Underpinning in Liverpool and Merseyside

What is underpinning, and do you actually need it?

A foundation spreads the weight of a house into the ground beneath it. When that ground shrinks, softens, washes away or swells, the foundation moves with it and the walls above crack. Underpinning extends the foundation downwards, or transfers the load onto piles or bases, so the building is carried by ground that is no longer affected by the movement. It is a proper structural solution, and for the right house it is the correct one. It is also disruptive, needs Building Regulations approval and often involves the neighbours, so it should never be the first idea on the table.

The RICS consumer guide on subsidence says fewer than 5% of affected properties need underpinning, and that the Institution of Structural Engineers recommends it only as a last resort. In practice that means the first job is diagnosis. A leaking drain can be repaired; a thirsty tree can be managed on an arboriculturist’s and engineer’s advice; seasonal movement can be monitored until it is understood. Once the cause has gone and the ground has stabilised, the cracks themselves can usually be repaired without touching the foundations.

Underpinning comes into its own where the cause cannot be removed, where the original footings are simply too shallow for the ground they sit on, or where a structural engineer’s investigation shows that movement will carry on without it. Typical examples include a house close to a large protected tree on shrinkable clay, an old building on soft or made ground, a bay window on much shallower footings than the main walls, or an extension that was never founded deeply enough.

Which signs suggest foundation movement?

Not every crack is a foundation problem. Plaster shrinks, new houses settle, timber dries out and lintels sag for reasons that have nothing to do with the ground. The signs that are more often linked to subsidence or heave, and are worth having looked at, include:

• new cracks in plaster or outside brickwork, or existing cracks that are getting wider;
• cracks that are wider at the top than at the bottom, or that run diagonally from the corners of windows and doors;
• cracks that carry on through the damp-proof course into the masonry below ground level;
• doors and windows that start to stick or jam for no obvious reason;
• wallpaper rippling or tearing at the joins where wall meets ceiling;
• a new slope in a solid floor, or a gap opening between skirting boards and the floor;
• a bay window, porch or extension that seems to be pulling away from the house.

The RICS guidance is that cracks which appear suddenly and are wider than 3 mm are the main cause for concern, but width is not the whole story. A fine crack that keeps growing can matter more than a wider one that has not moved in decades. Our guide to subsidence and house cracks explains crack categories, common patterns and what each one can point to, so you know what to photograph and what to tell an engineer.

Underpinning and structural repair services we carry out

Because underpinning is rarely the whole answer, we cover the investigation, the repair and the making good, so one contractor follows the engineer’s scheme from start to finish. Our work falls into five broad groups.

Finding out what is really happening

• Structural engineer surveyBefore anyone talks about foundations, a structural engineer’s survey of the property looks at the crack pattern, the age and construction of the house and the likely cause of movement.
• Soil and site investigationTrial pits, boreholes and soil testing show how deep the footings go, what they bear on, whether roots are present and how the clay or sand behaves.
• Crack and movement monitoringWhere the picture is unclear, monitoring cracks and levels over time shows whether movement is seasonal, progressive or has stopped.
• Drains and subsidenceLeaking drains are a common cause of washed-out or softened ground, so drainage-related subsidence repairs start with a CCTV survey and repairs to the drains themselves.

Underpinning methods

• Mini-piled underpinningSmall-diameter piles taken down to firm ground and connected to the walls by reinforced concrete needles or beams, suited to deep soft ground, made ground and tree-affected clay.
• Mass concrete underpinningThe traditional method: mass concrete underpinning dug in short bays in a planned sequence, so the wall is never left unsupported along its length.
• Resin injectionWhere the soil and the cause suit it, resin injection underpinning fills voids and stiffens the ground under a footing through small holes, with far less excavation.
• Beam and baseA reinforced concrete beam carries the wall load to concrete bases at intervals; we explain when beam and base underpinning makes sense.
• Cellars and basementsMany older Liverpool houses have cellars, and cellar and basement underpinning needs careful sequencing, temporary support and attention to water.

Subsidence and ground movement repairs

• Subsidence repairsOur subsidence repair work in Liverpool covers the whole process: removing the cause, stabilising, and repairing the structure and finishes.
• Bay windowsVictorian, Edwardian and inter-war bays often sit on shallower footings than the main walls, so bay window subsidence repair is one of the most common jobs we see.
• ExtensionsAn extension on different foundations can move separately from the house; extension subsidence repair starts by finding out why the junction has cracked.
• HeaveClay that swells after a large tree is removed or the ground is saturated can lift a house; heave damage repair needs a different approach from shrinkage.
• Sinking floorsSolid floors that drop away from the skirting, often because the fill beneath has compacted, are dealt with through sinking floor repair designed for the cause.

Walls, masonry and openings

• Structural crack repairOnce movement has stopped, structural crack repair restores the masonry inside and out rather than just filling the gap.
• Crack stitchingCrack stitching with stainless steel helical bars bonded into the bed joints ties cracked brickwork back together.
• Bowing wallsA wall leaning out at a gable or between floors can be caused by failed ties, poor restraint or movement; bowing wall repair follows the engineer’s assessment.
• Wall tiesCorroded mild steel ties in older cavity walls cause horizontal cracking and bulging, and wall tie replacement fixes stainless steel remedial ties into both leaves.
• LintelsCracking above windows and doors is not always subsidence; often it is a failed steel or timber lintel, solved by lintel replacement with temporary support.
• Retaining wallsGarden and boundary walls holding back ground on sloping plots can lean or crack, and retaining wall repair deals with drainage, foundations and the wall itself.

