Foundations & Groundworks
110 sources in the library on foundations & groundworks. Each one says what the document covers and what it is good for. Name a source to see which document it is and where to read it. One at a time. Page 2 of 3.
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The Concrete Society
A free, citable data sheet giving the density ranges a note needs when explaining block types or estimating dead load. Published 3 June 2025 and filed under Buildings, Domestic (low rise). Dense aggregate blocks have a density in the range 1,800 to 2,100 kg/m3. Lightweight aggregate blocks, also called medium dense, are in the range 650 to 1,500 kg/m3. Aircrete blocks are in the range 400 to 900 kg/m3. Concrete bricks are 1,900 to 2,100 kg/m3 for Commons, Facing and Engineering quality, and 1,400 kg/m3 for lightweight bricks. The sheet points onward to the Concrete Block Association and the Autoclaved Aerated Concrete Products Association for more detail.
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Anglian Water
A true or false self-assessment checklist that decides whether an application is needed at all for work over or within three metres of a public sewer. The eight criteria: the sewer flows by gravity and is not pumped; the sewer is less than 3 metres deep; the sewer is 150mm diameter or less; the structure is not a new build premises; there are no manholes or access points inside the building before any alterations; the foundations are designed so the sewer is suitably protected; the sewer pipe is not pitch fibre or asbestos cement; and the length of sewer passing under the proposed building does not exceed six metres. The last two apply only where the sewer is actually built over, not where the building is merely close. A false answer on the pumped sewer question is fatal: work near a pumped sewer is never allowed, whatever is submitted. Answer true to all eight and no consultation with Anglian Water is required. Otherwise a build over or near application costs £692 including the Build Over Agreement; a consultation service to resolve any 'not sure' answers costs £163, and that £163 is deducted from the £692 if a full application follows. Submitting an application does not guarantee approval, and approval is especially unlikely if the work is not compliant with Building Regulations Part H4; a copy of the completed self-assessment should be given to the Building Control Body.
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Cadent Gas
What is and is not allowed over a gas easement, and what to do after a strike. Normal cultivation including ploughing to a maximum depth of 0.5m is permitted without further reference; anything deeper, including sinking fence and gate posts to a depth greater than 0.5m, requires contacting Cadent first, as does storing material above the pipeline or planting trees and shrubs on the easement. Enquiries go through the LinesearchbeforeUdig online service, which returns results within minutes from a grid reference or postcode and issues asset plans plus the Specification for Safe Working in the vicinity of Cadent assets; where the work is close, a Cadent technician visits site to locate and mark out the pipeline. Emergency procedure after damage: call the National Gas Emergency Service immediately on 0800 111 999, remove and extinguish potential ignition sources, evacuate all personnel from the area and ensure nobody approaches the asset. Specific higher-risk activities that always need Cadent's own guidance and safe working distances include explosives and blasting, piling, boring, construction, demolition and deep excavation.
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Electricity North West
Before breaking ground, check the location of underground services on network plans and then follow safe digging techniques. Underground services are commonly found in roads, footpaths, on sites and across open land; always assume they are present and treat any cable as live. Service cables and pipes are routinely confused, and the specific trap named is that black plastic covered electricity cable looks like plastic water pipe. Network plans are obtained through LinesearchbeforeUdig. The reference safe-digging document is HSE HSG47, Avoiding danger from underground services, which should be read before commencing work on site.
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HomeOwners Alliance
Basement conversion costs and constraints. Converting an existing dry cellar with no structural change £900 to £1,400 per m2. Excavation and underpinning £1,500 to £2,000 per m2, so a 40 m2 basement runs about £100,000 to £160,000. Adding a lightwell or extending beyond the footprint pushes rates to £2,500 to £3,000 per m2 and, at the top end, £5,000 to £7,500 per m2. Add about 20% for fees. Individual costs quoted: structural engineer £1,500 to £3,000, householder planning application £206 or £462 where a new unit of accommodation is proposed, party wall surveyor at least £750 for the owner and at least £700 per neighbour. Party wall notice is triggered by excavating within 3 metres of a neighbour's building and below the level of their foundations, or within 6 metres where a 45 degree line from the bottom of their foundations is intersected. Recommends a 2.4m finished ceiling height and warns at least 2m headroom is needed over the stairs.
