Types of foundations in Irish homes

Ireland is dominated by various soil types, and this diversity impacts which foundation is most suited to the area. Factors such as ground conditions, load requirements and type of building are considered when determining the best foundations. Here’s a quick guide to the most common foundation types in Ireland.

Strip foundations

As the name suggests, strip foundations consist of a continuous strip of concrete that supports load bearing, spreading the weight of the building across a stable layer of soil. Whilst this is the most common type of foundations used in Ireland, it’s not immune to problems, some of the most issues include: 

• Differential settlement

• Clay shrinkage and swelling

• Cracks in walls

Signs of foundation problems may appear as: diagonal cracks in walls, especially near corners and door frames, or sticking doors and windows.  

Trench fill foundations

This type of foundation is similar to strip foundations but involves filling the whole trench with concrete. It’s often used when surface soil is weak and cannot support the building’s load alone. 

Trench fill foundations offer several advantages:

• Quicker to construct

• Reduced labour

• Suitable for a range of soil types

Whilst trench fill foundations increase stability of the ground, movement may still affect the property. Poor drainage can also weaken the concrete and surrounding soil.

Raft foundations

Raft foundations, often referred to as mat foundations, are large reinforced concrete slabs that cover the entire footprint of the building. This type of foundation spreads the load evenly, making it ideal for soils with low bearing capacity. It can also be used where there is a risk of uneven settlement. 

However, slab cracking can occur if the concrete is poorly reinforced. Additionally, if the coil beneath the rafts shifts or weakens, it can lead to settlement. 

Pad foundations

This type of foundation consists of isolated concrete pads, which support individual columns or key structural points. Pad foundations are often used for extensions, garages, or modern frame buildings.

Some potential problems can occur. As each pad is individual, there may be uneven settlement under the surface. There can also be movement between the pads, leading to structural misalignment. 

Piled foundations

These are deep foundations that transfer building loads to stable soil layers deep underground and may be driven or bored into the ground. Pile foundations are commonly used in areas with poor soil or high-water tables.  

In some cases, however, pile movement can occur under load. Also, if the soil shifts between the piles, this can lead to settlement.

Common foundation problems in Irish homes

Property foundations can experience problems over time, mainly because of soil movement, water changes, poor ground preparation or ageing structures. These issues can cause cracks, uneven floors, and structural instability. The key is recognising issues early to prevent further damage. 

Subsidence

Subsidence occurs when the ground beneath a property’s foundation sinks, often because of a  destabilisation in soil conditions or inadequate drainage. Signs of subsidence include:

• Stepped cracks in brickwork

• Sinking or uneven floors

• Leaning walls

Although this sounds concerning, a professional assessment can treat affected soil, support foundations and incorporative preventative measures to avoid further damage. 

Foundation settlement

Settlement refers to the gradual downward sinking of a building. it can be classified into two types:

• Uniform settlement: this is where the building sinks evenly. It’s usually harmless.

• Differential settlement: uneven sinking. This poses a structural risk to your property.

How to tell if your property is experiencing differential settlement? Here are the warning signs you should watch for: 

• Cracks above doors and windows

• Sloping floors

• Gaps in exterior joints

Water and drainage issues

Water leaking or pooling on the surface because of poor drainage systems or blocked gutters can severely impact your foundations. Excess water can wash away soil, reducing its strength and causing foundations to shift. Increased moisture in the soil can also make it softer, reducing its bearing capacity to support the foundations. 

Modern solutions for foundation problems

Although traditional underpinning is required in some cases, it’s costly and often requires extensive excavation. Modern ground engineering methods, provide a more direct approach to stabilise foundations with minimal disruption. 

Resin injection ground improvement

One of the most innovative solutions is resin injection. The technique involves injecting expanding resin into the soil beneath a foundation, which fills voids, strengthens the ground, and even lift and relevel a structure if needed. Resin injection offers several advantages: 

• Minimal disruption to the home

• Fast installation, often completed in a few hours

• No major excavation required

Structural engineers such as Mainmark Ireland, specialise in non-invasive methods such as resin injection, providing a modern and efficient alternative to traditional solutions.

When should you get your foundations checked?

You should consider arranging for a subsidence survey if you notice the following: 

• New cracks appearing or if existing cracks are widening

• Uneven or sloping floors

• Doors or windows sticking

• Visible ground movement around the property

Remember, an early assessment of your home can prevent minor issues from becoming a major structural issue requiring costly repairs. 

Understanding your home’s foundations

Whilst each foundation type can experience movement or cracking over time, knowing the early warning signs of foundation problems can help prevent serious structural damage.

Although traditional underpinning methods may be necessary in some cases to fix foundation problems, modern solutions, such as resin injection ground improvement, allow foundations to be supported without major excavation, reducing both cost and disruption. 

If you’re uncertain about your property foundations, seeking professional advice from specialists such as Mainmark Ireland can protect your property and provide reassurance.

FAQs

What type of foundation is most common in Ireland?

Strip foundations are the most common in Ireland. Strip foundations are a continuous strip of concrete that supports load bearing, spreading the weight of the building across a stable layer of soil.

Are foundation problems common in Ireland?

Yes, foundation problems are common in Ireland, particularly in areas dominated by clay-rich soils and peat. 

What causes foundation problems in Irish homes?

Subsidence, soil movement, poor drainage and tree roots extracting moisture are some of the most common causes of foundation problems in Ireland.  

What soil types affect house foundations in Ireland?

The main soil types that affect property foundations in Ireland are clay, peat, silty soils and made ground. These soil types can cause significant structural issues thanks to their low bearing capacity or continuous moisture changes. 

How serious are cracks in house foundations?

Not all cracks are a cause for concern. Some cracks are a result of natural building settlement over time; however, some cracks indicate structural issues. Horizontal cracks, diagonal cracks, or any with a gap wider than 3mm can suggest subsidence. 

What are the warning signs of foundation problems?

Foundation problems can appear as diagonal, horizontal, or stair-step cracks in walls and floors, sticking doors or windows, uneven floors, and bowing basement walls. These issues require a professional assessment to prevent structural damage.

Can foundations be repaired without excavation?

Yes, foundation repairs are possible without major excavation using modern, non-invasive techniques. Resin injection and computer-controlled grouting are popular methods to improve sinking foundations. 

How much does foundation repair cost in Ireland?

In Ireland, foundation repair costs can vary significantly and depends on the cause, severity and method of repair. Underpinning for example, can cost between €1,150–€1,700 per linear metre. 

Should I get my foundations checked by a professional?

Yes, you should get your foundations checked by a professional if you notice any signs of structural damage. Early intervention can prevent any costly remedial works in the future.