Corrugated fibre concrete roofing sheets
Local, low-cost method
Inexpensive durable roofing material
Good, if properly manufactured and installed
Thorough training and constant quality control
Simple, locally made, transportable moulds
Resistance to earthquake
Resistance to hurricane
Good, if well installed and secured
Resistance to rain
Resistance to insects
Stage of experience
Fairly mature technology
Corrugated FC sheets
· were the first FC roofing
elements to be developed, as the aim was to substitute gci and ac sheets;
· require fairly simple, locally
made equipment and a very well coordinated working team of at least two workers;
· consume about the same amount
of cement es asbestos cements sheets (15 kg per m2), on account of their greater
thickness and production method by manual tamping, but require no electricity;
· are difficult to handle when
fresh and to cure in water tanks, because of their large size;
· are difficult to transport and
install without breakage, and do not tolerate inaccurately constructed and
flexing supporting structures;
· withstand strong wind forces
because they are heavy and have few overlaps.
In most cases FC/MC tiles are easier to produce and install than
FC sheets and therefore represent the more appropriate solution.
Further information: RAS c/o SKAT, Vadianstrasse 42, CH-9000 St.
Bibl. 11.03,11.05,11.07,11.08,11.12, 11.15.
Production of Corrugated FC Sheets
Materials and equipment
· Cement: ordinary portland
cement (Skgper 10 mm thick corrugated sheet of 60 x 60 cm) corresponding to
cement: sand ratio of 1: 1; a pozzolana (eg rice husk ash) can be added to
improve fibre durability and reduce cement content, but causes slow setting,
which necessitates a larger number of moulds and larger workspace.
· Sand: (5 kg per sheet)
preferably with angular particles and good grain size distribution between 0.06
and 2 mm, free from silt and clay.
· Fibre: (0.1 kg per sheet)
mainly natural, such as sisal, jute, coir, or banana fibre, but also synthetic
fibres, eg polypropelene or glass fibre, can be used. Long fibres can be used,
but require a different (more difficult) manufacturing process and result in
weaker products. Short fibres, chopped to lengths of 12 to 25 mm, are easy to
process, provide cohesiveness to the wet mortar, permitting reshaping without
cracking, and also help to prevent cracking due to drying shrinkage.
· Water: preferably drinkable
water, just enough to make the mortar mix workable (water: cement ratio 0.5-0.65
· Admixtures: such as
waterproofers may be used, if the sand is not well graded, and colorants, if the
grey cement colour is not desired.
· Screeding board: a flat
horizontal board with outer frame, to define the FC sheet size and clamp down
the polythene interface sheet.
· Corrugated setting moulds: gci
or ac sheets, enough for two days production. All sheets should be obtained from
a single batch made from a single master mould, as sheets from different batches
or different producers are likely to have dissimilar corrugations. Accuracy in
the corrugations is vital for proper installation and trouble-free performance.
· Other equipment: standard
Moulding and curing
· The correctly proportioned and
well-mixed mortar is trowelled evenly onto the polythene sheet, which is fixed
on the screeding board; the mortar is tamped, levelled to a uniform thickness of
10 mm and smoothed off with the trowel.
· The frame is removed, the
edges of the mortar layer trimmed and the screeding board tilted, such that the
polythene sheet with the wet fibre concrete is allowed to gradually slide onto
the corrugated mould held below.
· The fresh FC sheet and mould
is placed on a stack for primary curing for 24 hours, after which they are hard
enough to be demoulded and placed upright for further curing (by regular
watering), or completely immersed in water tanks for about 2 weeks.
· Demoulding should not be done
later than 48 hours after moulding, as the sheets tend to shrink on drying, and
will crack if resisted by the setting mould.
Production of FC Ridge Tiles
· Materials and equipment: same
as for sheets, but different shape of frame, and screeding board made with
hinges, so that it can be bent and used as the setting mould, held in a
· Moulding and curing: same as
Installation of FC Roofing with Corrugated Sheets
The corrugated FC sheets are laid on timber roof structures in
much the same way as gci and ac sheets. However, FC sheets are less flexible and
can be damaged if the loads are not evenly distributed. Therefore, care must be
taken in constructing the substructure, to ensure that the top edges of all
members are properly aligned. If nails or bolts are used, holes (of slightly
larger diameter) should be drilled beforehand. Alternatively, nibs with wire
loops can be cast-in during moulding, avoiding the need for drilling. Mitred
corners are essential for a weathertight fit.