Steel Lintels for London Victorian Terraces: RSJ Beams, Catnic, and IG S-Beam Installation

THE CORRECT STEEL ELEMENT FOR A NEW OPENING IN A LONDON VICTORIAN TERRACE DEPENDS ON: THE SPAN OF THE OPENING (MEASURED CLEAR OPENING + 2 X MINIMUM BEARING — TYPICALLY +300MM EACH SIDE = TOTAL BEAM LENGTH), THE LOAD ON THE BEAM (ROOF LOAD, UPPER FLOOR LOAD, MASONRY LOAD ABOVE, OR SIMPLY THE WEIGHT OF THE BRICK OVER THE OPENING TO THE RELIEVING ARCH), AND WHETHER THE BEAM WILL BE FULLY CONCEALED IN A HOLLOW STEEL LINTEL SECTION (CATNIC/IG) OR WILL BE AN EXPOSED RSJ USED AS A FEATURE BEAM OR IN A WIDER STRUCTURAL SCHEME.

CATNIC HEAVY DUTY LINTEL (CATNIC CG90 — THE STANDARD SPECIFICATION FOR MOST NEW DOOR AND WINDOW OPENINGS IN LOAD-BEARING BRICK WALLS IN LONDON VICTORIAN TERRACES): THE CATNIC CG90 IS A PRESSED STEEL LINTEL (GALVANISED STEEL — BS EN 10346) IN AN L-SECTION OR BOX SECTION PROFILE — DESIGNED TO SPAN OPENINGS IN CAVITY OR SOLID EXTERNAL WALLS AND INTERNAL LOAD-BEARING WALLS. CATNIC CG90 (COMMERCIAL GRADE — HEAVY DUTY): FOR OPENINGS UP TO APPROXIMATELY 2400MM CLEAR. CATNIC CHD (HEAVY DUTY): FOR OPENINGS UP TO 3600MM CLEAR IN STANDARD RESIDENTIAL LOADING. CATNIC LIMITS: CATNIC LINTELS ARE LOAD-TABLES-DESIGNED — CATNIC PROVIDES FREE LOAD TABLES FOR EACH LINTEL SERIES SHOWING MAXIMUM CLEAR SPAN FOR A GIVEN LOAD (EXPRESSED IN KN/M OR MASONRY LEAF HEIGHT). ALWAYS CHECK CATNIC LOAD TABLES BEFORE SELECTING A CATNIC LINTEL FOR A SPECIFIC OPENING — DO NOT ASSUME A CATNIC LINTEL IS APPROPRIATE FOR ANY OPENING WITHOUT CHECKING THE LOAD TABLE.

IG S-BEAM (IG LINTELS — IBSTOCK GROUP — S/L SERIES): AN ALTERNATIVE PRESSED STEEL LINTEL — SIMILAR CONCEPT TO CATNIC — AVAILABLE IN S/L 110 (EXTERNAL SOLID WALL), S/L 140, AND HEAVIER DUTY SERIES FOR WIDER OPENINGS. USED WIDELY IN LONDON RESIDENTIAL RENOVATION AND NEWBUILD.

RSJ (ROLLED STEEL JOG — OR MORE CORRECTLY: UB — UNIVERSAL BEAM — BS EN 10025-1 S275 GRADE STRUCTURAL STEEL): FOR LARGER OPENINGS (OVER 2400MM CLEAR), HEAVIER LOADS (UPPER FLOORS, ROOFS, AND MULTIPLE STOREYS ABOVE THE BEAM), OR WHERE THE BEAM IS TO BE EXPOSED AS A DESIGN FEATURE: A UNIVERSAL BEAM (UB — THE I-SECTION STRUCTURAL STEEL MEMBER COMMONLY CALLED AN RSJ) IS THE CORRECT SPECIFICATION. MOST COMMON UB SIZES FOR LONDON VICTORIAN TERRACE RESIDENTIAL OPENINGS (STRUCTURAL ENGINEER DESIGN REQUIRED): UB 203X133X25 (203MM DEPTH, 133MM FLANGE WIDTH, 25KG/M — TYPICAL FOR A 2400-3600MM CLEAR OPENING CARRYING MODERATE RESIDENTIAL LOADS). UB 254X146X31 (254MM DEPTH, 146MM FLANGE WIDTH, 31KG/M — TYPICAL FOR 3600-4500MM OPENINGS OR HEAVIER LOADS). UB 305X127X37 OR UB 305X165X40 (FOR WIDER SPANS OR HIGHER LOADS — COMMON IN REAR KITCHEN EXTENSIONS AND OPEN-PLAN GROUND FLOOR SCHEMES IN LONDON VICTORIAN TERRACES).

