Loft Conversions
122 sources in the library on loft conversions, 40 on this page cited in a published note. Each one says what the document covers and what it is good for. Name a source to see which document it is and where to read it. One at a time. Page 1 of 4.
- very strong RN-BBJ6HJ cited
Contracts Finder (Crown Commercial Service)
Contracts Finder award notice for Rotherham Council's 2025 conversion of an end-terrace attic into a fourth bedroom with stair access and one rear dormer, awarded at £64,449.
Cited in Dormer Loft Conversions: Cost, Types & Is One Right for You?.
- very strong RN-DNUSE8 cited
Department of Finance (Northern Ireland)
Northern Ireland's equivalent of Approved Document L Volume 1. This edition came into effect on 30 June 2022 and gives guidance on regulations 39 to 47 of the Building Regulations (Northern Ireland) 2012, which set the requirements for conservation of fuel and power in dwellings, including the limiting U-values a replacement window or door must meet in Northern Ireland. It replaced the 2012 version, and the Department publishes an awareness briefing and FAQ setting out the differences. The full text is at https://www.finance-ni.gov.uk/sites/default/files/publications/dfp/TB%20Part%20F1%202022_On-Line%20Publication.pdf. Cite this rather than Approved Document L whenever a note gives a window U-value for a reader in Northern Ireland.
Cited in Industrial Style Windows: Cheaper Alternatives, 2026 Costs, Insulation: The Complete Guide.
- very strong RN-O9PW8F cited
GOV.UK
GOV.UK guidance on the planning process after applying. It gives 8 weeks as the usual decision period, and 13 weeks for unusually large or complex applications.
Cited in Adding Porch, Hip-to-Gable Loft Conversions Explained, Renovating a Victorian House: Costs, Order & Common Pitfalls, Roof Light vs Dormer Loft Conversion: Which to Choose.
- very strong RN-POJ8CE cited
LABC
LABC guidance on trussed rafter roofs: the W-shaped webs carry the loads, and a case where cutting them for a DIY loft conversion led to cracking and replacement trusses.
Cited in Non-Habitable Loft Conversion: Loft Rooms & the Rules.
- very strong RN-AW0FCY cited
Ministry of Housing, Communities and Local Government
The second volume of Approved Document B, needed when a homeowner project crosses out of purely domestic use. Paragraph 0.1 draws the line: Volume 1 deals solely with dwellings INCLUDING blocks of flats, so a flat conversion stays in Volume 1, while Volume 2 covers every other building type. Table 0.1 sets the purpose groups: 1(a) flat, 1(b) dwellinghouse with a habitable storey at least 4.5m above ground up to 18m, 1(c) dwellinghouse with no habitable storey 4.5m above ground, then 2(a) residential institutional, 2(b) residential other (hotel, boarding house, hall of residence, hostel), 3 office, 4 shop and commercial, 5 assembly and recreation, 6 industrial, 7(a) storage and 7(b) car parks for vehicles up to 2,500kg gross. Its notes keep work within purpose group 1: surgeries, consulting rooms or offices forming part of a dwellinghouse and used by an occupant in a professional capacity stay in group 1 provided they total no more than 50m2, and a detached garage or open carport of no more than 40m2 stays in group 1(c). Paragraph 0.21 requires a separate purpose group for an ancillary use if that use is a flat, or if the building or compartment exceeds 280m2 and the ancillary use is more than one fifth of the total floor area; paragraph 0.22 requires separate purpose groups for genuinely independent uses such as shops with offices above, and the more onerous guidance applies where there is doubt. Paragraphs 0.23 and 0.24 require Volume 1 to be consulted as well for mixed use buildings that include dwellings, and paragraph 3.2 requires separate escape routes, or other effective protection of common escape routes, where a building has storeys or parts of storeys in different purpose groups.
Cited in Carpet Tile Installation Cost: 2026 UK Price Guide.
