Understanding building foundations – where to start

Foundations are essential when it comes to building stability and safety. Every structure needs proper foundations to create a solid base. This means if you’re planning a new construction project or are having issues with your homes’ structural integrity, you’ll need to know more about building foundations.

So, where do you start when it comes to building foundations? Well, the two key factors here are soil conditions and the size and weight of your home. Soil can be made up of a range of different materials including:

• Clay
• Rock
• Gravel
• Sand
• Chalk
• Peat

Each of these soil types will impact the type and depth of foundations you need to keep your home secure. For example, rock is strong and can hold heavy loads, while clay is softer, so you’ll need to dig deeper foundations. One of the best ways to learn more about your soil and how this affects your property is through a soil survey, but this is not essential.

Another key consideration is the load from your home, and this will affect the type of foundation you need (more on this later). For example, if your building is particularly heavy, you’ll likely need deep strip foundations to support the load. You could also use wide strip foundations that are reinforced with steel.

Other common foundation types include:

• Standard strip foundations
• Trench fill foundations
• Raft foundations
• Pad foundations

Read on for further details on these different foundation types.

Foundation building regulations

In order to safely support your property, the appropriate foundations are needed. This is where foundation building regulations come into play. These regulations dictate the type and depth your foundations need to be in order to properly stabilise your building.

Some things to consider when it comes to following building regulations for foundations include:

• Trees: Trees with deep routes near to your home can be a real issue when it comes to foundations. The tree will absorb moisture from the soil under your home, causing the ground to shrink and destabilise your building.
• Soil: Depending on the type of soil under your property, you’ll need to make sure it’s able to bear the load of the structure by digging the right depth and type of foundations.
• Drains: Any drains that are located next to your home may impact your foundations. Building regulations state that foundations should be dug at least as deep as any drains or sewers.
• Other structures: When you’re digging foundations always ensure you don’t impact the foundations of other structures near your home. This can even include researching and following building regulations for porch foundations. You can avoid any issues by digging your new foundations to the depth of the other structures’ foundations.

Types of foundation

Strip foundations

The most common type of foundations used in construction are strip foundations. Building strip foundations are a great choice as they can be used for most types of soil, plus they work well at supporting your home and other structures.

Types of strip foundation include:

• Deep strip foundations
• Concrete strip foundations
• Wide strip foundations
• Reinforced concrete strip foundations

These are the advantages and disadvantages of strip foundations:

• Affordable
• Not too complex
• Can take a while to install
• May need further support

Trench fill foundations

Rather than using bricks for support, trench fill foundations involve filling a trench with concrete for stability. They can also be narrower than other types of foundation, which saves time for installation. Often trench fill foundations are used in places where the soil is looser or if trees are nearby. These foundations are generally safer than strip foundations but require a lot of concrete.

Raft foundations

Like trench fill foundations, raft foundations use concrete for stability. However, rather than filling a trench, concrete is used to cover the entire area under a building.

If you’re curious when to use raft foundation construction, the best time is when soil isn’t strong enough to bear the load of a structure, which is often the case under industrial buildings. The advantages and disadvantages of concrete raft foundations include:

• The design of raft foundations means they’re perfect for supporting heavy buildings when the soil isn’t stable
• You may not need to install a floor on top of the foundations
• If not properly installed, they can be prone to cracks
• The cost of raft foundations can be high
• If your home is near trees, raft foundations may be a good choice.

Pad foundations

Generally used to support loads in a localised point, pad foundations use a concrete ‘pad’ to hold up columns and smaller structures. In addition, pad foundations are great for timber frame buildings.

Some common pad foundations advantages and disadvantages include:

• Less time needed for excavation
• Quite flexible in terms of shape and size
• Can be vulnerable against certain forces
• If the load is high, these foundations will need to be much bigger.

Foundations for single storey buildings

Single storey buildings like bungalows are usually lighter than higher properties which means the foundations need to support a lighter load.

In this case, the best foundations for single storey buildings are either reinforced concrete strip foundations or reinforced pad foundations.

Building foundations over drains

When it comes to property construction you may be relieved to know that building foundations over drains is possible. It is however vital that you check the depth and location of the drain to ensure your foundations are sufficient and you don’t have any building stability issues. For example, if the drain is particularly deep, it’s recommended your foundations are at least at an equal depth.

Planning an exciting new construction project?

If you’re ready to go ahead with a new construction project, getting the foundations right is well worth any time and effort. By hiring a professional you can ensure you have the best foundations at the correct depth to support your building for years to come. Using a recommended tradesperson will mean that you can be safe in the knowledge that your structure is built to the highest standards.

Every Checkatrade member has to pass 12 checks to join and then Checkatrade checks their reviews to make sure they’re written by real people, about real jobs. Added to this, we offer a  guarantee, in the unlikely occasion that anything goes wrong with your job (T&Cs apply).

To find a tradesperson your neighbours recommend, simply enter your postcode into our search.

Looking for further support and guidance? Check out the HomeOwners Alliance website. They have a range of articles designed to help homeowners when it comes to renovations, insurance and even legal matters.

How much do foundations cost to be installed by a professional?

The cost of foundations will depend on a range of factors such as the type of foundations, the depth and the soil type.

Take a look at our new home foundation cost guide for prices and considerations, so you can budget for your project.

Which tradesperson should I use?

If you’re planning to build a new home, you’ll need the services of a general builder or building contractor to lay your foundations. Always check the tradesperson you’re hiring is someone you work well with for a happy, relaxed atmosphere at home.