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HomeOwners Alliance
Costed flood resilience measures for a house. Air brick covers £50 to £300, to be removed once flooding passes so the bricks can dry. Non return valves on drains and pipes to stop sewage backflow £50 to £500. Raising electrical sockets to about 1.5m £1,000 to £4,000. Raising door thresholds above flood level, front door and porch, £1,000 to £10,000. Sealing exterior walls around £500, with a warning it can trap damp in poor condition brickwork. Water resistant air bricks £500 to £1,000, needing careful maintenance to avoid seepage. Flood boards or flood resistant doors and windows £500 to £3,000, requiring permanently visible fixings. A pump, the most effective answer to groundwater, £50 to £2,500, with the inlet installed lower than the water being pumped. Basement tanking £10,000 to £20,000. On insurance, Flood Re is funded by a levy all UK home insurers must pay, and a home qualifies only if it was built before 2009 and is in council tax bands A to H.
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Northern Powergrid
When an extension or a new low carbon technology forces a supply change rather than just new circuits. The named triggers for increasing or decreasing capacity or changing the size of the main fuse are adding new rooms, extensions, electric vehicle chargers, heat pumps, or additional appliances. Applications need a site location plan, submitted through the online mapping tool or as an Ordnance Survey or Land Registry plan. Three parties are always involved in moving an electrical service: Northern Powergrid moves the service cable and mains fuse, the electricity supplier moves the meter and must be booked to attend on the day of the works, and a qualified electrician handles anything on the customer's own internal wiring.
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Northumbrian Water
Three routes to consent for building over or within 3 metres of a sewer: the build meets the consent criteria; minor alterations are made to the network so that it does; or the build falls outside the criteria and a formal legal agreement or a payment in lieu is required. Typical criteria failures named are existing pipework deeper than 2m or an internal diameter larger than 150mm. Option 1, the Building Over Indemnity Undertaking, is a signed and witnessed legal agreement giving Northumbrian Water the right to move all or part of the building for future sewer repair without paying compensation, fee £431.00. Option 2, payment in lieu, buys the same right but with Northumbrian Water fully reinstating the building at its own cost, charged by floor area used for building regulations purposes: under 6 sq m £582 single storey / £966 two storey; 6 to under 10 sq m £682 / £1,165; 10 to under 15 sq m £812 / £1,355; 15 to under 20 sq m £930 / £1,551; 20 to under 30 sq m £1,045 / £1,745; 30 to under 40 sq m £1,167 / £1,939; 40 sq m or over £1,794 / £2,920. A CCTV survey is normally carried out within 15 working days of receiving the completed form and is paid for by the applicant. Minor alterations on small diameter sewers less than 1.05m deep may be done by the homeowner's own builder after an initial site visit, with 48 hours notice for inspection before anything is covered over, fee £120.00; deeper sewers or those over 150mm diameter must be altered by Northumbrian Water's contractors against an estimate agreed in advance. Payments on 0345 850 0514 quoting reference BOS plus house number and postcode.
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Northumbrian Water
Consent is required from Northumbrian Water where there is a public sewer within 3 metres of the proposed work, both to protect the property and the sewer from damage and to preserve future access to the drainage system. The trigger is stated as planning to build within 3 metres of the public sewer. The team is contactable 9am to 4pm Monday to Friday and responds to enquiries within two working days. Applicants are directed to the published charges document before applying.
