ALTERNATIVE TECHNOLOGIES FOR COST EFFECTIVE HOUSING

Do you know that Times Towers, a 38 story building (140 Miters) - the tallest in East and Central Africa can be build in 45 days?

Have you ever wondered why Chinese albeit being the lowest bidders in construction tenders are blossoming?

Alternative technology is one thing I would highly recommend that would help Kenya in building construction. It would speed up the work while making the buildings stronger, said Raymond Chisholm, Civil Engineer, Developer, Planner and Cost Engineer during the Kenya Private Developer Association (KPDA) quarterly seminar.

Chisholm said Kenya Housing construction is stuck in the past thus very little has changed over the years in building materials and building code.

He pointed out that most houses and flats are still built with stone or concrete blocks and the building code is still not updated. Even the 2009 proposed code links everything to the British Standards.

But even in Britain they do not use British Standards anymore. As of July 2010 BS Codes in Britain become obsolete. Britain has since switched to the Eurocode Standards.

Here are the old and new construction materials. Which one will you prefer?

Stone and Concrete Block

Some of the most beautiful buildings in the world are made of Stone. In Kenya we use both sawn and chipped stone. However, stone and concrete houses are very expensive in Kenya notwithstanding it takes longer in building and installation of electrical and plumbing is more expensive and slow.

Structural Insulated Panels (SIPs)

The panels are typically made by sandwiching a core of rigid foam plastic insulation between two structural skins of oriented strand board (OSB).

SIPs are manufactured under factory controlled conditions and can be custom designed for each home. The result is a building system that is extremely strong, energy efficient and cost effective. Building with SIPs will saves time, money and labor according to the proponents.

You still have to put an exterior façade or cladding and something such as gypsum board on the interior walls.

The SIPs enable a construction to be done relatively fast. There insulation properties are excellent, but, you have to have a factory to be guaranteed enough sales volume to justify building the factory.

Precast Concrete Panels (PCP)

PCP offer good quality control and are quick to install. Bamburi has a potential of making them in their factory. Currently Eco Homes does them for small Homes.

However, they are heavy hence requiring a crane on site to lift them. They are heavy loads to transport to site. In constructing using those panels must be joined and they are not monolithic.

Sprayed Concrete Panels (SCP)

Sprayed concrete panels have an Expanded Polystyrene Core (EPS). On each side is a 2 inch grid of welded wire meshes where low velocity concrete is sprayed on the panels. SCP is economical and has a good insulating property. The problem posed by using SCP in Kenya is that quality control is difficult.

Gypsum Board and Metal Frames (GBMF)

Over 75 percent of USA homes use gypsum board for interior walls, since the 1940s. But it is a new technique or alternative technology to Kenya.

Gypsum walls and ceilings are fire retardant, soundproof, and light weight. The weight is 10 percent of a block wall. Foundations and columns for GBMF can be smaller and cheaper.

GBMF save timber and tree - hence environmental conservation. They are very easy and much faster to install. Installing plumbing and electrical wiring is a dream in these walls. Time is money and electrical installation will be cheaper. Gypsum boards are great for ceilings too.

Composite Floors

Marion Okemwa built her 60 flat in 84 days. Marion had composite Floors which were installed all the floors in one day, Sunday, and on Tuesday the tiles were placed.

A composite slab consists of steel decking working together with in-situ reinforced concrete.
The decking not only acts as permanent formwork to the concrete it also provided sufficient shear bond with the concrete, so the two materials act compositely together.

Composite floor beams are hot-rolled steel sections. Mabati Rolling Mills could supply the steel sections. Composite action is normally achieved by welding shear studs through the steel decking and onto the top of the beams before pouring the concrete. The shear connectors provide sufficient longitudinal shear connection between the beam and the cured concrete so they act as the composite.

With composite floor you can save not only time but have a thinner slab and save on concrete. You should have a specialty contactor and pump the floors with Ready – Mix. And of course it is much faster and time is money.

Wall Ties Shutters (WTF)

The WTF formwork system has been used in the construction of hundreds of thousands of structures including residential and commercial structures in single story, low rise, and high-rise construction. It has been proven to be very successful in the construction of mass housing projects worldwide. It is fast, simple, adaptable and very cost effective.

The WTF system can be erected by unskilled labor and without the need for hoisting cranes. The largest panel weight is not more than 35 kilograms. This enables a single worker to handle the WTF formwork components.

The panels and other sections are secured and fixed by steel pins and wedges with formwork ties. The only tool required is a hammer. The WTF system can save as much as 15 percent of the total cost of construction in comparison to traditional methods such as block or post and beam construction. But the most important savings is time.

WTF System Benefits

The WTF formwork system is unique because it forms all of the concrete in the structure including, walls, floor slabs, columns, beams, stairs, window details, balconies and various decorative features in exact accordance with the architect’s design.

WTF requires no cranes or heavy lifting equipment. You pour walls and floor slabs monolithically. You can remove floor slab formwork without disturbing shoring. Yes, during constructing WTF form stairs in place as part of work cycle.

Additionally, they require no skilled labor. They are suitable for single story and high rise construction. Their equipment adapts to different designs. And there is no need for using of timber or plywood.

Ministry of Housing is putting up a housing project off Jogoo Road using Post and Beam technology.

Pumping Ready Mix Concrete (PRMC)

In the rest of the first world over 90 percent of construction projects use Ready Mix Concrete.
Everything from massive high rises to neighborhood sidewalks are built using Ready Mix Concrete.

PRMC offer proper amount of cement mixing with other materials. Saves a contractor or a developer from being over charged by aggregate and sand suppliers. No waste on the ground at site. Proper concrete test are carried before the ready mixed concrete is brought to the site.

Raymond Chisholm said there is a lady in Kiambu who is now facing a long prison sentence and the sad thing is she probably could had completed her project quicker and cheaper using Ready Mixed Pumped Concrete.

Further, PRMC is easy and takes less time to move around on the site than when using a wheel barrel. Chisholm said, “I am sure you have seen the Chinese contractor working on Thika Road or the by-passes. Every time you can see a Ready Mix truck delivering their concrete. And they consistently tender cheaper than Kenyan Contractors. It should not take a Rocket Scientist to figure out one of the reasons why?”

The civil engineer who is running a construction related company in Kenya, asked: “Did you know that your engineer knows the unreliability of your contractor’s concrete strength and has overdesigned your building to allow for this?”

“Did you know you could finish your project 25 percent faster just by using Ready Mix concrete?”

“Figure out how much it would save you to build your building 25 percent faster.”

Most Important Benefit

Pumping Ready Mix Concrete is computer controlled. The computer weights, proportions and mixes exactly what you requirements are.

You can get Ready Mix from Transfleet, Epco, Cementers, Laxmanbhai, and Victory Ready Mix. Transfleet right now is increasing their capacity from 150 m3 per hour to 300 m3 per hour.

However, some developers during the KPDA seminar said some of these technologies should not be copied and pasted in Kenya from reasons varying from security to lack of competent workforce to use them. They argued that technology transfer is necessary in Kenya housing construction as well as training Kenyans on the use of these alternative technologies.