Rainwater Management for London Victorian Terraces: Gutters, Downpipes, and Drainage

MOST LONDON VICTORIAN TERRACES WERE ORIGINALLY FITTED WITH CAST IRON GUTTERS AND DOWNPIPES (CAST IRON — THE STANDARD MATERIAL FOR RAINWATER GOODS IN THE UK FROM THE MID-19TH CENTURY THROUGH TO THE 1960S AND 1970S, WHEN UPVC BEGAN TO REPLACE IT AS THE DOMINANT MATERIAL FOR NEW INSTALLATIONS AND REPLACEMENT WORK). THE ORIGINAL CAST IRON RAINWATER GOODS ON A LONDON VICTORIAN TERRACE TYPICALLY CONSIST OF: EAVES GUTTER (HALF-ROUND SECTION — THE MOST COMMON GUTTER SECTION ON VICTORIAN TERRACES — TYPICALLY 100MM (4-INCH) HALF-ROUND FOR MOST LONDON VICTORIAN TERRACES — CAST IRON HALF-ROUND GUTTER IS AVAILABLE IN CAST IRON SECTIONS OF 1.8M (6FT) LENGTH — JOINED BY UNION CLIPS AND SEALED WITH A NON-SETTING MASTIC (BLACK LEAD MASTIC OR BITUMINOUS SEALANT) — SUPPORTED BY CAST IRON FASCIA BRACKETS AT APPROXIMATELY 900MM CENTRES). BOX GUTTER (A WIDER RECTANGULAR CAST IRON GUTTER USED ON SOME HIGHER-SPECIFICATION VICTORIAN TERRACES AND SEMI-DETACHED PROPERTIES WHERE LARGER ROOF AREAS OR ARCHITECTURAL FEATURES SUCH AS PARAPET WALLS REQUIRED A LARGER WATER CARRYING CAPACITY). DOWNPIPE (ROUND SECTION — TYPICALLY 63MM (2.5-INCH) DIAMETER ROUND DOWNPIPE — OR 75MM (3-INCH) ON LARGER TERRACES — CAST IRON ROUND DOWNPIPES FITTED INTO A CAST IRON SHOE AT THE BASE — DISCHARGING INTO THE UNDERGROUND DRAINAGE SYSTEM VIA A BACK-INLET GULLY OR DIRECTLY INTO A TRAPPED GULLEY AT THE FOOT OF THE WALL). ADVANTAGES OF ORIGINAL CAST IRON GUTTERING (WHERE WELL MAINTAINED): LONGEVITY (CAST IRON GUTTERING IN GOOD CONDITION CAN LAST 100+ YEARS — MANY LONDON VICTORIAN TERRACES STILL HAVE THEIR ORIGINAL 1880S-1910S CAST IRON GUTTERING — WHEN PROPERLY MAINTAINED, CAST IRON FAR OUTLASTS UPVC); ARCHITECTURAL CHARACTER (CAST IRON HALF-ROUND GUTTERING IS ARCHITECTURALLY APPROPRIATE TO A LONDON VICTORIAN TERRACE — IN CONSERVATION AREAS, CAST IRON GUTTERING IS OFTEN SPECIFIED BY THE LOCAL PLANNING AUTHORITY AS THE PREFERRED REPLACEMENT MATERIAL IF ORIGINAL GUTTERING IS REPLACED); STRENGTH AND RIGIDITY (CAST IRON IS NOT DEFORMED BY THERMAL MOVEMENT OR UV DEGRADATION IN THE WAY THAT UPVC CAN BECOME BRITTLE AFTER 20-25 YEARS OF UV EXPOSURE). DISADVANTAGES: WEIGHT (CAST IRON IS HEAVY — THE FASCIA BOARDS AND RAFTER FEET THAT CARRY THE GUTTERING MUST BE SOUND — DAMAGED OR DECAYED FASCIAS MAY NOT ADEQUATELY SUPPORT CAST IRON GUTTERING); CORROSION (CAST IRON CORRODES IF THE INTERNAL COATING IS ALLOWED TO FAIL — THE TRADITIONAL INTERNAL FINISH IS BLACK BITUMINOUS PAINT — WHICH MUST BE REAPPLIED EVERY 5-8 YEARS TO PREVENT INTERNAL RUSTING — A RUSTED CAST IRON GUTTER WILL EVENTUALLY CRACK OR DEVELOP PINHOLE LEAKS); JOINT SEALANT FAILURE (THE BLACK MASTIC SEALANT AT CAST IRON GUTTER UNIONS DRIES OUT AND FAILS OVER TIME — TYPICALLY EVERY 10-20 YEARS — ALLOWING WATER TO LEAK FROM THE JOINT ONTO THE WALL BELOW).

