Lignacrete – A high density, robust, loadbearing block, suitable for internal and external walls, above and below ground. For total design flexibility select from a range of sizes, strengths and finishes.


Available throughout the east, south east, london & BEYOND

Visit our merchant locator to the left for our current list of merchants. We have the ability to deliver nationally, please contact our sales team for further details.


A range of high density, robust, loadbearing units, suitable for internal and external walls. For total design flexibility select from a range of sizes, strengths and finishes.

General Properties – Table 1

Face Size 440mm x 215mm(1)
Dimensional Tolerances Category: D1
Mean Unit Strength (2) 7.3, 10.4, 17.5, 22.5, 30N/mm2
Net Dry Density Blocks <20.0N/mm2: 2000 kg/m3   Blocks >20.0N/mm2: 2100 kg/m3
Thermal Conductivity 1.33 W/mK at 3% moisture content (internal use)
1.43 W/mK at 5% moisture content (external use)
Moisture Movement <0.6mm/m
Reaction to Fire Class A1
Air Tightness
Configuration Solid Blocks: Group 1,  Cellular & Hollow Blocks: Group 2
Specific Heat Capacity 1000 J/kg/K
Water Vapour Diffusion Coefficient µ =  5/15 (Tabulated value from BS EN 1745)


(1) Some products have an alternative face size as described in this Data Sheet

(2) Cellular and hollow blocks are produced in 7.3 and 10.4N/mm2 strengths

(3) Blocks finished using an emulsion paint

  • High strength blocks from 7.3 to 30N/mm2
  • Standard and Paint Grade finishes
  • For use internally and externally above and below ground
  • High levels of air tightness, sound insulation and fire resistance.

Lignacrete dense blocks are suitable for a wide range of applications. They have excellent levels of sound insulation and high strength capability, making them especially suitable for use in separating and partition walls. They can also be used as infill blocks in beam and block flooring systems.

Lignacrete dense blocks generally have a face size of 440mm x 215mm. Certain products are produced in an alternative size. For example, Midi blocks are solid 140mm units with a face size of 290mm x 215mm and have been developed for ease of handling whilst providing all the performance associated with conventional size solid blocks.


The design of walls incorporating Lignacrete blocks should be in accordance with relevant design standards including BS 8103: Part 2, BS EN 1996-1-1 and the requirements of the Building Regulations.

Surface Finish Recommendations

Drylining – Application to be as manufacturer’s recommendations.

Dense Plaster – Apply either 1:1:6 cement:lime:sand or 1:4 ½ Masonry cement:sand or 1:5 ½ cement; sand and plasticiser. Alternatively: Thistle Bonding or Thistle Hardwall or Knauf Ultimate backing plaster.

Finishing Coats – Thistle plaster finish or Thistle multi-finish or Knauf Multi cover.

External Rendering – Rendering to be in accordance with BS EN 13914-1. Avoid over strong mixes. Ensure the first coat of render is applied to a greater thickness than successive coats. An initial spatterdash coat is advisable, consisting of 1 part cement, 1 part sand, gauged with a proprietary bonding agent (SBR).

Builders considering the use of proprietary render systems must exercise caution to accurately adhere to the render manufacturers’ design and specification instructions. Detailed guidance is also published in the NHBC Standards, Chapter 6.11- Render.

Strictly adhere to the specific application instructions, paying particular attention to prevailing weather conditions and the minimum recommended thickness of single coat renders.


Lignacrete blocks are medium grey to buff in colour with a texture, depending on grade suitable for plastering, rendering, directly painted or fair face.

Blocks are available in cellular, hollow or solid form.


Lignacrete blocks are BSI Kitemarked approved to BS EN 771-3. They are Category 1 masonry units manufactured under a BSI certified Quality System complying with BS EN 9001.


The mortar type for work above ground level should be designation (iii) / Compressive Class M4. Stronger mixes may be used only with the permission of the designer. Stronger mixes may also be required for work below ground in accordance with PD 6697.

Movement Control

Movement joints should be considered in accordance with PD 6697 at approximately 6.0 metre spacings. In areas of concentrated stress, such as those above and below openings, consideration should be given to the use of bed joint masonry reinforcement.


Lignacrete can be considered for use in the following locations:

  • The inner and outer leaves of external cavity walls,
  • Internal walls including fire break walls
  • Separating walls including those conforming to Robust Detail specifications
  • High strength, loadbearing walls – blocks up to 30N/mm2 available
  • External and internal walls below ground
  • Infill units to beam and block flooring
  • Hollow blocks to construct reinforced retaining walls

Unit and Laid Weights

Unit and laid weights (including mortar) are shown in Table 2. All weights are approximate and subject to normal variations in raw materials.

