What affects the cost of a home extension in Gauteng?

Most homeowners start by asking what an extension costs per square metre. It is a fair question, but the answer can mislead you. Two rooms of the same size can cost very different amounts, depending on what sits under them, what goes inside them and how they join your home.

This guide explains what moves the price most, so you know what to ask about before you get quotes.

Bigger costs more, but not in a straight line. Every extension has fixed costs, such as plans, setting up the site and joining the new work to the house, that you pay whether you add one room or three. A simple rectangular shape is also cheaper to build than one with lots of corners and angles.

Foundations depend on the soil. Clay, sloping stands, filled ground and dolomite areas, which occur in parts of Tshwane, can need deeper or reinforced foundations, or a soil report before the council will approve plans. Often you only know this once someone has looked at the site.

Building out needs more foundations and more roof. Building up saves garden space, but an engineer must first confirm that your existing walls and foundations can carry the extra load, and you need a suspended floor slab and a staircase. Neither is automatically cheaper. It depends on your house and your stand.

Breaking through walls, matching floor levels, tying the new roof into the old one and matching brick, plaster and paint all take time and skill. A good quote spells this work out instead of hiding it in one line.

Finishes are where budgets drift most. Floor and wall tiles, cupboards, taps and sanitaryware, aluminium or timber windows and the roof covering all come in a wide range of prices. Choose them early and get them written into the quote, so there are no surprises halfway through the build.

A new bathroom or kitchen needs drainage and water supply, so it costs more than a bedroom of the same size. Electrical work must be done by a registered electrician and come with a certificate of compliance. If your distribution board is old, it may need upgrading as well.

An extension normally needs approved building plans, drawn by a registered architect or draughtsperson. Depending on the work, you may also need a structural engineer, and in an estate the estate must approve the design too. These fees are part of the real cost, so include them in your budget. Our guide on approved building plans explains the process.

If materials and machines cannot get close to where the work happens, everything takes longer. Narrow side passages, steep driveways and estate rules on working hours or deliveries can all add time and labour.

Older homes can hide surprises: cracked foundations, old wiring, rusted pipes or roof timbers that are not strong enough to tie into. A careful site visit picks up most of these before work starts, so they are in the quote and not a nasty surprise later.

Ask for a detailed bill of quantities (BOQ) that lists materials and labour line by line, not one lump sum. Then you can see exactly what is included, compare quotes fairly and spot anything that has been left out.

At MC Developments SA, every quote comes with a detailed BOQ and a fixed price. If you already have plans, our quantity surveying service can price them before you commit. See our additions and alterations page for the kind of work we do.

• Keep the shape simple.
• Choose your finishes before you accept a quote, not during the build.
• Place a new bathroom or kitchen close to existing drains where you can.
• Get plans approved before you book a builder, so the quote matches what will be built.
• Keep some money aside for things nobody can see until the ground is opened.

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