--- title: "Raft Foundations Brighton | Specialist Raft Foundation Contractors | Masters Group" description: "Specialist raft foundation design and construction in Brighton & East Sussex. Engineered solutions for poor ground conditions, new builds, and extensions. 30+ years experience." lang: en json-ld: | [ { "@context": "https://schema.org", "@type": "Service", "name": "Raft Foundation Construction Service", "description": "Specialist raft foundation design and construction in Brighton and East Sussex for new builds, extensions, and projects on challenging ground conditions.", "provider": { "@type": "LocalBusiness", "name": "Masters Group", "telephone": "01273110607", "url": "https://mastersgroup.uk", "address": { "@type": "PostalAddress", "streetAddress": "17 Colebrook Road", "addressLocality": "Brighton", "postalCode": "BN1 5JH", "addressCountry": "GB" } }, "areaServed": [ { "@type": "City", "name": "Brighton" }, { "@type": "City", "name": "Worthing" }, { "@type": "City", "name": "Eastbourne" }, { "@type": "City", "name": "Horsham" } ] }, { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [ { "@type": "Question", "name": "When is a raft foundation needed instead of strip foundations?", "acceptedAnswer": { "@type": "Answer", "text": "Raft foundations are specified when ground bearing capacity is low, when soil conditions vary across the site, when there is a risk of differential settlement, or when trees have been removed causing clay heave risk. Your structural engineer will advise based on ground investigation results." } }, { "@type": "Question", "name": "How much does a raft foundation cost in Brighton?", "acceptedAnswer": { "@type": "Answer", "text": "Raft foundations typically cost £120–£200 per square metre including ground preparation, reinforcement, and concrete. For an 80m² footprint, expect £10,000–£16,000. We provide fixed-price quotes after site investigation." } }, { "@type": "Question", "name": "How long does a raft foundation take to build?", "acceptedAnswer": { "@type": "Answer", "text": "Ground preparation takes 2–4 days. Reinforcement and service installation takes 1–2 days. The concrete pour itself is typically completed in one day. Allow 7 days minimum curing before loading." } }, { "@type": "Question", "name": "Can a raft foundation be built in winter?", "acceptedAnswer": { "@type": "Answer", "text": "Yes, with appropriate precautions. We use warm concrete mixes, insulating blankets during curing, and avoid pouring when temperatures are forecast below 2°C. Winter construction is entirely feasible with proper planning." } }, { "@type": "Question", "name": "Do I need a raft foundation for my extension?", "acceptedAnswer": { "@type": "Answer", "text": "Not necessarily. Standard strip or trench fill foundations are suitable for most extensions on stable ground. A raft is specified when ground conditions are poor or variable. We assess this during the initial site survey." } }, { "@type": "Question", "name": "What areas do you cover?", "acceptedAnswer": { "@type": "Answer", "text": "We cover Brighton, Hove, Worthing, Eastbourne, Littlehampton, Bognor Regis, Burgess Hill, Haywards Heath, Horsham, and the wider East Sussex area." } } ] }, { "@context": "https://schema.org", "@type": "BreadcrumbList", "itemListElement": [ { "@type": "ListItem", "position": 1, "name": "Home", "item": "https://mastersgroup.uk/" }, { "@type": "ListItem", "position": 2, "name": "Services", "item": "https://mastersgroup.uk/#services" }, { "@type": "ListItem", "position": 3, "name": "Raft Foundation Construction Service" } ] } ] --- 17 Colebrook Road, Brighton, BN1 5JH info@mastersgroup.uk [![Masters Group](/assets/masters-logo-Dn445ZsE.png) MASTERS GROUP ](/) [Home](/)[About](/about) Services Areas [Our Work](/our-work)[Warranty](/warranty)[Reviews](/reviews)[Blog](/blog)[Contact](/contact) [01273 110607](tel:01273110607)[Get Estimate](/contact) ![Raft Foundation Construction Service services by Masters Group Brighton](/assets/raft-foundations-BlP9HroM.jpg) - [Home](/) - [Services](/#services) - Raft Foundation Construction Service Masters Group # Specialist Raft Foundation Design & Construction in Brighton & East Sussex When standard foundations won't work, a raft foundation distributes your building's load across its entire footprint — eliminating differential settlement risk and providing a stable platform on even the most challenging ground conditions. [Request Free Estimate](/contact) [01273 110607](tel:01273110607) 30+ years experience · Complex ground expertise · Fully insured · LABC approved 30+ Years Foundation expertise Structural Engineers In-house design team LABC Approved Building control partnership Fixed-Price Quotes No hidden costs ## What Is a Raft Foundation and When Do You Need One? A raft foundation is a reinforced concrete slab that covers the entire footprint of a building, distributing structural loads evenly across the ground surface. Unlike strip or trench foundations that concentrate loads along wall lines, raft foundations spread the weight across a much larger area, reducing ground pressure and minimising settlement. Raft foundations are specified when ground bearing capacity is low, when soil conditions vary across the building footprint, or when differential settlement could cause structural damage. They are common on sites with clay soils prone to shrinkage, areas of made ground, or locations with high water tables. In Brighton and East Sussex, raft foundations are frequently used for new builds on brownfield sites, extensions on properties with known ground problems, and developments in areas where trees have been recently removed (causing clay heave). Masters Group works with structural engineers to design raft foundations tailored to your specific site conditions. We manage ground investigation, design, construction, and building control approval as a single coordinated process. ### Related Services - [Foundations](/services/foundations) - [New Builds](/services/new-builds) - [Retaining Walls](/services/retaining-walls) - [Commercial](/services/commercial) ### Areas We Serve - [Brighton](/areas/brighton) - [Worthing](/areas/worthing) - [Burgess Hill](/areas/burgess-hill) - [Horsham](/areas/horsham) ## What