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Royal Horticultural Society
Identification, spread and disposal of Japanese knotweed on a renovation site. Stems are bamboo like with reddish purple speckling, conspicuous nodes and hollow centres, usually reaching about 2m (6 and a half feet) by late summer; leaves are spade shaped with flat bases, about 14cm (5 and a half inches) long, set in a zig zag along the stem, with creamy white flower clusters in late summer and early autumn. Rhizomes are thick and woody with an orange layer under the dark brown skin, commonly extending 1m (3 and a third feet) or more down, and a fragment as small as 1cm can grow into a new plant, so digging and careless disposal are the main spread routes; rhizomes can lie dormant in soil for many years. It is listed on Schedule 9 Section 14 of the Wildlife and Countryside Act 1981, so planting or causing it to grow in the wild is an offence carrying fines and imprisonment, and it and any soil containing it are controlled waste under the Environmental Protection Act duty of care regulations, requiring the Environment Agency to be informed, a registered waste carrier, an authorised disposal site and waste transfer permits. On sale and purchase, its presence must be declared on the TA6 form and lenders typically require a professional eradication management plan with a transferable insurance backed guarantee, usually supplied by the seller before completion. Glyphosate based weedkiller is the practical chemical control for a home gardener.
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Royal Horticultural Society
Defines the six garden soil types and gives the particle size boundaries used to classify them: clay less than 0.002mm, silt 0.002 to 0.05mm, sand 0.05 to 2mm, and stones larger than 2mm. Characterises the behaviour of each: clay soils are heavy, high in nutrients, wet and cold in winter and baked dry in summer; sandy soils are light, dry, warm, low in nutrients and often acidic. Useful for judging shrinkable clay, drainage and planting near a new extension or foundation.
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Scottish and Southern Electricity Networks (SSEN)
SSEN's published service alteration prices, all excluding VAT and excluding extras such as digging on the customer's land and traffic management. Scotland: basic overhead £435.18, basic underground £293.45, extended overhead £505.49, extended underground £505.49. England excluding London: basic overhead £380.13, basic underground £256.33, extended overhead £458.29, extended underground £458.37. London (priced higher because working costs in London differ): basic overhead £398.40, basic underground £268.51, extended overhead £477.65, extended underground £412.71. A basic alteration reuses the cable already in place; an extended alteration is needed when the new meter position requires additional cable to be bought and added. SSEN moves the service cable and main fuse only; the energy supplier moves the meter and must be booked for the same day so power is back on, and an electrician is needed for the consumer unit. A personalised quote is issued within 5 to 15 days. Appointing a private groundworker for the excavation is often more cost effective and SSEN will reduce the quotation scope accordingly.
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Scottish Water
Two separate distances that both bind a build near a water main, with published tables. Access Distance, the legally supported clearance kept in every direction so the main can be repaired, maintained or renewed, measured from the outside of the pipe, with no buildings, structures or development permitted inside it: up to 180mm internal diameter, 3m; over 180mm up to 14 inch/350mm, 4.5m; over 350mm up to 18 inch/450mm, 6m; over 450mm up to 24 inch/600mm, 8m; over 600mm, minimum 10m depending on site conditions. Those minima assume a pipe invert up to 2 metres deep and may increase with depth, difficult topography or a main deeper than 2m; in constrained urban situations NJUG guidelines apply in pavements for small diameter distribution mains, larger mains in constrained urban roads need a risk assessment and method statement, and strategic mains over 600mm need detailed design referencing the Washington Suburban Sanitary Commission Pipeline Design Manual. Stand-off Distance is separate: the minimum distance habited property should sit from the main so a burst does not damage it, based on the crater size at the main's operating pressure: 2 bar 2.5m, 4 bar 5.0m, 6 bar 7.5m, 8 bar 10m, 10 bar 12m, 12 bar 14.5m, 14 bar 17m, 16 bar 19.5m, 18 bar 22m. Stand-off distances may be increased where the main is high pressure or deeper than 2m to invert, or where the property is at increased flood or damage risk if the main fails.
