In earlier times, land was readily available and buyers could opt out of buying plots with black cotton soils in favor of others with better soils. Currently, the land available has become scarce and expensive so buyers have no choice but take what is available.

Black cotton soil is found abundantly in most regions in Kenya. For example in parts of Kajiado, Nairobi, Rift Valley, Kiambu, Machakos, and Nyanza. Within the Nairobi metropolitan area this type of soil is common in Kitengela, Syokimau, Athi River and even Kamulu areas along Kangundo road.

Why is it risky to build Foundations in Black Cotton Soil?

Black cotton soil, a cohesive soil, is considered a problematic soil for civil engineers. It has characteristics of swelling during rains and shrinking during summer. In both the conditions, it poses problems.

The continuous expansion and shrinkage of the soil creates a very unstable environment to build a foundation on. It is what causes the cracking in floors and walls due to the uneven settlement in foundations.

Special care must be taken into consideration when building foundations on this type of soil. This is why the cost of building is usually higher in these soils.

How should you build on black cotton soil?

There are two common ways of dealing with the soil: one can excavate all of it or have a floating foundation.

Option 1: Mass Excavation

When building on land with black cotton soil, the entire top soil is always removed through excavation using building machinery.

Once the soil has been excavated, you can start construction using the normal strip foundation that is common for residential houses.

The additional costs that the homebuilder incurs here include the costs of hiring an excavator, transportation costs of the excavated soil, and backfill materials.

Option 2: Using floating foundations

Generally, if the black cotton soil is more than 1.5m in depth and the homebuilder has no intention of creating a basement, it becomes uneconomical to excavate the whole of it.

This requires a suspended type of foundation whereby columns are dug till solid rock or firm ground and protrude slightly above the ground level.

The suspended type of foundation is known as the pad foundation. Here excavation will be done only for the load-bearing components of the house, which are the columns and ground beams. These columns and beams will then support the entire structure above the soil near the surface.

Waste water management

Black cotton soil has poor drainage. When constructing soak pits in the terrain with this type of soil, water doesn’t percolate. In stead it stagnates on ground. 

In such areas its advisable to fill in the soak pit with large sized quarry chips to make the soakage faster. Alternatively the soak pit will have to be dug deeper till one reaches the stone.

Please ensure you engage a professional before undertaking any building project.

Need help with your construction project? Talk to us

The post How to Build on Black Cotton Soil appeared first on My Building Code.

Kenya lies in the equatorial zone receiving plenty of sunshine all year round. This makes solar a very viable source of energy. If you were thinking of making the switch to solar, here is all the information you need:

1. Types of Solar Panels
   • Solar Thermal Panels
     • Pricing of solar water heating systems
   • Solar PV Panels
2. How Solar PV Systems Work
   • The Solar Module
   • Inverter
   • Solar Battery
   • Charge Controller
   • Load, Cabling and Connections
3. The Different Solar PV Systems and their associated costs
   • Plug and play Solar Kits
   • Component Based Systems

Types of Solar Panels

There are two types of solar panels:

1. Solar Thermal Panels

Solar Thermal is usually used for water heating. It’s a simple technology with three key components:

• Collectors: These are the solar thermal panels mounted on your roof. They absorb sunlight and transfer its heat to a fluid. Flat plate collectors and evacuated/vacuum tubes are the most popular types of collectors. The vacuum tube is more efficient in that it works on the thermos principle: therefore very little heat is lost.
• Pump & Controller: The pump ensures the transfer fluid is circulated between the collectors and the water cylinder efficiently.
• Water Cylinder: the panels on your roof are the collectors of sunlight, thus heating up the liquid in the tubes which is then transported into your cylinder ready for use.

Pricing of solar water heating systems

The cost of installing a solar thermal/ water heating system will depend on the brand and the type of solar water heater, i.e. whether it’s flat plate or evacuated tubes, pressurized or non-pressurized system. The prices range from Ksh 50,000 (USD 425) to an upwards of Ksh 200,000 (USD 1,700).

