Products > Brick

RIBA Core Curriculum
- Design, construction and technology

Knowledge level
- General Awareness

This CPD looks at situations where problems have arisen from movement in brickwork. The course also covers the basic British Standard requirements for designing as well as how to recognise issues and minimise the risk of damage.

In this section
- Movement joint materials
- Movement joint fillers
- Examples of movement joints
- General principles

            
                    
Navigate through each step of the CPD using the left and right arrows to review the content. At the end of each section are some questions, these are required if you wish to obtain a certificate upon completing the course.                     
                                     
            
    

Continuity of Joint
It is important that where joints are incorporated, there should be a continuity through other materials, particularly with cappings.

Movement in Brickwork
In this example the joint is ineffective – the main brickwork may well be bonded to the lower section (with no visible damp proof course), and the capping is continuous; potentially the capping would require even more joint provision being the least restrained element.

Movement Joint Materials

Compressible filler

PD 6697 : 2010 refers to compressibility of 50%

Looking at the construction of joints, it is important to consider suitable materials for both the backing filler, and the face sealant; the replacement document for the former Code of Practice (BS 5628) refers to materials which should be easily compressible to approx. 50% of the original thickness (and highlights unsuitable materials).

Movement in brickwork
Certain materials are not suitable! ‘Flexcell’ for instance is not compressible enough for movement joints in clay masonry.

Movement Joint Fillers

Not recommended

  • Hemp
  • Fibreboard
  • Cork

Similar materials should not be specified – the backing or joint filler requires a high capacity for compression.

Recommended

  • Flexible Cellular Polyethylene
  • Cellular Polyurethane
  • Foam Rubber

 

Movement in Brickwork
There are two methods of forming a movement joint, but essentially a compressible filler should be installed, either during or post bricklaying, as a backing to, but not bonded to, the face sealant.

Movement in Brickwork

Movement Joint Materials

  • Compressible filler
  • Face sealant (BS 6213)

BS 6213, revised in 2010 provides guidance on the specification of construction sealants; these would generally be silicone or polysulphide based materials.

Movement Joint Materials

It is appropriate to consult manufacturers for further information, although this can be very detailed with consideration of movement accommodation factors (MAF) slump characteristics and sealant geometry (i.e. width of joint to depth ratio).

Movement in Brickwork
Installation of the filler on the left, and the finishing of the joint with a gun applied sealant – note the basic protection by masking tape as good site practice.

Movement in Brickwork
A spatula may also be used to apply the sealant, although consideration should be given to the colour and the effect this may have!

Movement in Brickwork
Sadly, workmanship can sometimes spoil the appearance.

Movement joints can be subtle and effective
Movement joints can be subtle and effective

Examples of movement joints

Movement Joints
A common question is whether vertical joints should stop at DPC level, or continue down below ground.

Movement Joints
Personal preferences are often for joints to be continuous, which is not a difficult detail to achieve, and particularly if ground level varies below damp proof courses.

Movement in Brickwork
Face sealants are available in different colours to provide a complementary joint, particularly where contrasting bricks are specified.

Movement in Brickwork
Clearly cavity walls are the most common form of construction in modern buildings, but the separation of the outer leaf requires suitable wall tie provision to offer lateral restraint and a stable, efficient construction, with additional provision around openings for instance.

Movement in Brickwork
Numerous proprietary ties and fittings have been developed for cavity wall construction, including provision for differential movement between elements, as we see here.

Sliding ties
to allow for movement

Brickwork :
e.g. Ancon PPS

Blockwork :
e.g. Ancon PP21

Vertical Movement in Brickwork
We think most often of movement in a horizontal plane, but consideration is needed – at the design stage – for vertical movement, particularly with taller framed buildings

Movement in Brickwork
Again, wall ties are readily available to deal with differential vertical movement, and indeed where the coursing height of bricks may be different to standard block sizes.

Movement in Brickwork
Vertical movement can be cumulative, and with external brickwork expanding, and the frame potentially contracting, it is often more practical to deal with movement in smaller sections.

Movement in Brickwork
This is a typical detail where a rebated (or pistol) brick is able to accommodate the shelf angle support, avoiding an excessive horizontal joint; brickwork below the angle can expand vertically compressing the filler material.

Timber Framed Buildings

  • Clay Brickwork expansion
  • Timber shrinkage
  • Allowance
    • 3mm to ground floor sill
    • 9mm to first floor sill
    • 6mm per storey height

It is important to recognise the potential differential movement between bricks and timber frames.

Document PD 6697 recommends an allowance of 3mm between ground floor level and sill, 9mm from ground floor up to first floor sill, and 15mm to second floor sill, in other words, 6mm per storey.

Bed Joint Reinforcement
Bed joint reinforcement can be considered in some circumstances to increase the spacing between movement joints (say 18 metres); its primary use is in stack bonded brickwork, to compensate for the lack of natural overlap, by offering more restraint.

Bed Joint Reinforcement
In this particular example, although the overall length of panels was not excessive, bed joint reinforcement was specified because of the stack bonding.

Movement in Brickwork
Each panel however displayed vertical cracking, generally in a central position, and the conclusion reached after investigation was that the ‘standard’ length of reinforcement was approx. 3 metres, and that there was no overlap between pieces, leading to a weakness within the central area of the panel.

Movement in Brickwork

General Principles

  • Normal spacing 10 – 12 metres
  • Return elements
  • Change in Height and Thickness
  • Short Returns
  • Freestanding walls (5 – 6 metres)

General Principles

  • Consider movement joint positions
  • Horizontal and vertical movement
  • Movement joint materials
  • Consider at an early stage in the design process
  • Site practice

In summary, there are several aspects in the provision of movement joints to consider at the design stage.

The general principle of spacing applies to conventional construction (with longer allowance with reinforced masonry).

The plan form of the building and type of walling, should be considered, and, as we have seen, more movement can be anticipated with less restrained conditions.

The positioning of joints is important, but equally so is the specification of materials, and indeed the execution of details on site.

You should not feel constrained in design necessarily simply because movement joints are required.

Movement_64
Jongerencentrum by Casper Schuuring, Monk Architecten

This is a Dutch Architect’s interpretation of brick and mortar in combination.

Movement_65
And they have considered potential movement!

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CPD Q&A

You’ve reached the end of the CPD. To make sure you’ve taken on board the key learnings of this course, please fill out the quick multiple choice Q&A below. This will certify that you have completed the CPD and provide you with an email certificate, which, if the course is accredited, you can share with RIBA.

Question

What year was 'BS 6213 - Selection of construction sealants' last updated?

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Question

Which of these statements an incorrect recommended allowance for timber frames, according to document PD 6697?

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