Lignacrete Midi Block
Lignacrete Midi are 140mm solid units with a face size of 290mm x 215mm. They have been developed for easier handling while providing all the performance associated with conventionally sized solid dense blocks.
There are options to specify Standard or Paint Grade finishes, and with unit weights of less than 20kg (the recommended maximum weight for manual handling), Midi blocks are the perfect choice for all commercial and industrial projects.Datasheet
Range of Strengths
With strengths ranging from 7.3 to 30N/mm2, these blocks will cater for demanding loadbearing applications as well as standard ones.
Lignacrete Midi blocks are frost-resistant, which means they are suitable for use above and below ground.
Ease of Handling
Midi block weights are well below the recommended limit of 20kg for single-person repetitive manual handling.
A1 Fire Rated
These non-combustible blocks make no contribution to fire, earning them a Class A1 rating.
Excellent Sound Insulation
The high mass of 140mm Midi blockwork results in outstanding acoustic performance with sound insulation in excess of 50dB (Rw).
Specification & Application
Lignacrete Midi blocks are BSI Kitemarked and approved to BS EN 771-3. They are Category 1 masonry units manufactured under a BSI-certified Quality Management System, which complies with BS EN 9001.
Standard blocks are medium grey to buff in colour. They can be finished with all recognised treatments, including plastering, drylining and rendering, as well as cladding. Paint Grade blocks should be specified for walls where a consistent close-textured face is required for direct painting.
Lignacrete Midi blocks can be used for all general-purpose walling applications above and below ground. Paint Grade blocks should be specified for walls that are to receive direct decoration.
- The inner leaves of external cavity walls
- Internal walls, including fire break walls
- Separating walls
- Below ground
|Face Size||290mm x 215mm|
|Mean Unit Strength||7.3. 10.4, 17.5, 22.5, 30N/mm²|
|Configuration||Group 1, solid blocks|
|Dimensional Tolerances||Category D1|
|Net Dry Density||Blocks 7.3-17.5/mm²: 2100 kg/m³.Blocks 22.5-30/mm² : 2100 kg/m³.|
|Thermal Conductivity||Typical 1.33 W/mK at 3% moisture content (internal use).1.43 W/mK at 5% moisture content (external use).|
|Reaction to Fire||Class A1|
Weights & Pack Sizes
All weights are approximate and subject to normal variations in raw materials.
Table 1 – Block Weights and Pack Sizes
|Size mm nominal|
(L x W x H)
|Laid weight inc. mortar|
|No. of blocks per pack|
|No. of blocks per pack|
|440 x 290 x 215||17.5||279||48||48|
(1) The weight of Midi blocks with a compressive strength >17.5N/mm² will be approximately 5% greater than those shown.
Lignacrete Midi blockwork can provide excellent levels of sound insulation between buildings and adjoining rooms. The Weighted Sound Reduction Index (Rw) for walls with various surface finishes is shown in Table 2.
Table 2 – Sound Reduction Values
Weighted Sound Reduction Index: Rw, (dB):
|No finish||Paint finish||Plaster finish|
(1) Sound insulation values are based on technical assessments and tests to BS EN ISO 140-3.
(2) Paint finish is based on emulsion paint applied to both wall faces.
(3) The sound reduction of unfinished and painted blockwork is based on tests using Paint Grade blocks.
Lignacrete Midi blocks are rated as Class A1, in accordance with BS EN 13501-1:2007+A1:2009. A1 materials are completely non-combustible and make no contribution to fire.
The fire resistance periods of Lignacrete Midi loadbearing and non-loadbearing walls are shown in Table 3. The data is derived from the National Annex of BS EN 1996-1-2. The fire resistance of loadbearing walls is influenced by the proportion of the load on a wall and annotated in the National Annex as a ≤1.0 or a ≤ 0.6. The fire values presented are based on the worst loading case (≤1.0) and can therefore be safely used for all loading conditions.
The thicknesses shown are for masonry alone and exclude finishes. For the fire resistance of walls with finishes, refer to the Lignacite Design Guide – Fire Resistance.
Table 3 – Fire Resistance
(Group 1 units) No finish
|140mm Midi||4 hours||3 hours|
The thermal resistance values (m² K/W) for Lignacrete Midi blocks are shown in Table 4. The values are applicable to Standard as well as Paint Grade products.
Table 4 – Thermal Resistance Values
(m² K/W): 3% m/c
(m² K/W): 5% m/c
(1) 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.
Block Environmental Management and Responsible Sourcing
Our manufacturing plants operate to a BSI-certified Environmental Management System (EMS), which complies with ISO 14001.
Lignacite Ltd also meets the requirements of BES 6001 – Framework Standard for the Responsible Sourcing of Construction Products (Certificate No: BES 580823). This independently awarded Responsible Sourcing Certification confirms that our products have been made with constituent materials that have been responsibly sourced. This extends to organisational governance, supply chain management and environmental and social aspects, all of which must be addressed in order to ensure the responsible sourcing of construction products. Certification to BES 6001 allows credits to be gained under environmental assessment schemes such as BREEAM.
Block Energy Management
A BSI-certified energy management system compliant with ISO 50001(Certificate No. ENMS 751020) is used to help manage energy use.