Note: Installation of Solar water Heaters in Kenya is guided by the Energy and Petroleum Regulatory Authority (EPRA), thus it is important that your installation is handled by an individual with the certifications required by EPRA.

2. The Photovoltaic solar panel (Solar PV)

Solar PV converts sunlight into electricity and can be used to power appliances. Read more about how the solar PV panels work here.

The Solar PV has a higher capital cost than solar thermal. Solar PV also requires larger area of space for installation compared to solar thermal.

Still, the solar PV has a big advantage over solar thermal in that it generates electricity. This allows solar PV owners to sell excess electricity back to the grid and generate a sustainable second income.

The choice between the two will depend on your needs. But we’ve seen many households opting to install both types of solar, utilizing the solar thermal panels for hot water and the solar PV for electricity generation.

How Solar PV Systems work

We’ve already explained how the solar thermal panels work so for the rest of the article we shall focus mostly on solar PV system and its various components.

The Solar Module

The Solar PV panels, also referred to as solar module, is made of photovoltaic (PV) cells. Solar radiation emitted by the sun is absorbed by the PV cells when the sun shines directly on them.

Most PV cells have two layers of semi-conductor material, one positively charged and one negatively charged. When light shines on the semi-conductor the electric field across the junction between these two layers causes electricity to flow, generating direct current (DC).

Note: Solar PV electric panels do not require bright sunlight in order to operate, meaning you can still generate electricity on cloudy days. However in general, the greater the intensity of light the higher the flow of electricity

Inverter

Direct Current (DC) needs to be converted into alternating current (AC) so it can be used in a domestic building; this is performed by an inverter. Once converted, the AC current is fed into the electricity supply for use in the home, with any surplus electricity fed back into the national grid.

Solar Battery

It is important to realize that you can only use your free solar electricity when it is being generated – but if you invest in solar batteries you’ll be able to store power for use in the evenings and at night when the panels are not producing electricity.

Charge Controller

The charge controller serves as a current and/or voltage regulator. It ensures that the solar batteries are not overcharged during the day, and that the power doesn’t run backwards to the solar panels overnight and drain the batteries. Some manufacturers put the charge controller and inverter into one thing for simplicity.

Load, Cabling and Connections

In solar terminology, the term “load” refers to the power consumption of the device(s) that are being used in the system. Understanding your loads is critical to maintaining a well functioning power system.

The loads will determine the size of cables that will be used. Cabling for solar done wrong will most definitely burn your house down. The right size of cable from PV to charge controller, and from charge controller to battery is absolutely necessary.

The way they are connected is solar panel to charge controller to battery + charge controller to DC loads + charge controller to inverter to AC loads. And that’s what a solar system is.

The different Solar PV systems and their associated costs.

Plug and Play Solar Kits

These are relatively inexpensive kits capable of providing lighting and power for AC & DC applications anywhere. They come ready to use, with preinstalled accessories: you just just plug and play.

Their installation costs are minimal since once you purchase, you can either ask for someone to put it on your roof or do it yourself.

The cost for the kits will vary depending on the accessories and payment method. A spot check across various manufacturers show the average retail price of a simple PV system with solar panel, battery, a couple of light bulbs, radios and torch will range between Ksh 35,000 (USD 300) – Ksh 45,000 (USD 385). If the accessories include a TV etc, the price will be higher.

Some sellers offer a ‘Pay-As-You-Go’ financing model where you pay a deposit and monthly installments.

The main disadvantage with these kits is that it comes attached to its own loads i.e. bulbs, TV etc. You can’t add your own to the system. This is why some people opt for Component Based Systems (CBS).

Component Based Systems

For CBS you buy the components separately and they are assembled to form a household solar system like the one we described here.

For CBS installation, you’ll need to involve a solar practitioner who is licensed by the Energy and Petroleum Regulatory Authority (EPRA)- the Kenya Energy Regulator. You van verify the practitioners license from the EPRA website. Incase of issues, you can lodge a complaint with EPRA and they’ll send an inspector.