Insurers and neighbours

• Insurance claimsIf you think you have subsidence, speak to your buildings insurer first. Our page on subsidence insurance claims explains how the process usually runs and where a contractor fits in.
• Party wallsUnderpinning in a terrace or semi usually means considering the Party Wall etc. Act 1996; we explain how party walls and underpinning work alongside the surveyors.

How do the main underpinning methods compare?

The engineer chooses the method after investigation, based on the depth to suitable ground, the soil type, nearby trees and drains, access and the neighbours. This table is a general guide, not a recommendation for any particular house.

What happens when you call us?

1. We talk it through. We ask what you have noticed: where the cracks are, roughly how wide, whether they are new or growing, and whether doors, windows or floors have changed. We also ask about the age and type of house, nearby trees, drains, bays and extensions, and whether an insurer, buyer, lender or neighbour is involved.
2. We visit and look. We arrange a visit to see the cracking and the surroundings for ourselves, inside and out.
3. The cause is investigated. If the cause is not clear, we recommend a chartered structural engineer’s inspection and, where needed, trial pits, soil tests, a CCTV drain survey or monitoring before any repair is chosen.
4. You get the options in plain English. We explain what the engineer’s findings mean and give a written quote for the engineer-designed scheme.
5. Permissions are dealt with. We handle the Building Control notice and work alongside party wall surveyors where the Act applies.
6. The work is done in planned stages. Underpinning is carried out section by section, in the order the engineer sets, followed by crack repairs and making good.
7. The work is signed off. The engineer and Building Control inspect and sign off the work as applicable, so you have the paperwork a future buyer or lender will ask for.

Underpinning and your buildings insurance

Buildings insurance usually covers subsidence damage to the home itself, according to the Association of British Insurers. If you think your house is moving, contact your insurer before you commission any repairs. The insurer, through its loss adjuster and engineer, decides on investigation, monitoring, whether a tree or drain needs dealing with, and which repair is needed, including whether underpinning is needed at all. Starting work yourself first can complicate a claim.

At the end of an insurance-funded repair, the insurer’s engineer often provides a certificate of structural adequacy, and buyers’ solicitors commonly ask for it when the house is sold. If the work is privately funded, the engineer’s design, the Building Control completion certificate and the engineer’s sign-off serve the same purpose.

Building Control and party walls

The Planning Portal states that approval under the building regulations will normally be required if you propose to underpin an existing foundation. Underpinning is structural work under Part A of the Building Regulations 2010, so Building Control from Liverpool, Sefton, Knowsley, St Helens, Wirral or Halton council, or a registered building control approver, inspects the excavations and the finished work.

In a terrace or semi-detached house, digging near or below a neighbour’s foundations usually brings in the Party Wall etc. Act 1996. Notice has to be served before work starts, and if the neighbour does not consent, surveyors are appointed to agree a binding written decision covering how the work is done. We are not party wall surveyors and do not give legal advice, but we work with the surveyors and build their requirements into the programme.

Underpinning across Liverpool and Merseyside

The ground across the Liverpool city region varies a great deal. The British Geological Survey describes bedrock largely of Sherwood Sandstone, with much of the district covered by glacial clay and, along the Sefton and north Wirral coasts, blown and dune sand. Some places have soft river and coastal deposits, made ground or backfilled former clay pits. None of this tells you what is under a particular house, which is why investigation comes first, but it explains why the causes we see differ from one part of Merseyside to another.

Housing matters just as much. In south Liverpool, underpinning in Allerton, Mossley Hill and Aigburth often involves Victorian, Edwardian and inter-war homes with bay windows and mature trees close by. Further east, calls from Woolton, Childwall and West Derby frequently concern extended semis and larger gardens. In north Liverpool, the dense terraces of Walton mean party walls are almost always part of the conversation.

On the Sefton coast, homes in Crosby, Formby and Southport can sit on sandy ground, where leaking drains are a common worry. In St Helens, the former coal-mining legacy means a GOV.UK coal mining search is a sensible early step, and our page on underpinning in St Helens explains why. Across the river, the Victorian terraces and villas of Birkenhead and the large sloping gardens of Heswall raise their own questions. Our page on the areas we cover in Merseyside lists every town and suburb we work in, including Huyton, Prescot, Widnes and Wallasey.

How much does underpinning cost?

There is no honest single price for underpinning, because the job changes completely with the method, how deep the engineer needs to go to reach suitable ground, how much wall is involved, access for machinery and spoil, and what has to be done to drains, trees and the inside of the house. Investigation, monitoring, engineer’s fees, Building Control fees and party wall surveyors’ fees can all sit on top of the building work. For an insurance-funded repair, the insurer decides the scope and the policy sets the excess.

Our guide to underpinning costs in Liverpool sets out the main cost factors, quotes published national figures with their sources, and explains how to compare quotes fairly. We only price a scheme once the engineer has designed it.

When is it urgent?

Most structural movement is slow, measured in millimetres over months or seasons, and there is time to investigate properly. Get urgent professional advice if cracks open quickly, a wall leans noticeably, a doorway distorts badly or a ceiling looks unsafe. Keep people away from the area, and if a building is dangerous the council’s building control (dangerous structures) team can be contacted. If movement has damaged a gas pipe and you smell gas, leave the property and call the National Gas Emergency Service on 0800 111 999.

In the meantime, the safe things to do are simple: photograph each crack with a ruler or coin beside it and note the date, write down any doors or windows that begin to stick, keep gutters and drains running freely, and do not start building work or tree work until you have advice. Please do not fill and paint over cracks before the cause is known, because the history of how a crack has changed is exactly what an engineer needs to see.