Cellar and Basement Movement in Bradford

What a cellar wall is actually doing

In a hillside terrace the cellar wall on the uphill side is a retaining wall that also carries a house. It resists lateral earth pressure - which rises sharply when the ground behind it is saturated - while simultaneously taking vertical load from everything above.

Those two jobs pull in different directions, and old cellar walls were built with neither calculated. Stone or brick, lime mortar, no drainage layer behind, no tanking, and a floor that is often little more than flags on soil. They have generally performed well for a very long time, which is worth saying - but when they do move, it is usually because water changed the lateral load.

What is normal in a Bradford cellar

Most of what alarms people down there is ordinary for the building's age:

• Damp walls, salting and a musty smell - a cellar of this construction was never tanked and was never meant to be dry in the modern sense
• Open or eroded lime mortar joints
• Old, decorated-over or dirt-filled cracking that has plainly been there for decades
• A stone flag or earth floor, and a coal chute or grate opening
• Some unevenness in the walls, particularly in rubble-built work
• Brick or stone arches over openings, occasionally cracked and still perfectly stable

What is worth taking seriously

The markers that turn an old cellar into a structural question:

• A horizontal crack, particularly in the lower half of a wall retaining ground - this indicates bending under lateral pressure and is the pattern that matters most
• Bulging inwards, which is the same mechanism further along. Sight along the wall from a corner at a shallow angle.
• Water actively running in, rather than general dampness - it points at a defective drain, gutter or culvert, and washout is both a cause and a symptom
• Movement in the wall above, on the same line, suggesting the cellar wall is not doing its job
• Loose or displaced stones, or a section that has moved forward relative to its neighbours
• Cracking that is fresh, or measurably growing
• Anything that has changed since the neighbours did work - excavation next door is transmitted through a terrace

Lowering the floor: the alteration to think hardest about

Cellar conversion is popular here because the space exists and headroom is usually the only thing missing. Lowering the floor to gain it means underpinning walls that are already retaining ground and already carrying a house that is restrained by two or three neighbours. It is a structural operation, not fitting-out work.

What it needs designing:

• What the existing foundations actually are and what they bear on - established by trial pit, not assumed
• The underpinning design, and critically the sequence: which bays are excavated in what order, and what is propped meanwhile
• The retained height after lowering, which increases the lateral load on a wall that was marginal to begin with
• Groundwater and drainage, designed together with the waterproofing rather than bolted on afterwards
• Party wall notices - in a terrace, and especially a back-to-back, you are likely to be serving on more than one neighbour, and the notice periods belong in the programme
• Building Control approval, because underpinning is notifiable work

Water is usually the story

Most cellar structural problems in this city start as water problems. Bradford Beck and a number of the district's other watercourses were culverted in the nineteenth century, drains are old, and hillside sites move a lot of water through the ground.

A defective drain or culvert doing two things at once - raising the pressure behind a cellar wall and washing fines out from beneath a foundation - is a common and comparatively cheap thing to find, and it is one of the first things we test for. Fixing a cellar wall without fixing the water is a repair with a return date.

What we do

Inspect the cellar and the building above it as one structure, classify any cracking against the BRE Digest 251 categories, sight and measure for bulge and lean, and identify whether water is involved. Where one visit cannot establish whether a wall is still moving, monitoring across the seasons will.

The most common conclusion is that the cellar has looked like that for a century and the building is stable. We do not carry out remedial works and take no commission from anyone who does. A structural survey and report is a fixed £580 + VAT, with the report inside 10 working days of the inspection, guaranteed.