It is not recommended that you buy the solar panel and other components off the shelf then just connect them together. EPRA technicians need to design the system for you based on the loads you want to be powered.

The cost of installing a CBS, Solar PV system will depend on the loads, size of the inverter and size of the battery. The price on average typically starts from Ksh 90,000 (USD 770) for a 2KVA Inverter, 100Ah Battery that will be sufficient for lighting and WIFI needs running on single phase power. The more the loads the higher the price.

Note: Powering all loads you have with solar might be costly. A good technician will advise you to start with the crucial loads. This will be more affordable as opposed to doing the whole house.

Got any questions regarding solar? Type below in our comments section.

The post A Cheat Sheet for the Best Solar Panels to install for Your Home appeared first on My Building Code.

Consequently, many millennials would opt for light gauge steel technology if they were made to understand the myriad of opportunities it presents. Sure, we all know about structural or heavy steel as a common construction material favored for large construction projects without which, skyscrapers wouldn’t be in existence.

Steel, unlike masonry, wood and other construction support materials, has a terrific strength-to-weight ratio and is very flexible: it can bend without cracking. That’s why a steel building can flex when pushed to one side either by great wind pressure or an earthquake.

Light gauge steel construction gives you speed, strength and sustainability at a fraction of the weight and at a more affordable cost compared to conventional construction. The difference between structural steel and light gauge steel lies in how they are manufactured.

Light gauge steel sections are cold formed sections, meaning that the sections are shaped into strong “C” or “Z” forms, capable of holding heavy loads, at room temperature.This is in contrast to thicker hot rolled sections, that are shaped while the steel is molten hot to form structural steel.

Light gauge steel is then coated with zinc (called galvanized) to protect it from corrosion. From the manufacturing process, lower production costs are realized since LGS does not involve heat input and its associated expense.

The foundations for an LGS structure will be similar to the conventional masonry building method for example strip footings etc. but will require less reinforcement because steel frames are lighter than masonry frames.

In construction, time equals money. LGSF system, design, production & shipping can happen within days or weeks, instead of months. Because most of the construction components are manufactured in the factory, frame erection and construction at site can begin immediately due to the pieces being exact specification, pre-cut, pre-punched & pre-marked.

No additional work to be done at site. Additional advances in the speed of projects are attributed to the near 100% computer controlled accuracy(+/-0.5mm) of the frame ensuring a near 100% square and straight frame which benefits other trades. Its lightness makes for easy handling on site that contributes to faster erection.

The uptake of LGS in Kenya is now fast growing with developers mainly testing it as a truss structure replacing traditional timber trusses. Unlike wood, steel is stronger and more durable.Steel does not burn or rot and is not susceptible to moisture damage, termites or other wood destroying insects.

It helps preserve our environment for the future by decreasing the consumption of wood. It is 100% recyclable, can be used again and again, without losing its properties.

An economical LGS frame system is increasingly being used in America, Europe, Australia and New Zealand as a serious alternative to lumber in residential construction where wood frame construction was previously popular.

Light gauge steel framing has a few minor disadvantages first being with regard to its fire resistance properties. Although noncombustible and thus will not fuel the fire, the steel studs are directly affected by high temperatures.

Since there is not much mass to the steel studs and joists in this type of construction, the steel trusses and bar joists are likely to be weakened quickly by heat and are prone to early collapse.

An easy way to work around this is ensuring the steel is clad by fire resistant material and provide cavity insulation material.This will protect the steel sections from heating up rapidly when exposed to fire.

The issue of thermal conductivity has been a concern especially since steel is a good conductor of heat. This could potentially result in increased heating costs in cold climates, and in hot climates heat gain could result in moisture damage. Again, insulation placed between the steel frame (batt insulation), will give a better overall thermal performance of LGSF walls.

The pros far outnumber the cons and the technology can be widely used in residential, commercial, and industrial construction.

The post Construction in the digital age: a glimpse into light gauge steel technology appeared first on My Building Code.