For decades, the construction industry has used block-and-beam flooring in commercial buildings. But, it’s only recently that the method has become popular in the UK for domestic construction.
Overall, the cost per m2 for block-and-beam flooring is more than for a concrete slab floor. But, labour charges are cheaper, and the installation takes much less time. The average cost of a block-and-beam floor ranges between £210-£250/m2, depending on factors we’ll discuss later. Therefore, a four-bedroom detached house, with a footprint of 75m2, costs £15,750-£18,750 to install a block-and-beam floor.
This guide shows the advantages of using a block-and-beam floor in your home, how much it costs, and the answers to other questions you might have. Unless you’ve had experience using this construction method, we advise that it’s not suitable for DIY. Instead, use the Competent Person Register to find an appropriate professional approved by your local authority. Alternatively, use the form on this page to receive quotations from reputable contractors.
How Much Do Block-and-beam Floors Cost?*
The table below shows a block-and-beam price comparison, which you can use as a cost calculator to benchmark against your own quotes. For this purpose, we assume the price range for a block-and-beam floor is £210-£250/m2.
|House Size||Estimated Cost Range||Average Cost|
|2-Bed Terraced House 32m2||£6,720-£8,000||£7,360|
|3-Bed Semi-detached House 45m2||£9,450-£11,250||£10,350|
|4-Bed Detached House 75m2||£15,750-£18,750||£17,250|
|3-Bed Bungalow 75m2||£15,750-£18,750||£17,250|
|Single Garage 18m2||£3,780-£4,500||£4,140|
*We compiled these details from various online resources. Every building is different and might not be suitable for using these floors, especially if the house is a lightweight structure. Therefore, these figures are estimates, and you should ask for an accurate quote from professionals skilled in this construction method. Alternatively, complete the form on this page, and we’ll submit your project details to suitable companies on your behalf.
The above scenarios assume various sized new-build properties, each with a ground floor footprint as specified. The price might vary depending on the house’s configuration, which will affect the length of each beam, and whether the floor needs intermediate supports.
The assumed average cost of £230/m2 includes the following details:
- Labour charges, £65/m2.
- Materials, £140/m2.
- Plant hire, £25/m2.
However, these might also vary.
Block-and-beam Floor Price Factors
Various factors may affect the cost. These are as follows:
As you’d expect, a floor with a larger area will cost more to cover than a smaller area. Although the cost per m2 will remain approximately the same, the total will vary with size.
The main benefit of block-and-beam floors is that the floor only needs trench foundations rather than slab foundations that cover the entire floor area. However, the trenches must be deep enough to provide a stable footing, regardless of the soil conditions. Therefore, you must excavate to the required depth before adding hardcore and concrete, and this depth won’t be apparent until you finish excavation.
The time taken to excavate the foundation trench will increase as depth increases. Furthermore, a deep trench increases the volume of excavated soil, and the number of waste skips necessary. The trench’s depth also determines the amount of hardcore used. A typical strip-fill foundation 10m long x 0.6m wide x 1m deep costs around £1,000, while a trench-fill foundation of the same dimensions costs £1,200-£1,500.
Ready-mix concrete costs £80-£150/m3 depending on the grade, and you might have to hire concrete pumps at £300-£400/day if the construction site is far from the main road. Deeper trenches will also impact the number and size of waste skips to remove the excavated soil. A mini-skip costs from £100/week, while a large skip costs up to £400/week.
The block-and-beam floor design must comply with the Approved Document A of the UK Building Regulations. To comply, structural engineers design the floor and concrete foundations, which supports their weight and that of the structure above. Typically, the engineer works with an architect who provides the construction details and drawings used by the concrete beam supplier to cut the beams to length.
Structural engineers charge £100-£200/hr or £1,000-£1,500 for the structural calculations. In comparison, architects usually charge around 6% of the project cost or a flat fee for a small project.
