07576 538436Salford, WN2 4BN Mon – Fri · 7:00 AM – 7:00 PM · Sat · 8:00 AM – 4:00 PM · Sun · Closed ServicesHouse ExtensionsStructural Work & SteelsLoft Conversions & DormersRoofingGarage ConversionsPorchesFull RenovationsBasement Conversions & UnderpinningKitchens & BathroomsView all → Service AreasSalfordManchesterBoltonWiganStockportOldhamRochdaleBuryWarringtonView all → AboutOur WorkReviewsContact07576 538436Request Estimate Home/Services/Basement Conversions & Underpinning Building Service · Greater Manchester # Basement Conversions& Underpinning in Salford & Manchester.Engineered. Tanked. Signed off. Add a fully habitable lower storey, bedroom, gym, cinema room, annexe, to a property that has nowhere else to grow, on a basement-specialist contract with structural engineer and waterproofing designer in-house. Request Estimate Call 07576 538436 Chartered structural engineer · Type C cavity-drained waterproofing · Building Control signed off 40+ yrs Combined experience 200+ Projects delivered Written guarantee Workmanship Fully insured Insurance Within 48 hrs Quote response Overview ## What it is, who it's for and why it matters. ### What it is A basement conversion converts an existing cellar (or creates a new sub-floor) into a habitable, tanked, insulated, Building Control-approved room. Where structural lowering is required, we underpin the property in engineer-designed pin sequences before the floor is dropped. ### Who it's for Homeowners on tight urban plots in Manchester and Salford where extension is no longer possible. Property investors maximising floor area in inner-zone Victorian terraces. Families needing a self-contained annexe, cinema room or gym below ground. ### When you need it When you have run out of side, rear and roof options, basements are the last frontier of habitable space. Many Greater Manchester period properties already have a cellar; lowering, tanking and finishing is dramatically cheaper than digging a new one. ### Why professional help matters Basement conversions are the highest-risk class of domestic build. Water management mistakes destroy the room within 18 months; underpinning mistakes destroy the house. Done properly by a basement-specialist team, the room is dry, warm, code-compliant and adds significant capital value. Done badly, it is uninsurable. What goes wrong ## The failures we are most often asked to put right. Basement failures are the most expensive class of building failure. The causes are well documented and entirely preventable. 01 ### Tanking failure Cementitious tanking applied to a damp wall fails the first winter. Type C cavity-drained systems with a sump-and-pump are the only acceptable approach in modern UK basements. 02 ### Underpinning out of sequence Underpinning pins are designed in a hit-and-miss sequence. Pin them consecutively and the wall above moves. Cracks, deflection, partial collapse, we have repaired this. 03 ### Inadequate ventilation A basement with no MVHR or extract becomes a condensation chamber. Habitable basements need designed mechanical ventilation, not a trickle vent. 04 ### Missed structural surveys Existing cellar walls in 1880s Salford terraces are often single-skin, on bedrock or on questionable footings. A proper structural survey before underpinning is non-negotiable. Our process ## A clear, repeatable system, from first visit to final sign-off. - Step 1 ### Structural and waterproofing survey We attend with chartered structural engineer and CSSW-qualified waterproofing designer. Investigate existing walls, floor and water table. - Step 2 ### Design & approvals Structural calculations, waterproofing design certificate, Building Control full-plans application, Party Wall notices served. - Step 3 ### Fixed-price contract & programme Line-by-line written contract, fixed for 90 days. Stage-payment schedule. - Step 4 ### Build phase Underpinning in engineer-designed sequence (where required), floor lowering, drainage and sump install, cavity drainage membrane, screed, walls and ceiling lined, electrics, plaster, second fix. - Step 5 ### Sign-off & guarantee Building Control completion, waterproofing designer's certificate, electrical certification, written workmanship guarantee, sump and pump service schedule. Why work with Renovo ## Concrete outcomes, not vague promises. ### Space without footprint Adds 25–60m² of habitable space without growing the building outwards or upwards. Unique on inner-city plots. ### Highest-spec waterproofing Type C cavity-drained waterproofing per BS 8102:2022, water managed actively, not optimistically held back by tanking. ### Quiet, warm, dark Basements are inherently acoustically isolated and thermally stable, ideal for cinema rooms, gyms, music rooms and master bedrooms. ### Engineering certainty Underpinning designed and signed off by chartered structural engineer (MIStructE/CEng). No 'we've done this before' approximations. ### Capital value Correctly built basement conversions in Greater Manchester reliably add 1.5–2x their construction cost in capital value on inner-zone period property. ### Single contract Structural engineer, waterproofing designer, builder and electrician under one contract. No subcontractor finger-pointing. Detail & specification ## The technical detail, for people who want to know how the work is done. Read the technical detailHide the technical detail + ### Work we carry out Basement work falls into three families, lowering, conversion and underpinning, and we handle all three. - Cellar conversion (no lowering), existing cellar with adequate head-height tanked, insulated and