Structural Steel Beam Guide for London Homes in 2025: RSJ, UB, UC, Compound Beams, Structural Engineer, Temporary Support, Padstones, Fire Protection, and London Structural Steel Costs

Types of structural steel beams used in London residential construction (RSJ, UB — Universal Beam, UC — Universal Column, compound beams, flitch beams), the structural engineer design and Building Control process, temporary support (Acrow props, RSJ strongbacks), padstone specification (engineering brick, dense concrete block), and the most specified structural steel products in London residential construction in 2025: TYPES OF STRUCTURAL STEEL BEAMS USED IN LONDON RESIDENTIAL CONSTRUCTION IN 2025: UNIVERSAL BEAM (UB — ALSO WIDELY KNOWN AS RSJ OR I-BEAM IN LONDON RESIDENTIAL CONSTRUCTION) — THE MOST INSTALLED STEEL SECTION TYPE IN LONDON RESIDENTIAL STRUCTURAL ALTERATIONS IN 2025: A UNIVERSAL BEAM (UB) IS AN I-SHAPED STEEL SECTION COMPRISING A WEB (VERTICAL PLATE) AND TWO FLANGES (HORIZONTAL PLATES) — THE SHAPE PROVIDES HIGH BENDING STIFFNESS IN THE VERTICAL PLANE AT MINIMAL WEIGHT — UNIVERSALLY USED WHERE A BEAM MUST SPAN HORIZONTALLY AND RESIST VERTICAL BENDING LOADS; UB SIZE DESIGNATIONS: THE MOST COMMONLY USED UB SIZES IN LONDON RESIDENTIAL STRUCTURAL ALTERATIONS IN 2025 (IN ORDER OF FREQUENCY): 203×133×25 UB (25.1 kg/m — THE MOST INSTALLED UB IN LONDON RESIDENTIAL SINGLE WALL REMOVAL PROJECTS IN 2025 — USED FOR SHORTER SPANS OF 1.5-2.5m WITH LOW TO MODERATE LOADING — TYPICALLY REMOVING A SINGLE INTERNAL LOAD-BEARING STUD PARTITION OR SHORT RETURN WALL); 254×146×31 UB (31.1 kg/m — THE SECOND MOST INSTALLED UB IN LONDON RESIDENTIAL STRUCTURAL ALTERATIONS IN 2025 — USED FOR SPANS OF 2.5-4.0m WITH MODERATE LOADING — TYPICAL FOR INTERNAL WALL REMOVAL ACROSS A STANDARD LONDON TERRACE GROUND FLOOR LIVING ROOM TO KITCHEN OPENING OF 3.0-3.5m); 305×165×40 UB (40.3 kg/m — THE THIRD MOST INSTALLED UB IN LONDON RESIDENTIAL STRUCTURAL ALTERATIONS IN 2025 — USED FOR SPANS OF 4.0-6.0m WITH MODERATE TO HIGH LOADING — TYPICAL FOR A LONDON REAR EXTENSION STEEL SPANNING THE FULL REAR ELEVATION OF A SEMI-DETACHED PROPERTY (4.5-5.5m) OR CARRYING FLOOR LOADS FROM ABOVE IN ADDITION TO THE ROOF); NOTE: THE EXACT BEAM SIZE IS ALWAYS DETERMINED BY THE STRUCTURAL ENGINEER'S CALCULATIONS — THE ABOVE SIZES ARE FOR GUIDANCE AND CONTEXT ONLY; UNIVERSAL COLUMN (UC): A UC SECTION HAS SUBSTANTIALLY EQUAL FLANGE AND WEB DIMENSIONS — IT IS DESIGNED