ANY NEW OR ENLARGED OPENING THROUGH A LOAD-BEARING WALL IN A LONDON VICTORIAN TERRACE THAT REQUIRES A STRUCTURAL STEEL LINTEL IS A NOTIFIABLE STRUCTURAL ALTERATION UNDER BUILDING REGULATIONS APPROVED DOCUMENT A (STRUCTURE).

BUILDING REGULATIONS REQUIREMENTS FOR STEEL LINTEL INSTALLATION: BUILDING NOTICE OR FULL PLANS APPLICATION: FOR ANY STRUCTURAL ALTERATION (REMOVING PART OF A LOAD-BEARING WALL, INSTALLING A NEW LINTEL, INSERTING A STEEL BEAM), A BUILDING REGULATIONS NOTICE MUST BE SUBMITTED TO THE LOCAL AUTHORITY BUILDING CONTROL (LABC) OR AN APPROVED INSPECTOR (SUCH AS BRE, NHBC, OR APPROVED INSPECTORS LTD). FOR A FULL PLANS APPLICATION: A STRUCTURAL ENGINEER'S DESIGN (CALCULATION PACKAGE AND DRAWING) IS TYPICALLY REQUIRED SHOWING: BEAM SIZE (UB OR CATNIC/IG), PADSTONE DESIGN, TEMPORARY PROPPING SCHEME, AND CONFIRMATION THAT THE REMAINING STRUCTURE IS ADEQUATE. FOR A BUILDING NOTICE: BUILDING CONTROL WILL INSPECT THE WORKS IN PROGRESS AND MAY REQUIRE A STRUCTURAL ENGINEER'S DESIGN IF THE OPENING IS SIGNIFICANT.

STRUCTURAL ENGINEER: FOR ANY OPENING OVER 1800MM CLEAR (OR FOR ANY OPENING IN A WALL CARRYING SIGNIFICANT LOADS — ROOF, UPPER FLOOR, OR MULTIPLE STOREYS), A STRUCTURAL ENGINEER'S DESIGN IS ESSENTIAL. THE ENGINEER WILL CALCULATE: BEAM SIZE (BASED ON SPAN, LOAD CASE, DEFLECTION LIMIT — TYPICALLY L/360 FOR MASONRY-SUPPORTED BEAMS — THAT IS, MAXIMUM DEFLECTION = CLEAR SPAN/360). PADSTONE SIZE (BASED ON BEARING STRESS — TYPICALLY LIMITED TO 0.7-1.0 N/MM² FOR CLASS A ENGINEERING BRICK, 3.0-5.0 N/MM² FOR REINFORCED CONCRETE PADSTONE). PROPPING REQUIREMENT (NUMBER, SIZE, AND SPACING OF ACROW PROPS OR GROUNDFORCE SHORING FRAMES REQUIRED TO SAFELY CARRY THE LOADS DURING THE INSTALLATION PERIOD). CONNECTIONS (BOLT SIZE AND SPACING WHERE BEAMS ARE BOLTED TOGETHER OR TO COLUMNS). EXPECTED STRUCTURAL ENGINEER DESIGN COST: £300-600 FOR A SINGLE BEAM CALCULATION. £500-1,200 FOR A MORE COMPLEX SCHEME (MULTIPLE BEAMS, UNUSUAL LOADINGS, NEED FOR BUILDING CONTROL SUBMISSION).

A PADSTONE IS THE ELEMENT AT EACH END OF A STEEL LINTEL OR BEAM THAT DISTRIBUTES THE POINT LOAD FROM THE BEAM BEARING INTO THE MASONRY WALL BELOW — WITHOUT A PADSTONE, THE CONCENTRATED POINT LOAD FROM THE BEAM BEARING WOULD BE APPLIED TO A SINGLE BRICK COURSE, RISKING CRUSHING AND SPLITTING OF THE BRICK IMMEDIATELY BELOW THE BEAM.

