Movement in Masonry: Movement Joints, Why?

Why You Need Movement Joints in Modern Homes

Historically builders did not always use movement joints in residential buildings. Today things have changed so it’s not worth the gamble.  Modern mortar is less forgiving to movement and there are design changes in wall construction methods, building shape and layout. There is also a greater emphasis on complying with regulations and more rigorous policing of warranty and manufacturer requirements.

It means that you need to include them and you need to understand how many to install, where and how to do it properly.  Our free CPD called “Modern Movement” explains what you need to do, and our second blog in this series will also outline what you need to consider.  Here we address the why you need to install them.

Masonry movement

Quite simply masonry moves, it will expand and contract depending on moisture, temperature and other factors.  If you leave this unaddressed it will have a catastrophic effect on a building’s appearance, function and longevity.

In Victorian times a : sand mortar would for some movement albeit incorporating movement joints would still be better.  Today it is simply not good enough to ignore them for a number of reasons.

First modern durable cement rich mortars are less able to accommodate movement than older ones and will increase the tendency for masonry crack.  But even if you opt for a natural hydraulic lime mortar, that may not be enough on its own to accommodate the movement seen in modern buildings.

The move to higher density housing in recent years means there are more terraced properties and apartment blocks leading to longer continuous runs of brickwork.  While expansion over a small area may be small, it is magnified significantly in buildings with long continuous runs of brickwork; which means the total scale of expansion and contraction is greater and more likely to lead to problems.

This is exacerbated with the inclusion of windows and doors since there will be more movement along long uninterrupted lengths of brickwork, and less movement along a length that has doors or windows between them.  This means that some areas will move more than others and further increase the stresses on the structure.

In addition, different materials have different rates of expansion and contraction which you will need to allow for.

Climate change

Masonry, whether it is clay brick, aerated or aggregate blocks will expand or contract in response to a number of factors including temperature change and moisture.

Typically, you will have a delivery of bricks and other masonry to site and they will be left outside. Our weather today is noticeably wetter with greater extremes of temperature.  This means that bricks and other masonry may get wetter and could potentially dry out faster – so they can expand and contract more over a shorter period of . It is therefore important that you protect masonry when it is in storage and during construction from rain frost and excessive heat.

Over the long-term clay brick will expand and aerated and aggregate block will shrink.  You need to allow for this by using movement joints.

While this is generally accepted practice for commercial and public buildings, they have in the past been forgotten in domestic buildings.  Ultimately a brick or block does not know what type of building it is in and will expand and contract in just the same way.  Getting it wrong by not installing them at all or installing them incorrectly will cost you far more to put it right than making sure that you install them correctly in the first place.

We run a free CPD accredited training session called “Modern Movement”.  Register here to find out more.