ACO Linear Drainage for London Victorian Terrace Extensions and Bi-Fold Door Thresholds

ACO TECHNOLOGIES (BÜDELSDORF, GERMANY — THE WORLD'S LARGEST CHANNEL DRAINAGE MANUFACTURER — UK OPERATIONS AT ACO BUILDING DRAINAGE LTD, SHEFFORD, BEDFORDSHIRE): THE MOST SPECIFIED LINEAR DRAINAGE PRODUCTS FOR LONDON VICTORIAN TERRACE REAR EXTENSION AND BI-FOLD DOOR THRESHOLD APPLICATIONS:

ACO DESIGN DRAIN (THE MOST WIDELY SPECIFIED LINEAR DRAIN FOR RESIDENTIAL BI-FOLD DOOR THRESHOLD APPLICATIONS IN THE UK): A STAINLESS STEEL CHANNEL DRAIN DESIGNED SPECIFICALLY FOR THE FLUSH THRESHOLD DETAIL — KEY FEATURES: WIDTH: APPROXIMATELY 65-70MM WIDE STAINLESS STEEL GRATE (THE NARROW WIDTH MINIMISES THE VISUAL INTERRUPTION AT THE THRESHOLD — FAR LESS OBTRUSIVE THAN A TRADITIONAL SQUARE CHANNEL GRATE). DEPTH: SHALLOW CHANNEL PROFILE (ALLOWS INSTALLATION WITHOUT REQUIRING A DEEP EXCAVATION INTO THE EXISTING PATIO SLAB — CRITICAL WHERE THE PATIO IS CLOSE TO THE DAMP-PROOF COURSE LEVEL AND DEEP EXCAVATION IS NOT POSSIBLE). GRATE: STAINLESS STEEL SLOT GRATE (THE NARROW SLOT DESIGN — TYPICALLY 5-8MM WIDE SLOTS — PROVIDES THE MINIMUM INTRUSION ON THE THRESHOLD AESTHETICS — AVAILABLE IN POLISHED, BRUSHED, OR SATIN STAINLESS STEEL FINISHES). CAPACITY: APPROXIMATELY 14-16 LITRES PER SECOND PER METRE AT 1/100 FALL (THE STANDARD HYDRAULIC CAPACITY FOR A RESIDENTIAL LINEAR DRAIN — ADEQUATE FOR A PATIO AREA OF UP TO 25M² DRAINING TO A SINGLE CHANNEL DRAIN — FOR LARGER PATIO AREAS, A CALCULATION USING THE CIRIA SUDS MANUAL C753 METHODOLOGY IS REQUIRED). CHANNEL BODY: AVAILABLE IN POLYPROPYLENE (STANDARD DOMESTIC GRADE) OR POLYMER CONCRETE (STRONGER — FOR VEHICULAR AREAS — NOT TYPICALLY REQUIRED FOR A PEDESTRIAN PATIO). END OUTLET (110MM): THE CHANNEL BODY CONNECTS TO THE 110MM DRAIN RUN VIA A 110MM SOCKET END OUTLET — EITHER AT ONE END OF THE CHANNEL (SINGLE END OUTLET) OR AT BOTH ENDS (DOUBLE END OUTLET FOR LONGER CHANNEL RUNS WHERE A SINGLE OUTLET WOULD BE HYDRAULICALLY INSUFFICIENT). ACO DESIGN DRAIN PRICE: APPROXIMATELY £80 TO £150 PER METRE (SUPPLY ONLY — INCLUDING GRATE AND CHANNEL BODY — 1M UNIT LENGTH — LARGER PROJECTS USE MULTIPLE UNITS CONNECTED END-TO-END).

ACO KERBDRAIN K200 (THE ALTERNATIVE PRODUCT FOR COMBINED KERB AND DRAINAGE APPLICATIONS — MOST APPROPRIATE FOR THE DRIVEWAY-ADJACENT PATIO OR WHERE THE PATIO EDGE REQUIRES A KERB AS WELL AS DRAINAGE): COMBINES A PRECAST POLYMER CONCRETE KERB (150MM HEIGHT) WITH AN INTEGRATED CHANNEL DRAIN — ALLOWING THE PATIO EDGE KERB AND THE DRAINAGE CHANNEL TO BE FORMED IN ONE UNIT — ELIMINATING THE NEED FOR SEPARATE KERB AND CHANNEL ELEMENTS. GRATE: STAINLESS STEEL SLOT GRATE (SAME AS ACO DESIGN DRAIN).