PADSTONE SPECIFICATION FOR STEEL LINTELS IN LONDON VICTORIAN TERRACES: CLASS A ENGINEERING BRICK PADSTONE (THE SIMPLEST PADSTONE — USED FOR LIGHTER LOADS — TYPICALLY FOR CATNIC AND IG S-BEAM LINTELS UP TO 2400MM SPAN WITH MODERATE LOADS): 2-3 COURSES OF IBSTOCK BLUE ENGINEERING BRICK (CLASS A — COMPRESSIVE STRENGTH > 75 N/MM² — WATER ABSORPTION < 4.5%) OR WIENERBERGER STAFFORDSHIRE BLUE (CLASS A) LAID IN CEMENT MORTAR (1:3 CEMENT:SAND — NOT LIME MORTAR — THE PADSTONE MORTAR MUST BE STRONG ENOUGH TO DISTRIBUTE THE LOAD). PADSTONE SIZE: TYPICALLY 215 X 215 X 112MM (ONE FULL BRICK LENGTH X ONE FULL BRICK LENGTH X 1.5 COURSES HIGH) FOR CATNIC LINTELS. FOR HEAVIER LOADS (UB 203X133X25 OR ABOVE): THE PADSTONE SIZE MUST BE CALCULATED BY THE STRUCTURAL ENGINEER — TYPICALLY A LARGER FOOTPRINT (300 X 215 X 100MM OR 440 X 215 X 150MM PRECAST CONCRETE PADSTONE) TO KEEP THE BEARING STRESS WITHIN SAFE LIMITS.

PRECAST CONCRETE PADSTONE (FOR HEAVIER LOADS — UB 203 SERIES AND ABOVE): PRECAST CONCRETE PADSTONE (25 N/MM² OR 40 N/MM² CONCRETE — MADE TO THE ENGINEER'S SPECIFIED DIMENSIONS): THE MOST COMMON PADSTONE FOR A UB 203X133X25 OR ABOVE IN A LONDON VICTORIAN TERRACE RENOVATION. TYPICALLY SUPPLIED BY STRUCTURAL PRECAST SPECIALIST OR CAST IN-SITU (USING FORMWORK AND C30 CONCRETE WITH LIGHT REINFORCEMENT — A393 MESH OR 2 X 10MM BARS BOTTOM — WHERE SPECIFIED BY THE ENGINEER). STANDARD PRECAST PADSTONE SIZES (WIDELY AVAILABLE FROM BUILDERS' MERCHANTS — MARSHALLS PRECAST OR HANSON PRECAST): 215 X 215 X 100MM (FOR LIGHTER UB BEAMS). 327 X 215 X 150MM (FOR HEAVIER UB BEAMS). 440 X 215 X 150MM (FOR LONGEST SPAN OR HEAVIEST LOAD UB BEAMS).

SEAT (WELDED STEEL PLATE): FOR THE LARGEST BEAMS (UB 305 AND ABOVE) OR WHERE A VERY COMPACT PADSTONE IS REQUIRED: A STEEL SEAT (WELDED PLATE — TYPICALLY 10-15MM STEEL — WELDED TO THE BOTTOM FLANGE OF THE UB) CAN ACT AS THE BEARING PLATE AND DISTRIBUTES THE LOAD OVER THE MASONRY. THIS IS DESIGNED BY THE STRUCTURAL ENGINEER.

THE TEMPORARY PROPPING OF THE STRUCTURE ABOVE DURING STEEL LINTEL INSTALLATION IS ONE OF THE MOST SAFETY-CRITICAL ASPECTS OF STRUCTURAL ALTERATION WORK IN A LONDON VICTORIAN TERRACE.

