Beam and Block Floors: Complete Guide for Homeowners

If you’ve ever watched a house being built or planned your own home extension, you’ve likely heard the term “beam and block flooring”. It might not sound all that glamorous, but it’s one of the most popular and practical flooring methods used in modern construction. And there are good reasons why.

Kaichaungxing Product Page

In this in-depth guide, we’ll walk you through everything you need to know about beam and block floors: what they are, why they’re used, how they’re constructed, and when they’re the ideal choice for home construction or extensions. We’ll also look at the key building requirements, weigh up the pros and cons, and wrap up with a handy FAQ for all those lingering questions.

What Are Beam and Block Floors?

Beam and block floors, sometimes called rib and block floors, are a type of suspended concrete block flooring system. They consist of precast concrete floor beams that span the gap between load-bearing walls, and concrete blocks that are slotted between them. The resulting surface is robust, level, and ready to be topped off with screed or your finished floor surface.

Think of it as giant Lego: the beams are the structural supports and the blocks are the fillers. Once everything is in place, the floor becomes an incredibly strong, stable platform that doesn’t creak or bounce underfoot. This method is used mostly for ground floors but is also popular for upper floor levels in some builds. It’s especially suited for residential construction projects on uneven or sloped ground where a traditional concrete slab might be tricky to pour.

Why Are Beam and Block Floors Used?

You might be wondering, why go with beam and block floor systems instead of just pouring a concrete slab? Great question. Here are the main reasons why builders and homeowners love this system:

1. Speed of Installation

Precast beam flooring and blocks can be delivered to a site and installed quickly. There’s no need to wait for concrete to cure or for formwork to be dismantled.

2. All-Weather Construction

Because there’s no curing time, this type of block and beam floor can be installed in almost any weather, making it ideal for the unpredictable UK climate.

3. Great for Poor Ground Conditions

Got a site with uneven ground, tree roots or poor soil quality? Beam and block is often the answer. The suspended nature of the system means the floor doesn’t rely on the ground beneath for support.

4. Thermal Mass and Insulation

Concrete floors help with thermal mass, meaning they retain and slowly release heat. Plus, insulation layers can be added on top or between blocks.

5. No Need for Ground Preparation

Unlike slab foundations that require excavation, hardcore, and compacting, beam and block floors require less ground prep, saving time and effort.

6. Durability and Strength

Once installed, a block beam floor is incredibly strong. They resist rot, insect damage, and damp – especially valuable in areas prone to flooding or moisture.

When Are Beam and Block Floors Typically Used?

You’ll find beam and block floors used in various types of construction:

• New Builds: Common in housing developments due to their speed and efficiency.
• Home Extensions: Ideal for rear or side extensions, especially where access for concrete pouring is restricted.
• Conversions: Useful in garage or barn conversions where ground conditions are uneven.
• Flood-Prone Areas: A go-to solution for low-lying areas where suspended floors prevent water damage.

Builders often choose this system when the site has:

• High water tables
• Expansive or clay soils
• Tree roots
• Sloping ground

How Long Does It Take To Install A Beam And Block Floor?

For a typical home extension, installing a beam and block floor usually takes approximately 1 to 2 days.

Here’s a quick breakdown:

• Smaller extensions (like a single room, ~20–30 m²): The floor can often be fully installed in a single day, especially if the site is well-prepared and access is good.
• Larger extensions or more complex shapes: It might take up to 2 days to place the beams, fit the blocks, and complete any minor adjustments.
• Additional time might be needed if you also plan to immediately lay insulation, damp-proof membranes, or screed over the top.

A big advantage of beam and block is that installation isn’t weather-dependent, so rain or cold typically won’t cause delays like it would with poured concrete.

How Is a Beam and Block Floor Constructed?

Installing a beam and block floor is a relatively straightforward process, but must be executed with precision. Here’s a step-by-step breakdown of typical beam and block floor installation for domestic extensions, which will ensure a smooth installation of your flooring system. 

1. Get The Foundations Ready

• Before anything starts, the trench foundations (strip foundations) must be completed and cured. Although the beam and block floor itself doesn’t need a solid ground layer, it does require solid support from its foundations. 
• For a solid block and beam foundation, any necessary internal sleeper walls are built up to the correct height. These are short internal walls that are built across the footprint of the house to carry the middle span of the beams.
• Ventilation gaps need to exist too; because it’s a suspended floor, air must circulate underneath to prevent damp buildup. Airbricks and ventilation channels are essential and must comply with building codes.
• Engineers will check everything is at the right level and strong enough to support the beams.

2. Prepare The Site

• Clear any leftover debris from the foundations.
• Mark out beam positions if not already indicated.
• Sometimes a sand blinding (thin layer of sand) is spread if needed for neatness or to support the damp-proof membrane later.

