Author: A4KENYA

Wall plasters are commonly made of a mortar mix of cement and sand, in a ratio of 1 to 3 or 1 to 4 This cement plaster is usually quite rigid and water proof. This does not allow moisture trapped within the wall to escape, leading to moulds on the walls later on.
Cement plaster.

Also, due to the rigidity, cement plasters are prone to cracks when the wall support shifts during settling. The advantage of cement plaster is the ability to set and harden within a very short time.

Solution.

Lime.

Lime plasters have been used for hundreds of years.Cement is a relatively new product, less than 100 years old.
Lime plaster is mixed in the same 1 to 3 and 1 to 4 ratio as cement. The advantage of lime plaster is the special effect of self healing, whereby cracks on the wall fill up with the calcium carbonate emanating form the rest of the lime plaster. Lime also allows the wall to breath, letting out any trapped moisture in the middle.

Cement plus Lime.

Cement can also be mixed with lime and sand to add to the cement and lime advantages into plaster. A ratio of 1 to 2 to 9 for cement, lime and sand.
There is a church built in the 1940s in the United Kingdom with the same mix and is still standing to date.
http://ihbc.org.uk/context_archive/53/Limemortar_dir/Limemortar_2.htm

The initial layer that supports to the existing wall can be made abit stronger to help in bonding. The subsequent layers that stick on to the initial later can have a weaker mix.

Lime addition helps to improve the workability of the plaster, making it easier to spread with a trowel.

Francis Gichuhi Kamau, Architect.
info@a4architect.com
0721410684

Land 1 acre for sale at Syokimau.
Located 3.1 km from Mombasa road.
Price guide kes 20m. call 0721410684 or email info@a4architect.com for more info.

[googlemaps https://maps.google.com/maps?f=d&source=s_d&saddr=Syokimau+-+Katani+Rd&daddr=Katani+Road&hl=en&geocode=FVP16v8d1XozAg%3BFb446_8dds8zAg&sll=-1.362284,36.95348&sspn=0.012142,0.021136&t=h&mra=dme&mrsp=1&sz=16&ie=UTF8&ll=-1.362284,36.95348&spn=0.012142,0.021136&output=embed&w=425&h=350]

Earthbag building currently being constructed at Kiserian, Nairobi.
Cost breakdown.

Foundation. 142 bags=kes 3,000.
Super structure walling.70m2 =kes 21,000
Roofing.kes 22,800.

Floor=kes 30,000
Doors. 2 No. @ kes 5000=kes 10,000
Windows. 2 No. @ kes 2,500=kes 5,000

Wall plaster. =kes 28,000.

Paint=kes 28,000.

Plumbing and electrical works=kes 20,000

TOTAL=KES 167,800.

Earthbag houses have walls made from polypropylene bags filled in with soil.
Cost of wall.

Cost of 1 bag of dimensions 850mm by 450mm by 100mm is kes 20. 12 bags make 1 m2. Cost of bags per m2 =12 x 20 =kes 240.

Cost of soil.
Assuming the soil is available on site for free, the costs will be only labour costs.
With Manual labour of kes 500 per day, a man can dig up 3m x 3m x 0.5m =4.5m3 volume per day.
One sack contains a volume of 0.7 x 0.45x 0.1=0.0315 m3 of soil.

One man can fill in 142 bags per day. At a cost of kes 500 daily, this works out to kes 3.50 per bag. For 1 m2 or 12 bags, this works out to kes 42 per m2.

Cost of earthbag walling per m2 is kes 240 plus kes 42=kes 282. Add miscellaneous to total kes 300 per m2.

This is the lowest cost possible for walling compared to stabilised cement blocks at kes 500 and stone at kes 1000 per m2.

A 30m2 bedsitter room, with 64m2 wall surface, will cost kes 19,200 for walling.

Advantages.
The thick walls are strong enough to carry heavy loads hence another storey can be added on top. Buildings such as Fort Jesus, standing till today after construction 500 years ago, have similar thick sized walls which support several storeys.

Its also easier to create indent patterns which can be infilled with glass blocks or glass plus LED lights to create interesting wall facades.

https://www.youtube.com/watch?v=VtMRiKMbQ2U

Earthbag construction project at Kiserian on a leased property.

30 degree roof pitch.

The round curvilinear room has a pitch of 30 degrees for roof. The roof surface area is 60m2. Asuming gauge 32 mabati roof at kes 300 per m2, the iron sheet cost is kes 18,000.

The truss length is 40m.Assuming 3 x2 cypress timber at kes 120 per meter, the cost is kes 4,800.
Total roof cost is kes 22,800.

The plinth area of the room is 32m2.
The cost per m2 for roof will be kes 760.

Roof pitch 5 degrees.

With a 5 degrees pitch, cost will be as below.

Roof surface. Assuming Mabati gauge 32 at kes 300 per m2, the area is 54m2.
Cost of roof surface will be kes 16,200.

Timber structure.

The length of the timber trusses will be 35 meters.
Cost of timber , assuming 3 x2 cypress timber section at a cost of kes 120 per meter, will be kes 4,200.

Total flat roof pitch cost will be kes 20,400.

Cost per m2 will be kes 640.

Comparison.

Flat roof is cheaper by kes 2,400.
This is 11.7 % cheaper.

The cost reduction quite small.