Extension pulling away repairs in Hampshire

Area: Hampshire
Pricing region: South East
Ground: Shrinkable clay widespread
Towns listed: 22

Is Hampshire prone to ground movement?

Ground movement here is more often linked to soils, drains and trees than to mining. What you mostly find across Hampshire: Victorian terraces in Portsmouth and Southampton, 1930s semis, and large post-war and new-build estates.

How we usually approach extension pulling away repairs

Movement joint and making good

Where some seasonal movement is expected to continue, the junction is formed into a proper flexible movement joint with a compressible filler and sealant, so the two parts can move without cracking. Flashings and internal finishes are detailed to suit.

Best for: Minor ongoing movement that does not threaten the structure

Underpinning the extension

If the extension is still dropping because its footings are too shallow or on poor ground, they are taken deeper by mass concrete, beam-and-base or mini-piles. The engineer designs the scheme, and the junction is repaired once the new foundation is in.

Best for: Active movement from shallow footings, roots or soft ground

Junction crack repair with stainless ties

The open joint is cut out, stainless ties or helical bars are fixed across it into both the old and new masonry, and the joint is repointed or rendered to match. Inside, the corner is replastered. This suits extensions that moved once and have since stopped.

Best for: Settled extensions with a stable gap at the junction

What happens during extension pulling away repairs, step by step?

Show us the junction
Send photos of the crack outside, the internal corner and any flashing above, with a measure for scale. We give a free initial assessment and an initial view on whether the gap is likely old or still opening.
Choose the fix
The engineer decides between ties, a movement joint or underpinning. We confirm a fixed price in writing once the repair is specified, covering the junction, flashings, internal finishes and any foundation work.
Repair the junction
Drains are repaired first if they are leaking. The joint is then tied, formed as a movement joint or rebuilt after underpinning, with roof flashings reset so the junction stays watertight. Building control is handled where needed.

What to look for before calling about extension pulling away repairs

A vertical crack or gap where the extension meets the house
Mastic or render at the joint repeatedly splitting open
Floor level dropping where the extension and house floors meet
Patio doors or windows in the extension starting to bind

Extension pulling away repairs prices in Hampshire

The ranges below reflect typical South East costs for extension pulling away repairs, including VAT. Scaffold, access and making good can push a job to the top of the range.

Guide prices inc VAT on South East rates. Items marked est. are our estimates.
Item	Guide price	Per
Junction crack repair with stainless tiesest.	£670 – £2,250	per junction
Movement joint and making goodest.	£450 – £1,350	per junction
Underpinning the extension where needed	£1,100 – £2,800	per metre of wall

Extension pulling away: tapered gap at the junction tied in with stainless bars. Indicative drawing, not to scale.

Do you need approval for extension pulling away repairs in England?

In England, underpinning and other work that alters or strengthens a wall or foundation is building work under the Building Regulations (Part A, structure), so building control approves and inspects it. Like-for-like repairs often are not, and we tell you which applies before a price is agreed. Work to a party wall, or excavation close to a neighbour’s foundations, can also need a notice under the Party Wall etc. Act 1996.

Towns in Hampshire we cover for extension pulling away repairs

Questions about extension pulling away repairs in Hampshire

Is the ground in Hampshire prone to subsidence?

Central Hampshire is chalk, while the south around Portsmouth, Southampton and the New Forest fringe and the north-east around Farnborough sit on London Clay, Reading Beds and other clays and sands. The clay areas see seasonal movement near trees. Ground movement here is more often linked to soils, drains and trees than to mining. Only an investigation on site can say why a particular building has moved.

How much will extension pulling away repairs cost in Hampshire?

On South East rates, extension pulling away repairs starts from about £670 per junction, including VAT. The written price depends on the extent of the damage, access and whether an engineer or building control is needed.

Why is my extension pulling away from my house?

Usually because the extension and the house sit on different foundations that react differently to the ground. Shallow extension footings, leaking drains under the extension, nearby roots and weak tie-ins between old and new walls are the common causes.

Can I just fill the gap with mastic?

Mastic can keep water out short term, but it does not stop movement or reconnect the walls. If the gap reopens after filling, something is still moving. Photograph and measure it over a few months first, so an engineer can see the trend.

Will my extension need underpinning?

Often not. Many separating extensions are fixed by repairing a drain, tying the junction or forming a movement joint. Underpinning is for extensions that keep dropping because their footings are too shallow or the ground beneath is poor, as shown by monitoring.