Party wall glossary

Part 1: Party Wall Act terms

Adjacent excavation

Digging foundations near a neighbouring building or structure. It's notifiable under section 6 if it's within 3 metres and deeper than the neighbour's foundations, or within 6 metres and cutting below a 45° line drawn down from them. One month's notice is required, with plans and sections. See extensions.

Adjoining owner

The owner of the neighbouring property affected by the proposed work: the person who receives the notice. Usually the neighbour, but it can include a freeholder and leaseholders. See owner.

Agreed surveyor

A single surveyor appointed jointly by both owners to resolve a dispute impartially. Usually the quickest and most cost-effective route to an award.

Appeal

Either owner can appeal against an award to the County Court within 14 days of it being served.

Award (party wall award)

The legally binding document made by the surveyor or surveyors to settle a dispute. It sets out what work will be done, how and when, how the neighbouring property will be protected, and who pays the fees. Often called a "party wall agreement". See party wall awards.

Building owner

The owner who wants to carry out the work and serves the notice. They normally pay the surveyors' fees.

Consent

The adjoining owner agrees in writing to the notice, so the work can proceed without an award. Their home is still protected by the Act, and they can make a schedule of condition a requirement of their consent.

Counter notice

A notice an adjoining owner can serve in reply to a party structure notice, within one month, asking for additional work for their own benefit, such as chimney copings, breasts or flues, or piers or recesses.

Dissent

The adjoining owner doesn't consent, or doesn't reply within 14 days, which counts as dissent. A dispute then arises, and surveyors must be appointed to make an award. Dissenting doesn't mean objecting to the project itself.

Ex parte appointment

If an owner fails to appoint a surveyor within 10 days of being asked in writing, the other owner can appoint a surveyor on their behalf, under section 10(4).

Flashing

A strip of lead or similar material that weatherproofs a junction, such as where a roof meets a wall or chimney. Cutting a new flashing into a party wall is notifiable under section 2.

Line of junction

The boundary line between two properties. Building a new wall on or up to it is notifiable under section 1, with one month's notice.

Making good

Repairing any damage, or disturbance to finishes, caused by the work, at the building owner's expense. Alternatively, the adjoining owner can ask for a payment instead.

Notifiable work

Work covered by the Act that needs notice: work to a party wall or structure (section 2, two months), building at the line of junction (section 1, one month), or adjacent excavation (section 6, one month). Use our notice checker.

Notice lapse

A party wall notice lapses if the work it covers hasn't started within 12 months of the notice being served. A new notice is then needed.

Owner

Under the Act, a freeholder, a leaseholder with more than a year of the lease left, or someone entitled to receive the rent. Tenants on shorter terms aren't owners.

Padstone

A block of concrete or engineering brick set into a wall under the end of a beam, to spread its load. Common in loft conversions.

Party fence wall

A wall of any material that stands astride the boundary, separates two pieces of land and isn't part of a building, such as a shared garden wall. Fences aren't included. See garden walls.

Party structure

A party wall, floor partition or other structure separating parts of a building in different ownership, such as the floor between two flats. See flats.

Party wall

Either a wall that stands on the land of two owners and forms part of a building, or a wall on one owner's land that separates buildings in different ownership, such as the wall between two semi-detached houses. See what your party wall is made of.

Rights of entry

Section 8 gives the building owner, their builders and the surveyors the right to enter the neighbouring property to carry out work under the Act, usually after 14 days' notice (less in an emergency).

Schedule of condition

A dated, photographed record of the neighbouring property's condition before work starts, used to settle any later question of damage. See schedules of condition.

Security for expenses

Money the adjoining owner can ask the building owner to provide before work starts, under section 12, in case the work is left unfinished. Most common for basements.

Special foundations

Foundations reinforced with steel beams or rods to spread the load, such as reinforced concrete. They can only be placed under a neighbour's land with that neighbour's written consent.

Third surveyor

Where each owner appoints their own surveyor, the two surveyors select a third surveyor at the outset. The third surveyor is only called on if the two can't agree, or at either owner's request.

Underpinning

Deepening or strengthening the foundations of an existing wall. Underpinning a party wall is notifiable under section 2. It's common in basement work.

Part 2: Terms used in our schedules of condition

A schedule of condition records the state of a property before building work starts next door. These are the terms we use to describe what we find.

Internal decoration and finishes

Architrave

The moulded trim around a door or window opening.

Blistering

Visible bubbles or lifting in paintwork.

Blown plaster

Plaster that sounds hollow when tapped because it has lost its key (bond) to the wall behind.