THE FLUSH BI-FOLD DOOR THRESHOLD WITH ACO LINEAR DRAIN IS ONE OF THE MOST TECHNICALLY DEMANDING CONSTRUCTION DETAILS IN A LONDON VICTORIAN TERRACE REAR EXTENSION — AND ONE OF THE MOST FREQUENTLY EXECUTED INCORRECTLY ON RESIDENTIAL PROJECTS, RESULTING IN WATER INGRESS THROUGH THE THRESHOLD AFTER COMPLETION.

KEY PRINCIPLE: THE INTERIOR FLOOR LEVEL AND THE EXTERIOR PATIO SURFACE MUST BE EXACTLY ALIGNED (FLUSH) — AND THE ACO LINEAR DRAIN MUST BE POSITIONED IMMEDIATELY OUTSIDE THE BI-FOLD DOOR THRESHOLD SILL — SO THAT ANY WATER ON THE EXTERIOR PATIO SURFACE RUNS TOWARD THE DRAIN RATHER THAN TOWARD THE DOOR SILL. THIS REQUIRES: (A) THE EXTERIOR PATIO SURFACE TO FALL AWAY FROM THE BUILDING (MINIMUM 1:60 FALL TOWARD THE DRAIN CHANNEL — MORE THAN THE MINIMUM — THE PATIO FALLS TOWARD THE DRAIN, WHICH IS RECESSED INTO THE PATIO SURFACE AT THE THRESHOLD). (B) THE DRAIN CHANNEL TO BE SET AT A LEVEL MARGINALLY BELOW THE PATIO SURFACE — THE GRATE SURFACE IS TYPICALLY 5-10MM BELOW THE FINISHED PATIO LEVEL (FLUSH AT THE PATIO OR VERY SLIGHTLY RECESSED — NEVER PROUD OF THE PATIO SURFACE). (C) THE DRAIN HAS ADEQUATE CAPACITY TO RECEIVE THE PATIO DRAINAGE AT THE DESIGN RAINFALL INTENSITY.

FLOOR LEVEL ALIGNMENT — THE CRITICAL BUILD-UP DETAIL: INTERIOR FLOOR LEVEL (ASSUME 65MM HANSON CEMFLOOR LIQUID SCREED OVER 100MM KINGSPAN KOOLTHERM K3 PIR INSULATION OVER NEW CONCRETE SLAB — STANDARD GROUND FLOOR BUILD-UP FOR A LONDON VICTORIAN TERRACE REAR EXTENSION WITH UFH): TOTAL FLOOR BUILD-UP FROM SLAB TOP TO FINISHED FLOOR SURFACE = APPROXIMATELY 180-200MM. EXTERIOR PATIO LEVEL (MUST MATCH THE INTERIOR FLOOR LEVEL): PATIO BUILD-UP FROM THE SAME STRUCTURAL SLAB LEVEL = PAVING SLAB OR PORCELAIN TILE (25-30MM THICK) + MORTAR BED (25-50MM) + COMPACTED TYPE 1 OR CONCRETE LEVELLING SLAB (AS REQUIRED TO ACHIEVE LEVEL) = APPROXIMATELY 50-80MM TOTAL. NOTE: THE PATIO BUILD-UP IS MUCH SHALLOWER THAN THE INTERIOR BUILD-UP (BECAUSE THE INTERIOR HAS PIR INSULATION AND UFH SCREED) — THIS MEANS THE EXTERIOR PATIO SLAB MUST BE SET AT A SIGNIFICANTLY LOWER STRUCTURAL LEVEL THAN THE INTERIOR SLAB TO ACHIEVE A FLUSH FINISHED SURFACE. TYPICAL DETAIL: THE EXTERIOR PATIO SLAB IS POURED AT APPROXIMATELY 120-130MM LOWER THAN THE INTERIOR STRUCTURAL SLAB — THEN THE PATIO BUILD-UP (MORTAR BED + PAVING) BRINGS THE FINISHED SURFACE UP TO MATCH THE INTERIOR FLOOR LEVEL.

