Professional Beam & Plank Suspended Floor Estimator
Precast concrete plank floors, commonly known as beam and plank flooring systems, represent one of the most popular suspended floor solutions for UK residential and light commercial construction. These prefabricated concrete elements provide rapid installation, excellent structural performance, and cost-effective floor construction compared to traditional timber joists or in-situ concrete slabs. Understanding plank specifications, span capabilities, and installation requirements ensures successful project planning and execution.
The precast plank system consists of individual reinforced concrete planks spanning between supporting beams or load-bearing walls, with infill grout poured between planks to create a solid monolithic floor. Standard plank thicknesses of 75mm, 100mm, and 150mm accommodate different span requirements and loading conditions, with 100mm planks being most common for typical domestic applications. Plank widths vary from 300mm to 600mm, with 400mm and 450mm widths representing the industry standard for efficient coverage and ease of handling.
Precast concrete planks are manufactured to BS EN 13224 standards, ensuring consistent quality and performance characteristics. The planks feature reinforced concrete construction with steel bars or mesh embedded to provide tensile strength and resist bending under loads. Surface finishes are typically smooth on the underside for direct ceiling application and textured on top to provide mechanical key for the infill grout, creating composite structural action across the floor.
Standard plank lengths range from 2.4 metres to 6.5 metres, manufactured in 300mm increments to suit common building dimensions. The planks are designed as simply supported elements, resting on minimum 90mm bearing at each end on supporting beams, walls, or steel structures. Weight varies by thickness and length, with typical 100mm thick planks weighing approximately 55-60 kg per square metre, requiring mechanical lifting equipment for lengths exceeding 4 metres.
The maximum spanning capability of precast planks depends primarily on thickness and loading conditions. Standard 75mm planks typically span up to 3.5 metres for residential floor loadings of 1.5 kN/m² imposed load plus dead load. The more common 100mm planks extend this capability to approximately 4.5 metres span, suitable for most domestic room dimensions. Heavy duty 150mm planks can span up to 6.0 metres, accommodating larger spaces and higher loading requirements in commercial applications.
Load capacity must account for both dead loads from the floor construction itself and imposed loads from occupancy and furnishings. UK Building Regulations specify minimum imposed loads of 1.5 kN/m² for domestic dwellings, 2.5 kN/m² for offices, and higher values for storage or commercial uses. Structural calculations verify that selected plank thickness and span combinations satisfy both strength and deflection criteria, with professional engineering input required for spans exceeding standard tables or non-standard loading conditions.
Determining the number of planks required involves dividing the floor length by the plank width to establish how many planks fit across the span direction. For example, a floor 10 metres long using 400mm wide planks requires 25 planks per span. The plank length must match or slightly exceed the floor width, allowing for minimum bearing requirements. Standard lengths in 300mm increments mean selecting the next size up from the exact span measurement.
Wastage allowances of 3-5% account for cutting, damage, and layout optimization. Complex floor shapes with multiple rooms or irregular geometries may require higher wastage factors. Some layouts benefit from using mixed plank widths to minimize cutting and optimize material usage. Professional suppliers provide take-off services, calculating exact quantities from building plans and recommending efficient plank size combinations for cost-effective procurement.
The joints between planks require filling with structural grout to create a solid monolithic floor surface. Grout volume depends on joint width and plank depth, typically representing 15-20% of the total floor area in volume terms for standard installations. A C25/30 concrete mix or proprietary grout product provides adequate strength, pumped or poured into the joints and finished flush with the plank surface.
For 100mm deep planks with typical 20-30mm joint gaps, approximately 0.02-0.03 cubic metres of grout per square metre of floor area is required. This translates to roughly one 25kg bag of dry grout mix per 2 square metres of floor, or about 50 bags for a typical 100m² floor installation. The grout bonds to the textured plank surfaces, creating composite action that enhances floor stiffness and distributes loads effectively across multiple planks.