Block Weights – Table 2



Form Unit Weight (kg) Laid Weight


75 Solid 14.4 149
100 Solid 18.9 198
140 Solid 26.5 278
140 Solid Midi 17.5 279
140 C/H 20.0 214
190 Solid 35.9 377
190 Hollow 25.0 269
215 Solid 40.7 427
215 Hollow 27.5 297
Note: For blocks above 20N/mm2, the unit and laid weights will be

approximately 5% greater than those indicated. Weights are based on 3% moisture content by weight.

Fire Resistance

The fire resistance periods of Lignacrete loadbearing and nonloadbearing walls are shown in Tables 5a and 5b.

This data is only valid for walls complying with BS EN 1996 Part 1-1, Part 2 and Part 3. For walls designed in accordance with BS 5628, fire resistance values can be confirmed with our Technical Department.

Fire resistance of Lignacrete solid blocks  – Table 5a

Solid blocks (Group 1 units) –

no finish

Non-loadbearing wall

(criteria E1)

Loadbearing wall

(criteria RE1)

a 1.0 a 0.6
75mm 1 hour 1 hour
100mm 3 hours 2 hours 3 hours
140mm 4 hours 3 hours 4 hours

Fire resistance of Lignacrete cellular and hollow blocks – Table 5b

Cellular and

hollow blocks (Group 2 units) –

no finish

Non-loadbearing wall

(criteria E1)

Loadbearing wall

(criteria RE1)

a 1.0 a 0.6
100mm 1 hour 1 hour 1.5 hours
140mm 3 hours 3 hours 3 hours


  1. These Tables are only valid for walls complying with BS EN 1996 Part 1-1,

Part 2 and Part 3. For walls designed in accordance with BS 5628, fire

resistance values from that Standard are available on request.

  1. Criteria E1 refers to walls with a separating function. Criteria RE1 refers to walls with a separating and loadbearing function.
  1. This Table is derived on data from the National Annex to BS EN 1996-1-2. References to a ≤ 1.0 and a ≤ 0.6 refer to the proportion of load on a wall.

If unknown, we suggest the values for a ≤ 1.0 are used as these are ‘worst case’ values.

Thermal Bridging

A significant factor in thermal assessments is the heat loss through thermal bridges (known as non–repeating or linear thermal bridges).

These occur at junctions between elements or where the continuity of the external fabric insulation is interrupted (e.g. at junctions with external walls, floors and roof). Assessors will need to apply a PSI (y) value to the particular junction being measured.

The Concrete Block Association (CBA) have developed a comprehensive set of junctions that have been independently assessed. The results clearly demonstrate that constructions using Lignacrete aggregate blocks can be assigned improved performance when compared to the Government’s Accredited Construction Details and Default values shown in Appendix K of SAP 2012.

As a member of the CBA, Lignacite Ltd is able to advocate the use of these enhanced bridging details. This information will be of interest to designers and SAP assessors as well as builders who will have the responsibility for correctly constructing the various junctions.

Junction details and PSI (y) values can be accessed at


Responsible sourcing – Lignacite Ltd operates its manufacturing plants to a BSI certified Environmental Management System (EMS) complying with ISO14001. Lignacite Ltd. complies with the requirements of BES 6001 – Framework Standard for the Responsible Sourcing of Construction Products, Certificate No: BES 580823. This independently confirmed Responsible Sourcing Certification provides re-assurance to our customers that they are procuring products responsibly and sustainably. Credits can also be gained under environment assessment schemes such as BREEAM and the Code for Sustainable Homes.

Environmental ratings – Summary green guide ratings applicable to Lignacite blocks can be obtained from the BRE Green Guide to Specification.

Thermal Resistance

The thermal resistance values (m2K/W) for Lignacrete are shown in Table 3. The values are derived by dividing the block thickness by its thermal conductivity (W/mK).

Thermal Resistances  – Table 3

Thermal Resistance (m2 K/W)


Form 3%




100 Solid 0.075 0.070
140 Solid 0.105 0.098
140 Solid Midi 0.105 0.098
140 C/H 0.162 0.155
190 Solid 0.143 0.133
190 Hollow 0.195 0.187
215 Solid 0.162 0.150
215 Hollow 0.207 0.199
Note: 3% moisture content (m/c) should be used for protected locations such as the inner leaf, and 5% for exposed locations such as the outer leaf when rendered.

Thermal insulation

Lignacrete blocks can be used to satisfy the requirements of Part L of the Building Regulations.