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Severn Trent Water
Severn Trent's homeowner route. A Formal Build Over Application is required where the sewer is larger than 150mm, where a manhole must be moved, altered or built over, or where the project fails the self-certification criteria; smaller works can use the self-certification form. The company states it cannot grant approval retrospectively. Review of a formal application takes up to 10 working days, then provisional approval with conditions, then building, then a post-construction CCTV survey report before final approval; any remedial cost falls on the applicant. Permitted development rights and planning permission do not remove the need for the sewer approval, because utility locations are not considered in the planning process. Since the October 2011 private sewer transfer Severn Trent maintains most shared drains and sewers in its region, and most of those transferred pipes do not appear on maps. Advises early contact where the sewer is 300mm diameter or over, as permission may not be granted. A protective strip, measured from the centre of the pipe, must be kept clear for maintenance, sized by pipe diameter.
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Severn Trent Water
The technical rules a builder actually needs. Fees: Class 1 up to and including 150mm sewers £169.50, Class 2 225mm sewers £194.70, Class 3 complex applications at cost. A complete application normally gets a decision within 10 working days. Applies to existing homes extending over small diameter sewers of 100mm to 225mm; not for new-build. Construction rule for both building close to and building over: where foundations come within 1.0m of the sewer at any point they must be taken down below the invert level of the sewer; beyond 1.0m a 45 degree line may be taken from a point one metre clear of the sewer up to the required footing level. The 3.0m proximity is measured from the nearest point of the building including foundations to the centreline of the sewer, and depth is measured to the pipe invert. No pre-works CCTV and electro-location survey is needed for 100mm or 150mm sewers if the position is demonstrated and the foundation shown to be harmless, or for 225mm sewers if the building is no closer than 1 metre; otherwise a survey is required, and a post-works CCTV survey is always required. Any access chamber or rodding eye falling inside the new building must be replaced by a new manhole on the sewer line outside the building, with connections re-laid. Complex cases include a formal easement in the deeds, sewer depth over 3 metres, pressurised rising mains (never permitted to be built over), strategic sewers, and piling or ground stabilisation. All work must comply with Building Regulations 2010 Part H4 and be approved by building control before backfilling. CCTV surveys must follow the WRc Model Contract Document for non-man-entry sewer inspection and the UK Water Industry Manual of Sewer Condition Classification.
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Society for the Protection of Ancient Buildings
Douglas Kent's technical advice note on dampness in buildings predating about 1919. Key figures: relative humidity becomes detrimental at 70% or higher; rising damp usually extends only 10 to 50mm above internal floor level, though it can reach 900mm or more depending on external ground levels, masonry type, water table and evaporation rate; timber in a normal dry living environment sits at roughly 9 to 16% moisture content and becomes susceptible to fungal decay above 21%. States that most pre 1919 buildings were built without damp proof courses or damp proof membranes by design, that rising damp is usually far less of a problem than commonly supposed, and that inserted DPMs and chemical injection are frequently unnecessary treatments applied after misdiagnosis, where maintenance and occupancy changes plus respecting the building's need to breathe are the appropriate response. Also covers rainwater penetration, condensation on porous lime surfaces and hygroscopic salts, and notes listed building consent may be required.
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Southern Water
Two routes are offered, a self-declaration and a formal approval, with published criteria and fees. Self-declaration criteria include: pipe diameter 225mm or less and less than 3m deep; trench fill foundations designed to be at least 150mm below the pipe invert where within 3m horizontally of the public sewer; a minimum 300mm headroom between the underside of the new floor slab and the crown of the pipe; total coverage of the sewer less than 6 metres including pipework already built over; a minimum 1m width left between the boundary and the proposed extension so the garden is not built across its full width; and, where the sewer passes through a load-bearing wall, a foundation design complying with Part H4 and Southern Water's design criteria. The self-declaration is reviewed within 5 days for completeness and a conditional approval letter follows within the next 2 weeks; relocating a manhole chamber or doing minor pipe repairs adds an £84 inspection fee. Formal applications include a CCTV survey in the fee, and £200 is refunded if the applicant supplies their own compliant CCTV survey or if no survey turns out to be needed. A Sewer Protection Agreement carries a separate legal fee of approximately £250 for domestic or residential property and £400 for commercial. Required drawings: existing and proposed site plan at 1:100 or larger showing sewers and manholes, a site location plan at 1:1250 or larger, and a cross-section foundation design at 1:100 or larger. Practical location tips for homeowners: check the deeds, look for manholes and ask neighbours, trace the line and cautiously dig a trial hole, and run a tap or flush drain tracing dye and watch a manhole with a torch to establish direction of flow.