TO RESIST AXIAL COMPRESSIVE LOADS — USED IN LONDON RESIDENTIAL PROJECTS WHERE STEEL POSTS OR COLUMNS ARE REQUIRED (FOR EXAMPLE, ON THE SIDES OF A BIFOLD DOOR OPENING IN AN EXTENSION, OR AS A COLUMN IN AN OPEN-PLAN SPACE): MOST INSTALLED UC SIZE IN LONDON RESIDENTIAL CONSTRUCTION IN 2025: 152×152×23 UC (THE MOST INSTALLED UC SECTION IN LONDON RESIDENTIAL NEW EXTENSION STEEL PORTAL FRAMES IN 2025 — SLIM COLUMN PROFILE FOR BIFOLD DOOR REVEALS AND OPEN-PLAN SPACES); COMPOUND BEAMS (THE MOST INSTALLED STRUCTURAL SOLUTION FOR LONG SPANS OR VERY HEAVY LOADS IN LONDON RESIDENTIAL CONSTRUCTION IN 2025 — WHERE A SINGLE UB SECTION WOULD NEED TO BE EXCESSIVELY DEEP OR HEAVY FOR THE SPAN AND LOAD — TWO OR MORE STEEL SECTIONS ARE BOLTED OR WELDED TOGETHER): MOST COMMON COMPOUND BEAM TYPE IN LONDON RESIDENTIAL IN 2025: PAIR OF UBs BOLTED BACK TO BACK (MOST INSTALLED COMPOUND BEAM IN LONDON RESIDENTIAL EXTENSION PROJECTS IN 2025 — PARTICULARLY FOR THE MAIN REAR EXTENSION BEAM SPANNING 4.5-6.0m IN A SEMI-DETACHED OR DETACHED LONDON PROPERTY WHERE A SINGLE UB WOULD BE TOO DEEP FOR THE FLOOR ZONE); FLITCH BEAM (A STRUCTURAL SANDWICH COMPRISING TWO TIMBER MEMBERS (TYPICALLY C24 OR HIGHER GRADE STRUCTURAL TIMBER) WITH A STEEL PLATE (FL-PLATE) BOLTED BETWEEN THEM — THE MOST SPECIFIED HIDDEN STRUCTURAL BEAM IN LONDON RESIDENTIAL RENOVATION PROJECTS IN 2025 WHERE HEADROOM IS CRITICAL AND THE BEAM MUST FIT WITHIN THE DEPTH OF A STANDARD CEILING JOIST): MOST SPECIFIED FLITCH BEAM STEEL PLATE IN LONDON RESIDENTIAL IN 2025: 10mm MILD STEEL FLAT PLATE (MOST SPECIFIED FL-PLATE THICKNESS FOR LONDON RESIDENTIAL FLITCH BEAM APPLICATIONS IN 2025); STRUCTURAL ENGINEER DESIGN AND BUILDING CONTROL PROCESS FOR A LONDON STRUCTURAL STEEL ALTERATION IN 2025: ALL STRUCTURAL STEEL WORK IN A LONDON HOME (INCLUDING REMOVING ANY LOAD-BEARING WALL, INSERTING A NEW BEAM, OR MODIFYING THE STRUCTURAL FRAME) REQUIRES: A STRUCTURAL ENGINEER (IStructE OR ICE MEMBER — THE STRUCTURAL ENGINEER WILL VISIT THE SITE, ASSESS THE EXISTING STRUCTURE, AND PREPARE STRUCTURAL CALCULATIONS AND DRAWINGS SPECIFYING THE BEAM SIZE, PADSTONE DESIGN, TEMPORARY SUPPORT REQUIREMENTS, AND BUILDABILITY NOTES); BUILDING CONTROL APPROVAL (EITHER THROUGH THE LOCAL AUTHORITY BUILDING CONTROL (LABC) OR AN APPROVED INSPECTOR (AI) — THE STRUCTURAL ENGINEER'S CALCULATIONS AND DRAWINGS ARE SUBMITTED TO BUILDING CONTROL — A BUILDING CONTROL OFFICER WILL INSPECT THE WORKS AT KEY