Presented are the U-values for a range of wall constructions based on 100mm Lignacrete blocks in conjunction with full and partial cavity insulation. The outer leaf is facing brick, but a rendered block outer leaf will usually achieve at least the same U-value.

For constructions not shown please contact our Technical Department (tel 01842 810678) who will be pleased to provide confirmation of performance.

Full Cavity Fill and
100mm Lignacrete blocks

U-values (W/m 2 K)


Cavity fill type

12.5mm plasterboard    on dabs 13mm lightweight plaster
Internal finish
100mm DriTherm Cavity Slab 32 Ultimate 0.27 0.28
100mm DriTherm Cavity Slab 34 Super 0.29 0.30
100mm Isover CWS 32 0.27 0.28
100mm Isover CWS 36 0.30 0.31
100mm Xtratherm Cavity Therm 0.19 0.20
100mm Kingspan Kooltherm K106 0.18 0.18
125mm DriTherm Cavity Slab 32 Ultimate 0.22 0.23
125mm DriTherm Cavity Slab 34 Super 0.24 0.24
125mm Isover CWS 32 0.22 0.23
125mm Isover CWS 36 0.25 0.26
125mm Xtratherm Cavity Therm 0.16 0.16

Partial Cavity Fill and 100mm Lignacrete blocks

U-values (W/m K2)


Cavity fill type

12.5mm plasterboard    on dabs 13mm lightweight plaster
Internal finish
50mm Celotex CW4000 0.29 0.30
50mm Kingspan Kooltherm K108 0.25 0.26
60mm Celotex CW4000 0.25 0.26
60mm Kingspan Kooltherm K108 0.22 0.23
75mm Celotex CW4000 0.22 0.22
75mm Kingspan Kooltherm K108 0.19 0.19

 Notes to tables:

  1. The U-values shown are based on the use of various proprietary insulation products. Alternative products can be used, provided they can achieve an equivalent thermal resistance (m2K/W).
  2. Wall ties are assumed to be stainless steel with a cross-sectional area of no more than 12.5mm for structural cavities up to 125mm wide.
  3. The suitability of full fill cavity insulation materials will depend on exposure conditions and should be confirmed by the designer. For partial cavity fill, a 50mm residual should be maintained. In some cases it may be possible to reduce the cavity width to a minimum of 25mm. The insulation manufacturer should be consulted for guidance.

Sound Insulation

Lignacrete blockwork provides excellent levels of sound insulation between buildings and adjoining rooms. It can be used in cavity and solid party wall constructions in dwellings, satisfying the specifications for dense blockwork in accordance with Approved Document E to the Building Regulations. It can also be used to construct party walls meeting Robust Detail specifications eg. Robust Details E-WM-1, 3, 16, 18 and 19.

The Weighted Sound Reduction Index (Rw) values of various Lignacrete wall constructions are shown in Tables 5(a) and 5(b).

Table 4(a) presents sound values for Lignacrete blockwork with conventional finishes. Table 4(b) presents values for Lignacrete blockwork with acoustic linings to one side of the wall. These constructions will be of interest where higher levels of sound insulation are required without increasing the block wall thickness and are based on the use of 140mm Lignacrete Midi blocks in conjunction with a standard specification acoustic panel.

Sound Reduction – Lignacrete wall with conventional finishes – Table 4a

Weighted Sound ReductionIndex Rw (dB)



Block Type L/tweight Plaster Dry






75 Solid 48 46 41 40
100 Solid 51 49 44 43
140 Solid 55 53 53 52
140 Solid Midi 55 53 53 52
140 Cellular/Hollow 52 50 48 47
190 Solid 57 56 56 55
190 Hollow 55 55 53 52
215 Solid 58 57 58 57
200-215 Collar Jointed Wall


leaves (1)

56 55 53-55 52-54
215 Hollow 55 54 53 53
(1)  2 leaves of 100mm solid blocks laid back to back and tied together.


1. The above values are based on technical assessments and tests to

     BS EN ISO 140-3.

2. Surface finishes are assumed to be applied to both wall faces.

Sound Reduction – Lignacrete wall with acoustic linings – Table 4b

Block Type Acoustic Lining Specification Weighted Sound Reduction Index Rw (dB)
140mm Lignacrete Midi – Lining to one face 12.5mm Soundbloc or similar plasterboard on 50mm steel C stud located 20mm from the wall face, 50mm acoustic quilt between studs. All exposed edges fully sealed. 65
 Note: The Isowave system is supplied by Isomass Ltd.

140mm Lignacrete solid blockwork with acoustic lining to one side.

Sound insulation = 65 Rw, dB