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Thames Water
Sets the trigger distances: an application is likely to be needed if you are building within 3 metres of a public sewer, or within 1 metre of the point where the pipe serving only your property crosses the boundary and becomes a public lateral drain. States plainly that planning permission does not grant permission to build over a sewer or drain, and that work should not start before the agreement is in place because the design may have to change. For a wholly new property, including a car port or shed not attached to the house, Thames Water requires the sewer to be diverted rather than built over. Liability for damage caused to sewers or drains during construction rests with the property owner. Asset maps can be viewed free of charge by appointment at Clearwater Court, Vastern Road, Reading RG1 8DB, or bought from utility search companies or the Property Searches department.
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Thames Water
Thames Water's homeowner build-over process, with its published 2026 fee scale and timescales. Three classes by sewer internal diameter: Class 1 £130 (175mm or less), Class 2 £490 (176mm to 350mm), Class 3 £585 (over 350mm) plus additional legal costs starting at £1,000. Class 1 and Class 2 agreements are usually issued within 21 days of receipt of all required information; Class 3 involves legal contracts and the full process can take more than 3 to 6 months. Class 2 fees include pre- and post-construction CCTV surveys; Class 3 adds two surveys by an approved contractor plus impact assessments. Applicants on disability benefit get a £130 discount on proof of entitlement (DWP letter or Blue Badge). Retrospective applications are accepted but need a CCTV or on-site survey to prove no damage, and may be refused if the pipework was not protected to specification. Self-service sewer diversion is offered where the internal diameter is 150mm or less, with a refundable £2,000 cash deposit returned after satisfactory post-construction inspection. Every application needs a location plan, an existing and proposed drainage layout showing manholes and flow direction, and a sectional drawing of the foundations against the sewer with invert levels; piling foundations need a piling method statement and raft foundations need structural calculations.
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UK Power Networks
Separates the four things homeowners confuse. The electricity supply (the incoming service cable and cut-out) is moved by the DNO, and the stated common triggers are extending or renovating, building a conservatory, or moving it somewhere more accessible. An overhead power line into the property is moved by the DNO, typically because the cable is in the way of an extension, because fascia, cladding or windows are being replaced, because the pole is in the way and the customer wants the run put underground, or purely for appearance. The electricity meter is legally owned by the electricity supplier and only the supplier can move it; UK Power Networks can move the electricity board, but the supplier must still return to reconnect the meter. The consumer unit or fuse box is neither the DNO's nor the supplier's work: only a qualified electrician can advise and carry it out, although the supplier may need to attend to turn the electricity off.
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University of Bath
Tests the widespread belief that laying an impermeable ground bearing slab in a building with no damp-proof course drives ground moisture up the adjacent walls by capillary action. Wall, soil and atmospheric moisture content were measured over a three-year period in a historic building before and after a vapour-sealed ground floor was installed. Using timber dowel measurements, the moisture content within the adjacent rubble-fill wall did not vary in response to wall evaporation rates and did not increase after the vapour-proof barrier was installed above the floor, indicating the moisture levels in that wall were not driven by capillary rise. The finding matters because the opposite assumption is routinely used to argue against sealing a solid floor in an old house.
