Building a concrete foundation might seem complicated, but it’s actually quite straightforward when you break it down. The key is doing each step properly and in the right order. Let’s walk through the whole process so you know what to expect.
Planning and Preparation
Before any digging starts, you need a proper plan. This means having detailed drawings that show exactly where the foundation goes, how deep it needs to be, and what size it should be.
The first job is marking out where the foundation will go. This is done with wooden stakes and string lines to show the exact outline. Everything gets measured twice because getting this wrong means big problems later.
You also need to check for things like gas pipes, water mains, or electricity cables. These are marked clearly so the diggers know where they are. The last thing you want is to hit a gas pipe whilst digging.
Site Preparation and Excavation
Once everything is marked out, the digging begins. This needs to go down to what’s called the formation level – that’s the bottom of where your foundation will sit.
The depth depends on several things. The type of soil matters a lot. Clay soil means you might need to go deeper because it moves more when it gets wet or dry. Sandy soil is usually more stable.
The size of your building matters too. A small garden shed needs much less than a two-storey house. Your structural engineer will tell you exactly how deep to go based on soil tests and building loads.
All the soil that comes out needs to go somewhere. Usually it gets taken away by lorry, though sometimes you can use some of it elsewhere on site for landscaping.
Setting Up the Formwork
Formwork is basically the mould that holds the concrete in the right shape whilst it sets. For foundations, this is usually made from timber boards or steel panels.
The formwork needs to be dead straight and properly supported. If it moves whilst the concrete is being poured, you’ll end up with a wonky foundation. That’s not something you can easily fix later.
Everything gets checked with spirit levels to make sure it’s perfectly level and square. The formwork also needs to be the right height to give you the correct thickness of concrete.
Oil or release agent gets sprayed on the inside surfaces so the formwork comes off easily once the concrete has set.
Installing Reinforcement
Most foundations need steel reinforcement bars (called rebar) to make them stronger. These get laid out in a grid pattern and tied together with wire.
The rebar needs to be held at the right height in the concrete. This is done with plastic spacers that lift the steel off the bottom of the excavation. You want the steel in the middle of the concrete thickness, not sitting on the bottom.
All the joints between rebar pieces need proper overlap lengths. This makes sure the reinforcement works as one continuous piece rather than lots of separate bits.
The rebar also needs to be clean – no rust, oil, or mud on it. Dirty steel doesn’t bond properly with the concrete.
Preparing for the Pour
Before any concrete arrives, everything gets checked one more time. The formwork, the reinforcement, the levels – everything needs to be right because you can’t stop halfway through a concrete pour to fix problems.
You need clear access for the concrete trucks. They’re heavy and need firm ground to drive on. If they can’t get close enough, you might need a concrete pump to get the concrete where it needs to go.
The weather gets checked too. You can’t pour concrete if it’s going to freeze before it sets properly. Very hot weather can also cause problems by making the concrete set too quickly.
Pouring the Concrete
This is where all the preparation pays off. The concrete needs to be placed quickly and evenly. Most foundation pours happen in one go to avoid weak spots where different batches join together.
The concrete gets poured in layers, usually about 500mm thick at a time. Each layer gets vibrated to remove air bubbles and make sure it fills all the corners properly.
Vibration is really important. Air bubbles make concrete weak, so you need to get them out. This is done with special vibrating tools that go into the wet concrete.
The concrete also needs to be level. This is done with screeds – long straight boards that get dragged across the surface to make it flat and smooth.
Curing and Protection
Once the concrete is poured and levelled, the work isn’t finished. Concrete needs time to get strong, and it needs the right conditions to do this properly.
For the first few days, the concrete needs to stay damp. If it dries out too quickly, it doesn’t reach full strength. This might mean covering it with plastic sheeting or spraying it with water.
In cold weather, the concrete might need protecting from frost. This could mean covering it with insulation or even using heaters in very cold conditions.
The concrete gets stronger over time. It’s usually strong enough to take the formwork off after a few days, but it keeps getting stronger for weeks.
Quality Checks
Throughout the whole process, there are checks to make sure everything is being done properly. The concrete mix gets tested to make sure it’s the right strength.
Samples of concrete get taken during the pour and tested later to check they meet the required strength. If they don’t, you need to find out why and what to do about it.
The finished foundation gets measured to check it’s the right size and in the right place. The levels get checked to make sure everything is square and level.
Common Problems to Avoid
The most common problems come from rushing or skipping steps. Poor ground preparation leads to uneven settling. Dirty reinforcement doesn’t bond properly. Formwork that moves gives you walls that aren’t straight.
Weather problems can be avoided with proper planning. Don’t pour concrete if the weather forecast shows frost or very hot conditions.
Getting the concrete mix wrong is another common issue. The mix needs to be right for the specific job. Too wet and it’s weak. Too dry and it doesn’t flow properly.
Working with Professionals
Foundation work isn’t usually a DIY job. The planning, the excavation, the reinforcement – it all needs to be done by people who know what they’re doing.
At Base Concrete, we handle foundation projects from start to finish. We work with structural engineers to make sure everything is designed properly. Our experienced crews know how to handle each step of the process.
We also coordinate with other trades like groundworkers and builders to make sure everything happens in the right order. Good foundations are the starting point for any successful building project.
The key is getting it right first time. Fixing foundation problems later is expensive and disruptive. Do it properly from the start, and you’ll have a solid base that lasts for decades