STAGES (TEMPORARY SUPPORT IN PLACE, BEAM INSTALLED, PADSTONES CONFIRMED)); PADSTONE SPECIFICATION: A PADSTONE IS THE BEARING ELEMENT BELOW EACH END OF THE STEEL BEAM — IT SPREADS THE CONCENTRATED POINT LOAD FROM THE END OF THE BEAM INTO THE WALL OR COLUMN BELOW OVER A LARGER AREA THAT THE EXISTING MASONRY CAN SUSTAIN WITHOUT CRUSHING: MOST SPECIFIED PADSTONE MATERIAL FOR LONDON RESIDENTIAL STRUCTURAL STEEL BEAMS IN 2025: ENGINEERING BRICK CLASS B (MOST INSTALLED PADSTONE MATERIAL IN LONDON RESIDENTIAL STRUCTURAL ALTERATIONS IN 2025 — A DENSE, HIGH-COMPRESSIVE-STRENGTH BRICK (MINIMUM 50 N/mm² COMPRESSIVE STRENGTH — BLUE ENGINEERING BRICK CLASS A HAS ≥75 N/mm² AND IS SPECIFIED WHERE LOADS ARE HIGHER) — MOST INSTALLED BRAND: IBSTOCK BLOCKLEYS FROGGED ENGINEERING BRICK CLASS B (THE MOST INSTALLED BLUE ENGINEERING BRICK PADSTONE IN LONDON RESIDENTIAL STRUCTURAL ALTERATION PROJECTS IN 2025)); DENSE CONCRETE BLOCK PADSTONE (MEDIUM DENSE AGGREGATE CONCRETE BLOCK — SECOND MOST INSTALLED IN LONDON RESIDENTIAL STRUCTURAL ALTERATIONS 2025 — MUST BE SPECIFIED BY THE STRUCTURAL ENGINEER AS A "SOLID PADSTONE BLOCK" OF APPROPRIATE STRENGTH — MOST USED FOR SMALLER LOADS WHERE ENGINEERING BRICK IS NOT AVAILABLE ON SITE); BED MORTAR FOR PADSTONE INSTALLATION: MOST INSTALLED MORTAR FOR STEEL BEAM PADSTONE INSTALLATION IN LONDON RESIDENTIAL IN 2025: PERMASET ECOFIX 3 (NON-SHRINK PRECISION GROUT — THE MOST INSTALLED NON-SHRINK BEDDING GROUT FOR STEEL BEAM PADSTONE INSTALLATION IN LONDON RESIDENTIAL PROJECTS IN 2025 — ENSURES FULL BEARING CONTACT AND PREVENTS DIFFERENTIAL SETTLEMENT UNDER THE PADSTONE); TEMPORARY SUPPORT (CRITICAL SAFETY REQUIREMENT — ALL LOAD-BEARING WALL REMOVAL IN A LONDON HOME REQUIRES TEMPORARY SUPPORT OF THE STRUCTURE ABOVE THE PROPOSED BEAM POSITION BEFORE ANY MASONRY IS REMOVED): MOST INSTALLED TEMPORARY SUPPORT FOR LONDON RESIDENTIAL STRUCTURAL ALTERATIONS IN 2025: ACROW ADJUSTABLE STEEL PROPS (MOST INSTALLED TEMPORARY SUPPORT IN LONDON RESIDENTIAL WALL REMOVAL PROJECTS IN 2025 — AVAILABLE IN STANDARD PROP SIZES: ACROW PROP SIZE 3 (2.0-3.4m) MOST INSTALLED FOR STANDARD LONDON ROOM HEIGHTS OF 2.4-2.7m IN 2025); STEEL STRONGBACK RSJ (A SHORT STEEL BEAM LAID ACROSS THE TOPS OF A ROW OF ACROW PROPS AT CEILING LEVEL TO DISTRIBUTE THE TEMPORARY LOAD ACROSS MULTIPLE PROPS — THE MOST INSTALLED STRONGBACK BEAM FOR LONDON RESIDENTIAL TEMPORARY SUPPORT IN 2025: 203×133×25 UB SHORT LENGTHS OF 1.2-1.5m).