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Wessex Water
A set charge of £325 (non-refundable) applies to applications to build over or near a public sewer. The submission needs a plan and a sectional drawing showing the type and depth of the proposed foundations, with structural calculations where the chosen foundation type requires them. Wessex Water normally expects strip or trench fill foundations wherever possible, and treats raft, piling and cantilever footings as designs needing extra justification. Work must not start on site until formal approval is granted. Where piling foundations are used, Wessex Water carries out a post-works CCTV survey; other further inspections are undertaken by the council's building control. The company recommends locating the sewers well in advance of starting any building work.
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Wessex Water
Six criteria which, if all met, let a homeowner build near (not over) a public sewer without notifying Wessex Water at all. Development type must be a single new dwelling, a domestic extension, a domestic garage or minor outbuilding, or a single block of flats; multiple dwelling developments and multiple unit industrial or retail schemes are excluded. Foundation type must be strip, trench or pad footing; raft, piling and cantilever footings are not eligible. Foundations must be a minimum of 500mm (0.5m) clear from the edge of the closest public sewer including the outer wall of any chambers. Foundations installed between 500mm and 2000mm clear of the sewer must be taken to a depth below the bottom of the sewer pipe. The sewer must be gravity-based (foul, rainwater or combined), meaning an open pipe visible in the manhole rather than the fully enclosed pipe of a pumped system. The sewer must not be strategic; strategic sewers typically run 12 inches (300mm) diameter or greater but can be smaller, and Wessex Water will check its records on 01225 526333. If all six are met, save the printable PDF of the conditions for the record and give a copy to building control, and keep photos and drawings as evidence.
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Yorkshire Water
Consent is needed before starting building work over or within 3 metres of a public sewer. If a Building Regulations application has been made, the local authority building control consults Yorkshire Water on the applicant's behalf and the applicant should ask for a copy of the response; without a Building Regulations application, a direct build-over enquiry can be submitted for an upfront fee. Fees: £144 for a desktop study only, £449 for a desktop study plus site inspection. Acknowledgement within 5 working days of application and payment; the technical assessment takes about 14 days and checks the location and condition of nearby assets, past blockages, and land rights such as easements and protected strips. Hard limits: no building over any access point (manhole, gully or inspection chamber), and nothing near pipes larger than 225mm diameter or deeper than 3m. Minor alterations, meaning removing or relocating a manhole, gully or inspection chamber, altering chamber levels, or replacing pipework, are only permitted on pipes inside the property boundary up to 225mm diameter, less than 3m deep and no more than 20m long; anything bigger, deeper or a rising main needs a sewer diversion instead. A property built after 2011 may have unadopted pipework, and a NAV rather than Yorkshire Water may be the sewerage provider. Contact technical.sewerage@yorkshirewater.co.uk. The acceptance letter should be kept for building regulations and for sale of the property.
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ACO Technologies
HexDrain B 125 is a polypropylene channel to BS EN 1433 Load Class B 125, for domestic drives and small private car parks. Overall channel depth 100 mm. Supplied with a corrosion resistant black composite HeelGuard grating using 8 mm slots, held by the Drainlock bar-less locking device with an anti-shunt feature. Accessories: 110 mm diameter vertical outlet connector part 11285, roddable foul air trap 110 mm part 11191, closing endcap part 11085 and sump part 11385 with silt bucket.
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ACO Technologies
HexDrain is a recycled polypropylene channel drain rated Load Class A 15 to BS EN 1433, suitable for pedestrian domestic use on paths, patios and cycleways. Overall channel depth 80 mm, which makes it the shallow option where dig depth is limited. Channels clip together and the range includes corner units, outlets, an accessory bag (part 19287) and a sump unit (part 19558). ACO state that fitting a B 125 grating to a HexDrain channel does not raise the system rating, which stays at A 15 because it is set by the channel body; HexDrain B 125 is the product for light vehicles.