3. Delivery of Beams and Blocks

• Precast concrete beams and infill blocks arrive on-site.
• They’re often unloaded as close to the work area as possible to save time.

4. Lifting and Placing Beams

• Using a crane, a hiab, or even manual lifting if they are lightweight beams, your builders will place the beams across the foundation walls or sleeper walls.
• They usually start at one end and work methodically across the footprint.

5. Slotting in Blocks

• Concrete blocks are manually placed between the beams, a bit like assembling a giant jigsaw.
• Care is taken to tap them snugly into place without gaps.
• Workers check levels frequently as they go to ensure a flat surface.

6. Fitting Closure Blocks

• At the edges or awkward spots, specially cut blocks (closure blocks) are installed to close any small gaps.

7. Laying the Damp-Proof Membrane (DPM)

• A DPM sheet is laid across the whole floor to prevent rising damp.
• Joints are taped and sealed carefully.

8. Installing Insulation (If Required)

• If building regulations require it (which they almost always do now), rigid floor insulation boards are placed over the DPM.
• Boards are often interlocked for better coverage.

9. Applying Screed

• Finally, a sand/cement screed or liquid screed is poured to create a completely level top surface ready for your chosen floor finish (tiles, timber, carpet, etc.).
• Screed may be applied immediately or a few days later depending on builder’s schedule.

Beam and Void Building Requirements

Typically, precast concrete beams used in beam and block flooring come in two common sizes:

150mm deep beams are the go-to for most home extensions and new builds because they’re lighter, easier to handle, and perfectly strong for typical spans (up to about 4–5 meters without intermediate supports).

225mm deep beams are chosen if you need to span longer distances (say 5–7 meters) or if you have a very heavy loading (like a large open-plan area without internal walls underneath).

Both types usually have the same width (around 100mm), so the blocks that slot between them are standardized too — usually 100mm wide concrete infill blocks.

The void space beneath a beam and block floor is a crucial part of the design, especially for ventilation and moisture control.

The typical minimum void space between the underside of the floor beams and the ground is 150mm (6 inches).

In many cases, especially for better ventilation or in damp-prone areas, a void of 225mm to 300mm may be recommended or specified.

Pros and Cons of Beam and Block Floors

Like any construction method, beam and block flooring has its strengths and limitations. Here’s a balanced look at the pros and cons of beam & block. 

Pros

There are numerous advantages of choosing a beam and block floor, including: 

• Quick Installation: Especially useful for fast-paced building schedules where construction time is important. 
• Weather Independent: Installation of a block & beam foundation is not affected by weather conditions and can continue regardless of rain or frost, leading to the best experiences.
• Minimal Ground Preparation: There’s no extensive ground preparation required, which saves time and money.
• Robust and Durable: Compared to a traditional beam, pre-stressed concrete beams are resistant to pests, rot, and moisture and have good structural integrity. Plus, they are fire resistant and damp proof.
• Good Load-Bearing Capacity: The high quality floor is excellent for supporting heavy internal walls or machinery.
• Flexible Insulation Options: Can meet high thermal insulation and acoustic performance standards with added layers.

Cons

It’s important to acknowledge there are also disadvantages of opting for a block & beam floor construction, such as:

• Manual Labour Required: Placing blocks between beams can be physically demanding for builders. 
• Heavier Material Costs: Precast elements can be more expensive than traditional materials.
• Ventilation Must Be Managed: Poor airflow under the floor can lead to damp issues.
• Special Equipment Needed: Beams often require mechanical lifting gear for placement.
• Not Ideal for Complex Layouts: If the site conditions are more complex, a block and beam floor may be unsuitable. Realistically, this type of floor construction project is best suited to simple rectangular floor plans.

Final Thoughts

Beam and block floors are a brilliant example of modern form of construction that balances efficiency, durability, and cost-effectiveness. Whether you’re planning a new build, extending your current home, or converting an old space into something new, this type of flooring offers solid benefits you can count on.

With quick installation, minimal site disruption, and strong long-term performance, beam and block floors deserve their place as a go-to solution for builders and architects across the UK.

So the next time you walk across a solid, squeak-free floor structure in a new home, you might just have beam and block to thank for it!

Frequently Asked Questions

Q: Can I install beam and block floors myself?

Technically yes, especially if you’re confident with structural work and have help. But for safety and Building Regulation compliance, it’s wise to work with professionals.

Q: How much does a beam & block floor cost?

Costs vary based on project size, location, and ground conditions. On average, expect to pay between £70 – £90 per square metre for supply and install.

Q: Is insulation included?

Not automatically. You’ll need to include insulation above or within the floor as per your energy efficiency requirements.

Q: Can it be used on upper floors?

