Question 1

Article 4 Direction

Accepted Answer

An Article 4 direction removes particular permitted development rights, such as replacing front windows, altering roofs or building rear extensions, so that work which would normally be allowed needs planning permission. They are common in conservation areas. We check for Article 4 directions on every property before design starts.

Question 2

Build Over Agreement

Accepted Answer

Many extensions are built over or close to shared sewers that belong to the water company. Before building within the protected distance you need their approval, usually a build over agreement, and the sewer may need a CCTV survey or protection. In most of London this is Thames Water. We check sewer records at survey stage.

Question 3

Building Control

Accepted Answer

Building Control is the authority, either the local council or a private approved inspector, that checks construction work complies with Building Regulations. They review plans and inspect at key stages including foundations, damp proof course, oversite concrete, drainage, insulation, and completion. Building Control fees range from £500 to £1,500 depending on work scope. The Completion Certificate they issue is essential when selling the property, and solicitors will request it during conveyancing.

Question 4

Building Regulations

Accepted Answer

Building Regulations are technical standards covering structural integrity, fire safety, energy efficiency, accessibility, and more. All extensions, loft conversions, and structural alterations require Building Regulations approval. Approval is obtained via Full Plans submission (detailed drawings checked in advance) or Building Notice (less detail, more risk). Building Control inspectors visit at key stages (foundations, damp proof course, insulation, drainage, completion). Completion Certificates are essential for selling the property.

Question 5

Cavity Wall

Accepted Answer

Modern external walls are built as two leaves, usually brick outside and block inside, separated by a cavity that holds insulation and stops rain crossing to the inside. Wall ties link the two leaves. New extensions are built this way to meet Building Regulations for insulation and weathertightness.

Question 6

CDM Regulations

Accepted Answer

The Construction (Design and Management) Regulations 2015 (CDM) are health and safety regulations for construction projects. For domestic clients (homeowners), duties transfer to the contractor. Key requirements include: appointing a Principal Designer for projects with multiple contractors, preparing a construction phase plan, and maintaining a health and safety file. CDM applies to all construction work including extensions and renovations. Non compliance can result in enforcement action and unlimited fines.

Question 7

CIL (Community Infrastructure Levy)

Accepted Answer

The Community Infrastructure Levy is a charge on new development, calculated per m² of new floor space. Rates vary by local authority, often from £20 to £200+ per m² in London. CIL funds infrastructure like schools, transport, and parks. Some developments are exempt, including self-build homes, charitable use, or under 100 m² via self-build exemption. CIL must be paid before construction starts. Failure to submit required forms before work begins can result in surcharges and loss of exemptions.

Question 8

Conservation Area

Accepted Answer

Conservation areas are designated by councils to protect the character of historic streets. Permitted development rights are reduced: for example side extensions, cladding and some roof alterations need planning permission, and demolition may need consent. Designs are expected to use materials and proportions that suit the area. Many London boroughs have dozens of conservation areas.

Question 9

Defects Liability Period

Accepted Answer

After practical completion there is usually a defects period (three months on our projects) during which the builder puts right any defects that appear, such as settlement cracks or doors that need adjusting. A small retention is often held back from the contract sum until it ends.

Question 10

Dormer

Accepted Answer

A dormer projects from the slope of a roof, with vertical walls and its own window, turning sloping loft space into full-height floor space. Rear box dormers are the most common type; smaller pitched or flat-roof dormers are used where planning or appearance matters, such as on the front of a house.

Question 11

DPC (Damp Proof Course)

Accepted Answer

A Damp Proof Course is a barrier, typically slate, plastic, or bitumen, inserted in walls to prevent moisture rising from the ground through capillary action. Modern DPCs are 150mm above external ground level. Missing or bridged DPCs cause rising damp, visible as tide marks, salt contamination, and decaying skirting boards. Retrofit DPCs can be installed via chemical injection, usually £50 to £100 per metre, or physical DPC insertion. DPCs are distinct from damp proof membranes in floors.

Question 12

First Fix

Accepted Answer

First fix is the stage where electricians, plumbers and heating engineers install everything that will be hidden: cables to switch and socket positions, water, waste and heating pipes, and back boxes. It happens after the shell is weathertight and before plastering, so layouts need to be agreed at this point.

Question 13

Foundation Types

Accepted Answer

Foundations transfer building loads safely to the ground. Common types include: Strip foundations (continuous concrete strip under walls, typical for houses), raft foundations (reinforced concrete slab covering entire footprint, for poor ground), piled foundations (deep piles with ground beams, for very poor ground or steep slopes), and pad foundations (isolated pads under columns). Foundation choice depends on ground conditions, structural loads, and adjacent structures. Typical strip foundations are 600 to 1000mm deep in London.

Question 14

Hip-to-Gable Loft Conversion

Accepted Answer

On semi-detached and end-of-terrace houses with a hipped roof, the sloping side is rebuilt as a vertical gable wall, extending the ridge to create more usable loft space. It is usually combined with a rear dormer and is one of the most common loft conversions on 1930s London semis. It can often be built under permitted development.