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ACO Technologies
RainDrain is made from ACO high strength polymer concrete rather than plastic, and is rated up to Load Class A 15 for domestic use; RainDrain B 125 is the version for cars or frequent loading. Channels interlock. A Brickslot grating variant is available in B 125 for driveways where a slot rather than a visible grating is wanted. ACO note two-person handling for the polymer concrete bodies.
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Brett Martin
PVC-U underground drainage from 110 mm to 400 mm diameter, made to BS EN 1401-1 with BBA certificate 87/1898 for the 110 mm PVC-U pipe. Plain ended pipe wall thicknesses: B4001 110 mm x 3 m and B4011 110 mm x 6 m are 3.2 mm; B6001 160 mm x 3 m and B6011 160 mm x 6 m are 4.1 mm; the SN8 160 mm versions B6001 SN8 and B6011 SN8 are 4.7 mm. Socketed pipe socket depths: 70 mm at 110 mm, 95 mm at 160 mm, 110 mm at 200 mm. Both 110 mm and 160 mm ranges come in SN4 and SN8 stiffness. Gradient guidance: for flows under 1 l/s, pipes not exceeding 100 mm nominal bore at gradients not flatter than 1:40 have proved satisfactory; where peak flow exceeds 1 l/s a 100 mm bore may be laid at not flatter than 1:80 provided at least one WC is connected; a 150 mm bore may be laid at not flatter than 1:150 provided at least five WCs are connected. With a high standard of design and workmanship, 1:130 at 100 mm and 1:200 at 150 mm have been used successfully. The guide states that increasing pipe diameter to compensate for insufficient fall is not a satisfactory solution because it reduces velocity and depth of flow and encourages deposits. Also covers bedding materials, trench preparation, ground load protection and inspection chamber assemblies.
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Cordek
Cellcore HX Plus sits beneath reinforced concrete floor slabs to protect against ground heave while also insulating. Construction is a cellular expanded polystyrene core bonded to a Filcor insulation layer and protected by a thin polypropylene sheet, moulded to tolerance. BBA certified and meets NHBC Technical Standards. Specification is a two-step process Cordek set out explicitly: first fix the Cellcore HX depth and grade to suit the heave potential and the construction loading, then calculate the Filcor insulation thickness needed for the target U-value. Standard range covers common combinations of soil heave potential, concrete depth and U-value requirement.
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Cordek
Filcor expanded polystyrene lightweight structural fill, offered in a range of compressive strength grades to match the loading, from pedestrian to vehicular. Standard sheet or block size 2400 mm long x 1200 mm wide with the depth made to order, minimum depth 25 mm and maximum depth 1200 mm; any shape or profile can be cut, and Cordek hire out a hot wire cutter. Flame retardant grades available. Where Filcor may contact petroleum, hydrocarbons or solvents it must be encapsulated in Puraflex VOC membrane, either on site or supplied pre-wrapped. Water resistant with a long design life, and provides insulation as well as fill.
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Cordek
Compressible low density expanded polystyrene, coloured green, used against lateral heave on the inside face of piled ground beams or deep trench fill foundations. Thickness selection table against soil analysis: modified plasticity index 10-20, low shrinkage potential, NHBC recommended void zero, Heaveguard thickness zero; 20-40, medium, 25 mm void, 50 mm Heaveguard; 40-60, high, 35 mm void, 75 mm Heaveguard. Above 60 or higher than high, Cordek must be consulted. Critical limitation stated on the page: Heaveguard and all other compressible polystyrenes do not compress significantly until loads exceed 20 kN/m2, and 40 kN/m2 is needed to produce 50% compression, so Heaveguard is not recommended under ground floor slabs, piled beams or pile caps. Meets NHBC Technical Standards. Also available as a pile collar.
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Delta Membrane Systems
HDPE cavity drain membrane. Stud height 20 mm, sheet thickness 1 mm, roll size 2.0 m x 20 m. Compressive strength 150 kN/m2. Drainage capacity 10 litres per second per metre, equal to 600 litres/min/m or 36,100 litres/hour/m, and 1.25 litres/second/m2. Air volume between studs 14 litres/m2. R value 0.18 m2K/W. Temperature resistance -30 C to +80 C. Reaction to fire Class E to EN 13501-1. The 20 mm stud gives roughly four times the drainage rate of the 8 mm product at the cost of depth taken off the room.
