Removing Internal Walls in London Houses: Steel Beams, Building Control, and Structural Guide

NOT ALL INTERNAL WALLS IN A LONDON TERRACE ARE STRUCTURAL. THE FIRST AND MOST IMPORTANT TASK IS ESTABLISHING WHETHER THE WALL YOU WANT TO REMOVE IS LOAD-BEARING — I.E., WHETHER IT CARRIES LOADS FROM FLOORS OR ROOF STRUCTURE ABOVE — OR WHETHER IT IS A SIMPLE PARTITION WALL THAT CAN BE REMOVED WITHOUT STRUCTURAL CONSEQUENCE.

THE GENERAL RULES FOR IDENTIFYING STRUCTURAL WALLS IN A TYPICAL LONDON TWO-STOREY TERRACE ARE AS FOLLOWS. EXTERNAL WALLS ARE ALWAYS STRUCTURAL. THE PARTY WALL (SHARED WITH THE NEIGHBOURING PROPERTY) IS ALWAYS STRUCTURAL. INTERNAL WALLS RUNNING PERPENDICULAR TO THE FLOOR JOISTS ARE USUALLY STRUCTURAL — IN A TYPICAL TERRACE, THE FLOOR JOISTS RUN FRONT-TO-BACK (PARALLEL TO THE PARTY WALLS), MEANING THAT THE WALL RUNNING ACROSS THE MID-POINT OF THE HOUSE (THE STAIRCASE SPINE WALL) AND ANY WALL PERPENDICULAR TO THE JOIST DIRECTION IS STRUCTURAL. INTERNAL WALLS RUNNING PARALLEL TO THE FLOOR JOISTS ARE USUALLY NON-STRUCTURAL PARTITIONS.

HOWEVER, THESE RULES ARE NOT ABSOLUTE. A WALL PARALLEL TO THE JOISTS MAY STILL BE STRUCTURAL IF IT CARRIES A PURLIN, A RIDGE BEAM, OR AN UPPER FLOOR JOIST THAT SPANS PERPENDICULAR TO THE MAIN JOIST DIRECTION. IN ANY CASE OF DOUBT — WHICH IS MOST CASES IN REAL LONDON PROPERTIES WHERE PREVIOUS ALTERATIONS MAY HAVE CHANGED THE STRUCTURAL LOGIC — A STRUCTURAL ENGINEER'S OPINION IS ESSENTIAL BEFORE ANY WORKS BEGIN.

THE STRUCTURAL ENGINEER WILL TYPICALLY VISIT THE PROPERTY, VIEW THE WALL FROM BOTH SIDES, CHECK THE FLOOR ABOVE AND BELOW FOR EVIDENCE OF LOAD-BEARING MEMBERS, INSPECT THE LOFT SPACE FOR PURLIN ARRANGEMENTS, AND CONFIRM DEFINITIVELY WHETHER THE WALL IS STRUCTURAL. THIS VISIT TYPICALLY COSTS £150 TO £350 AND IS MONEY WELL SPENT BEFORE ANY COMMITMENT IS MADE.

WHEN A STRUCTURAL WALL IS REMOVED AND REPLACED WITH AN OPENING, A STEEL BEAM MUST BE INSTALLED TO CARRY THE LOADS THE WALL WAS PREVIOUSLY TRANSFERRING TO THE FOUNDATION. THE BEAM MUST BE SIZED BY A STRUCTURAL ENGINEER BASED ON THE SPECIFIC SPAN, THE LOADS FROM ABOVE (FLOORS, WALLS, ROOF), AND THE BEARING CONDITIONS AT EACH END.

FOR LONDON TERRACED HOUSES, THE MOST COMMON BEAM SIZES IN RESIDENTIAL STRUCTURAL ALTERATIONS ARE AS FOLLOWS. FOR OPENINGS OF 1.5M TO 2.5M CARRYING ONE FLOOR ABOVE ONLY: UB 152X89X16 OR UB 178X102X19 (UNIVERSAL BEAM, DIMENSIONS IN MILLIMETRES WIDTH-X-HEIGHT-X-KG/M). FOR OPENINGS OF 2.5M TO 3.5M CARRYING ONE FLOOR: UB 203X133X25 — THE MOST COMMONLY SPECIFIED BEAM FOR A STANDARD GROUND FLOOR OPENING IN A LONDON VICTORIAN TERRACE. FOR OPENINGS OF 3.5M TO 4.5M OR CARRYING TWO FLOORS: UB 254X146X31 OR UB 305X127X37. FOR LARGER OPENINGS OR LOFT CONVERSIONS WITH SIGNIFICANT ROOF LOADS: UB 305X165X40 OR UB 356X171X45.