Yes, beam and block can be used on upper floors, particularly in multi-storey apartment blocks or commercial buildings.

Q: How long does installation take?

Most floors can be installed in a day or two, depending on size. It’s a very quick process compared to pouring a concrete slab.

Want more information on ground beam formwork(ru,fr,nl)? Feel free to contact us.

Q: What kind of floor finishes can I use on top of a block and beam floor?

Pretty much anything: tile, laminate, carpet, hardwood. Just ensure your screed layer is properly cured and level.

Q: Are beam & block floors noisy?

They’re actually very quiet underfoot. Add acoustic insulation for extra soundproofing, especially for upper floors.

0

On the residential part of our practice, we do a lot of pier and beam foundations. There are other options available to us -some include post-tensioned slab on grade and plain ol’ slab on grade, and all of these options are fine under the right circumstances but if I had my pick (which I normally do) we recommend the pier and beam structural foundation. The soil in my area of practice tends to be expansive because it contains a healthy dose of clay, which expands and contracts as moisture enters the equation. Add water, through rain and irrigation, and the soil expands. Remove water due to hot and dry conditions, and the soil contracts. All this soil movement adds up to cracks in the house. Because we like to help eliminate the movement issues that come along with expansive soil, we like designing with a pier and beam foundation.

Most people have heard of a pier and beam foundation at some point in their lives but more times than not, they don’t really understand how it works – even the “experts” get it wrong. I had a home inspector tell me, as he was inspecting a house I was in the process of buying, that the house had structural issues because there wasn’t dirt under the grade beam where he had checked.

Home Inspector: This house has structural issues.
Bob: Really? What did you find?
Home Inspector: I noticed when I was in the crawl space that there were gaps under the grade beam where the dirt was missing.
Bob: Right … and exactly what was the problem?
Home Inspector: Your beam will eventually sag if it isn’t supported properly. You’ll need to get someone down in the crawl space and put some dirt in.
Bob: What?!? There isn’t supposed to be dirt under the grade beam … you do know that dirt doesn’t hold the beam up, that’s the job of the piers.
Home Inspector: Son, I’ve been doing this a long time.
Bob: Uh-huh … right.

For the record, if it wasn’t already clear, dirt DOES NOT support the grade beam in a pier and beam foundation.

Since a number of people don’t seem to understand this concept, I thought I would whip together some sketches to help illustrate my point. If you can’t read drawings, hopefully my explanation will be good enough for you to understand.

Here is a typical wall section through a pier and beam foundation. The grey part is the house and for our purposes, it doesn’t matter in this conversation. The important thing to note is that a pier (think of it as a concrete column) is drilled down through the dirt until it can bear on rock. That’s important because rock doesn’t expand or contract based on the water content of the surrounding areas.

The grade beam is a concrete beam that spans from pier to pier – just like a beam that’s probably in the ceiling above your head spanning from wall to wall.

Underneath the grade beam are “void cartons” or “void forms” (it would have helped if I had labeled them in the sketch above, as it is, it is shown as a gray rectangle with two diagonal lines in it.) Believe it or not, void forms are made out of cardboard, and the concrete gets poured on top of them. They are strong enough to support the weight of wet concrete but over time, long after the concrete has cured and become hard, the cardboard will rot away and leave a void.

The last thing to note in the sketch above are the “soil retainer boards”. These are basically plastic boards that keep the surrounding dirt out of the space the void carton creates when it rots away.

This is a look at a typical grade beam when the void form has rotted away. There is now an airspace between the bottom of the grade beam and the dirt below. This is a good thing … it’s an important thing, you want this gap.

Why would you want a gap? You want it so that when the surrounding dirt absorbs water and expands, the dirt doesn’t push up against the underside of the grade beam. Having this gap is what allows you to not worry about cracks in your brickwork, or having doors stick seasonally. Piers, bear on bedrock, grade beams sit on piers, and no dirt under your grade beam means your house doesn’t move.

#scoreboard

I told you all that so that maybe these pictures would make a little more sense. We poured the grade beams at the KHouse recently and it was quite the show for a residential project. 13 concrete trucks, spaced 30 minutes apart, helped get this foundation pour done and we are now about 80% complete. All that’s left are the basement walls, driveways, sidewalks, and exterior stairs.

In order to reach all points on the site without damaging the trees, the contractor had to use a concrete pump truck with a giant arm on it. This machine takes the concrete in at the rear and pushes it through a bunch of pipes connected to the arm.

All the concrete goes into the hopper here … easy.

This was one of the trees we had to avoid messing with – it was a main consideration in deciding how the concrete would be placed. I don’t get to use these pump trucks too often on residential jobs, but they are extremely common on commercial jobs.