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Delta Membrane Systems
HDPE cavity drain membrane with DELTASAFE additive. Stud height 8 mm, sheet thickness 0.5 mm, roll size 2.4 m x 20 m. Compressive strength greater than 250 kN/m2. Drainage capacity 2.25 litres per second per metre, equal to 135 litres/min/m or 8,100 litres/hour/m. Air volume between studs 5.3 litres/m2. R value 0.12 m2K/W. Temperature resistance -30 C to +80 C. Reaction to fire EN 13501-1:2018 Class B-s2,d0, which is a higher fire classification than the Class E typical of plain HDPE cavity drain membranes.
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Forterra
Thermalite Floor Block 4 for beam and block floors. Compressive strength 4 N/mm2, design lambda 0.16 W/mK, dry density 660 kg/m3. Single size: height 215 mm, length 440 mm, width 100 mm, weight 7.7 kg, face dimensions 440 x 215 mm.
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Forterra
Thermalite Hi-Strength 7 Trenchblock, tongue and groove with integrated hand holds. Compressive strength 7.3 N/mm2, lambda below ground 0.29 W/mK, dry density 730 kg/m3, face dimensions 440 x 215 mm and 440 x 140 mm. Classified DS1-4 for resistance to ground contamination, so usable across a wide range of ground conditions. All 140 mm high trenchblocks are supplied flat-ended, without hand holds or tongue and groove. Manufactured to BS EN 771-4.
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Forterra
Thermalite Trenchblock 3.6 tongue and groove for below-ground construction. Compressive strength 3.6 N/mm2, lambda below ground 0.24 W/mK, dry density 600 kg/m3, height 215 mm, length 440 mm, widths 255 mm and 300 mm. Note the below-ground lambda is quoted separately from the 0.15 W/mK design value used above DPC for the equivalent 3.6 N/mm2 block.
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GRAF UK
EcoBloc Inspect Flex crate, 800 x 800 x 320 mm, void ratio 96%, stackable and inspectable. GRAF's distinguishing claim is that the module accepts inspection cameras and maintenance jetting equipment through the crate, so the system can be checked and cleared rather than sealed and forgotten. Published capacities for the same unit: gross volume 0.205 m3 and net volume 0.199 m3, polypropylene, 8 kg, vertical ultimate compressive strength 340 kN/m2 and lateral 82 kN/m2, and installable to 5 metres depth under heavy loads.
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H+H UK
Celcon Foundation Blocks for below ground work. Two strengths, 3.6 N/mm2 and 7.3 N/mm2, at densities 600 kg/m3 and 730 kg/m3. Thermal conductivity below ground is quoted separately as 0.24 W/mK and 0.29 W/mK, and H+H note explicitly that these figures differ from the above-DPC values because moisture content below ground is higher. A single foundation block replaces two skins of blockwork below DPC.
- supplier figure RN-A9044P
IKO PLC
IKO Hyload Original damp proof course: 1.25mm thick, supplied in 20m (20,000mm) rolls in widths of 100, 112.5, 150, 175, 225, 275, 300, 337.5, 350, 360, 375, 400, 450, 500, 525, 600, 650, 700, 750, 800, 900 and 1000mm. BBA certified since 1967 and CE marked.
- supplier figure RN-9LL9I8
IKO PLC
IKO Hyload Universal damp proof membrane, available as 1200 gauge (300 micron, 0.3mm) or 2000 gauge (500 micron, 0.5mm). Roll lengths 12,500mm and 25,000mm. CE marked. IKO notes this membrane type has been specified as a damp proofing material since 1973. The gauge-to-micron conversion is useful because merchants quote gauge and specifications quote microns.