ACO DRAIN POSITION: THE DRAIN CHANNEL BODY IS SET INTO THE PATIO SURFACE (OR INTO THE CONCRETE SLAB BELOW THE PATIO — A RECESS MUST BE CAST INTO THE PATIO SLAB TO ACCEPT THE DRAIN CHANNEL BODY — COORDINATED WITH THE STRUCTURAL ENGINEER AND GROUNDWORK CONTRACTOR AT CONCRETE POUR STAGE). THE GRATE TOP SURFACE IS SET 5-10MM BELOW THE FINISHED PATIO PAVING SURFACE TO CREATE A RECESS THAT ENCOURAGES WATER TO FLOW INTO THE DRAIN.

LINEAR DRAINAGE PRODUCTS INSTALLED IN THE UK MUST COMPLY WITH BS EN 1433:2002 (DRAINAGE CHANNELS FOR VEHICULAR AND PEDESTRIAN AREAS — CLASSIFICATION, DESIGN AND TESTING REQUIREMENTS) — AND MUST BE SELECTED WITH THE CORRECT LOAD CLASS FOR THE INTENDED APPLICATION.

BS EN 1433 LOAD CLASSES: CLASS A15 (THE LOWEST LOAD CLASS — SUITABLE FOR PEDESTRIAN AND CYCLE AREAS ONLY — MAXIMUM AXLE LOAD 1.5 TONNES): THE CORRECT SPECIFICATION FOR A RESIDENTIAL PATIO LINEAR DRAIN (THE PATIO IS PEDESTRIAN ONLY). ACO DESIGN DRAIN IS RATED CLASS A15 — APPROPRIATE FOR RESIDENTIAL PATIO AND TERRACE USE. CLASS B125 (SUITABLE FOR LIGHT VEHICULAR AREAS — MAXIMUM 12.5 TONNES): APPROPRIATE FOR DRIVEWAYS AND CAR PARKING AREAS. CLASS C250 TO F900: PROGRESSIVELY HEAVIER LOADING — NOT REQUIRED FOR RESIDENTIAL GARDEN AND PATIO APPLICATIONS.

SURFACE WATER DRAINAGE CONNECTION — THE TWO COMPLIANT OPTIONS: OPTION 1 — CONNECT TO THE EXISTING SURFACE WATER DRAIN (WHERE A SEPARATE SURFACE WATER DRAINAGE SYSTEM EXISTS SERVING THE PROPERTY): THE 110MM OUTLET FROM THE ACO CHANNEL CONNECTS TO THE EXISTING SURFACE WATER GULLEY OR DRAIN RUN VIA A 110MM PUSHFIT UNDERGROUND DRAIN (POLYPIPE UNDERGROUND ORANGE 110MM PUSHFIT — THE STANDARD RESIDENTIAL UNDERGROUND DRAIN) — EITHER DIRECT CONNECTION OR VIA A CATCH PIT (P-TRAP GULLEY WITH RODDING ACCESS — POLYPIPE SQUARE TRAPPED GULLEY — PREVENTS BLOCKAGES IN THE CHANNEL BODY FROM PROPAGATING INTO THE MAIN DRAIN). OPTION 2 — SOAKAWAY (WHERE NO SURFACE WATER DRAIN EXISTS — THE MOST COMMON SITUATION FOR A LONDON VICTORIAN TERRACE PATIO WHERE THE ORIGINAL DRAINAGE WAS TO SOAK INTO THE GARDEN — OR WHERE THE THAMES WATER SURFACE WATER DRAIN IS NOT ACCESSIBLE): A SOAKAWAY (CRATE SOAKAWAY — POLYSTORM RECYCLED POLYPROPYLENE CRATE — CAPACITY SIZED TO SATISFY BS 6031:2009 AND CIRIA SUDS MANUAL C753 FOR THE PATIO AREA AND LOCAL RAINFALL INTENSITY) IS CONSTRUCTED WITHIN THE GARDEN (MINIMUM 5M FROM THE BUILDING FOUNDATION — BS 6031) AND THE ACO CHANNEL OUTLETS TO THE SOAKAWAY VIA 110MM UNDERGROUND DRAIN.