Happens When Raft Foundations Are Poorly Designed? An incorrectly designed raft foundation defeats its entire purpose. If the slab is too thin, lacks sufficient reinforcement, or is not properly connected to the superstructure, it cannot distribute loads effectively. The result is the same differential settlement the raft was supposed to prevent. Poor ground preparation beneath raft foundations causes long-term problems. If fill material is not properly compacted, or if drainage is inadequate, water accumulation beneath the slab can cause heave or washout. Both compromise the foundation's performance and the building above. Concrete specification errors — particularly using the wrong grade or failing to specify sulphate resistance where needed — accelerate deterioration. In Brighton's clay soils, sulphate attack is a real concern that must be addressed in the concrete specification. Remediation of a failed raft foundation is extraordinarily disruptive and expensive. The entire building above must typically be temporarily supported while the foundation is reinforced or replaced. Costs can exceed £50,000 for even modest structures. Our Process ## How We Deliver Every Project 1 ### Ground Investigation Detailed site investigation including trial pits, soil sampling, and assessment of bearing capacity, water table, and soil chemistry. 2 ### Structural Design Structural engineers design the raft specification — thickness, reinforcement layout, edge beam details, and concrete grade — based on site data and building loads. 3 ### Site Preparation Excavation to formation level, removal of unsuitable material, and installation of compacted sub-base and blinding layer. 4 ### Reinforcement & Services Steel reinforcement placed to design specification. Below-slab drainage, radon membrane, and service ducts installed before concrete pour. 5 ### Concrete Pour Continuous pour of specified concrete mix to achieve monolithic slab. Vibration, levelling, and power-floating to required finish. 6 ### Inspection & Handover Building control inspection at each stage. Curing period before loading. Full documentation and certificates provided. ## Why This Matters for Your Project ### Eliminates Settlement Risk Load distribution across the entire footprint prevents the differential settlement that damages buildings on poor ground. ### Works on Difficult Sites Engineered for clay, made ground, variable fill, and high water table conditions where standard foundations would fail. ### Integrated Insulation Raft foundations can incorporate insulation below and within the slab, improving energy performance and meeting current Building Regulations. ### Speed of Construction Once ground preparation is complete, a raft foundation can be poured in a single day — significantly faster than strip or pile-and-beam alternatives. ### Cost-Effective on Poor Ground Where ground conditions would require deep strip foundations or piling, a raft foundation often provides a more economical solution. ### Building Control Confidence Fully engineered design with calculations means straightforward building control approval through our LABC partnership. ## Raft Foundations: Specifications, Construction & Technical Detail A standard domestic raft foundation consists of a reinforced concrete slab typically 200–300mm thick, with thickened edge beams around the perimeter and beneath internal load-bearing walls. The edge beam is usually 450–600mm deep and 400–500mm wide, providing additional rigidity and resistance to edge loading. Reinforcement typically consists of two layers of steel mesh (A393 or A252) with additional bars in edge beams and beneath point loads. The reinforcement design is specific to each project and is calculated by the structural engineer based on building loads and ground conditions. Below the concrete slab, the build-up typically includes: 150mm compacted Type 1 sub-base, 50mm sand blinding, damp proof membrane (DPM), and rigid insulation board (typically 100–150mm of PIR or EPS). The insulation position — above or below the slab — depends on the structural design and thermal requirements. Concrete specification for raft foundations in Brighton typically calls for C30 or C35 concrete with a maximum water-cement ratio of 0.50. Where sulphate exposure is classified as DS-2 or higher (common in Brighton's clay soils), sulphate-resisting Portland cement or ground granulated blast-furnace slag (GGBS) is specified. Services below the raft — drainage, water supply, electrical ducts — must be installed before the concrete pour. Any services that pass through the raft require sleeves or proprietary penetration seals to maintain the integrity of the DPM and structural slab. Raft foundation costs in Brighton typically range from £120–£200 per square metre, depending on thickness, reinforcement density, and ground preparation requirements. For a typical 80m² extension or new build footprint, expect £10,000–£16,000 for the complete raft foundation. ## Frequently Asked Questions ### When is a raft foundation needed instead of strip foundations? ### How much does a raft foundation cost in Brighton? ### How long does a raft foundation take to build? ### Can a raft foundation be built in winter? ### Do I need a raft foundation for my extension? ### What areas do you cover? ![Professional construction project — Masters Group building contractors](/assets/cta-bg-CbvIn_eS.jpg) ## Need a Raft Foundation for Your Project? Get a free, no-obligation estimate. Engineered design, site-specific solutions, and fixed-price delivery from ground investigation to building control sign-off. [Request Free Estimate](/contact) [01273 110607](tel:01273110607) [Home](/) · [Contact](/contact) ![Checkatrade 5-star rated building contractors](/assets/checkatrade-RMX7Lkai.webp)![Federation of Master Builders member](/assets/fmb-fkL6zBWX.png)![NICEIC Approved Contractor for electrical work](/assets/niceic-ByVGzec0.png)![Gas Safe Register certified contractor](/assets/gas-safe-8KDBuy0S.png) ### Masters Group Brighton's trusted building contractors. Over 30 years of experience delivering exceptional construction projects across East Sussex. 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