The floor design includes thermal insulation that satisfies Approved Document L of the Building Regulations. The insulation cost varies with the type. For example, high-grade thermal insulation like Kingspan might need only be 100mm to provide the required U-Value. In contrast, 300mm of low-grade mineral wool might give the same U-Value.
The floors must have an unbroken damp-proof course between the beams and their supporting blockwork to comply with Approved Document C of the Building Regulations.
Each floor must be finished with a sand/cement screed to level the floor and cover underfloor heating systems.
The floor spans (distance between supports) will affect the overall price. If the floor spans large spaces, you must provide intermediate supports for the beams. The structural engineer will identify this need and specify the location and type of foundations and support. Therefore, large spans increase labour and material cost.
Depending on where you live in the UK, the project costs will vary, mainly because of the higher labour costs and other overheads in that region. Typically, the most expensive areas are London and Southeast England, where prices are up to 15% higher than other regions.
Block & Beam vs Concrete Slab
Generally, block-and-beam flooring is an alternative to pouring a concrete slab floor. However, although it’s more expensive to buy, it costs less to install. Firstly, concrete slab floors are useless if the ground requires a lot of time and effort to excavate, level the ground, add substrate and pour ready-mix concrete. Moreover, some areas of the UK have soil conditions or a water table that might cause excessive drying-out of the ground, with subsequent subsidence and cracking of a concrete slab floor. Therefore, using a block-and-beam floor supported by masonry, on strip-fill or trench-fill foundations makes sense.
Traditionally, we usually find block-and-beam floors in commercial buildings. But, recently, their use in residential structures has increased steadily as architects, builders, and homeowners realise that it’s easier and quicker than using a concrete slab and has other benefits.
Overall, concrete slab flooring is cheaper to buy. But, it’s more labour intensive and takes a long time to complete. In contrast, block-and-beam floors initially cost more to purchase but need much less labour. Furthermore, you don’t have to wait for days for the floor to cure before carrying on with work. And, it’s usual to leave the ground exposed underneath the suspended flooring without a concrete oversite, unless the area is likely to flood.
Here is a list of pros and cons, comparing concrete slabs with block-and-beam flooring. Note that both methods require radon gas ventilation in specific geographical locations as required by the Approved Document C of the Building Regulations. However, this ventilation is easier to install in block-and-beam underfloor cavities than beneath concrete slabs.
- Cheaper to buy the materials than block-and-beam.
- Pour concrete directly from a ready-mix lorry.
- The concrete slab needs a long time to cure.
- Labour costs are higher than block-and-beam floors.
- The entire area needs excavation and hardcore infill.
- The ground must be firm and level across the entire floor area.
- We can only use concrete for the ground floor.
- It’s relatively easy to lay a block-and-beam floor as a DIY project if you have previous experience.
- Needs minimal excavation compared to concrete slab flooring.
- Great for sloping ground.
- It takes less time to complete than a concrete slab.
- Use this method for all floors with suitable support.
- Unsuitable for timber-frame buildings unless you provide additional supporting structures.
- Difficult to chase out and drill the floor for pipework and cables. However, you can contain them within the screed.
- Not suitable as a DIY project if you have no experience of block-and-beam floors.
- Materials are more expensive than a concrete slab.
- Beams are heavy to lift, so will need mechanical lifting equipment
Block-and-beam vs Concrete Slab Cost
Overall, the material costs for block-and-beam are more costly than those for a concrete slab. In contrast, block-and-beam labour charges are less than for a concrete slab. Overall, it’s better to choose block-and-beam flooring where you have a choice. Generally, the cost to lay a concrete slab will be around £100/m2, including all preparation and labour. In contrast, for a block-and-beam floor, expect to pay around £220/m2. However, as we’ve mentioned before, you need only wait a few days to complete a block-and-beam floor. In contrast, the concrete slab takes a lot longer to cure. The choice is yours.