- very strong RN-X4J5YY cited
Ministry of Housing, Communities and Local Government
The 2026 edition takes effect on 24 March 2027 for work not connected with higher-risk building work, and 24 September 2027 where it is, with transitional arrangements in Circular Letter 01/2026. Table 3.1 sets limiting U-values for new dwellings: all roof types 0.16, wall 0.26, floor 0.18, window 1.6, rooflight 2.2, doors 1.6 W per square metre per kelvin, with air permeability 8.0 cubic metres per hour per square metre at 50Pa. Table 3.2 covers new elements in existing dwellings, that is extensions and loft conversions: roof 0.15, wall 0.18, floor 0.18, window 1.4 or Window Energy Rating Band B, rooflight 2.2. Table 3.3 covers upgrading existing elements: a roof with a U-value worse than the 0.35 threshold must be improved to 0.16, and note 2 confirms that for dormer windows the roof figure covers the roof parts and the wall figure the cheeks, while note 3 allows a higher U-value where the standard would limit head room provided the insulation plus air gap is at least the depth of the rafters.
Cited in External Wall Insulation (EWI) Systems & Finishes, Insulation: The Complete Guide, Triple Glazing: Worth the Cost?.
- very strong RN-R7QZ7M cited
Ministry of Housing, Communities and Local Government
Supports Part O of Schedule 1 to the Building Regulations 2010 (requirement O1 and regulation 40B); the 2021 edition took effect on 15 June 2022 in England, with transitional relief for work notified before that date and started before 15 June 2023. Critically, paragraph 0.3 limits the guidance to NEW residential buildings only (dwellings, residential institutional and residential other, plus shared communal rooms, common spaces and live/work units), and paragraph 0.7 applies it only to the residential parts of mixed-use buildings. Compliance is by the simplified method (Section 1) or dynamic thermal modelling to CIBSE TM59 (Section 2); the simplified method splits England into a high risk location (urban and some suburban London listed in Appendix C, with guidance for parts of central Manchester) and a moderate risk location (the rest of England). Table 1.1 (cross-ventilated) caps glazing as a percentage of floor area at north 15 high risk / 18 moderate, east 18/18, south 15/15, west 18/11, with the most glazed room capped at north 37/37, east 37/37, south 22/30, west 37/22. Table 1.2 (no cross-ventilation) caps glazing at north 15/18, east 11/18, south 11/15, west 11/11, most glazed room north 26/26, east 18/26, south 11/15, west 18/11.
Cited in Glass Box & Bifold Extensions: Cost & Ideas, Glazed Extensions: The Complete UK Guide, Glazing Explained: U-values, Low-E, Argon & Spacers, Rooflights & Skylights: Materials & Types.
- very strong RN-YKXWWE cited
Ministry of Housing, Communities and Local Government
The government's technical guidance on householder permitted development. It explains the Class B similar-materials condition for dormer roofs, faces and sides.
Cited in Do You Need Planning Permission for a Loft Conversion?, Types of Loft Conversion: Dormer, Mansard, Hip-to-Gable.
- very strong RN-6IW4DX cited
Planning Portal
The Planning Portal's loft conversion guidance. It states that building regulations approval is needed to turn a loft into a liveable room, whatever the planning position.
Cited in Building Control: What It Is & When You Need It, Dormer Bungalow Conversions: Adding a Room to a Bungalow, How to Insulate a Loft (DIY), Loft Boarding & Building Regs: What You Need to Know and 4 more.
- very strong RN-TWAXC6 cited
Planning Portal
The Planning Portal's guidance on loft floors. It says existing ceiling joists are rarely adequate for a habitable room and new, usually larger, joists are fitted between them.
Cited in Dormer Bungalow Conversions: Adding a Room to a Bungalow, Strengthening Loft Floors for Conversion.
- very strong RN-ITXSTK cited
Planning Portal
Explains that fitting a rooflight generally means cutting away part of one or more rafters or joists, so new support must be introduced, usually two pieces of timber fixed together spanning the new opening on either side. It directs the U-value limit to Approved Document L1 Volume 1, Table 4.2, and states that the room the rooflight serves must be ventilated, with the rooflight able to provide both rapid (purge) and background ventilation, and that ventilation of the roof void must also be considered.
Cited in Glazed Extensions: The Complete UK Guide, The Complete UK Roofing Guide (2026).