THE FOLLOWING FAILURE MODES ARE MOST COMMONLY ENCOUNTERED IN THE RAINWATER MANAGEMENT SYSTEMS OF LONDON VICTORIAN TERRACES: BLOCKED GUTTERS (THE MOST COMMON AND MOST PREVENTABLE RAINWATER SYSTEM FAILURE — LEAVES, MOSS, AND DEBRIS ACCUMULATE IN GUTTERS OVER TIME — PARTICULARLY WHEN THERE ARE DECIDUOUS TREES ADJACENT TO OR OVERHANGING THE PROPERTY): CONSEQUENCES: THE STANDING WATER IN A BLOCKED GUTTER PROVIDES AN IDEAL ENVIRONMENT FOR MOSS AND PLANT GROWTH — WHICH CAUSES FURTHER BLOCKAGE — IN SEVERE CASES, THE WEIGHT OF STANDING WATER AND DEBRIS IN A BLOCKED CAST IRON GUTTER CAN CAUSE THE FASCIA BRACKETS TO FAIL OR THE FASCIA BOARD ITSELF TO ROT; OVERFLOWING WATER FROM A BLOCKED GUTTER RUNS DOWN THE FACE OF THE WALL BELOW, SATURATING THE BRICKWORK OR RENDER AND CAUSING PENETRATING DAMP; PREVENTION: CLEAR GUTTERS AT LEAST ONCE A YEAR (TWICE A YEAR WHERE TREES OVERHANG — ONCE IN SPRING AFTER SEEDS AND FLOWERS FALL, AND ONCE IN AUTUMN AFTER LEAF FALL); GUTTER GUARDS (SNAP-IN PLASTIC GUTTER GUARDS — RAINCLEAR GUTTER GUARD OR SIMILAR — REDUCE DEBRIS BUILD-UP BUT DO NOT ELIMINATE THE NEED FOR PERIODIC CLEANING); CRACKED OR FRACTURED CAST IRON GUTTER OR DOWNPIPE: CAST IRON CRACKS AND FRACTURES ARE TYPICALLY CAUSED BY FROST (BLOCKED GUTTER FILLS WITH WATER — FREEZES — EXPANDS — CRACKS THE GUTTER OR DOWNPIPE) OR IMPACT DAMAGE (LADDER DAMAGE, DEBRIS IMPACT); A HAIRLINE CRACK IN A CAST IRON GUTTER CAN OFTEN BE REPAIRED WITH A LIQUID RUBBER SEALANT OR EPOXY REPAIR COMPOUND (BOSTIK CEMENTONE WATERPLUG OR FERNOX F4 LEAK SEALER) BRUSHED OVER THE CRACKED AREA — BUT A GUTTER THAT HAS FRACTURED ACROSS THE FULL CROSS-SECTION REQUIRES SECTION REPLACEMENT; FAILED JOINT SEALANT (JOINT SEALANT DETERIORATION AT CAST IRON UNION CLIPS — ALLOWS WATER TO LEAK FROM THE JOINT AT THE UNION): JOINTS THAT ARE LEAKING VISIBLY (WATER RUNNING FROM THE UNION DURING RAIN) CAN OFTEN BE REPAIRED WITHOUT REMOVING THE GUTTER SECTION — THE JOINT IS CLEANED, DRIED, AND RE-SEALED WITH A FLEXIBLE WATERPROOF SEALANT (GEOCEL 2300 CRYSTAL CLEAR OR EVERBUILD 502 CLEAR SEALANT — BOTH SUITABLE FOR METAL-TO-METAL JOINTS IN WET CONDITIONS); ROTTEN FASCIA BOARDS: THE FASCIA BOARDS (TYPICALLY 25MM SOFTWOOD BOARD NAILED TO THE ENDS OF THE RAFTERS — ORIGINALLY PAINTED SOFTWOOD ON LONDON VICTORIAN TERRACES) CARRY THE GUTTER BRACKETS AND ARE A COMMON SITE OF TIMBER DECAY (WET ROT — PARTICULARLY WHERE GUTTER OVERFLOW HAS SOAKED THE FASCIA REPEATEDLY) — A ROTTEN FASCIA BOARD CANNOT ADEQUATELY SUPPORT THE GUTTER BRACKETS AND MUST BE REPLACED BEFORE NEW GUTTERING IS INSTALLED; DISCONNECTED OR BLOCKED DOWNPIPES: DOWNPIPES CAN BECOME DISCONNECTED AT JOINTS (THE PUSH-FIT SOCKET CONNECTIONS ON A CAST IRON DOWNPIPE ARE VULNERABLE TO BEING DISLODGED BY LADDER IMPACT OR FROST MOVEMENT) — A DISCONNECTED DOWNPIPE SECTION DIRECTS WATER ONTO THE WALL BEHIND THE PIPE — SATURATING THE BRICKWORK AND CAUSING PENETRATING DAMP; BLOCKED DOWNPIPES (TYPICALLY FROM LEAF AND DEBRIS ACCUMULATION AT THE DOWNPIPE OUTLET GRILL OR WITHIN THE PIPE) ARE CLEARED BY RODING FROM ABOVE WITH A DRAINAGE ROD OR A SPECIALIST DRAIN CLEARANCE HIGH-PRESSURE JET.