finished as habitable space. - Cellar lowering and underpinning, existing cellar lowered by 300–800mm with full pin-sequence underpinning to enable habitable head-height. - New basement excavation, full-depth dig under an existing property, with retaining wall design and sequenced underpinning. - Underpinning for subsidence remediation, separate from conversion; pin sequence designed by engineer to stabilise a settling foundation. - Light-well formation, external excavation outside basement windows to provide daylight, ventilation and a fire escape route. ### Waterproofing approach We design every basement to BS 8102:2022, typically Type C (drained protection) using a cavity drainage membrane fixed to retained walls and floor, drained to a perimeter channel and twin-pump sump with battery back-up. Type A (barrier) cementitious tanking is rarely specified alone for habitable basements; where it is used, it sits as belt-and-braces behind Type C. Waterproofing design is certified by a CSSW-qualified designer. ### Underpinning sequence Underpinning is designed in 1m sections, executed in a hit-and-miss sequence (typically 1–4–2–5–3–6), with mass-concrete pins poured into excavated trenches and dry-packed to the underside of the existing foundation. The sequence is critical, pin a continuous run of three and the wall above moves. Our engineer designs the sequence and an experienced underpinning gang executes it. ### Planning, Party Wall & Building Control Basement work below the existing footprint is usually Permitted Development, but light-wells and lowered external ground levels often need planning. Party Wall etc Act 1996 applies on every project where excavation is within 3m of a neighbour's foundation or 6m if deeper. We serve notices, appoint the surveyor and manage the schedule of condition. Building Control full-plans submission is mandatory. Recent work ## A look at recent projects across Greater Manchester. A selection of finished builds. See the full set on the Our Work page. See all projects Areas covered ## Basement Conversions & Underpinning across Salford, Manchester and Greater Manchester. SalfordManchesterBoltonWiganStockportOldhamRochdaleBuryWarrington FAQ ## Straight answers to the questions clients actually ask. Still got a question? Call us on 07576 538436 or request a callback. How much does a basement conversion cost in Salford?+Cellar conversion without lowering: £40,000–£70,000 depending on size and spec. Lowering and underpinning: £85,000–£160,000. New excavation: £160,000+. Fixed written quote after specialist survey. How long will it take?+Cellar conversion (no lowering): 8–12 weeks. Lowering and underpinning: 16–24 weeks. New excavation: 28–40 weeks. Written programme issued with the contract. Will the basement be dry?+Yes, by design. Type C cavity-drained waterproofing with twin-pump sump and battery back-up manages water actively. Designed and certified to BS 8102:2022. Do I need planning permission?+Most below-footprint basements are Permitted Development. Light-wells and external excavations usually need planning. We check on every project. What about Party Wall?+Almost always required. We serve all relevant notices, appoint the surveyor and manage the schedule of condition for adjoining owners. What guarantees come with the work?+Written workmanship guarantee, plus waterproofing system manufacturer warranty (typically 30 years) and sump/pump manufacturer warranty. All issued at handover. Will my house insurance be affected?+Notify your insurer ahead of works. Most underwriters accept properly engineered and certificated basement work without premium loading, we provide the document set. Is underpinning always required?+Only where head-height needs to increase or where existing foundations are inadequate for habitable loading. For 'as-existing' cellar conversions, no underpinning is required. Related services ## Often combined with basement conversions & underpinning. ### Structural Work & Steels Wall removals, RSJ installs, underpinning and structural alterations, in-house. ### House Extensions Single, double & wrap-around extensions designed around the way you actually live. ### Full Renovations Whole-house refurbishments managed end-to-end, from strip-out to final coat. Next step ## Find the extra storey you already have. Book a basement-specialist survey. We attend with structural engineer and waterproofing designer and follow up with a fixed written price within 14 working days. Request Estimate 07576 538436 Reassurance - Fixed-price written quote, no day-rate surprises. - Single accountable team, no subcontractor finger-pointing. - Stage payments tied to milestones, no large upfront deposit. - Building Control sign-off and written workmanship guarantee. Specialist extension and structural builders serving Salford, Manchester and the wider North West. Fixed-price quotes, project-managed end-to-end. 07576 538436 jake@renovodesignandbuild.co.uk107 Castlehill RoadSalford, WN2 4BN Mon – Fri · 7:00 AM – 7:00 PM · Sat · 8:00 AM – 4:00 PM · Sun · Closed - @renovodesignandbuild ### Services House Extensions - Structural Work & Steels - Loft Conversions & Dormers - Roofing - Garage Conversions - Porches - Full Renovations - Basement Conversions & Underpinning - Kitchens & Bathrooms ### Service Areas - Salford - Manchester - Bolton - Wigan - Stockport - Oldham - Rochdale - Bury - Warrington ### Company - About - Our Work - Reviews - Contact © 2026 Renovo Design & Build Ltd. All rights reserved. Privacy PolicyTerms & ConditionsCookie PolicyBuilt to last. Fully insured. Salford-based. Call NowFree Estimate