- very strong RN-OSL7G4 cited
Scottish Government (gov.scot)
SCOTLAND. Clause 4.3.2 Table 4.3 sets private stair geometry at minimum rise 100 mm, maximum rise 220 mm, minimum going 225 mm, tread not less than the going and maximum pitch 42 degrees, so Scotland's minimum going is 225 mm against England's 220 mm in Approved Document K. Any other stair, including within the common area of a building containing flats, is limited to 170 mm rise, 250 mm going and 34 degrees. The aggregate of the going plus twice the rise must be between 550 mm and 700 mm, and note 6 warns the maximum rise and minimum going must not be used together. The going at the narrow end of a tapered tread must be at least 50 mm. Clause 4.3.16 requires clear headroom of at least 2.0 metres over the whole effective width, with reduction permitted only outside the area needed to maintain effective width, so Scotland does not carry England's 1.9 metre centre and 1.8 metre edge loft conversion concession. Text verified identical in the April 2026 PDF handbook.
Cited in Spiral Staircases: Sizes, Building Regs & Cost, Staircase Types & Costs: Straight, Winder & Spiral.
- very strong RN-C6XFB7 cited
The National Archives (legislation.gov.uk)
A party structure notice must be served at least two months before the date on which the proposed work will begin, and must state the building owner's name and address, the nature and particulars of the proposed work (with plans, sections and load particulars where special foundations are proposed) and the date the work will begin. The notice ceases to have effect if the work has not begun within twelve months of service or is not then prosecuted with due diligence. Two months for a party structure notice against one month for a section 6 excavation notice is the distinction to cite.
Cited in Building Regulations Explained for Homeowners, Building Regs for Loft Conversions: Homeowner Checklist, Cellar Tanking & Waterproofing, Chimney Repair, Removal & Flashing Costs and 26 more.
- very strong RN-QBUTY2 cited
The National Archives (legislation.gov.uk)
The exact wording of the two excavation triggers that decide whether a basement or a deep foundation needs a party wall notice, worth quoting rather than paraphrasing. Section 6(1) applies where the building owner proposes to excavate, or excavate for and erect a building or structure, within a distance of 3 metres measured horizontally from any part of a building or structure of an adjoining owner, and the excavation will within those 3 metres extend to a lower level than the level of the bottom of the neighbour's foundations. Section 6(2) applies within 6 metres measured horizontally where the work will within those 6 metres meet a plane drawn downwards in the direction of the excavation at an angle of 45 degrees to the horizontal. Section 6(5) requires the building owner to serve notice on the adjoining owner at least one month before beginning to excavate. Section 6(7) provides that if the adjoining owner does not serve a notice indicating consent within 14 days, they are deemed to have dissented and a dispute has arisen, which is what triggers the surveyor and award process.
Cited in Basement & Cellar Conversions: Cost, Basement Conversion Cost & Feasibility (UK), Bedroom Extension Cost: 2026 UK Price Guide, Build Basement Cost: 2026 UK Price Guide and 28 more.
- very strong RN-R4P8KA cited
The National Archives (legislation.gov.uk)
Regulation 4(1) requires building work to be carried out so that it complies with the applicable requirements of Schedule 1 and does not cause a previously compliant part of the building to breach a requirement. Regulation 4(3) is the rule that matters for extensions, loft conversions and re-roofing: on completion of an extension or material alteration the building must be no more unsatisfactory in relation to the requirement than before the work was carried out. It also sets out the narrower Part L and Part F only route for controlled services and fittings that are not material alterations.
Cited in How to Tell If a Wall Is Load-Bearing, Strengthening Loft Floors for Conversion, uPVC vs Timber vs Aluminium Windows.
- very strong RN-5QRXP7 cited
The National Archives (legislation.gov.uk)
Class C permits any other alteration to the roof of a dwellinghouse, which is the right rooflight and Velux loft conversions rely on. Paragraph C.1(b) makes development not permitted if the alteration would protrude more than 0.15 metres beyond the plane of the roof slope, measured perpendicular to the original roof plane, and C.1(c) if the highest part of the alteration would be higher than the highest part of the original roof. C.1(d) excludes chimneys, flues, soil and vent pipes and solar equipment from the class, and condition C.2 requires any window in a roof slope forming a side elevation to be obscure-glazed and non-opening below 1.7 metres above the floor of the room.