ALL STRUCTURAL STEELWORK IN UK RESIDENTIAL CONSTRUCTION IS DESIGNED IN S275 STEEL GRADE (YIELD STRENGTH 275 N/MM') AS STANDARD UNLESS THE STRUCTURAL ENGINEER SPECIFIES S355 FOR A HEAVILY LOADED SHORT-SPAN APPLICATION. BEAMS MUST BE PROTECTED AGAINST CORROSION — IN A DRY INTERNAL ENVIRONMENT, ONE COAT OF RED OXIDE PRIMER IS STANDARD, WITH FURTHER DECORATION AS REQUIRED.

BEAMS ARE ALMOST ALWAYS FITTED AS A PAIR OF PARALLEL SECTIONS STRAPPED TOGETHER (A FLITCH BEAM) OR AS A SINGLE SECTION. WHERE THE BEAM MUST BE CONCEALED WITHIN THE CEILING HEIGHT, A FLAT PLATE CAN BE WELDED BETWEEN TWO C-CHANNELS (RSC SECTIONS) TO CREATE A SHALLOW PROFILE — THIS IS MORE EXPENSIVE TO FABRICATE BUT PRESERVES CEILING HEIGHT.

A STEEL BEAM TRANSFERS ITS ENTIRE LOAD INTO TWO BEARING POINTS AT EACH END. THE BEARING POINT MUST BE CAPABLE OF DISTRIBUTING THIS CONCENTRATED LOAD INTO THE MASONRY OR CONCRETE BELOW WITHOUT CAUSING LOCAL CRUSHING OR SETTLEMENT.

IN A BRICK MASONRY WALL, THE STANDARD SOLUTION IS A PADSTONE: A PRECAST CONCRETE OR ENGINEERING BRICK PAD OF SUFFICIENT PLAN AREA TO REDUCE THE BEARING STRESS TO WITHIN THE CAPACITY OF THE MASONRY. A STRUCTURAL ENGINEER WILL CALCULATE THE REQUIRED PADSTONE SIZE. TYPICAL PADSTONES FOR RESIDENTIAL BEAM INSTALLATIONS ARE 215MM X 215MM X 100MM PRECAST CONCRETE OR 215MM X 327MM X 215MM (TWO COURSES OF ENGINEERING BRICK IN ENGINEERING BRICK BED JOINT) FOR LARGER LOADS. PADSTONES MUST BE BEDDED IN CLASS II MORTAR (1:0.5:4.5 CEMENT:LIME:SAND) AND ALLOWED TO CURE BEFORE THE BEAM IS LOWERED ONTO THEM.

WHERE THE BEAM BEARS INTO A PARTY WALL OR EXTERNAL WALL, THE PADSTONE IS BUILT INTO THE WALL AT THE CORRECT HEIGHT DURING THE PROPPING AND TEMPORARY WORKS PHASE. WHERE THE BEAM BEARS INTO A TIMBER STUD WALL OR EXISTING TIMBER FRAME, SOLID TIMBER OR STEEL END-PLATES MUST BE PROVIDED — A STRUCTURAL ENGINEER MUST CONFIRM THE ADEQUACY OF THE EXISTING STRUCTURE TO RECEIVE THE BEAM LOAD.

REMOVING A STRUCTURAL WALL WITHOUT ADEQUATE TEMPORARY SUPPORT IS EXTREMELY DANGEROUS AND WILL RESULT IN CATASTROPHIC STRUCTURAL FAILURE. TEMPORARY PROPPING MUST BE IN PLACE BEFORE ANY STRUCTURAL MASONRY IS REMOVED.