This is the pump arm expanding out – you can start to get a good feel for just how far it can reach. Pouring concrete is incredibly difficult and back-breaking work, I frequently think that other than being a roofer in the summer, this is the worst job on a construction site … except for the guy who controls the pump arm – that’s the sweetest gig ever on a construction site.

Here is a look at the controller for the pump arm. It’s really like playing video games all day – at least that’s what the guy told me, and he ought to know. He stands in the shade fiddling with the joy sticks while everyone else is breaking their back pushing wet concrete around.

These were some of the guys locating the concrete into the plywood forms. As I took this picture, the guy in the front wearing the plaid shirt said “you really don’t want to stand there”. I know, but I wanted to take the picture …. and about 5 seconds later, an air bubble came through the line, the concrete coming out kind of spluttered a little bit and then *BOOM* I was splattered head to toe in concrete (I didn’t take a picture of that). The only saving grace, as all the concrete guys were laughing, was that the contractor was standing right next to me and got covered as well.

Speaking of the contractor – that’s him in the white polo shirt sitting atop the concrete mixing truck. That’s called “doing your job.”

This is looking across the top of the grade beams – the dark gray stripe in the middle is the wet concrete. From the top of the grade beam, you can get a sense of how deep the crawl space will be – just under 4′ total. In this project, we are installing our air-handling units below the floor and this is where they will go.

Just because no post where pouring concrete is discussed would be complete without talking about a vibrator, I feel it is incumbent on me to point it out. As the concrete is poured into the formwork, the vibrator is inserted into the concrete to make sure that the aggregate is uniformly distributed and that there aren’t any air pockets. Pretty simple job but there is some skill required … too little vibration and you don’t get the concrete distributed correctly, too much and you can over mix the concrete and settle the aggregate towards the bottom rather than uniformly.

The last thing I wanted to point out is the concrete testing. This doesn’t happen on many residential projects but this isn’t just any residential project. An independent testing company came out and check the concrete from two concrete trucks (selected at random) to perform slump tests and to take compression core samples. They measure the temperature of the concrete to make sure that the concrete hasn’t been sitting in the truck too long since it came from the batching plant and is still suitable for use.

Here is a collection of images showing a slump test being performed. They way it works is that the metal cone is filled in three loads, each load being tamped down 20 times with the metal rod. Then the cone is slowly lifted off and the cone placed next to the pile of concrete that it just uncovered. The metal rod is placed across the top and a measurement is taken from the rod down to the top of the “slumping” concrete. The amount of slump that takes place is an indicator of the strength of this load of concrete. I believe the structural engineer called for 3,500 psi concrete so we were looking for a 4″ slump – which is what we got. Too much slump and the concrete would have been rejected.

Just a few days later, all the plywood formwork gets removed and you can see the finished concrete product. Considering I know just how much work went into getting to this point, I am always amazed at how simple every looks … but looks can be deceiving. Getting something wrong here means everything after will be wrong. All the embed plates, drop heights, brick ledges, inverted brick ledges, joist pockets, etc. have to be coordinated and resolved. It looks simple because that’s the point.

Here is a detailed look at what soil retainer boards look like … corrugated plastic. Surprised?

In this picture you can see the three things that we’ve talked about in today’s post; the concrete grade beam, the soil retainer boards (the black panels above) and the cardboard void form (look to the left of the guy above – you can still see the void forms before they get covered up by the soil retainer boards).

And here is a close up finished look at a corner – see that notch cut out of the soil retainer boards? That part of concrete is just a tiny bit of the pier that the grade beams sit on (if you want to see more about the piers on this project, read this).

Finally, this is the detached garage on the right and the main house on the left with a walkway in between. Soil retainer boards have been put in place on the house and you can see the pier at the bottom left-hand corner of the house. In the trenches, that you see to either sir of the walkway space, will be perimeter drainage pipes … but that’s a different post for a different day.

I’ve tried to walk the line between keeping things simple, but include enough information as to be of some benefit. On the day the concrete was poured at the KHouse, we brought a bunch of the staff out to see how things worked. We even met the owner on site and walked the concrete pour with him and explained what was happening. This sort of thing can seem really dry and boring but as I’ve mentioned on many occasions, you have to understand something in order to appreciate it. This is not an inexpensive foundation or project so all indications would tell me that the time we spend explaining what is going on at the site with the owner, the more excited he is becoming to what he will eventually receive.

I have no doubt that the stories our client will tell folks about his house will include more than just “this is white oak flooring” or “this is a pier and beam foundation.” He’ll be able to talk about the cut of the flooring and tell people “this is white oak flooring and this pattern is called “cathedraling” and that it took 13 loads of concrete to pour his grade beams … and I think that’s pretty cool.

Cheers,

Contact us to discuss your requirements of Scaffold Coupling For Construction. Our experienced sales team can help you identify the options that best suit your needs.