Technology Profile
re s ourc e s
Material and labour
requirement for
Materials Unit Quantity
construction of a
FC channel roof of Ce me nt Ba g s 10
size 12’ x15’ Coarse Sand m3 0.75
Chicke n me sh S q.m 35
20mm a g g re g a te m3 0.15
16mm re inforceme nt Kg 60
Binding wire Kg 1.5
Welding me sh Kg 7
Ferrocement
Labour Channel
Ma s on Ma n da ys 2 Roof
La bour Ma n da ys 12
conce p t
Ba r be nde rs Ma n da ys 1
The building system uses pre-cast ferrocement roofing channels of a segmental arch
profile which are placed adjacent to each other and spanning over two supports. After
partly filling the valley between channels with concrete, the channels form an idealized
a p p li ca ti on T-beam and are able to carry the load of a roof / floor. Ferrocement comprises of a uniform
distribution of reinforcement by use of chicken wire mesh and welded mesh encapsulated
in rich cement mortar, thereby achieving significant reduction in both steel reinforcement
and dead weight of roof. This composition provides a more uniform distribution of
strength as compared to RCC.
Ferrocement Institutional Building
at TARA Nirman Kendra Delhi (left) and com p one nts
Core house – Cyclone Resistant Shelter
in Orissa (right) Pre-cast Ferrocement Channels
FC Channels are pre-cast shell units made with rich cement mortar (1:2 to 1:3) and reinforcement
consisting of a continuous layer of chicken mesh with steel bars provided at two ends of the channel.
know how These shell units are cast either manually on a masonry mould or mechanically on steel moulds
mounted on table vibrator. The channels are supported on ends either on load bearing masonry or on a
Jointly published by: frame structure (RCC or steel).
Restraining Beams
TARA Nirman Kendra Development Alternatives Building Materials & Technology Any lateral moment and deflection of FC Channel gets balanced by thrust of adjacent channel. In order
Village Ghittorni World Headquarters: Promotion Council to balance the channel movement at ends, restraining beams must be provided to prevent differential
Mehrauli-Gurgaon Road B-32, TARA Crescent Ministry of Urban Affairs & Employment movement of FC roof in case of any instability in the support structure. The restraining beam will be a
New Delhi-110030 Qutub Institutional Area Govt. of India
India
part of RCC bands required for structural strengthening, specially in disaster prone areas.
New Delhi-110016 Core 5-A, First Floor, India Habitat Centre
Phone: 91-11-26801521, 26800398 India Lodi Road, New Delhi-110003 Concrete Filling
Web: www.devalt.org India
Phone: 91-11-24638096, 24638097, 24636759 After the Channels have been placed side by side, they are joined together with a concrete infill of
at least M15 grade (1:2:4) laid to 150 mm thickness. This concrete completes the T-beam structural
action of the FC Channels and creates a basic roof. In case of an intermediate floor, the remaining
TARA portion of the valley can be filled the with lean concrete, brick jelly lime concrete or light-weight material
Nirman Development and finished with a floor.
Kendra Alternatives
de ta i ls a dv a nta ge s
Ferrocement channel roof provides light weight roofing – 60% reduction in dead weight as compare to RCC
Pre-casting of roof leads to substantial reduction in construction time
Ferrocement channel 20% saving in cost possible because of reduction in steel quantity and elimination of coarse aggregates and
shuttering
Welded wire
mesh 25 mm Creates employment as the roof components can be locally produced and delivered through micro level
square opening enterprise
Chicken mesh Much better quality control can be maintained during pre-fabrication
5
290 Versatile technology – w.r.t profiles of roofing channels (subject to structural design)
R 38
15
Double layered stacking of channels is possible, if stack area in site is less
R4
Reinforcement
40
40
bar (as per span Nlb of channel
45 750 45
of channel) s p e ci fi c a ti ons
100
Ferrocement Clear bay length : 750 mm (Outer dimension 840 mm, including
FerrocementChannel FerrocementChannel Channel two 40 x 45 mm nibs at bottom)
Profile (FC 290) S ection(FC 290) Rise of arch : 290 mm
(all dimensions in mm)
Shell thickness : 25 mm
Unit weight : 50 kg per meter length
Length : Upto 5.4 m
Design mix : Cement: Fine Aggregate 1:2 to 1:3 by weight, M25 grade
Parapet wall Terrace Water: Cement ratio 0.45 to 0.55
Gola for terrace Fine Aggregate should be coarse sand confirming to
cement concrete 1:2:4 Water-proofing layer grading Zone II as per IS Code 383-1970
Lean concrete filling Standard flooring / Terracing Mesh reinforcement : 200 mm strip of MS weld mesh of 12 gauge,
or brick bat concrete 25 mm square opening along crown of channel
Ferrocement roofing channels
GI wire chicken mesh of hexagonal 12 mm opening,
22 gauge, throughout the shell and double layer of
1 m length at both ends of channel
Nib reinforcement : Roof application: from 6 mm for 3 m span to
(1 no. In both nibs)12 mm for 5.4 m span
Floor application: from 8 mm for 3 m span to
Valley concrete125 mm Beam / Band as per
Beam / Band thick M 15 grade
16 mm for 5.4 m span
structural requirement
as per structural Design load : As per BIS: 875
requirement Load carrying capacity of FC Channel roof varies from 650
Support structure of beams
2 2
kg/m to 1200 kg/m depending on the reinforcement
Inside / Ceiling
Plain cement concrete 1:2:4 upto 125 mm thickness and light weight local material for
Valley Filling the remaining depth
Ferrocement Channel Roof 620 MJ/sq.m as compared to 750 MJ/sq.m for a 4’’ thick RCC roof
Embodied MJ – Mega Joules
Energy
cons tru cti on