Cited in Do You Need Planning Permission for a Loft Conversion?, Loft Conversion Windows & Skylights: Complete Guide, Loft Storage Ideas: Maximising Space Safely, Non-Habitable Loft Conversion: Loft Rooms & the Rules and 11 more.
- very strong RN-1MN06H cited
The National Archives (legislation.gov.uk), Northern Ireland Statutory Rules
NORTHERN IRELAND, and the part letters mean different things from England, so quoting an England part letter into an NI note is a straight error. The parts are A interpretation and general, B materials and workmanship, C site preparation and resistance to contaminants and moisture, D structure, E fire safety, F conservation of fuel and power, G resistance to the passage of sound, H stairs, ramps, guarding and protection from impact, J solid waste, K ventilation, L combustion appliances and fuel storage systems, N drainage, P sanitary appliances, unvented hot water storage systems and reducing the risk of scalding, R access to and use of buildings, and V glazing. So NI Part D is England's Part A, NI Part E is England's Part B, NI Part F is England's Part L, NI Part K is England's Part F, NI Part L is England's Part J, NI Part N is England's Part H, NI Part P is England's Part G and emphatically NOT electrical safety, NI Part R is England's Part M, and NI Part V is glazing. There is NO part covering electrical safety anywhere in these regulations, so domestic electrical work in Northern Ireland is not notifiable building work as it is under England's and Wales's Part P. Regulation 41 imposes consequential improvements, regulation 42 change of energy status and regulation 43 renovation of thermal elements.
- very strong RN-G28L1V cited
Welsh Government
The Welsh Part K, and the clearest statement of when a loft may be reached by something other than a normal stair. The maximum pitch for a private stair is 42 degrees, and where a floor of the building is less than 100 square metres the going may be reduced to 250 mm. Paragraph 1.10 sets headroom at 2 m on the access between levels, and for loft conversions where that is impossible, 1.9 m measured at the centre of the stair width reducing to 1.8 m at the side is satisfactory. Paragraph 1.11 gives no minimum stair width, deferring to Part B for escape and Part M for disabled access. Paragraph 1.23 allows an alternating tread stair only in one or more straight flights, only for a loft conversion, only where there is not enough space for a conforming stair, and only for access to one habitable room, together if desired with a bathroom or WC, provided that WC is not the only one in the dwelling. Paragraph 1.24 requires uniform steps with parallel nosings, handrails both sides, slip resistant treads, and over the wider part of the step a maximum rise of 220 mm and minimum going of 220 mm. Paragraph 1.25 permits a fixed ladder with fixed handrails both sides on the same conditions, serving one habitable room only, and states plainly that retractable ladders are not acceptable for means of escape.
Cited in Staircase Types & Costs: Straight, Winder & Spiral.
- very strong RN-KXCXCY cited
Welsh Government (gov.wales)
WALES. First published 3 April 2017, last updated 7 April 2026. Wales publishes its own Approved Document F, and the page carries the current volume 1 for dwellings (910 KB PDF) and volume 2 for buildings other than dwellings, plus replacement volumes that TAKE EFFECT ON 4 MARCH 2027, the same changeover date as the Welsh Approved Document L and distinct from England's 24 March 2027. Welsh Part F diverged from England's when England issued its 2021 edition alongside Part L and Part O, so extract rates and background ventilator provisions for a Welsh bathroom, kitchen or loft conversion should be taken from this document rather than from England's Approved Document F.
Cited in Trickle Vents & Background Ventilation.
- very strong RN-CY8PF5 cited
Welsh Government (gov.wales)
WALES. Loft insulation must meet the minimum energy efficiency values in the Welsh Approved Documents, and where that upgrade is not technically or functionally feasible the element must instead be upgraded to the best standard achievable within a simple payback of no greater than 15 years. Installing loft insulation as part of a roof renovation where MORE THAN 25 PER CENT OF THE ROOF is being renewed triggers the full Approved Document standard, the Welsh version of the renovation of a thermal element trigger. The guidance warns against blocking ventilation at the eaves. Read alongside Table 4.1 of the Welsh Approved Document L Volume 1, which sets 0.13 W/m2K for roofs in both new and existing dwellings.
Cited in Insulation: The Complete Guide.