SUDS (SUSTAINABLE URBAN DRAINAGE SYSTEMS) COMPLIANCE: SINCE 2015 IN ENGLAND (SUDS PROVISIONS OF THE FLOOD AND WATER MANAGEMENT ACT 2010 — SUDS APPROVAL BY LOCAL AUTHORITY): ALL NEW DRAINAGE SYSTEMS FOR NEW OR SUBSTANTIALLY ALTERED PAVED AREAS IN EXCESS OF 5M² MUST, IN PRINCIPLE, COMPLY WITH SUDS PRINCIPLES — PRIORITISING INFILTRATION (SOAKAWAY), THEN ATTENUATION WITH CONTROLLED RELEASE, OVER DIRECT DISCHARGE TO PUBLIC SEWER. FOR A LONDON VICTORIAN TERRACE REAR EXTENSION PATIO: A SOAKAWAY IS THE PREFERRED SUDS SOLUTION WHERE THE GROUND CONDITIONS SUPPORT INFILTRATION. THAMES WATER (THE WATER AND SEWERAGE AUTHORITY FOR MOST OF LONDON) REQUIRES ADOPTION OF SUDS WHERE FEASIBLE BEFORE PERMITTING CONNECTION OF NEW SURFACE WATER TO THE PUBLIC SEWER SYSTEM.

THE INSTALLATION OF THE ACO DESIGN DRAIN IN A LONDON VICTORIAN TERRACE REAR EXTENSION PATIO THRESHOLD REQUIRES COORDINATION BETWEEN THE GROUNDWORK CONTRACTOR (SETTING THE DRAIN CHANNEL BODY IN THE PATIO SLAB), THE PAVING CONTRACTOR (LAYING THE PATIO PAVING TO THE CORRECT FALLS TOWARD THE DRAIN), AND THE DRAINAGE CONTRACTOR (CONNECTING THE DRAIN OUTLET TO THE UNDERGROUND DRAIN RUN OR SOAKAWAY).

INSTALLATION SEQUENCE:

STEP 1 — COORDINATE THE DRAIN POSITION WITH THE BI-FOLD DOOR THRESHOLD DETAIL: SET OUT THE CENTRE LINE OF THE ACO CHANNEL DRAIN BODY AT THE POSITION OF THE BI-FOLD DOOR THRESHOLD SILL — TYPICALLY 100-150MM OUTSIDE (IN FRONT OF) THE DOOR SILL. THE CHANNEL MUST RUN THE FULL WIDTH OF THE DOOR OPENING (AND IDEALLY 150-300MM BEYOND EACH SIDE OF THE DOOR FRAME) TO INTERCEPT ALL WATER FLOWING TOWARD THE DOOR.

STEP 2 — CAST THE RECESS IN THE PATIO SLAB (AT CONCRETE POUR STAGE): EITHER (A) CAST A RECESS IN THE PATIO CONCRETE SLAB TO ACCEPT THE ACO CHANNEL BODY (THE RECESS MUST BE THE SAME WIDTH AS THE CHANNEL EXTERNAL WIDTH + 50MM EITHER SIDE FOR HAUNCHING, AND DEEP ENOUGH FOR THE CHANNEL BODY PLUS THE MORTAR BED + PAVING ABOVE THE TOP OF THE CHANNEL) — OR (B) SAW-CUT THE RECESS INTO AN EXISTING PATIO SLAB AFTER CURING (LESS PREFERRED — RISK OF CRACKING THE ADJACENT SLAB).

STEP 3 — BED THE CHANNEL BODY IN MORTAR: PLACE THE ACO CHANNEL BODY IN THE RECESS ON A BED OF FAST-SETTING CONCRETE (1:2:4 MIX — OR RAPID-SETTING CONCRETE SUCH AS TARMAC POSTFIX OR SIMILAR) — PACKED TIGHT TO THE SIDES OF THE CHANNEL BODY (HAUNCHING). SET THE CHANNEL BODY LEVEL (BOTH ALONG THE CHANNEL RUN AND ACROSS THE CHANNEL WIDTH — CRITICAL: A TILTED CHANNEL BODY PRODUCES AN UNEVEN GRATE AND A VISIBLE AESTHETIC DEFECT).

