How Do You Insulate a Beam and Block Floor?

How do you Insulate a Beam and Block Floor

Domestic and residential floor construction uses the popular beam and block floor system because it is a cost-effective alternative to solid concrete floors due to the off-site manufacture of the concrete blocks and beams. Additionally, there is little requirement for specialist equipment or labour and they can be assembled quickly.

Also known as suspended concrete floors, beam and block floors have become popular flooring systems in UK house construction and as an alternative to traditional timber upper flooring. They are typically used when the site is sloping, where there is a likelihood of a ground volume shift, or in situations where the ground has poor bearing capacity. 

Additionally, a beam and block floor could be recommended for use if there are chemicals in the soil or if the groundwater level is high.

Some of the main benefits of concrete beam and block floors include:

  • Ease of installation requires no special construction skills
  • Economic flooring solution for both ground floors and upper floor level
  • Flexible option with high load capacity making it ideal for multiple situations
  • A great option even for sloping or uneven ground
  • Speedy construction provides a safe platform for further construction
  • Can opt for high quality non-standard beam and block flooring to improve thermal performance

How Are Concrete Beam and Block Floors Installed?

The internal load-bearing walls and perimeter walls support the precast concrete inverted T-beams. The depth of the prestressed concrete beams varies and can range from 130mm to 250mm, with lengths of up to 6m. They are often designed and produced to span certain distances. Beam depth and profiles are chosen based on loading requirements and span, as well as the type of block provided.

Lightweight concrete “Infill blocks” are then positioned between the T-beams, and a sand/cement “grout” is frequently scraped or brushed over the blocks’ surface, assisting in air tightness.  Additionally, this “grout” keeps pests and insects out, avoids movement in the concrete blocks, provides a good load distribution and fills any unwanted gaps.

Concrete Floor Beams
Concrete Floor Beams

How Do You Insulate a Beam and Concrete Blocks Floor?

Generally, it’s not really an option to install thermal insulation beneath the beam and block flooring so typically, lightweight rigid board (PIR) insulation such as Celotex XR4000 and GA4000 are installed on top of the deck, which is later covered with a screed or structural concrete topping. These are the most commonly available and thermally efficient insulation materials available.

To avoid thermal bridging, an upstand perimeter insulation which is usually a thinner PIR board such as Celotex TB4000 is put around the perimeter of the concrete topping or screed. To avoid intermittent condensation and the seepage of screed into any cracks in the insulation board. 

Many insulation board manufacturers advise adding a vapour control layer or damp proof membrane between the insulation board and the concrete screed to prevent any issues with your beam and block flooring with moisture.

Step-by-Step Guide to Beam and Block Floor insulation

1. The top surface first needs to be levelled with grout or a self-levelling topping.

2. In circumstances where a radon barrier (the polythene layer that stops radon gases and methane gases from entering a building) is required, this should be laid over the grouting layer and extended across the wall cavity to the outer leaf.

3. The insulation boards should be laid flat on top of the radon barrier or structural deck. The insulation boards need to be butted together tightly to cover the entire floor area. Any insulation boards required should be cut precisely around service accesses to minimise heat loss through gaps in the insulation.

4. Cover the entire area where the insulation boards have been laid with a sheet of polyethylene. This will protect the insulation boards from the floor screed, preventing moisture from the screed from seeping into cracks or junctions between the insulation boards and causing them to move.

5. Clips should be used to keep flexible piping in place if heating pipes are to be inserted in the screed until the screed has been laid.

6. Finally, finish the job by pouring the floor screed. You need to ensure that the insulation boards are fully protected.

Once the screed has dried completely you can consider what top layer of flooring you would like on your new floor.

Beam and block flooring insulation summary

The main objective of installing insulation under your floor as part of the block floor construction is to stop heat from escaping from your home during the winter by keeping it at a constant temperature. 

During the warm summer months, it prevents your home from overheating, and additionally, your house will be shielded from the airflow that circulates beneath it by a barrier of thermal insulation, keeping it comfortable throughout the year.

Installing insulation under your flooring for improved thermal performance essentially means that you are lowering your energy use, reducing your carbon footprint.

Your home will be significantly more eco-friendly than before because there will be less heat escaping from your property and therefore less demand for fossil fuel burning heating sources. This is especially important considering how energy prices have reached unprecedented levels in recent years. 

With wasted energy accounting for nearly 30% of a household’s heating bills. Limiting heat loss and improving thermal performance will help you keep your energy bills affordable and reduce your carbon footprint. That is why insulation should be a key consideration where a beam and block floor is being used.

On This Page
Get Your Insulation Quote