- very strong RN-156U72 cited
Welsh Government (gov.wales)
WALES, and this contradicts England outright. Wales has NO larger home extension prior approval route and no neighbour consultation scheme, so the 6 metre and 8 metre single-storey rear extensions England allows are simply not available. Under Class A a single-storey rear extension must not project beyond the rear wall of the original dwellinghouse by more than 4 metres for any house type, must not exceed 4 metres in height, must not exceed 50 per cent of the total area of the curtilage under A.1(a), must not have eaves higher than the eaves of the part it projects from, and must not be within 2 metres of a boundary where its eaves exceed 3 metres, nor exceed 4 metres in height within 2 metres of a boundary. A rear extension of more than one storey is limited to 4 metres at ground floor and 3 metres at first floor or above, and any storey above 4 metres in height must be at least 10.5 metres from the boundary opposite the rear wall. A side extension must be set back at least 1 metre from the principal elevation and must not make the widest part of the resulting house more than 50 per cent wider than the original. Verandas, raised platforms, roof terraces and balconies are excluded except a balcony complying with A.1(l)(ii), and materials must match under A.3(a).
Cited in Do You Need Planning Permission for a Garden Room?, Renovating a 1930s House.
- strong locally RN-8K32PE cited
Hart District Council
Hart District Council's 2026-27 planning fee schedule sets householder pre-application advice, including loft conversions, at £291 for a written response and £430 with a site meeting.
Cited in Annexe & Granny Flat: Cost, Planning & Rules, Flat-Roof vs Pitched-Roof Dormer: Which Is Right?.
- strong locally RN-UYILL6 cited
Mole Valley District Council
Mole Valley District Council's pre-application page sets its letter-based householder pre-application advice fee, increased on 1 April 2026, at £171.39 including VAT.
- strong locally RN-TMC26I cited
Westminster City Council
Westminster's supplementary planning guidance on roof extensions. Its general rules for mansards set the main slope at no more than 70 degrees.
Cited in Types of Loft Conversion: Dormer, Mansard, Hip-to-Gable.
- strong RN-C3NSSX cited
BSI (British Standards Institution)
The code of practice behind every balustrade, balcony, landing and decking guard rail, and the standard Approved Document K points to for barrier loadings. Paywalled, so only the BSI catalogue page is public; it confirms the current edition is BS 6180:2011, published 31 March 2011, status Current but Under Review, from BSI committee B/208 and ICS 91.060.99. The catalogue page confirms it is a full revision of the 1999 edition and that the two substantive changes were the inclusion of Table 2, minimum horizontal imposed loads for parapets, barriers and balustrades, and changed rules on deflection at clause 6.4.1, so a note needing barrier load figures should cite Table 2 by name. It covers design, structure, height and strength of barriers in aluminium and copper alloys, concrete, plastic, steel, stone, wood and glass, temporary and permanent, including protective, crash and crush barriers and those imposing a speed limit up to 16 km/h. It expressly does NOT apply to spectator sports areas or buildings, construction sites, or barriers protecting children younger than 24 months.
Cited in Newel Posts, Spindles & Balustrades.
- strong RN-IKHYR0 cited
BSI (British Standards Institution)
The residential fire safety code of practice that professionals use as the alternative to the Approved Document B route, described by BSI as the UK most widely used fire safety standard. Paywalled, so only the catalogue page is public; it confirms the current edition is BS 9991:2024, page-dated 24 September 2025, status Current, and that it superseded BS 9991:2015, which was withdrawn on 21 November 2024, which in turn superseded BS 9991:2011, withdrawn 31 October 2015. Scope for the 2024 edition covers dwellings (single-family houses, self-contained flats or maisonettes), blocks of flats, residential accommodation blocks with individual bedrooms and kitchen or sanitary facilities, specialized housing and care homes. Care homes are new to the 2024 scope: the 2011 edition expressly excluded residential care and nursing homes. The earlier editions confirm the standard applies not only to new buildings but to material alterations, extensions and material changes of use of an existing building, which is why it is cited on loft conversions and flat conversions, and that it complements BS 9999, the equivalent code for non-residential buildings. The 2015 edition renamed sheltered and extra care housing as specialized housing and added expanded recommendations for escape from basements, lifts, power supplies, cluster accommodation and management of additional needs and disabilities.