WHERE CAST IRON GUTTERING HAS FAILED BEYOND REPAIR (MULTIPLE CRACKED SECTIONS, FAILED INTERNAL COATING WITH EXTENSIVE INTERNAL RUST, FAILED FASCIA BOARDS REQUIRING FULL REFIXING OF ALL GUTTERING) OR WHERE A FULL REWTER IS BEING UNDERTAKEN, THE REPLACEMENT OPTIONS ARE: (1) CAST IRON REPLACEMENT GUTTERING (PREFERRED OPTION IN CONSERVATION AREAS — SOME LOCAL PLANNING AUTHORITIES REQUIRE CAST IRON REPLACEMENT AS A CONDITION OF PLANNING PERMISSION OR CONSERVATION AREA CONSENT): CAST IRON HALF-ROUND GUTTERING: CURRENTLY MANUFACTURED AND SUPPLIED BY: HARGREAVES FOUNDRY (CAST IRON DRAINAGE — LONGSTANDING UK MANUFACTURER — SUPPLY HALF-ROUND, BOX, AND OGEE PROFILES — 100MM HALF-ROUND AND 75MM ROUND DOWNPIPE MATCHING ORIGINAL VICTORIAN PROPORTIONS); SAINT-GOBAIN PAM (FRANCE — IMPORT-SUPPLIED CAST IRON GUTTERING — HIGH QUALITY — TYPICALLY POWDER-COATED BLACK AS STANDARD WITH OTHER COLOURS AVAILABLE TO ORDER); CAST IRON REPLACEMENT IS THE MOST EXPENSIVE OF THE THREE OPTIONS — BUT PROVIDES THE MOST ARCHITECTURALLY AUTHENTIC RESULT AND THE LONGEST SERVICE LIFE WHEN PROPERLY MAINTAINED; (2) UPVC GUTTERING (THE MOST COMMON REPLACEMENT MATERIAL USED IN THE UK — LOWER COST — LIGHTER WEIGHT — NO PAINTING REQUIRED — BUT LESS ARCHITECTURALLY APPROPRIATE FOR A LONDON VICTORIAN TERRACE AND NOT GENERALLY ACCEPTED IN CONSERVATION AREAS AS A LIKE-FOR-LIKE REPLACEMENT): STANDARD uPVC HALF-ROUND GUTTERING: FLOPLAST MINIFLO SC (HALFROUND — 112MM HALF-ROUND — ANTHRACITE GREY POPULAR AS A MORE ARCHITECTURALLY APPROPRIATE COLOUR — WIDELY AVAILABLE FROM TRAVIS PERKINS AND JEWSON); CAST IRON EFFECT uPVC (HUNTER PLASTICS OR LINDAB CI GUTTERING — uPVC MOULDED TO REPRODUCE THE VISUAL PROFILE OF CAST IRON HALF-ROUND GUTTERING — TYPICALLY IN MATT BLACK OR DARK GREY FINISH — A COMMON CONSERVATION AREA-ACCEPTABLE COMPROMISE WHERE CAST IRON COST IS PROHIBITIVE); SERVICE LIFE OF UPVC GUTTERING: TYPICALLY 20-30 YEARS BEFORE UV DEGRADATION CAUSES BRITTLENESS AND CRACKING — SIGNIFICANTLY SHORTER THAN WELL-MAINTAINED CAST IRON; (3) ALUMINIUM GUTTERING (THE PREMIUM MODERN ALTERNATIVE — SIGNIFICANTLY BETTER ENVIRONMENTAL CREDENTIALS THAN uPVC — LONGER SERVICE LIFE THAN uPVC — MORE APPROPRIATE FOR CONSERVATION AREAS THAN STANDARD uPVC — TYPICALLY POWDER-COATED IN A RANGE OF COLOURS INCLUDING BLACK AND ANTHRACITE GREY): LINDAB RAINLINE ALUMINIUM GUTTERING (HALF-ROUND AND BOX — 100MM HALF-ROUND AND 75MM OR 87MM ROUND DOWNPIPE — POWDER-COATED IN STANDARD COLOURS — COLOUR: DB502 BLACK — SERVICE LIFE: 40-50 YEARS); ALUMINIUM IS THE PREFERRED MODERN ALTERNATIVE WHERE CAST IRON IS NOT REQUIRED AND IS THE SPECIFICATION CHOICE OF MANY CONSERVATION AREA PLANNING AUTHORITIES WHEN ORIGINAL CAST IRON GUTTERING IS REPLACED ON VICTORIAN TERRACES.