Fire protection of structural steel beams in London residential buildings (intumescent paint, fire-resisting encasement, Part B FR30/FR60 requirements), the most specified intumescent paint systems in London residential construction in 2025, and structural steel costs (supply only and installed) in London in 2025: FIRE PROTECTION FOR STRUCTURAL STEEL BEAMS IN LONDON RESIDENTIAL BUILDINGS IN 2025: STRUCTURAL STEEL LOSES ITS LOAD-BEARING CAPACITY RAPIDLY WHEN HEATED — AT APPROXIMATELY 550°C, STRUCTURAL STEEL REACHES ITS CRITICAL TEMPERATURE AND CAN NO LONGER CARRY ITS DESIGN LOAD — THIS IS WHY BUILDING REGULATIONS PART B REQUIRES STRUCTURAL STEEL IN CERTAIN LOCATIONS TO HAVE FIRE PROTECTION TO MAINTAIN STRUCTURAL INTEGRITY FOR A MINIMUM PERIOD OF 30 OR 60 MINUTES WHILE OCCUPANTS ESCAPE; IN LONDON RESIDENTIAL BUILDINGS, THE FIRE PROTECTION REQUIREMENT FOR A STRUCTURAL STEEL BEAM DEPENDS ON ITS LOCATION: STEEL BEAMS THAT ARE FULLY ENCLOSED WITHIN A COMPARTMENT FLOOR OR CEILING (I.E., THE BEAM IS BOXED IN WITH PLASTERBOARD — THE MOST COMMON INSTALLATION IN A LONDON RESIDENTIAL EXTENSION OR LOFT CONVERSION WHERE THE BEAM IS HIDDEN ABOVE A PLASTERBOARD CEILING): THE PLASTERBOARD ENCASEMENT ITSELF PROVIDES FIRE PROTECTION — 2 LAYERS OF 12.5mm STANDARD GYPROC WALLBOARD ACHIEVES FR30 (30 MINUTES FIRE RESISTANCE); 2 LAYERS OF 15mm GYPROC FIRELINE (THE MOST SPECIFIED FIRE-RATED PLASTERBOARD FOR LONDON RESIDENTIAL STRUCTURAL STEEL BEAM ENCASEMENT IN 2025) ACHIEVES FR60 (60 MINUTES FIRE RESISTANCE); STEEL BEAMS THAT ARE EXPOSED (I.E., THE BEAM IS LEFT VISIBLE AS A DESIGN FEATURE — AN INCREASINGLY COMMON SPECIFICATION IN LONDON RESIDENTIAL OPEN-PLAN KITCHEN-DINER EXTENSIONS IN 2025 WHERE THE EXPOSED STEEL BEAM IS PART OF THE INDUSTRIAL OR CONTEMPORARY AESTHETIC): THE EXPOSED BEAM MUST BE TREATED WITH AN INTUMESCENT COATING TO ACHIEVE THE REQUIRED FIRE RESISTANCE; INTUMESCENT PAINT WORKS BY EXPANDING RAPIDLY IN A FIRE TO FORM A THICK INSULATING CHAR LAYER THAT PROTECTS THE STEEL FROM REACHING 550°C FOR THE REQUIRED PERIOD; THE FIRE PROTECTION REQUIREMENT IS DETERMINED BY THE STRUCTURAL ENGINEER AND BUILDING CONTROL — IN A LONDON TWO-STOREY RESIDENTIAL BUILDING, FR30 IS TYPICALLY THE MINIMUM REQUIREMENT FOR A STRUCTURAL BEAM BELOW A SEPARATING FLOOR; MOST SPECIFIED INTUMESCENT PAINT SYSTEMS FOR EXPOSED STRUCTURAL STEEL BEAMS IN LONDON RESIDENTIAL CONSTRUCTION IN 2025: NULLIFIRE SC902 (THE MOST SPECIFIED WATER-BASED INTUMESCENT COATING FOR EXPOSED STRUCTURAL STEEL IN LONDON RESIDENTIAL CONSTRUCTION IN 2025 — SINGLE COMPONENT WATERBORNE — NO STRONG SOLVENT ODOUR — ACHIEVES FR30 AT A LOWER DFT (DRY FILM THICKNESS — APPROXIMATELY 0.5-1.0mm PER COAT FOR FR30 ON A STANDARD 