Compliance with ISO 50001 is a valuable tool in helping to manage energy use. To meet its requirements, we must:
- Have a policy for more efficient energy use
- Fix targets and objectives to meet the policy
- Use data to better understand and make decisions about energy use
- Measure the results
- Review how well the policy works
- Continually improve energy management
Block Structural Design
The design of walls incorporating Lignacrete Midi 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.
Block Movement Control
Vertical movement joints should be considered in accordance with masonry design codes and the recommendations of Published Document PD 6697, at 6.0 – 8.0 metre spacings. In areas of increased stress, such as above and below openings in external walls, the blockwork may need to be reinforced to restrain movement.
Block Service Life
When properly constructed, the durability of walls built using Lignacrete products will match that of traditional masonry. This means that they will fulfil their intended function for the life of the building in which they have been installed (typically 100 years).
The blocks themselves will require no maintenance. Maintenance for walls will normally include actions such as the replacement of sealant in movement joints and at junctions/openings. Repointing for walls that are exposed to the elements may be necessary towards the end of their service life.
Block Wall Ties
Under normal conditions, wall ties should be embedded 50mm into the mortar on each leaf, staggered in alternate courses and spaced in accordance with the following.
Table 5 – Wall Tie Spacings
|Ties per m²|
|Less than 90mm||50 - 75||450||450||4.9|
|Over 90mm||50 - 150||900||450||2.5|
For unreinforced blockwork, the mortar type for work above ground level should be designation (iii) / Compressive Class M4. Stronger mixes may be required for work below ground.
Table 6 – Mortar Mixes
(as per BS 5628-3)
|Compressive Strength Class|
(as per BS EN 1996)
|Recommended mix proportions of materials by volume|
|(iii)||M4||1:1:5 to 6 - Cement:Lime:Sand.|
1:5 to 6 - Cement:Sand with or without air entrainment.
1:4 to 5 - Masonry Cement:Sand (with non-lime filler).
1:3½:4 - Masonry Cement:Sand (with lime filler).
|(ii)||M6||1:½:4-4½ - Cement:Lime:Sand.|
1:3 to 4 - Cement:Sand with or without air entrainment.
1:2½:3½ - Masonry Cement:Sand (with non-lime filler).
1:3 - Masonry Cement:Sand (with lime filler).
Block Surface Finish Recommendations
A mist coat followed by at least two coats of emulsion will provide a good finish. The actual coverage will depend on the quality of the paint and how it is applied (e.g., brush, roller or by spray). Always ensure that each coat of paint has fully dried before any further layers are added.
Standard plasterboard can be fixed using adhesive dabs or attached onto timber battens or metal studs.
Dense plasters can be applied using either 1:1:6 cement:lime:sand or 1:4 ½ masonry cement:sand or 1:5 ½ cement:sand and plasticiser. It is advisable to use a bonding treatment before applying cement render plasters. Lightweight plasters should be used in accordance with the manufacturer’s recommendations. Suitable plasters include British Gypsum’s Thistle Carlite Bonding coat. Finishing coats include British Gypsum’s Thistle Multi-Finish.
Lignacrete blocks have low to moderate suction.
Before rendering, all dirt and debris must be removed from the surface. It is advisable to use a bonding treatment, such as Rendaid, before applying the rendering. Traditional renders should be applied in 2 coats, with the first coat applied to a greater thickness than the top coat (the first coat should be 8-12mm thick and the top coat 6-8mm). Render designation iii/M4 should be used, as shown in Table 7.
It is important that blocks are protected from the weather before and during rendering.
Table 7 – Render Mixes
|Cement: Lime: Sand|
(with or without air entrainment)
(with or without air entrainment)
|Masonry Cement: Sand|
(with non-lime filler)
|Masonry Cement: Sand|
(with lime filler)
|1 : 1 : 5 or 6||1 : 5 or 6||1 : 4 or 5||1 : 3½ to 4|
Site Practice continued...
Block Safe Handling
- Block packs may be stacked on firm and level surfaces to a maximum height of 2 packs. Consideration of handling equipment's suitability for site terrain and safety limits should also be given. Hand-operated pallet trucks may not be suitable unless pallets specific for this purpose are used and loads do not exceed the limits of the pallet truck or its operator(s). Care should be taken when opening packs that are wrapped or banded to ensure that items do not fall or otherwise endanger persons handling the blocks or those nearby.
- Handling of blocks should be undertaken in accordance with HSE Construction Sheet No. CIS77 ‘Preventing injury from handling heavy blocks’ (Construction Industry Advisory Committee) and in accordance with the Manual Handling Regulations 1992 (as amended). This concludes that there is a high risk of injury to individuals who repetitively manually handle blocks in excess of 20 kg. Where practical, mechanical handling equipment should be used to transport block packs to the area of work.
- Blocks should not be installed if the temperature is at or below 3°C and falling.
- Blocks should always be laid on a full bed of mortar and vertical joints solidly filled.
- For walls built fair-faced, sample panels are recommended. These should be built prior to commencing block laying and serve as a benchmark for defining and specifying the quality of work required. Please note that for Paint Grade products, colour consistency is not guaranteed. It is advisable to view sample panels at a distance of about 3m from the wall in good natural light.
- For reinforced walls, the concrete infill strength and reinforcement should be specified by the project engineer.
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