6
	Slab
	Ceiling	Sqmr	1	1	3		3	9.00
	shaft area  800 X 800MM	Sqmr	-1	1	0.8		0.8	-0.64
	shaft side	Sqmr	1	4	0.8		0.15	0.48
	Deduct surface area but add side of shaft upto slab thickness
	Final quantity								8.84 Sqmr
					Total quantity			36.61	Sqmr
					Previous			0.00	Sqmr
					This Bill			36.61	Sqmr

Conclusion 

Understanding formwork deduction rules as per IS 1200 Part 5 helps engineers measure shuttering work correctly and avoid billing mistakes. Following these standard rules ensures accurate quantity measurement and transparency in construction projects.