Construction Techniques and Materials Calculation

You cannot build straight from a drawing

A finished design tells you WHAT to build. It does not tell you how much material to buy, in what order to do the work, or how to keep the site safe while you do it. All of that sits between the drawing and the finished structure, and it is the work this module is about. A build is not made in the order a drawing is read. It is made in an order that cannot easily be undone. Foundations go in before walls, and walls before the roof, because you cannot slide a footing under a wall that is already standing. Get the order wrong and the fix is to tear work out and do it again. So before a single brick is laid, three questions have to be answered, and answered in order. How much material does the job need? In what order must the work be done? And how is the site kept safe while it happens? Carry those three questions through everything that follows: from this source, how much, in what order, and how safely?

Words for turning a design into a building

Five terms, each defined by what it is. They are the language of getting a design actually built.

The order the work has to go in

Put these six stages of carrying out a construction task into a sensible order.

• Read the technical source to find out what has to be built and to what standard
• Work out the resources needed and calculate the materials, plus a wastage allowance
• Plan the order of work and organise the tools and labour
• Set up the site to control the risks before the work starts
• Carry out the construction techniques in the planned order
• Clear the waste and evaluate the finished work against the success criteria

Why work the quantity out first

A builder decides not to work out how many blocks a wall needs, and instead to buy more each time they run out. Why is calculating the quantity from the source first the better approach?

• It tells you how much to order in one go, so work is not stopped waiting for deliveries and money is not wasted on the wrong amount
• It makes the finished wall look neater
• It is only needed when the drawing has no scale on it
• Buying as you go is fine, because you can never order too much

Working it out, or finding out the hard way

The same job can be run two ways. Only one of them keeps moving.

How many bricks to order

A wall needs 800 bricks to build. To allow for cutting and breakage you order one extra brick for every ten. How many bricks should you order in total?

Three that keep a site safe

Select the THREE that are health and safety working practices, each controlling a real risk on site.

• Wearing a hard hat where objects could fall from above
• Stacking materials so a pile cannot topple onto anyone
• Keeping walkways clear of offcuts and waste
• Working faster to finish before the weather turns
• Leaving waste where it falls to save time

Three questions before a brick is laid

You cannot build straight from a drawing. Between the design and the finished structure there is a job to do, and it comes down to three questions asked in order. How much? Read the source, work out the quantities, then add a wastage allowance so you do not run short. In what order? Construction is sequenced and hard to undo, so agree the order of work before you start, not halfway through. How safely? Set up the site to control the risks before the tools come out, not after something has already gone wrong. Answer those three, in that order, and the build has a chance. Skip one and the site finds out for you.

Match each safety measure to its risk

Moving house, not building one

Step off the site for a moment and think about moving house. You do not just turn up with a van and hope. First you walk round and work out how many boxes you will need, and you grab a few spare, because some always turn out to be the wrong size or get crushed. Then you think about what to pack and load first. The heavy furniture goes in before the light bags, and the things you want first at the new house go in last, because you cannot lift the sofa back out once the van is full. And you lift carefully: bend the knees, keep loads close, and keep the hallway clear so nobody trips over a box. Six hours later the van is loaded and nothing is broken, and that is not luck. You worked out how much, in what order, and how to do it safely, before you picked up a single box. A building site runs on exactly the same three questions.

The facts a builder needs

Before any work starts you read the technical source and work out the _____ requirements: the materials, tools and labour the job needs. Working out how much material to buy is called materials _____, and you always add a _____ allowance on top, because cutting and breakage mean some is lost. Construction has to follow a fixed _____ of work, because you cannot easily undo it once it is built. At the end you _____ the finished work against the success criteria that were set at the start.

How much concrete to pour

A concrete base is 4 metres long, 3 metres wide and 0.2 metres deep. Volume is length times width times depth. What is its volume, in cubic metres?

Build the case for ordering extra

Assemble the reason a builder orders more material than the wall strictly needs.

Site knowledge quick-fire

Five quick decisions on getting a design built. Three lives.

A site that keeps stopping

An invented small building team keeps hitting problems on a job. Work out what went wrong and what to change.

• Halfway through a wall they run out of blocks, and the work stops for two days waiting for more. What was the real mistake?
• On the next job, what should they do before ordering anything?
• A tall stack of blocks is left right across the only walkway. What should happen?

Explain how a build gets made

A friend thinks building is just a matter of following the drawing. Explain what has to happen between reading a technical source and finishing a construction task, and why each part matters.

• Say what a technical source tells you, and what resources you work out from it
• Explain how you calculate the materials needed, and why a wastage allowance is added
• Explain why the order of construction work matters, using the idea that a build is hard to undo
• Give two health and safety working practices, and say what risk each one controls
• Say what the evaluation at the end compares the finished work against