STEP 4 — CONNECT THE OUTLET: CONNECT THE 110MM END OUTLET OF THE CHANNEL BODY TO THE UNDERGROUND DRAIN RUN BEFORE HAUNCHING IS COMPLETE (ACCESS TO THE OUTLET IS RESTRICTED ONCE THE CHANNEL IS BEDDED AND HAUNCHED).

STEP 5 — HAUNCH AND POINT: FILL THE GAPS BETWEEN THE CHANNEL BODY AND THE SIDES OF THE RECESS WITH FAST-SETTING CONCRETE OR MORTAR (HAUNCHING). ALLOW 24 HOURS FOR THE HAUNCHING TO CURE.

STEP 6 — LAY PATIO PAVING: LAY THE PATIO PAVING (PORCELAIN TILE OR NATURAL STONE) ON A CEMENT:SAND MORTAR BED, FALLING TOWARD THE CHANNEL DRAIN (MINIMUM 1:60 FALL — TYPICALLY 1:40 IS SPECIFIED TO ENSURE POSITIVE DRAINAGE IN ALL CONDITIONS). THE EDGE OF THE PAVING MUST BE CUT TIGHT TO THE EDGE OF THE CHANNEL GRATE FRAME ON EACH SIDE — A TIGHT NEAT CUT (1-2MM JOINT) IS ESSENTIAL FOR A QUALITY THRESHOLD APPEARANCE.

SEVERAL RECURRING INSTALLATION ERRORS ON LONDON VICTORIAN TERRACE PATIO LINEAR DRAIN PROJECTS LEAD TO POOR PERFORMANCE, AESTHETIC DEFECTS, AND WATER INGRESS AFTER COMPLETION.

MOST COMMON INSTALLATION ERRORS:

ERROR 1 — INSUFFICIENT FALL ON THE PATIO SURFACE TOWARD THE DRAIN: THE MOST COMMON CAUSE OF WATER INGRESS AT A FLUSH BI-FOLD DOOR THRESHOLD. SOLUTION: MINIMUM 1:60 FALL (APPROXIMATELY 16MM FALL PER METRE) FROM THE BI-FOLD DOOR SILL TOWARD THE DRAIN CHANNEL. CHECK: USE A SPIRIT LEVEL AND TAPE MEASURE OR A DIGITAL LEVEL TO VERIFY THE FALL AFTER PAVING COMPLETION — DO NOT ASSUME THE CONTRACTOR HAS ACHIEVED THE CORRECT FALL WITHOUT CHECKING.

ERROR 2 — GRATE SET TOO HIGH (FLUSH WITH OR PROUD OF THE PATIO SURFACE): A FLUSH GRATE DOES NOT COLLECT WATER FROM THE PATIO SURFACE EFFICIENTLY — WATER MUST FLOW INTO THE GRATE OPENING — WHICH REQUIRES THE GRATE TO BE SLIGHTLY LOWER THAN THE ADJACENT PATIO SURFACE (5-10MM RECESS). SOLUTION: SET THE CHANNEL BODY 5-10MM LOWER THAN THE FINISHED PATIO SURFACE SO THE GRATE SITS IN A SLIGHT DEPRESSION.

ERROR 3 — DRAIN CHANNEL NOT CONNECTED TO A FUNCTIONAL DRAIN (OUTLET TO NOWHERE): ON SOME PROJECTS, THE CHANNEL DRAIN IS INSTALLED BUT THE 110MM OUTLET IS NOT PROPERLY CONNECTED TO AN UNDERGROUND DRAIN OR SOAKAWAY — THE CHANNEL FILLS WITH WATER AND OVERFLOWS ONTO THE PATIO. SOLUTION: ALWAYS TEST THE CHANNEL DRAIN WITH A BUCKET OF WATER BEFORE THE PATIO PAVING IS COMPLETE — CONFIRM WATER FLOWS FREELY THROUGH THE OUTLET TO THE DRAIN CONNECTION.