Cornice

A decorative moulding, usually plaster, where the wall meets the ceiling. More ornate than coving.

Coving

Plaster or polystyrene mouldings along the junction between the ceiling and the walls.

Delaminated / debonded

Plaster or render that has lost its adhesion to the masonry behind it.

Dot and dab

Plasterboard fixed to a wall with dabs of adhesive.

Dry lining

Plasterboard fixed to a wall, instead of wet plaster applied directly to the masonry.

Flaking and peeling

Deteriorated paintwork lifting away from the surface.

Friable

Plaster that crumbles easily into powder and feels soft, chalky or weak.

Joist lines

Faint lines in a ceiling finish that show the position of the joists behind it.

Lath and plaster

Traditional wall and ceiling construction in older buildings: thin timber strips (laths) covered in lime plaster, often reinforced with horsehair.

Nib

A small unwanted lump or projection of plaster.

Shrinkage cracks

Fine cracks in new or recent plaster caused by it drying out. Usually cosmetic.

Skirting

The board running along the bottom of an internal wall.

Sloping ceiling junction

Where the roof slope cuts into a room, so the ceiling meets the wall at an angle rather than a right angle.

Textured coating (Artex)

A decorative textured finish on ceilings or walls. Coatings applied before about 2000 may contain asbestos and shouldn't be sanded or disturbed without testing.

Water staining / tide mark

Brown or yellow marks left by a past or present leak or damp. A tide mark is the edge of the stained area.

Masonry and brickwork

Bed joints

The horizontal mortar joints in brickwork.

Corbel / corbel course

Courses of brick or stone that each project further out than the one below, forming a stepped projection.

Crazing

A fine network of surface cracks in render or plaster.

Cryptoflorescence

Salt crystallising hidden inside brick or stone, which can cause the surface to spall.

Dentil course

A decorative course of small, tooth-like projecting bricks.

Efflorescence

White powdery salt deposits on masonry, left as moisture evaporates.

English bond

Brickwork with alternating courses of headers and stretchers. A strong traditional bond, typical of solid walls.

English garden wall bond

Three (sometimes five) courses of stretchers to every one course of headers.

Flank wall

A side wall of a building, rather than the front or rear, typically facing the neighbouring property or the boundary.

Flemish bond

Brickwork with headers and stretchers alternating within each course. Decorative and strong, typical of solid walls.

Flemish garden wall bond

Three (sometimes more) stretchers to every header within each course.

Frost damage (frost attack)

Cracking or spalling of brick or stone caused by water freezing in its pores.

Grinning through

Mortar joints or the masonry behind showing through thin render or paint. Also called visibly expressed.

Header bond

Brickwork with every brick laid with its short end (header) showing.

Kiln crack (firing crack)

A crack formed in a brick during manufacture, rather than resulting from stress or load in the wall.

Lintel

A beam of timber, concrete, stone or steel over a door or window opening, supporting the wall above.

Oversailing course

One or more projecting courses, especially at the top of walls, chimneys or gables.

Pebble-dash

Render with small stones thrown onto it while wet.

Perpends (perps)

The vertical mortar joints in brickwork.

Pointing

The mortar finish to the joints between bricks. Repointing replaces worn or eroded pointing.

Render

A sand and cement (or lime) coating applied to external walls.

Spalling

Flaking, cracking or breaking away of the surface of brick, stone or concrete, often from frost or salt damage.

Stretcher bond

Brickwork with every brick laid lengthways. Common in modern cavity walls.

String course / belt course

A single (or narrow) horizontal projecting course of brick or stone.

Damp and moisture

Bridging

Material such as soil, paving, render or debris that bypasses the damp-proof course, letting moisture through.

Condensation

Moisture forming on cold surfaces from warm, humid air. Often leads to black mould.

DPC (damp-proof course)

An impervious layer built into a wall, just above ground level, to stop rising damp.

DPM (damp-proof membrane)

A sheet membrane in a ground floor that stops moisture rising from the ground.

Penetrating damp

Rainwater getting in through walls or roofs, for example through cracks, poor pointing or defective flashings.

Rising damp

Moisture rising from the ground through masonry by capillary action, usually where a damp-proof course has failed or is missing.

Timber defects

Deathwatch beetle

A larger wood-boring beetle found in old hardwoods such as oak, often alongside fungal decay.

Dry rot

Serpula lacrymans: an aggressive fungal decay that can spread through masonry, leaving timber with deep cube-shaped cracking.

Wet rot

Fungal decay in persistently damp timber, leaving it soft and dark.