Question 15

Householder Planning Application

Accepted Answer

A householder planning application is the standard route for extending or altering a house when the work is not permitted development: for example two-storey extensions, larger side extensions, front dormers or work in a conservation area. Councils aim to decide them within eight weeks. The application includes drawings, a site plan and sometimes a design statement.

Question 16

JCT Contract

Accepted Answer

A JCT Contract is a standard form of building contract widely used in UK construction. For domestic projects, common types include the JCT Home Owner Contract for simple works and the JCT Intermediate Building Contract for larger projects with an architect or contract administrator. JCT contracts cover the contract sum, payment schedule, programme, variations, defects liability, insurance, and dispute resolution. Always use a written contract. Never rely on verbal agreements.

Question 17

Knock-Through

Accepted Answer

A knock-through opens up two rooms, for example a kitchen and dining room, into one space. If the wall is load-bearing, a structural engineer specifies a steel beam and padstones, the floors above are supported on temporary props while the wall is removed, and Building Control inspects the work.

Question 18

Lawful Development Certificate

Accepted Answer

A Lawful Development Certificate (LDC) is a formal decision from your local council confirming that a proposed extension or loft conversion falls within permitted development rights, so planning permission is not needed. It is optional, but it gives certainty before work starts and is often asked for by buyers and their solicitors when you sell.

Question 19

Lintel

Accepted Answer

A Lintel is a structural beam spanning openings like windows and doors, supporting the wall above. Lintels are typically steel (galvanised or stainless), concrete, or timber. Steel lintels are most common in modern construction, available in various sizes and load ratings. Lintels must have adequate end bearings (typically 150mm each side) and be installed level. Cavity wall lintels span both leaves with a thermal break. Missing or inadequate lintels cause cracking over openings.

Question 20

Listed Building Consent

Accepted Answer

Listed buildings are protected for their historic or architectural interest. Listed building consent is needed for alterations, extensions or demolition that affect their character, including many internal changes. Carrying out work without consent is a criminal offence, so specialist design and careful choice of traditional materials are essential.

Question 21

Load-Bearing Wall

Accepted Answer

Load-bearing walls support structure above them, so removing or altering one needs a structural engineer's design, a replacement beam or column, and Building Regulations approval. Non-load-bearing (partition) walls can usually be moved more freely, though services such as wiring and pipes may still run through them.

Question 22

Mansard Loft Conversion

Accepted Answer

A mansard replaces the rear roof slope with a steep one of around 70 degrees, finished in slate or tiles with dormer windows, creating almost a full extra storey. It is common on London terraces, especially in conservation areas where councils prefer its traditional look, and it normally needs planning permission.

Question 23

Outrigger

Accepted Answer

The outrigger (or back addition) is the rear section of many period terraces, often holding the kitchen downstairs and a bathroom or bedroom above. Extensions and loft dormers are frequently designed around it, for example an L-shaped dormer that runs over the outrigger roof.

Question 24

Padstone

Accepted Answer

Padstones are dense concrete or engineering-brick blocks set under each end of a steel beam or lintel. They spread the concentrated load so the masonry beneath is not crushed. Their size and position are specified by the structural engineer and checked by Building Control.

Question 25

Party Wall Agreement

Accepted Answer

A Party Wall Agreement is a legal requirement under the Party Wall etc. Act 1996 when building work affects a shared wall between properties. You must serve notice on adjoining owners before starting work. If neighbours consent, work can proceed. If they dissent, Party Wall Surveyors must be appointed, often costing £700 to £1,500 per surveyor. Common triggers include loft conversions, side extensions, and excavations within 3 to 6 metres of neighbouring foundations.

Question 26

Permitted Development

Accepted Answer

Permitted Development rights allow certain building works and changes of use without requiring full planning permission. For house extensions, PD covers single storey rear extensions up to 4m deep on detached homes or 3m on others, extendable to 6m or 8m with prior approval. Side extensions must be single storey and less than half the original house width. PD rights can be restricted by conservation areas, Article 4 directions, or prior removal of rights. A Lawful Development Certificate (£103) provides legal confirmation of PD compliance.

Question 27

Planning Permission

Accepted Answer

Planning Permission is consent from the local planning authority required for certain building works and changes of use. It considers impact on neighbours, local character, highway safety, and planning policy. Householder planning applications carry a nationally set fee, listed on gov.uk, and take 8 to 13 weeks to determine. Double storey extensions, properties in conservation areas, and new dwellings typically require planning. We can coordinate planning applications on your behalf as an optional service.

Question 28

Practical Completion

Accepted Answer

Practical Completion is the stage when construction work is substantially finished, with only minor snagging items remaining. At Practical Completion: the building is weathertight, all services are connected and working, and the property can be occupied. For JCT contracts, Practical Completion triggers release of half the retention fund, start of the defects liability period (typically 12 months), and transfer of insurance responsibility back to the client. A formal certificate is issued by the contract administrator.

Question 29

Prior Approval (Larger Home Extension)

Accepted Answer

Under the larger home extension scheme, single-storey rear extensions deeper than the standard permitted development limits can go ahead if the council grants prior approval. Neighbours are notified and can comment, and the council considers the impact on their amenity. It is quicker and cheaper than a full planning application but only applies where permitted development rights have not been removed.

