Floor Insulation: Insulating suspended beam and block floors

Slip block

Beam and block floor

Randon barrier / DPM on levelling screed

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Mannok Therm Floor/MF PIR insulation boards / EPS insulation boards

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Screed with u / f heating pipes on separate layer

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Timber flooring on polyethylene slip sheet

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Beam and block floor construction is suitable for domestic use and many commercial applications. The main benefits are the speed of construction and the fact that this method can be used where site conditions preclude a ground-bearing construction.

Concrete suspended floors are formed using precast concrete beams laid in rows suspended on the inner leaf of the main walls. The gaps between the beams are then infilled with blocks. The void beneath the deck should be vented to prevent problems with damp.

How to install insulation in a suspended beam and block floor

1. Ensure the top surface of the beam and block structure is levelled with grout or a levelling topping.

2. If a radon barrier is required, lay this over the grouting layer and extend it across the wall cavity to the outer leaf.

3. Lay the Mannok Therm Floor / MF PIR boards or Mannok’s EPS insulation boards on top of the structural deck or radon barrier. The insulation boards should be tightly butted together and laid in a continuous layer to cover the entire floor. Where required, cut the insulation boards neatly around service penetrations to minimise heat loss through cold bridging.

4. Overlay the insulation boards with a polyethylene sheet to isolate the insulation from the floor screed. This will prevent moisture from the screed penetrating board junctions and causing movement.

5. Where heating pipes are to be embedded in the screed a proprietary clip system should be used to keep flexible piping in place until the screed has been laid.

6. Finish with the floor screed, ensuring that the insulation boards are fully protected from damage in the process.

Recommended suspended beam and block floor insulation products

Required insulation thickness of Mannok Therm Floor / MF:

Perimeter / Area ratio
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Thickness (mm) U-value (W/m2K)
50 0.16 0.21 0.24 – – – – – – –
60 0.15 0.19 0.22 0.23 0.24 0.25 0.25 – – –
70 0.14 0.18 0.20 0.21 0.22 0.22 0.23 0.23 0.23 0.24
75 0.14 0.17 0.19 0.20 0.21 0.21 0.21 0.22 0.22 0.22
80 0.13 0.17 0.18 0.19 0.20 0.20 0.21 0.21 0.22 0.21
90 0.12 0.15 0.17 0.18 0.18 0.19 0.19 0.19 0.19 0.19
100 0.12 0.14 0.16 0.16 0.17 0.17 0.17 0.18 0.18 0.18
110 0.11 0.13 0.14 0.15 0.15 0.16 0.16 0.16 0.16 0.16
120 0.11 0.13 0.14 0.14 0.14 0.15 0.15 0.15 0.15 0.15
125 0.10 0.12 0.13 0.14 0.14 0.14 0.14 0.15 0.15 0.15
140 0.10 0.11 0.12 0.13 0.13 0.13 0.13 0.13 0.13 0.13
150 0.09 0.11 0.11 0.12 0.12 0.12 0.12 0.13 0.13 0.13

U-value results above based upon floor construction shown:

Suspended concrete beams infilled with concrete blocks; radon barrier /DPM; Mannok Therm Floor / MF; 60mm sand/cement screed with U/F heating pipes; timber flooring (floor finish omitted). Calculations performed to BS EN ISO 6946 and BS EN ISO 13370, taking account of repeating thermal bridges.

Required insulation thickness of EPS Pearl:

Perimeter / Area ratio

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Thickness (mm)
75 0.15 0.20 0.22 0.24 0.25 0.26 0.27 0.27 0.27 0.28
80 0.15 0.19 0.22 0.23 0.24 0.25 0.25 0.26 0.26 0.27
90 0.14 0.18 0.20 0.22 0.22 0.23 0.24 0.24 0.24 0.24
100 0.13 0.17 0.20 0.20 0.21 0.21 0.22 0.22 0.22 0.23
110 0.13 0.16 0.18 0.19 0.20 0.20 0.20 0.21 0.21 0.21
120 0.12 0.15 0.17 0.18 0.19 0.19 0.19 0.19 0.20 0.20
125 0.12 0.15 0.16 0.17 0.18 0.18 0.19 0.19 0.19 0.19
130 0.12 0.15 0.16 0.17 0.17 0.18 0.18 0.18 0.18 0.19
140 0.11 0.14 0.15 0.16 0.16 0.17 0.17 0.17 0.17 0.18
150 0.11 0.13 0.15 0.15 0.16 0.16 0.16 0.16 0.16 0.17
160 0.11 0.13 0.14 0.14 0.15 0.15 0.15 0.16 0.16 0.16
170 0.10 0.12 0.13 0.14 0.14 0.14 0.15 0.15 0.15 0.15
175 0.10 0.12 0.13 0.14 0.14 0.14 0.14 0.14 0.15 0.15
180 0.10 0.12 0.13 0.13 0.14 0.14 0.14 0.14 0.14 0.14
190 0.10 0.11 0.12 0.13 0.13 0.13 0.13 0.13 0.14 0.14
200 0.09 0.11 0.12 0.12 0.12 0.13 0.13 0.13 0.13 0.13

Need technical support?

For help and advice on any of our products and how they might fit your needs please contact our Technical by Mannok team.

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  • Flat Roof Insulation
  • Wall Insulation
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