THE DOWNSTREAM END OF THE RAINWATER DOWNPIPE MUST CONNECT TO A DRAINAGE SYSTEM THAT SAFELY DISPOSES OF THE COLLECTED ROOF WATER. ON A LONDON VICTORIAN TERRACE, THE TYPICAL DRAINAGE CONNECTION IS: BACK-INLET GULLY (THE MOST COMMON DRAINAGE CONNECTION ON LONDON VICTORIAN TERRACES — A TRAPPED GULLY AT GROUND LEVEL — THE DOWNPIPE SHOE DISCHARGES INTO THE BACK-INLET OF THE GULLY — THE GULLY TRAP PREVENTS DRAIN GASES FROM RISING BACK UP THE DOWNPIPE — IN OLDER LONDON VICTORIAN TERRACES, THE BACK-INLET GULLY MAY BE GLAZED STONEWARE OR SALT-GLAZED TERRACOTTA — IN MODERN REPLACEMENT, POLYPIPE OR ACO HDPE GULLY IS USED); COMBINED DRAINAGE SYSTEM (THE MAJORITY OF LONDON VICTORIAN TERRACES WERE ORIGINALLY BUILT WITH A COMBINED DRAINAGE SYSTEM — FOUL WATER SEWAGE AND SURFACE WATER (ROOF WATER) FLOW IN THE SAME DRAIN TO THE SAME COMBINED SEWER IN THE ROAD — IN LONDON, MANY OF THE ORIGINAL COMBINED SEWERS DATE FROM THE GREAT METROPOLITAN SEWERS COMMISSION WORK OF THE 1850S-1880S AND ARE STILL IN SERVICE CARRYING BOTH FOUL AND SURFACE WATER); SEPARATE DRAINAGE SYSTEM (FROM THE MID-20TH CENTURY ONWARDS, NEW DEVELOPMENTS IN LONDON WERE REQUIRED TO USE SEPARATE DRAINAGE — SURFACE WATER TO SURFACE WATER SEWER, FOUL WATER TO FOUL WATER SEWER — IN SOME AREAS OF LONDON, THAMES WATER HAS INCENTIVISED SURFACE WATER DISCONNECTION FROM THE COMBINED SEWER SYSTEM AS PART OF THE TIDEWAY TUNNEL WORKS AND COMBINED SEWER OVERFLOW REDUCTION PROGRAMME); SOAKAWAY (WHERE A CONNECTION TO THE PUBLIC SEWER IS NOT AVAILABLE OR IS NOT APPROPRIATE — A SOAKAWAY IS A PIT FILLED WITH GRANULAR MATERIAL OR A PROPRIETARY SOAKAWAY CRATE (POLYSTORM CELL OR ATLANTIS FREEFLOW GEOCELL) BURIED IN THE GARDEN — THE ROOF WATER PERCOLATES INTO THE SURROUNDING SOIL FROM THE SOAKAWAY — IN LONDON, SOAKAWAYS ARE OFTEN IMPRACTICAL DUE TO LONDON CLAY (WHICH HAS VERY LOW PERMEABILITY AND DOES NOT DRAIN FREELY — PERCOLATION TEST BEFORE INSTALLING A SOAKAWAY IN LONDON CLAY IS STRONGLY RECOMMENDED — BRE DIGEST 365 SOAKAWAY DESIGN PROCEDURE — IN MOST INNER LONDON LOCATIONS ON LONDON CLAY, A SOAKAWAY IS NOT A VIABLE OPTION AND CONNECTION TO THE COMBINED SEWER IS THE ONLY PRACTICAL DRAINAGE SOLUTION).

