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F10 Brick/Block Walling (Checklist) G#1647 N#1561

By 20 September 2014May 29th, 2019Checklist, Code, Encyclopaedia, New Build
GBE Lecture (21) Masonry Ext Walls S1

GBE > Encyclopaedia > Code > Checklist > New Build > F Masonry > G#1647 N#1561

F10 Brick/Block Walling Checklist

F10 Brick/Block Walling Checklist


  • Fired clay brick manufacture consumes high levels of energy
  • Primary or Virgin aggregates used in concrete blockwork
  • Ordinary Portland Cement (OPC) manufacture consumes high levels of energy and generates high levels of Carbon Dioxide (CO2)
  • OPC is used in concrete blockwork
  • Autoclaved Aerated Concrete (AAC) blocks consume high levels or energy, water and CO2 generating OPC
  • No fined concrete blocks make air permeable blockwork walls
  • Extruded cellular fired clay blocks have dry interlocking perpends and make air permeable walls
  • Parge coats need to be continuous with surrounding elements to avoid being air leaky at floors and roofs
  • Buried conduits are potential routes for air leakage since junction boxes are rarely airtight

Bad Habits:

  • Topping and tailing perpend mortar in brickwork and blockwork modifies the performance of the walls: strength and stability, fire, conduction thermal, radiant thermal, acoustic performances, airtightness, moisture permeability; and should be avoided
  • Mixing bricks and blocks in a wall to accommodate unco-ordinated lintels and pad stones and at heads of walls under slabs or between joists supported in walls: modifies the performance (see above) of the wall local to thermal bridging components to enlarge the thermal bridge area; and should be avoided.


  • Extruded clay cellular blocks and bricks use less energy to ‘cook’
  • Primary or Virgin Aggregate replacement with Recycled, Secondary or manufactured Aggregates (in blocks and mortar)
  • Manufacturers are now using many aggregate substitutes: Paper, wood particles, pumice (lightweight), plastics,
  • Lime in preference to OPC in aggregate concrete blocks
  • Blended GGBS and OPC in aggregate concrete blocks
  • Lime mortar in preference to OPC mortar in brickwork or blockwork
  • Ground Granulated Blast Furnace (GGBS) Cement in preference to OPC mortar (If height and speed not an issue)
  • Blended GGBS and OPC mortar in preference to OPC mortar (If height and speed are an issue)
  • Parge coats of clay or lime plaster make air permeable walls airtight and moisture permeable (Vapour open)
  • Parge coats of gypsum plaster or cement render make walls air and moisture tight (Vapour closed)
  • Brick and block offer decrement delay characteristics reducing radiant solar heat gains through external walls
  • Brick and dense block offer useful thermal mass if at wall surfaces to absorb radiant solar gains through windows


  • Stronger is not always best:
    • uses more high energy consuming and high CO2 generating materials than necessary
    • stronger mortar in facing brickwork or blockwork puts the brick or block at risk of frost damage
    • stronger mortar prevents reclaiming of bricks and blocks


  • Lime mortar in preference to OPC mortar. See Z21
  • Blended GGBS and OPC cement mortar in preference to OPC mortar, See Z21
  • Cement made from other than limestone


  • Surface mount conduits or run wiring in surface mounted hollow skirting/dado
  • Perforated and better still extruded cellular bricks and blocks:
  • Less material consumed
  • Less energy to ‘cook’
  • Lightweight to transport and handle
  • Lighter and less wear and tear on labourers
    • Handgrips moulded into block ends
    • Make door openings brick or block multiple widths and heights
    • Co-ordinate window and door opening with brick sizes and blocks modules
    • Co-ordinate lintels and pad-stones to brick sizes or block modules. See F31
    • Start full course of bricks and blocks on floors


  • In the UK we use to make 3 billion clay bricks each year
  • Use unfired clay bricks or blocks for walls, (low energy use in production)


  • Use non-porous blocks to make airtight walls
  • Use blocks with high percentage of recycled, secondary or manufactured aggregate
  • Use double skins to make up thick walls observing UK 20 kg maximum for one man lifting
  • There are cement-concrete block manufacturers that use GGBS and/or PFA cement substitution
  • There are cement-concrete block manufacturers that use secondary aggregates substitution for virgin or primary aggregates: recycled glass, china clay, slate and others
  • Use GGBC cement not OPC for recycled glass aggregate blocks
  • OPC replacement by GGBS or PFA cements
  • Lime based mortar and reclaim of blocks for reuse, which requires tough blocks
  • Plastics as aggregates for limiting crack propagation and improved tension strength
  • Pumice lightweight insulating aggregate blocks (Greek/French product)
  • Thermal Mass is really only useful if at the surface and exploited
  • Thermal mass and fairfaced dense block go together
  • Thermal mass and thermal insulating at the same time would be interesting to have but unlikely bedfellow