Cited in PIR vs Mineral Wool Insulation Compared.
- strong RN-VKPEGH cited
BSI (British Standards Institution)
STATUS: CURRENT (marked Under Review). BS EN 12150-1:2015+A1:2019 was published 31 May 2019 and supersedes BS EN 12150-1:2015, which had itself replaced BS EN 12150-1:2000. It establishes tolerances, flatness, edgework, fragmentation and the physical and mechanical characteristics of monolithic flat thermally toughened soda lime silicate safety glass for use in buildings. Curved toughened glass is described in Annex A but is not part of the standard, and glass built into laminated or insulating glass units, or coated after toughening, falls under the relevant assembly product standard instead. Part 2 (BS EN 12150-2) covers evaluation of conformity. The catalogue page confirms number, title, date, status and scope; the test detail is paywalled.
Cited in Splashbacks: Glass, Tile & Stone Options, Worktop Edges, Upstands & Splashbacks.
- good RN-41NIS2 cited
Federation of Master Builders
The FMB's homeowner cost guide gives average loft conversion costs by type, using prices from member firm Marken Lofts, and puts a dormer conversion at £50,000.
Cited in Dormer Bungalow Conversions: Adding a Room to a Bungalow.
- good RN-CV5OHA cited
The Steel Construction Institute
SCI Advisory Desk note reproducing the horizontal line loads from Table NA.8 of the UK National Annex to BS EN 1991-1-1:2002, which is the table Approved Document K points to for guarding and barrier loading. Category A, areas for domestic and residential activities: (i) all areas within or serving exclusively one dwelling including stairs, landings etc, characteristic horizontal load qx = 0.36 kN/m; (ii) residential areas not covered by (i), 0.74 kN/m. States these values replace those in Table 6.12 of BS EN 1991-1-1:2002 and should be treated as leading or accompanying variable actions combined per BS EN 1990 expression 6.10 or 6.10a/6.10b. The clean readable source for the single most misquoted number in domestic balustrade notes: 0.74 kN/m belongs to flats and communal areas, not to a house.
- fair RN-MK8GBN cited
Federation of Master Builders
The builders' trade body's homeowner guide to loft conversions; it gives 2.2 m as the working head-height figure and says how to measure it.
Cited in Dormer Bungalow Conversions: Adding a Room to a Bungalow, Extension vs Loft Conversion vs Moving House, How Much Does Loft Boarding Cost? (UK 2026), Loft Conversion Cost by London Borough and 5 more.
- fair RN-NQEPBP cited
HomeOwners Alliance
2026 loft conversion costs by type and by house type. Average across the UK about £50,000. Velux or rooflight conversion £27,500, dormer £50,000, hip to gable £60,000, mansard £65,000. By house type: semi detached £50,000, terrace with a dormer around £50,000, detached £62,500, bungalow £75,000. Rate per square metre £1,250 to £2,500 per m2, applied to the usable gross internal area measured where headroom is 1.5m or above. Element costs within a £50,000 dormer: stairs £1,000 to £1,500 for a standard flight, flooring £15 to £25 per m2 for vinyl or £10 to £65 per m2 for carpet, labour £14,000 to £35,000. Loft insulation costs cited from the Energy Saving Trust at about £900 for a three bedroom semi, £1,100 detached and £1,200 for a detached bungalow, saving about £300 a year. DIY on suitable elements can cut up to 40% of labour.
Cited in Does a Loft Conversion Add Value? UK Data & ROI, Hip-to-Gable Loft Conversions Explained.
- fair RN-5XVH97 cited
Which?
Which? loft conversion costing, updated 24 April 2026, using Building Cost Information Service data from 2025 with VAT included. Benchmarks a small conversion as 4 x 5 metres with two windows and a large conversion as 12 x 7 metres with four windows. Gives the budget split: labour 35 to 40%, materials 25 to 30%, fixtures and fittings 10 to 15%, planning and permissions up to 5%, and a contingency of no less than 10%, raised to 15 to 20% where structural work is involved. On value, a 2025 Nationwide report is cited: a loft conversion can add up to 24% to a property's value, a 10% increase in floor space adds about 5% to the price of a typical house, and adding a large double bedroom of about 13 m2 plus a bathroom to a three bedroom one bathroom house can add as much as 24%. On buildability, houses built before 1970 usually have open self supporting rafters and are easier to convert, while houses built after about 1970 tend to have trussed roofs, which need more structural work and can double the cost. Most conversions fall under permitted development, but an application where needed can cost up to £1,000.