THE STANDARD APPROACH FOR A GROUND FLOOR WALL REMOVAL IN A LONDON TERRACE IS AS FOLLOWS. FIRST, ASSESS THE FLOOR ABOVE THE WALL: IS IT TIMBER JOISTS (USUAL IN VICTORIAN PROPERTIES) OR CONCRETE (POST-WAR PROPERTIES)? SECOND, INSTALL TIMBER SPREADER PLATES AND ACROW PROPS IMMEDIATELY EITHER SIDE OF THE WALL AT 1.8M MAXIMUM CENTRES TO TRANSFER THE FLOOR LOAD TO THE GROUND FLOOR LEVEL. THIRD, INSTALL GROUNDFORCE SHORCO FRAMES OR ADDITIONAL ACROW PROPS IN THE BASEMENT (IF ONE EXISTS) OR CONFIRM THAT THE GROUND FLOOR CONCRETE SLAB CAN CARRY THE PROPPED LOADS — THIS REQUIRES STRUCTURAL ENGINEER CONFIRMATION. FOURTH, REMOVE MASONRY IN SECTIONS, INSTALLING TEMPORARY LINTELS IF THE STRUCTURAL OPENING IS WIDER THAN 900MM. FIFTH, FIT THE PERMANENT STEEL BEAM WITH THE PROPS STILL IN PLACE. SIXTH, ALLOW THE PADSTONE MORTAR AND ANY STRUCTURAL FILL ABOVE THE BEAM TO CURE BEFORE CAREFULLY REMOVING PROPS.

DO NOT REDUCE PROP SPACING BELOW 900MM WHEN REMOVING BRICKWORK ACTIVELY — THE DYNAMIC LOADING DURING DEMOLITION CAN EXCEED STATIC ASSUMPTIONS. DO NOT REMOVE ALL PROPS SIMULTANEOUSLY — REMOVE ONE AT A TIME AND MONITOR FOR SETTLEMENT.

CHIMNEY BREAST REMOVAL IS A SPECIFIC VARIANT OF INTERNAL WALL REMOVAL THAT PRESENTS ADDITIONAL COMPLICATIONS. IN A TYPICAL LONDON VICTORIAN TERRACE, THE MAIN CHIMNEY STACK SERVES TWO FIREPLACES — ONE ON THE GROUND FLOOR AND ONE ON THE FIRST FLOOR (SOMETIMES ALSO THE SECOND FLOOR) — WITH THE CHIMNEY BREAST PROJECTING INTO EACH ROOM ON A DIFFERENT FLOOR.

IF THE GROUND FLOOR CHIMNEY BREAST IS REMOVED BUT THE FIRST-FLOOR CHIMNEY BREAST IS RETAINED, THE RETAINED CHIMNEY BREAST AND THE FULL WEIGHT OF THE CHIMNEY STACK ABOVE HAVE NO SUPPORT. THIS LOAD MUST BE TRANSFERRED TO A STRUCTURAL STEEL GALLOWS BRACKET (A CANTILEVER STEEL FRAME FIXED INTO THE PARTY WALL OR CHIMNEY FLANK WALL AND PROJECTING TO SUPPORT THE BOTTOM OF THE RETAINED FIRST-FLOOR CHIMNEY BREAST). THE GALLOWS BRACKET MUST BE DESIGNED BY A STRUCTURAL ENGINEER AND IS TYPICALLY UB 152X89X16 OR UB 178X102X19 SECTIONS WELDED TO FORM AN L-FRAME, WITH A MINIMUM 600MM EMBEDMENT INTO MASONRY. FAILURE TO PROVIDE A GALLOWS BRACKET WHEN REMOVING ONLY THE GROUND FLOOR CHIMNEY BREAST HAS CAUSED STRUCTURAL COLLAPSE IN LONDON PROPERTIES — THIS IS A SERIOUS AND NON-NEGOTIABLE REQUIREMENT.

If THE ENTIRE CHIMNEY BREAST IS REMOVED ON ALL FLOORS, THE CHIMNEY STACK ABOVE ROOF LEVEL MUST ALSO BE TAKEN DOWN. PERMISSION IS NOT GENERALLY REQUIRED BUT THE STACK REMOVAL MUST BE COMPLETED AND THE ROOF MADE WEATHER-TIGHT BEFORE THE WORKS CAN BE SIGNED OFF BY BUILDING CONTROL.