PROPPING SEQUENCE (CRITICAL — FAILURE TO PROPERLY PROP BEFORE OPENING UP RISKS PARTIAL COLLAPSE OF THE STRUCTURE ABOVE): STEP 1 — PROP THE FLOOR/CEILING ABOVE: IF A FLOOR JOIST IS ABOVE THE OPENING (MOST COMMON IN LONDON VICTORIAN TERRACES WHERE GROUND FLOOR OPENINGS ARE BEING ENLARGED): ACROW PROPS (GROUNDFORCE PUSH-PULL PROP 20 OR GROUNDFORCE SHORING FRAME SF6) MUST BE ERECTED BELOW THE FLOOR JOIST AT A MAXIMUM OF 1200MM FROM THE WALL (DISTRIBUTING THE LOAD FROM THE FLOOR JOISTS BEING RELIEVED OF WALL SUPPORT) — BEFORE ANY BRICKWORK IS REMOVED. STEP 2 — PROP THE STRUCTURE ABOVE (ROOF OR UPPER FLOOR ON A GABLE OR CROSS WALL): WHERE THE WALL TO BE OPENED IS LOAD-BEARING (CARRYING ROOF RAFTERS OR UPPER FLOOR JOISTS): PROPS MUST BE POSITIONED ON SPREADER BOARDS (MINIMUM 150 X 50MM SOFTWOOD SPREADER PLANK) AT 1200MM CENTRES ALONG THE LENGTH OF THE WALL BOTH SIDES OF THE PROPOSED OPENING. STEP 3 — FORM THE OPENING: WITH ALL PROPPING IN PLACE, OPEN UP FROM THE TOP DOWN — FIRST EXPOSE AND REMOVE THE MASONRY FOR THE BEAM SEAT (PADSTONE BED) AT EACH END OF THE OPENING. STEP 4 — INSTALL THE BEAM: LIFT THE BEAM INTO POSITION (A UB 203X133X25 AT 3000MM LENGTH WEIGHS APPROXIMATELY 75KG — TYPICALLY REQUIRES 2-3 OPERATIVES). SEAT THE BEAM ON PADSTONES AT EACH END — CHECK LEVEL AND CONFIRM BEARING LENGTH ON EACH PADSTONE. STEP 5 — BUILD BRICKWORK ABOVE BEAM: PACK SOLID BETWEEN THE TOP FLANGE OF THE BEAM AND THE FIRST COURSE OF MASONRY ABOVE (USING ENGINEERING BRICK SLIPS OR GROUT — NO VOIDS). STEP 6 — REMOVE PROPS (ONLY AFTER MORTAR ABOVE BEAM HAS FULLY CURED — MINIMUM 7 DAYS FOR NHL MORTAR — 3 DAYS FOR PORTLAND CEMENT MORTAR).

INSTALLING A STEEL LINTEL OR RSJ IN A LONDON VICTORIAN TERRACE WALL THAT IS OR IS CLOSE TO A PARTY WALL HAS SPECIFIC PARTY WALL ACT 1996 IMPLICATIONS THAT MUST BE MANAGED BEFORE WORK COMMENCES.

WHEN PARTY WALL ACT APPLIES TO STRUCTURAL STEEL INSTALLATION: SECTION 2 OF THE PARTY WALL ACT 1996 (WORKS ON OR TO A PARTY WALL OR PARTY STRUCTURE): APPLIES WHERE THE PROPOSED STRUCTURAL ALTERATION INVOLVES: CUT TING INTO OR MAKING GOOD A PARTY WALL. CUTTING OR MAKING OPENINGS IN A PARTY WALL. RAISING OR REDUCING THE HEIGHT OF A PARTY WALL. INSERTING A DAMP-PROOF COURSE INTO A PARTY WALL. A TYPICAL EXAMPLE IN A LONDON VICTORIAN TERRACE: THE REAR RECEPTION ROOM PARTY WALL IS TO BE OPENED UP TO CREATE A KITCHEN-DINER — THE STRUCTURAL ALTERATION (REMOVING BRICKWORK AND INSTALLING A UB BEAM IN THE PARTY WALL) TRIGGERS SECTION 2 PARTY WALL ACT NOTICES. NOTICE PROCEDURE: A PARTY STRUCTURE NOTICE UNDER SECTION 3 (FOR WORKS TO THE PARTY WALL) MUST BE SERVED ON THE ADJOINING OWNER — MINIMUM 2 MONTHS BEFORE WORKS START. THE ADJOINING OWNER CAN: CONSENT (IN WRITING — WORK CAN PROCEED). DISSENT (TRIGGERING THE APPOINTMENT OF PARTY WALL SURVEYORS — AGREED OR SEPARATE). THE AGREED SURVEYOR (OR TWO SURVEYORS IF SEPARATE) WILL SERVE AN AWARD SPECIFYING HOW THE WORKS ARE TO BE CARRIED OUT. SECTION 6 NOTICE (EXCAVATION NOTICE): MAY ALSO BE REQUIRED WHERE THE STRUCTURAL ALTERATION INVOLVES EXCAVATION WITHIN 3M OF THE PARTY WALL TO A GREATER DEPTH THAN THE ADJOINING FOUNDATIONS.