Cited in Loft Conversion Mistakes to Avoid.
- supplier figure RN-JNPRWU cited
British Board of Agrément (copy published by the certificate holder, Flex-R)
The BBA Agrément certificate for ClassicBond non-reinforced EPDM roof waterproofing, hosted by the certificate holder, assessing its service life under normal conditions as at least 35 years.
- supplier figure RN-CXAGUH cited
Builder Depot
Builder Depot's product page for the Deanta Seville white primed FD30 internal fire door, sold in six sizes, showing its price range including VAT.
Cited in Velux Loft Conversions: The Cheapest Option Explained.
- supplier figure RN-I1EE5H cited
Kingspan Insulation
Rigid thermoset phenolic (PF) board to BS EN 13166: 2012 + A2: 2016, faced both sides with a low emissivity composite foil. Declared thermal conductivity 0.019 W/mK. Declared compressive strength 100 kPa to BS EN 826: 2013. Standard board 2.4 m x 1.2 m. BBA Certificate 16/5299 covers thicknesses 25 to 150 mm, made at Pembridge, Herefordshire. Published R-values (m2K/W): 25 mm 1.30, 40 mm 2.10, 50 mm 2.60, 60 mm 3.15, 70 mm 3.65, 75 mm 3.90, 80 mm 4.20, 90 mm 4.70, 100 mm 5.25, 110 mm 5.75. Fire: under System 4 AVCP, K107 has a Euroclass rating of F.
- supplier figure RN-AJ5JUJ cited
LCCL Construction
a London loft conversion contractor's own published price range for a hip to gable conversion, £45,000 to £75,000 in 2026, which is one of the two figures the cost book records for that type. A contractor publishing its own prices is evidence of what it charges rather than an aggregate of what other people say they charge
Cited in Average Loft Conversion Cost: Real 2026 Breakdown by Type, Extension vs Loft Conversion vs Moving House, How Much Does a Loft Conversion Cost in 2026?, Loft Conversion Cost by Region (London & Beyond).
- supplier figure RN-0Z4QTE cited
LCCL Construction
a London loft conversion contractor's own published price range for an L-shaped dormer, £45,000 to £80,000 in 2026, broken down as £45,000 to £55,000 standard and £55,000 to £70,000 mid-range. It is one of three contractor figures the cost book records for that type
Cited in Average Loft Conversion Cost: Real 2026 Breakdown by Type.
- supplier figure RN-L4L9HF cited
LCCL Construction
a London loft conversion contractor's own published price range for a mansard conversion, £60,000 to £120,000 in 2026, which is one of the two figures the cost book records for that type. A contractor publishing its own prices is evidence of what it charges rather than an aggregate of what other people say they charge
Cited in Extension vs Loft Conversion vs Moving House, How Much Does a Loft Conversion Cost in 2026?, Loft Conversion Cost by Region (London & Beyond), Loft Conversion vs House Extension: Which Adds More Value?.
- supplier figure RN-A1R6RI cited
LCCL Construction
a London loft conversion contractor's own published price range for a rooflight conversion, £18,000 to £48,000 in 2026, split into £18,000 to £30,000 for a basic one-room conversion and £28,000 to £48,000 with an ensuite. It is one of the two figures the cost book records for that type, and the two do not agree: the other contractor's floor is £40,000. A contractor publishing its own prices is evidence of what it charges rather than an aggregate of what other people say they charge
Cited in Average Loft Conversion Cost: Real 2026 Breakdown by Type, Extension vs Loft Conversion vs Moving House, How Much Does a Loft Conversion Cost in 2026?, Loft Conversion Cost by Region (London & Beyond) and 2 more.
- supplier figure RN-E6B6LH cited
Mapei UK
Mapei's product page for Mapegum WPS, confirming it is a liquid-applied tanking membrane for waterproofing bathroom and shower walls and floors before tiling.