ERROR 4 — GRATE BLOCKS (LEAF LITTER, DEBRIS): LINEAR DRAINS WITH SLOT GRATES CAN BLOCK WITH LEAF LITTER IN AUTUMN. SOLUTION: SPECIFY ACO DESIGN DRAIN GRATE WITH THE LARGEST PRACTICABLE SLOT APERTURE (8-10MM SLOTS — LARGER APERTURE = MORE RESISTANT TO LEAF BLOCKAGE BUT SLIGHTLY LESS AESTHETICALLY REFINED) — AND ENSURE THE CHANNEL BODY IS ACCESSIBLE FOR RODDING (THE CHANNEL BODY SHOULD BE DESIGNED WITH A SMOOTH INTERNAL PROFILE FOR EASY RODDING FROM THE END CAP).

ACO LINEAR DRAIN COSTS IN LONDON (2025) FOR A STANDARD REAR EXTENSION BI-FOLD DOOR THRESHOLD DRAINAGE INSTALLATION.

MATERIALS COSTS: ACO DESIGN DRAIN (STAINLESS STEEL SLOT GRATE — 1M UNITS — POLYPROPYLENE CHANNEL BODY): £80 TO £150 PER LINEAR METRE (SUPPLY ONLY — DEPENDING ON GRATE FINISH AND CHANNEL DEPTH). FOR A STANDARD 3M BI-FOLD DOOR WIDTH (3M OF ACO DESIGN DRAIN + 300MM EITHER SIDE = 3.6M TOTAL CHANNEL LENGTH): SUPPLY COST: £290 TO £540. ACO DESIGN DRAIN END CAP (BLANKING ONE END OF THE CHANNEL RUN): £8 TO £15. ACO DESIGN DRAIN END OUTLET (110MM OUTLET AT ONE END): INCLUDED IN STANDARD UNIT PRICE FOR MOST VERSIONS. ADDITIONAL MATERIALS: 110MM POLYPIPE UNDERGROUND DRAIN (ORANGE — PUSHFIT): £5-8 PER METRE (SUPPLY ONLY). POLYPIPE SQUARE TRAPPED GULLEY (P-TRAP — FOR CATCH PIT AT DRAIN CONNECTION): £25-50 (SUPPLY ONLY). POLYSTORM CRATE SOAKAWAY (IF NO SURFACE DRAIN AVAILABLE): APPROXIMATELY £150-350 FOR A RESIDENTIAL-SCALE SOAKAWAY SYSTEM (100-200 LITRE CRATE CAPACITY).

INSTALLATION COSTS (LONDON 2025 — GROUNDWORK CONTRACTOR): FORMING RECESS IN PATIO SLAB, BEDDING AND HAUNCHING CHANNEL BODY, CONNECTING 110MM OUTLET TO DRAIN RUN (HALF DAY — ONE GROUNDWORK OPERATIVE): £250 TO £500. UNDERGROUND DRAIN RUN (110MM — 5M FROM CHANNEL TO SOAKAWAY OR EXISTING DRAIN): £200 TO £400 (LABOUR + TRENCH EXCAVATION + BACKFILL + PIPE). CATCH PIT GULLEY: £50 TO £100 INSTALLATION.

TOTAL ACO LINEAR DRAIN INSTALLATION COST (3.6M BI-FOLD THRESHOLD — 5M DRAIN RUN TO SOAKAWAY — LONDON 2025): MATERIALS (ACO DRAIN + OUTLET + 110MM DRAIN + GULLEY + SOAKAWAY CRATE): £700 TO £1,100. INSTALLATION LABOUR (GROUNDWORK): £500 TO £1,000. TOTAL: £1,200 TO £2,100 (ACO THRESHOLD DRAIN + 5M UNDERGROUND DRAIN + SOAKAWAY CRATE — SUPPLY AND FIT — LONDON 2025). NOTE: THIS COST IS IN ADDITION TO THE PATIO PAVING COSTS — THE PATIO FALLS AND PAVING CUT-IN TO THE DRAIN GRATE SHOULD BE PRICED AS PART OF THE PATIO PAVING PACKAGE.