SCHEDULE OF CONDITION: REGARDLESS OF WHETHER THE ADJOINING OWNER CONSENTS OR DISSENTS, A SCHEDULE OF CONDITION OF THE ADJOINING PROPERTY (PHOTOGRAPHIC AND WRITTEN RECORD OF THE EXISTING CONDITION BEFORE WORKS START) SHOULD ALWAYS BE COMMISSIONED BY THE BUILDING OWNER — THIS PROTECTS BOTH PARTIES IN THE EVENT OF A SUBSEQUENT DISPUTE ABOUT DAMAGE CAUSED BY THE STRUCTURAL WORKS.

STEEL LINTEL AND BEAM INSTALLATION COSTS IN LONDON (2025) DEPEND ON THE BEAM SIZE, THE NATURE OF THE WALL (LOAD-BEARING SOLID BRICK — TYPICAL VICTORIAN TERRACE — VERSUS LIGHTER INTERNAL PARTITION), THE DEGREE OF PROPPING REQUIRED, AND WHETHER A STRUCTURAL ENGINEER'S DESIGN IS NEEDED.

CATNIC CG90 OR IG S-BEAM LINTEL (PRESSED STEEL — UP TO 2400MM CLEAR OPENING — TYPICAL SINGLE DOOR OR WINDOW ENLARGEMENT IN AN INTERNAL WALL — LONDON VICTORIAN TERRACE): LINTEL SUPPLY (CATNIC CG90 — 2400MM LENGTH): £60 TO £120. PADSTONES (2 X CLASS A ENGINEERING BRICK PADSTONES — 215X215X112MM): £30 TO £60. TEMPORARY PROPPING (1-2 ACROW PROPS): £50 TO £150 (HIRE + LABOUR). LABOUR (BRICKLAYER + LABOURER — 1 DAY): £350 TO £600. BUILDING CONTROL NOTICE: £150 TO £400. TOTAL CATNIC LINTEL INSTALLATION (INTERNAL DOOR/WINDOW ENLARGEMENT): £640 TO £1,330.

UB 203X133X25 RSJ BEAM (3000MM CLEAR OPENING — KNOCK-THROUGH BETWEEN TWO GROUND FLOOR ROOMS — LONDON VICTORIAN TERRACE): STRUCTURAL ENGINEER DESIGN: £300 TO £600. BUILDING CONTROL FULL PLANS APPLICATION: £150 TO £400. BEAM SUPPLY (UB 203X133X25 — 3600MM TOTAL — HOT-DIPPED GALVANISED OR PRIMED): £200 TO £450. PRECAST CONCRETE PADSTONES (2 X 327X215X150MM): £80 TO £160. TEMPORARY PROPPING (ACROW PROPS AND SPREADER BOARDS — 4-6 PROPS): £200 TO £500 (HIRE + LABOUR). LABOUR (STRUCTURAL ALTERATIONS — OPEN UP, INSTALL BEAM, FORM PADSTONE BEDS, REBUILD ABOVE): £600 TO £1,200 (2 BRICKLAYERS + LABOURER — 1-2 DAYS). PARTY WALL SURVEYOR (WHERE REQUIRED): £600 TO £1,200 (PER SURVEYOR). TOTAL RSJ BEAM INSTALLATION (WITHOUT PARTY WALL SURVEYOR): £1,530 TO £3,310.

LARGER UB 254X146X31 OR UB 305X127X37 (REAR EXTENSION STRUCTURAL BEAM OR WIDE OPENING — 4500-6000MM CLEAR — KITCHEN-DINER OPENING — LONDON VICTORIAN TERRACE): STRUCTURAL ENGINEER DESIGN: £400 TO £1,000. BEAM SUPPLY: £350 TO £800 (4500-6000MM LENGTH). PADSTONES (LARGE — 440X215X150MM PRECAST CONCRETE): £120 TO £250. TEMPORARY PROPPING (8-12 ACROW PROPS): £400 TO £900. LABOUR (3 BRICKLAYERS + LABOURER — 2 DAYS): £1,200 TO £2,400. BUILDING CONTROL: £200 TO £500. TOTAL LARGE BEAM (WITHOUT PARTY WALL): £2,670 TO £5,850.