RAINWATER SYSTEM MAINTENANCE SCHEDULE FOR LONDON VICTORIAN TERRACES (PREVENTIVE MAINTENANCE IS FAR LESS COSTLY THAN REPAIR OF DAMP DAMAGE CAUSED BY GUTTER FAILURE): ANNUAL GUTTER CLEARANCE (ONCE ANNUALLY MINIMUM — TWICE ANNUALLY WHERE TREES OVERHANG OR ADJACENT TO PROPERTY — LATE AUTUMN AFTER LEAF FALL AND SPRING AFTER SEEDS AND FLOWER FALL): CLEAR ALL DEBRIS, MOSS, AND ACCUMULATED SEDIMENT FROM GUTTERS — FLUSH WITH WATER TO CHECK GUTTER FALLS ARE CORRECT AND DOWNPIPES ARE CLEAR — CHECK ALL JOINTS AND BRACKETS FOR VISIBLE DAMAGE OR LOOSE FIXINGS — REPAINT CAST IRON GUTTERS INTERNALLY WITH BITUMINOUS PAINT (HAMMERITE BITUMEN BRUSH-ON — ANNUAL OR BIANNUAL APPLICATION TO MAINTAIN INTERNAL CORROSION PROTECTION); COSTS — GUTTER CLEARANCE (SINGLE FRONT/REAR RUN, TWO-STOREY LONDON VICTORIAN TERRACE — SPECIALIST CONTRACTOR USING SCAFFOLD POLE OR TOWER OR REACH-AND-WASH EQUIPMENT): APPROXIMATELY £60-180 (SINGLE RUN — FRONT OR REAR); £100-300 (FRONT AND REAR TOGETHER); GUTTER REPAIR COSTS (SPECIALIST CONTRACTOR): JOINT RE-SEAL (SINGLE JOINT — RE-CLEAN, RE-SEAL WITH GEOCEL OR EVERBUILD 502): APPROXIMATELY £40-80; SECTION REPLACEMENT (SINGLE 1.8M CAST IRON SECTION — SUPPLY AND FIT INCLUDING BRACKETS — SCAFFOLD OR TOWER REQUIRED): APPROXIMATELY £150-350 (CAST IRON SECTION — INCLUDING FIXINGS AND JOINT MATERIALS); GUTTER REPLACEMENT COSTS (FULL RUN — FRONT OR REAR ELEVATION — INCLUDING FASCIA BOARD CHECK/REPAIR — SUPPLY AND FIT — SPECIALIST CONTRACTOR): UPVC HALF-ROUND (STANDARD — INCLUDING DOWNPIPE): APPROXIMATELY £400-900 (FRONT OR REAR FULL RUN — TWO-STOREY TERRACE); CAST IRON EFFECT uPVC (HUNTER OR LINDAB CI — MATT BLACK — INCLUDING DOWNPIPE): APPROXIMATELY £600-1,400 (FRONT OR REAR FULL RUN — TWO-STOREY TERRACE); GENUINE CAST IRON (HARGREAVES FOUNDRY OR SAINT-GOBAIN PAM — SUPPLY AND FIT — FULL RUN): APPROXIMATELY £900-2,500 (FRONT OR REAR FULL RUN — TWO-STOREY TERRACE — HIGHER END WHERE SCAFFOLDING IS REQUIRED); ALUMINIUM (LINDAB RAINLINE OR SIMILAR — POWDER-COATED BLACK OR ANTHRACITE — INCLUDING DOWNPIPE): APPROXIMATELY £700-1,800 (FRONT OR REAR FULL RUN — TWO-STOREY TERRACE); FASCIA BOARD REPLACEMENT (ADDITIONALLY REQUIRED WHERE FASCIA IS ROTTEN — SUPPLY AND FIT NEW 25MM MOISTURE-RESISTANT MDF OR TREATED SOFTWOOD FASCIA — INCLUDING SOFFIT IF REQUIRED): APPROXIMATELY £150-400 (FRONT ELEVATION — TWO-STOREY TERRACE — ADDITIONAL TO GUTTER REPLACEMENT COST ABOVE).