REMOVING AN INTERNAL WALL IN A LONDON TERRACE ALWAYS REQUIRES BUILDING CONTROL APPROVAL UNDER BUILDING REGULATIONS PART A (STRUCTURE). BUILDING CONTROL MUST APPROVE THE STRUCTURAL ENGINEER'S CALCULATIONS AND BEAM SPECIFICATION BEFORE WORKS COMMENCE (UNDER A FULL PLANS APPLICATION) OR DURING WORKS (UNDER A BUILDING NOTICE). RCB ALWAYS RECOMMENDS FULL PLANS APPLICATION FOR STRUCTURAL WORKS, AS IT PROVIDES ADVANCE SIGN-OFF AND PROTECTS AGAINST LATER REINTERPRETATION.

BUILDING CONTROL INSPECTION REQUIREMENTS TYPICALLY INCLUDE: INSPECTION OF THE PROPPING ARRANGEMENT BEFORE MASONRY REMOVAL BEGINS; INSPECTION OF THE PADSTONES AND BEAM BEFORE MASONRY IS MADE GOOD AROUND THE BEAM; AND FINAL INSPECTION OF COMPLETED STRUCTURAL WORKS AND ANY ASSOCIATED FIRE PROTECTION (INTUMESCENT COATING IF THE BEAM IS IN A FIRE COMPARTMENT BOUNDARY).

IF THE WALL BEING REMOVED IS THE PARTY WALL — I.E., THE WALL SHARED WITH THE NEIGHBOURING PROPERTY — THE PARTY WALL ACT 1996 APPLIES UNDER SECTION 2 (WORK ON AN EXISTING PARTY WALL OR PARTY STRUCTURE). A PARTY WALL NOTICE MUST BE SERVED ON ALL ADJOINING OWNERS AT LEAST TWO MONTHS BEFORE WORK STARTS. CONSENT OR DISSENT MUST BE RECEIVED. IF THE NEIGHBOUR DISSENTS, THE PARTY WALL ACT DISPUTE RESOLUTION PROCESS APPLIES, INVOLVING APPOINTMENT OF A PARTY WALL SURVEYOR (OR AGREED SINGLE SURVEYOR). FAILING TO SERVE NOTICE BEFORE PARTY WALL WORKS IS A COMMON AND COSTLY MISTAKE — INJUNCTIONS CAN HALT WORKS MID-PROJECT.

THE TOTAL COST OF REMOVING AN INTERNAL STRUCTURAL WALL IN A LONDON TERRACE COMPRISES SEVERAL ELEMENTS. STRUCTURAL ENGINEER FEE FOR INITIAL ASSESSMENT PLUS BEAM CALCULATIONS AND DRAWINGS: £600 TO £1,400. BUILDING CONTROL FULL PLANS FEE WITH LONDON LOCAL AUTHORITY: £350 TO £700 FOR A STRUCTURAL ALTERATION. PARTY WALL SURVEYOR FEE (IF REQUIRED): £700 TO £1,500 DEPENDING ON WHETHER AN AGREED SURVEYOR OR TWO SURVEYORS ARE APPOINTED.

CONSTRUCTION COSTS FOR THE WALL REMOVAL AND BEAM INSTALLATION ITSELF (PROPPING, MASONRY REMOVAL, BEAM SUPPLY AND FIT, PADSTONES, MAKING GOOD, SKIMMING): £3,000 TO £7,000 FOR A STANDARD GROUND FLOOR OPENING IN A 2-BED VICTORIAN TERRACE, DEPENDING ON BEAM SPAN AND WALL COMPLEXITY. CHIMNEY BREAST REMOVAL (GROUND FLOOR ONLY WITH GALLOWS BRACKET) ADDS £2,000 TO £4,500 ABOVE A STANDARD WALL REMOVAL.

TOTAL PROJECT COST FOR A STRAIGHTFORWARD GROUND FLOOR OPENING OF 3M SPAN, NO PARTY WALL WORKS: £4,650 TO £9,600 INCLUDING PROFESSIONAL FEES AND CONSTRUCTION. WHERE KITCHEN REFURBISHMENT AND DECORATION FOLLOW THE STRUCTURAL WORKS, THESE COSTS ARE ADDITIONAL.