Precast plank installation requires careful planning and appropriate lifting equipment. Supporting beams or walls must be constructed to precise levels, with temporary propping positioned at mid-span for planks exceeding 4 metres length. Individual planks are lifted into position using a telehandler or crane, placed with minimum 90mm bearing at each end, and aligned to maintain uniform joint widths typically 20-30mm between adjacent planks.
Once all planks are positioned and checked for level, edge shuttering or formwork is installed along the floor perimeter to retain the infill grout. A light mesh reinforcement spanning across the joints enhances grout performance and controls cracking. The grout is then poured or pumped into the joints, worked thoroughly to eliminate voids, and finished flush with the plank surface. Curing for 7 days before applying floor finishes ensures adequate strength development.
Precast plank floor costs vary by plank thickness, project size, and regional factors, with typical material prices ranging from £35 to £55 per square metre for planks and grout combined. Individual 100mm thick planks cost approximately £15-22 each depending on length, with longer planks commanding premium pricing. Volume discounts apply for larger projects, and combined supply of both planks and supporting beams may reduce overall costs through package pricing.
Installation labor costs typically add £15-25 per square metre, covering crane hire, plank placement, grouting, and finishing. The speed of installation compared to traditional timber floors or in-situ concrete often results in overall project cost savings through reduced construction program duration. When comparing floor systems, consider the immediate load-bearing capability of plank floors, eliminating the curing time required for in-situ concrete and enabling faster follow-on trades.
Precast plank floors offer numerous benefits for residential and commercial construction. Rapid installation reduces construction time significantly, with typical floors completed in 1-2 days compared to weeks for traditional methods. The concrete construction provides excellent sound insulation, fire resistance, and thermal mass, contributing to comfortable and energy-efficient buildings. Unlike timber floors, precast planks are immune to rot, insect attack, and moisture-related degradation.
The suspended floor design accommodates services within the void below, facilitating electrical wiring, plumbing, and ventilation distribution. Structural performance is predictable and consistent due to factory manufacturing under controlled conditions, eliminating site weather delays and quality variables. The underside of planks provides a smooth ceiling surface requiring only skim plaster or direct decoration, while the upper surface accepts screed, tiles, or other finishes directly after grouting.
| Plank Thickness | Maximum Span | Weight (kg/m²) | Typical Application |
|---|---|---|---|
| 75mm | 3.5m | 45-50 | Light domestic, conservatories |
| 100mm | 4.5m | 55-60 | Standard domestic floors |
| 150mm | 6.0m | 80-90 | Commercial, heavy duty |
| Specification | Standard Value | Notes |
|---|---|---|
| Plank Widths | 300mm, 400mm, 450mm, 600mm | 400mm most common |
| Standard Lengths | 2.4m - 6.5m (300mm increments) | Custom lengths available |
| Minimum Bearing | 90mm each end | On beams or walls |
| Joint Width | 20-30mm | Between adjacent planks |
| Infill Grout Grade | C25/30 minimum | Or proprietary grout |
| Grout Volume | 0.02-0.03 m³/m² | Depends on joint width |
| Imposed Load (Domestic) | 1.5 kN/m² | Plus dead load |
| Fire Resistance | 60-120 minutes | Depends on thickness |
| Manufacturing Standard | BS EN 13224 | Quality assurance |
| Price per Plank (100mm) | £15-22 | Varies by length |
Typical domestic floors install in 1-2 days using mechanical lifting, significantly faster than traditional timber or in-situ concrete methods.
Most common configuration uses 100mm thick × 400mm wide planks spanning up to 4.5m for standard domestic room sizes.
Infill grout represents approximately 15-20% of floor volume, requiring about one 25kg bag per 2m² of floor area for 100mm planks.
Planks require 90mm minimum bearing at each end on supporting beams or walls to ensure adequate structural support and stability.
Concrete planks achieve 60-120 minutes fire resistance depending on thickness, meeting Building Regulations for residential and commercial use.