Woodworm (beetle infestation)

Small exit holes and bore dust caused by wood-boring insects, most commonly the common furniture beetle.

Structural movement

Cracking

Cracks are recorded by width, length, direction and location. Width is graded using the BRE Digest 251 crack categories (see the table at the end of this glossary).

Heave

Upward movement of the ground, for example when clay soil swells after trees are removed.

Lateral movement / bulging

A wall leaning or bowing outwards.

Roof spread

Outward movement at the top of the walls caused by a roof pushing outwards, usually through missing or failed ties or rafters.

Settlement

Initial downward movement as a new building beds into the ground. Usually historic and stable, as distinct from ongoing subsidence.

Subsidence

Downward movement of the ground supporting the foundations. Often shows as diagonal cracks that are wider at the top.

Underpinning

Deepening or strengthening the foundations of an existing wall. Underpinning a party wall is notifiable under the Party Wall Act.

Wall tie failure

Corrosion of the metal ties linking the two leaves of a cavity wall. It typically shows as horizontal cracking along the mortar joints.

Roof and external

Barge board

The board fixed along the edge of the roof at a gable end.

Coping / coping stones

The protective top course on a parapet, chimney or garden wall, shedding water away from the wall.

Eaves

The lower edge of a roof, where it overhangs the wall.

Fascia

The board along the eaves to which the gutter is usually fixed.

Flashing

A strip of lead or similar material that weatherproofs a junction, such as where a roof meets a wall or chimney.

Flaunching

The sloping mortar around the base of chimney pots on top of the stack.

Gable

The triangular upper part of an end wall, under a pitched roof.

Hip

The sloping external angle where two roof slopes meet. A hipped end is a roof end that slopes back instead of finishing with a gable.

Parapet

A low wall projecting above the roof line, at the edge of a roof or along a party wall.

Ridge

The top edge of a roof, where the sloping sides meet.

Soffit

The underside of the eaves overhang.

Valley

The internal angle where two roof slopes meet, forming a channel for rainwater.

Verge

The edge of a pitched roof at a gable end.

Roof structure (in the loft)

Battens

Horizontal timbers fixed across the rafters, on which the roof tiles or slates are hung.

Binder

A timber running across the ceiling joists, tying them together and supported by hangers.

Ceiling joist

A horizontal timber supporting the ceiling below and the loft floor.

Hanger

A vertical timber, in tension, linking the purlin (or rafters) to a binder that supports the ceiling joists.

Purlin

A horizontal beam running the length of the roof, supporting the rafters roughly midway along their span.

Rafter

A sloping timber running from the wall plate up to the ridge.

Sarking felt / roof membrane

The underlay beneath the battens and tiles that acts as a secondary barrier to wind and water.

Strut

A near-vertical or angled timber, in compression, carrying the purlin down to a load-bearing wall or binder below.

Wall plate

A timber laid along the top of a wall, on which the rafters and ceiling joists sit.

Windows and doors

Casement

A window that opens on hinges.

Fanlight

A small glazed panel above a door or window, often semi-circular.

Head

The top horizontal member of a window or door frame.

Horn

A short projection on the frame of a sash window, adding strength.

Jamb

The vertical sides of a window or door frame.

Mullion

A vertical bar dividing a window into sections.

Putty / glazing bead

The material or timber strip holding the glass in place.

Reveal

The side of a window or door opening, between the frame and the face of the wall.

Sash

The opening frame of a window that holds the glass. In a sash window, the sashes slide, usually vertically.

Sill / cill

The bottom horizontal member of a window or door frame, sloped to shed water.

Transom

A horizontal bar dividing a window, or separating a fanlight from the door below.

Drainage and general

Asbestos

A hazardous material found in many buildings constructed before 2000, for example in cement sheets, textured coatings, floor tiles and pipe lagging.

Carbonation

Loss of alkalinity in concrete over time, which can lead to its steel reinforcement corroding.

French drain

A gravel-filled trench, often with a perforated pipe, that collects and redirects groundwater. It can silt up over time.

Gully

A ground-level drain that takes water from downpipes, sinks or paved areas.

Inspection chamber (IC)

A shallow chamber giving access to drains for inspection and rodding, not intended for a person to enter. Typically under 1.2 m deep.

Manhole (MH)

A deeper drainage chamber, large enough for a person to enter.

Soakaway

An underground pit or crate that lets surface water drain away into the ground. It can block or fail over time.

Crack categories (BRE Digest 251)

We grade crack widths using the Building Research Establishment's widely used scale. Width is only one factor: the location, direction, length and number of cracks matter too.