We carry out underpinning and subsidence repairs in Maghull, L31, in Sefton, to the design of a chartered structural engineer. Housing here is mostly post-war and later semis and detached homes, and extensions are common, so many enquiries are about movement where an extension meets the original house. We help establish the cause first and only underpin where the engineer says it is the right repair.
Is it the house or the extension?
Ask a structural engineer where cracks appear on a later-20th-century semi and the junction with an extension will be near the top of the list. An extension may have gone up decades after the house, on foundations of a different depth, on ground disturbed by drainage work, or with a floor slab laid over fill. Any of those can let it move differently. The crack at the join is a symptom; the question is why.
Our page on extension subsidence repair goes into the usual causes. What we can say for Maghull homes in general is that the diagnosis normally comes before any talk of digging.
Warning signs worth noting
- A crack at the extension junction that is new, or wider than it was.
- Cracks wider at the top than the bottom, or running below the damp-proof course.
- Patio or kitchen doors in the extension starting to stick or drop.
- A solid floor that now slopes or has separated from the skirting.
- Cracks that appeared quickly and are wider than about 3 mm, which RICS identifies as the main cause for concern.
Write down the date you noticed each one, take photos with something for scale, and keep them. That record helps the engineer and, if subsidence is suspected, your insurer.
What tends to be investigated
On a Maghull visit we look at how the extension was built where it can be seen, where the drains run beneath or beside it, and any trees or large shrubs nearby. The engineer may then recommend a drain CCTV survey, a trial pit to see the extension footing and the ground under it, or a period of monitoring. Removing trees is never the first step: on clay ground it can trigger heave, and the tree may be protected.
Contact your buildings insurer first if you think the damage could be subsidence. The insurer decides how a claim is investigated and repaired, and whether underpinning is needed.
Possible repairs
Outcomes range from simply repairing a drain and then the cracks, to underpinning the extension alone with traditional concrete bays or mini-piles, to a beam and base scheme. Partial underpinning has to be designed so it does not create a stiff spot that the rest of the house moves against. We price the scheme only after the engineer’s design; our underpinning cost guide explains the factors that drive the figure.
From Maghull we also cover Formby, Crosby and north Liverpool. Read more about underpinning and subsidence repair in Liverpool or see how we approach foundation repairs on Merseyside generally.
Cracking where the extension joins?
Give us a ring on 07777 659786. Tell us when the extension was built, where the crack runs and whether it is changing, and we will arrange a time to come out.
Frequently asked questions
Our house is only about 50 years old. Can it still need underpinning?
It can, though it is uncommon. Newer homes usually have deeper footings than Victorian houses, but they can still be affected by leaking drains, trees on shrinkable ground, or extensions built on shallower foundations. Age alone tells you little; a structural engineer has to look at the cause.
Why is our kitchen floor sloping towards the extension?
A new slope in a solid floor can come from the ground floor slab settling, poorly compacted fill beneath it, or foundation movement. Each needs a different repair. Our sinking floor repair page explains the usual checks, and an engineer would confirm the cause before anything is lifted or filled.
A neighbour removed a big tree and now we have cracks. Could that be heave?
Possibly. When a large, long-standing tree is removed from clay ground, the soil can take up moisture and swell, pushing foundations upwards. It is one possibility among several. Note when the tree came down, photograph the cracks and get an engineer’s view; see our heave damage page for more.
Will I need Building Control approval for underpinning?
Normally yes. The Planning Portal says approval under the Building Regulations will normally be required to underpin an existing foundation. We lodge the notice for the engineer-designed scheme, and Building Control inspects the work and signs it off as applicable.
Can the extension be underpinned without touching the main house?
Sometimes only the extension is treated, but the engineer has to design the junction carefully so the two parts do not move against each other, creating a hard spot. In some cases the better answer is to deal with the cause and repair the junction instead.