Material costs of £35-55/m² plus installation at £15-25/m² provide competitive pricing with reduced construction program duration.
The maximum span for precast concrete planks depends on thickness and loading conditions. Standard 75mm planks span up to 3.5 metres, 100mm planks span up to 4.5 metres, and 150mm heavy-duty planks span up to 6.0 metres for typical residential floor loadings. These limits assume standard domestic imposed loads of 1.5 kN/m² plus dead loads. Longer spans or higher loads require engineering calculations to verify structural adequacy. Always consult span tables specific to your manufacturer and loading conditions.
Calculate the number of planks by dividing the floor length by the plank width. For example, a 10-metre long floor using 400mm wide planks requires 25 planks. The plank length must match or exceed the floor width to span the full distance. Add 3-5% wastage for cutting and layout optimization. Complex floor shapes may require additional planks for irregular areas. Our calculator above determines exact quantities based on your specific dimensions and automatically includes wastage.
The primary difference is spanning capability and load capacity. Standard 100mm planks span up to 4.5 metres for domestic loads and weigh approximately 55-60 kg/m², suitable for most residential applications. Heavy-duty 150mm planks span up to 6.0 metres and weigh 80-90 kg/m², designed for commercial use, larger rooms, or higher loading conditions. The thicker planks cost 30-40% more but eliminate intermediate beam requirements for longer spans, potentially reducing overall structural costs while providing enhanced fire resistance and acoustic performance.
Grout requirements depend on plank depth and joint width between planks. For 100mm deep planks with typical 20-30mm joints, approximately 0.02-0.03 cubic metres of grout per square metre of floor area is required. This translates to about one 25kg bag of dry grout mix per 2m² of floor. A 100m² floor would need approximately 2-3m³ of grout or 50-60 bags of dry mix. Use C25/30 concrete or proprietary grout products, ensuring thorough compaction to eliminate voids between planks.
Precast planks can be cut to length on site using a petrol disc cutter or angle grinder with masonry blade, though this should be minimized through careful planning and ordering standard lengths. Cutting reduces structural capacity and exposes reinforcement, requiring steel cutting and edge sealing. Width-wise cutting is not recommended as it compromises the reinforcement layout. Order planks in lengths matching your span plus bearing requirements to avoid cutting. Complex layouts may benefit from mixed plank widths to reduce cutting needs.
Precast planks spanning over 4 metres typically require temporary propping at mid-span during installation and grouting to prevent excessive deflection. Props are positioned to support planks until the infill grout achieves adequate strength, usually 7 days. Shorter spans under 4 metres generally do not require propping if planks have adequate bearing at each end. The grouted floor acts compositely, creating a stiffer structure than individual planks. Always follow manufacturer guidelines and structural engineer recommendations for propping requirements specific to your installation.
Precast plank floors accept virtually any floor finish after grouting and curing. A 50-75mm sand and cement screed creates a smooth level surface for tiles, vinyl, or carpet. Engineered wood flooring can be bonded directly to the grouted surface or installed on battens. The concrete surface also accepts self-leveling compounds for ultra-flat finishes required by some flooring types. Underfloor heating pipes install within the screed layer. The underside provides a smooth ceiling surface requiring only skim plastering or direct decoration, avoiding the need for suspended ceilings.
Precast plank floors offer several advantages over timber joist construction. Concrete provides superior sound insulation, typically achieving 10-15dB better performance than timber. Fire resistance is excellent at 60-120 minutes compared to 30 minutes for protected timber. Installation is faster, and the floor is immediately load-bearing without deflection issues. Concrete is immune to rot, insect damage, and moisture problems affecting timber. However, timber joists offer easier service integration, lighter weight reducing foundation loads, and lower material costs for small projects. The choice depends on project requirements, building type, and budget considerations.
For precast floor suppliers, visit Forterra | Marshalls | For building guidance, check Planning Portal UK