Block-and-beam flooring is very popular with homeowners as it’s quick to install, thus allowing work to carry on without the long wait that a concrete slab needs to cure. Furthermore, if you’re building on a slope, a brownfield site or a plot that requires a lot of work to excavate and level, a block-and-beam floor is ideal, as you only need to excavate the trench foundations. But, what is it, and how does it work?
The floor needs very little surface preparation and no oversite concrete slab. Excavate and build trench-fill or strip-fill footings with low supporting walls built to the correct height. Then, place the pre-cut to length, pre-stressed concrete beams, with an inverted T profile, onto the supporting walls. Next, fill the grooves with dense concrete blocks or foamcrete (aka aircrete), thus producing a level top surface. At this stage, install insulation, services and underfloor heating, then grout the blocks into place. Finally, cover everything with sand/cement screed. The floor is laid quickly and provides a working platform for other trades to work from.
Block-and-beam Floor Benefits
Although block-and-beam flooring costs more than other types, it has many benefits that weigh the balance in its favour.
Distributors can easily transport the block-and-beam flooring components and store them on-site, unlike liquid concrete, which has a deadline before it cures. However, the beams are heavy and require mechanical lifting, but as most construction sites have a crane or other mechanical handling devices, this shouldn’t be a problem.
You can install the blocks and beams quickly. Furthermore, unlike pouring concrete, you can pause work overnight or for break times.
You can install the floor in all weathers, and you’re not restricted to the same temperature range and conditions that liquid concrete needs.
After installing the blocks, other trades can use the surface as a working platform. However, they must use walking boards because the floor blocks haven’t achieved their full strength and integrity until grouted in place.
Damp and fire-resistant
Unlike a timber suspended floor, block-and-beam flooring is entirely draughtproof and fire-resistant. Moreover, it’s resistant to dampness, vermin and rot.
There’s no need to excavate and level the entire building footprint, unlike a concrete slab. Site preparation is minimal, requiring only trench excavation, foundation concrete pouring, and building a dwarf supporting wall. Block-and-beam floors only need a ventilation gap of at least 150mm between the floor’s underside and the ground.
Concrete slab flooring can have problems with underlying ground movement caused by drought conditions or subsidence. Furthermore, unlike a timber suspended floor, the ground doesn’t need a concrete oversite unless there’s a risk of flooding.
Block-and-beam flooring has good inherent thermal insulation when using foamcrete as an infill. Furthermore, thermal insulation (usually polystyrene foam slabs, but you can use mineral wool suspended by netting) protects the underside of the beams from heat loss. You can also place rigid insulation on top of the floor but below the screed. Furthermore, the appropriate infill blocks can achieve good acoustic insulation, thus complying with Approved Document E of the Building Regulations.
Can you build off block-and-beam floors?
Yes, because the floor is masonry and can carry heavy loads, you can build solid block walls anywhere, not just on supporting walls. However, first get a structural engineer’s approval, as the beams might need additional support.
What goes under a block-and-beam floor?
In the form of expanded polystyrene slabs, insulation sits under the concrete beams and infills between them. The complete system prevents cold bridging.
How strong is a block-and-beam floor?
A structural engineer will calculate the floor’s strength for your project. Typically, your structural engineer calculates the expected loads and specifies beam sizes, block sizes, and intermediate beam supports if necessary. Alternatively, many concrete beam manufacturers supply a service for calculating the optimum dimensions and configuration of the beams to suit your project. Remember that each beam is steel reinforced and pre-cut to fit the span and its position in the building’s construction drawings. When designed correctly, a block-and-beam floor can support almost any load.
Using a block-and-beam floor on your construction project has many advantages compared to other types of flooring. But, we don’t recommend that you use this method unless the builder has had the required experience. Therefore, you should contact an experienced builder for quotes. Alternatively, complete the form on this page, and we’ll ensure you receive local block-and-beam floor quotes from skilled contractors near you.