Question 30

Provisional Sum

Accepted Answer

A provisional sum is a figure included in a quote for work whose full extent is not known until later, such as foundations that depend on ground conditions. It is adjusted to the actual cost when the work is done. Good quotes keep provisional sums small and explain clearly what each one covers.

Question 31

Retaining Wall

Accepted Answer

A Retaining Wall is a structural wall designed to hold back soil or other materials where there is a change in ground level. Retaining walls must resist lateral earth pressure and water pressure. Types include gravity walls, cantilever walls, and sheet pile walls. Retaining walls over 1m high, or 600mm near highways, require Building Regulations approval. Garden retaining walls typically cost £200 to £500 per m² depending on height and construction.

Question 32

Retention

Accepted Answer

Retention is money held back from the final payment, typically 5% on our projects, and released at the end of the defects liability period once any snags have been fixed. It protects the client and gives the builder a clear reason to return promptly.

Question 33

Roof Lantern

Accepted Answer

A roof lantern sits on an upstand on a flat extension roof, with glazed sides and a pitched glass top. It brings daylight deep into kitchens and living areas. Lanterns must meet thermal requirements, are usually specified with solar-control glass, and need a properly detailed upstand to stay watertight.

Question 34

RSJ (Rolled Steel Joist)

Accepted Answer

A Rolled Steel Joist (RSJ) is a steel beam with an I or H shaped cross section, used to support structural loads when load bearing walls are removed during renovations or extensions. RSJs are specified by structural engineers based on the span and load they must carry. They must be installed with proper end bearings (typically 150 to 225mm on each side) and fire protection (plasterboard encasement or intumescent paint).

Question 35

Screed

Accepted Answer

Screed gives a flat, level base for the final floor finish. It is laid over insulation and often encases underfloor heating pipes. Traditional sand and cement screed needs several weeks to dry before moisture-sensitive floors such as timber can be laid; faster-drying liquid screeds are also used.

Question 36

Second Fix

Accepted Answer

Second fix follows plastering and drying. Electricians fit switches, sockets and lights; plumbers connect taps, WCs, basins and radiators; and carpenters hang doors and fit skirting and architraves. Kitchens and bathrooms are usually installed at the same stage, followed by decoration.

Question 37

Section 106 Agreement

Accepted Answer

A Section 106 Agreement is a legal agreement attached to planning permission for larger developments. It secures contributions to local infrastructure such as affordable housing, schools, transport, or open space. Section 106 agreements are common for new build developments of 2+ dwellings or 100+ m² of floor space. Contributions can range from thousands to millions depending on development size and location. They are negotiated with the local authority and can significantly impact development viability.

Question 38

Side Return

Accepted Answer

Many terraced houses have a narrow strip of outdoor space running alongside the back addition (the outrigger). A side return extension builds over it, usually with a glazed or part-glazed roof, to widen the kitchen. Combined with a rear extension it becomes a wraparound.

Question 39

Snagging

Accepted Answer

Snagging is the process of identifying defects, incomplete items, or work not meeting specification before handover. A snagging list documents items like paint touch-ups, loose fittings, scratched surfaces, or incomplete sealant. Professional snagging surveys cost £300 to £600 and can identify 50 to 200 items in a new build. We conduct thorough snagging inspections and rectify all items before final handover. The defects liability period, typically 12 months, covers issues discovered after move-in.

Question 40

Soakaway

Accepted Answer

A soakaway is a gravel-filled pit or crate system that takes rainwater from roofs and paving and lets it soak into the ground, rather than into the sewer. Building Control may require one for a new extension roof; it must sit a safe distance from buildings, and it only works in ground that drains well.

Question 41

Structural Engineer

Accepted Answer

A Structural Engineer is a qualified professional, typically CEng MIStructE, who designs and calculates structural elements such as beams, columns, foundations, and load-bearing walls. They produce calculations and drawings specifying steel sizes, foundation depths, reinforcement, and connection details. Structural engineers are essential for extensions, loft conversions, and any work removing load-bearing walls. Fees typically range from £500 to £2,000 depending on project complexity.

Question 42

Tanking

Accepted Answer

Tanking is a waterproof barrier applied to walls and floors below ground level. Modern basements often use a cavity drainage membrane with a sump and pump instead of, or as well as, a tanking layer. The system is chosen to suit the ground and water conditions, often following British Standard BS 8102.

Question 43

U-Value

Accepted Answer

A U-value measures heat loss through a building element. Building Regulations Part L sets maximum U-values for new walls, roofs, floors and glazing in extensions and new homes. Very large areas of glazing can make it harder to comply, which is sometimes balanced by extra insulation elsewhere or an energy calculation.

Question 44

Underpinning

Accepted Answer

Underpinning strengthens existing foundations by extending them deeper or wider. Methods include mass concrete underpinning, beam and base, and mini-piled underpinning. Underpinning is required when excavating below existing foundations, for example with basements, when foundations are inadequate, or when ground conditions have changed. Costs range from £1,500 to £3,000 per metre depending on method and depth.