Resource efficiency and waste minimisation by manufacture and by design

  • Cut blocks to size to minimise on site cutting
  • Design guidance on block size tables and work around openings and lintels and at abutments to minimise cutting waste


  • Use of cement mortar and cement concrete blockwork: cement production generates high levels of CO2
    • See E10
  • Chasing brickwork and blockwork to run buried conduits, a very dirty job making the building a no-go area whilst in progress
  • Filling conduit chases using cement based render
  • Cutting bricks and blocks: design walls and openings to co-ordinate with unit sizes


  • Use of OPC mortar
  • Cutting of blocks


  • Limecrete blocks (none as far as we know)
  • Hemp-lime blocks (UK/French)
  • Timber-lime blocks (Eastern Europe)
  • Cellular fired clay blocks (EU and UK)
  • Papercrete blocks (UK soon)


  • OPC and lime is alkali and bad for skin and eyes
  • OPC is very fine avoid breathing into lungs
  • Wear protective clothing and gloves


  • Some people like the solidity of brick houses
  • Some people do not like hollow partitions


  • Crushed fletton commons make good aggregates for brown roofs


  • Bricks, blocks and mortar are all heavy

Precautionary principle:

Resource Efficiency Issues:

  • Design For Demountability:
  • Thick blockwork walls used with external insulated render could be laid in lime mortar to encourage the possibility to reuse them at the end of the buildings life
  • Site walls made of solid brickwork could be laid in lime mortar to encourage reuse of bricks



  • Reclaimed Bricks originally laid in lime mortar
  • London Stocks are worth at least a £1.00 each
  • If your site has no use for them Architectural Salvage years will take them


  • Architectural Salvage Gateway: Salvo
  • Remember reclaimed brick may be imperial or metric dimensions
  • Reuse bricks local to the source to avoid transport impacts cancelling the advantage of reuse


  • Cement mortared brick and blockwork, crushed as hardcore or piling mat
  • Fletton common brick rubble as brown roof aggregates
  • Some block manufacturers use 85% recycled aggregates
  • Some recycled aggregate blocks manufacturers will only sell locally to the source of the aggregate


  • Wood particle aggregate would be difficult to burn out of the block when coated by cement

Waste Issues:

  • Cement mortar once gone off is likely to be inert
  • Lime mortar is not inert until completely hydrated which can take a long time if bulky
  • Fired clay bricks are inert
  • Concrete blocks are inert
  • Wood aggregate lime matrix blocks are potentially mixed active and inert

Hazardous waste & Deleterious Substances

  • Lime mortar is potentially hazardous until gone off and then inert, but landfill heat could reactivate its capacity to react with water and rehydrate

Waste statistics

  • 30 m tonnes (33% of 90 m. tonnes/year) of waste is offcuts (not all masonry)
  • In the UK we throw away 2 billion bricks each year and make another 3 billion

Waste minimization

  • Plan layouts, wall lengths and openings to acknowledge the size of bricks and blocks with minimum offcut waste

End of Life options

  • Use lime mortar to enable reclamation of bricks and blocks





Maintenance issue:

  • Bricks and block are both low maintenance materials

Industry/Sector Initiatives:

Information sources:

  • BDA
  • Brick Development Agency (BDA)

© GBE NGS ASWS BrianMurphy
aka BrianSpecMan
2001 – 19th September 2014 – 22nd August 2016

F10 Brick/Block Walling Checklist


Fig. 1 Book BDA Illustrated Guide to Brickwork Design



© GBE NGS ASWS BrianMurphy
aka BrianSpecMan
19th September 2014 – 22nd August 2016

F10 Brick/Block Walling Checklist
See Also:


  • Term
  • Z21
  • Mortar (Z21)


GBE Shop

GBE Checklist


  • F31
  • Z21


  • Accessories (F31)
  • Mortar (Z21)

GBE Links

  • Organisation/Website
  • BDA

GBE Manufacturers

GBE Products

Papercrete Bloc







  • Bat Roost and Bird Box coordination sizes for masonry and timber frame
  • WasteCost® Lite waste calculator





  • Robust Specification Clause
  • Robust Specification Work Section



© GBE NGS ASWS BrianMurphy
aka BrianSpecMan
19th September 2014 – 22nd August 2016

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