203×133×25 UB — SECTION FACTOR HP/A IS THE KEY VARIABLE THAT DETERMINES REQUIRED DFT) — MOST APPLIED IN LONDON RESIDENTIAL PROJECTS WHERE THE EXPOSED BEAM IS IN AN OCCUPIED SPACE AND MINIMAL DISRUPTION AND ODOUR IS A PRIORITY); JOTUN JOTACHAR 1709 (THE SECOND MOST SPECIFIED INTUMESCENT COATING FOR LONDON RESIDENTIAL EXPOSED STRUCTURAL STEEL IN 2025 — SINGLE COMPONENT EPOXY-BASED — HIGH SOLIDS — MOST SPECIFIED WHERE A HARDER, MORE ROBUST FINISH IS REQUIRED FOR A HIGH-TRAFFIC OR KITCHEN ENVIRONMENT); PRIMROSE HILLCOAT BASECOAT PRIMER (MOST INSTALLED PRIMER UNDER INTUMESCENT COATINGS FOR LONDON RESIDENTIAL EXPOSED STEEL BEAMS IN 2025 — REQUIRED UNDER NULLIFIRE SC902 AND MOST OTHER SYSTEMS — ENSURES ADHESION TO STEEL AND PREVENTS CORROSION); TOPCOAT OVER INTUMESCENT COATING (MOST INSTALLED TOPCOAT OVER INTUMESCENT COATING FOR LONDON RESIDENTIAL EXPOSED STEEL BEAMS IN 2025 FOR A SATIN BLACK FINISH — THE MOST SPECIFIED FINISH FOR AN EXPOSED STEEL BEAM IN A LONDON CONTEMPORARY EXTENSION IN 2025 — APPLIED AS A FINAL AESTHETIC COAT OVER THE INTUMESCENT SYSTEM): NULLIFIRE FC004 FINISH COAT SATIN BLACK (MOST INSTALLED TOPCOAT OVER NULLIFIRE SC902 IN LONDON RESIDENTIAL 2025); NOTE: THE INTUMESCENT COATING SYSTEM (PRIMER + INTUMESCENT + TOPCOAT) MUST BE AN APPROVED SYSTEM TESTED AND CERTIFIED TOGETHER (A TOPCOAT FROM A DIFFERENT MANUFACTURER MAY VOID THE FIRE CERTIFICATION OF THE INTUMESCENT) — ALWAYS USE A COMPLETE CERTIFIED SYSTEM; LONDON STRUCTURAL STEEL COSTS IN 2025 (SUPPLY + INSTALLATION — INCLUDES STRUCTURAL STEEL SUPPLY, DELIVERY TO LONDON SITE, INSTALLATION WITH TEMPORARY SUPPORT, PADSTONES, MAKING GOOD OF MASONRY AT BEAM ENDS — EXCLUDES STRUCTURAL ENGINEER FEES (TYPICALLY £400-£1,500 FOR A STANDARD BEAM CALCULATION) AND BUILDING CONTROL FEES (TYPICALLY £300-£800 FOR A STRUCTURAL ALTERATION)): SMALL SINGLE INTERNAL BEAM (203×133×25 UB — SPAN 1.5-2.5m — SINGLE LOAD-BEARING INTERNAL WALL REMOVAL — STANDARD LONDON TERRACE LIVING ROOM THROUGH-OPENING): approximately £1,500-£3,500; MEDIUM SINGLE INTERNAL BEAM (254×146×31 UB OR 305×165×40 UB — SPAN 2.5-4.0m — FULL INTERNAL WALL REMOVAL — GROUND FLOOR OPEN-PLAN LONDON TERRACE): approximately £3,000-£6,000; LARGE REAR EXTENSION BEAM (305×165×40 UB OR 356×171×45 UB — SPAN 4.0-6.0m — REAR WALL REMOVAL FOR LONDON EXTENSION): approximately £4,000-£9,000; COMPOUND BEAM (PAIR OF UBs BOLTED TOGETHER — SPAN 5.0-7.0m — LARGE REAR ELEVATION OPENING OR LONG SPAN OVER KITCHEN-DINER): approximately £6,000-£15,000; PARTY WALL BEAM (BEAM BUILT INTO THE PARTY WALL — MOST COMMON SECTION 2 TRIGGER — ADDS PROGRAMME TIME FOR PARTY WALL ACT COMPLIANCE — COST SIMILAR TO EQUIVALENT STANDARD BEAM BUT PARTY WALL SURVEYOR FEES ADD £1,500-£5,000).