BROKEN BOND

 Bricks are modular.  Bricks are subject to natural variations in size.

Some designers work to brick sizes, using rules like “15 brick lengths plus one joint” or 7 brick lengths minus one joint.”  That can be a topic for another time.  Sometimes there are other factors at play, and designers will just round off their dimensions, or choose lengths that deliver their target areas. 

Modular sizing is especially relevant to facework.  Where the wall is to be plastered, and/or the bricks are highly irregular in size, the modular approach is less relevant.

 

Bricklayers achieve irregular lengths by introducing “Broken Bond.”  This involves cut bricks, and/or header bricks in stretcher courses, to achieve the desired length.  On long walls it may be possible to simply tighten up the mortar joints, or perhaps widen them slightly.  But variable joint sizes should be used sparingly and within strict limits.  They can look very unsightly and lead to weakness.

I am using the BIM authoring platform “Revit” to represent brickwork bonding patterns.  My aim is to represent the full variety of possibilities, available to bricklayers. I think that the explanatory power and collaborative potential of the “BIM pencil” can help to open up this world to a wider audience.

I have stopped ends and corners, running-in and racking-back, four different bonds, various wall thicknesses.  So what about broken bond?  We need vertical stacks of cut bricks, placed in the middle of a run of walling.

Let’s start with English Bond. 

 

 

 

Where a full brick will not fit, we can use a cut.. There are three cases to model: three-quarter bat, half-bat or quarter-bat.  English Bond comprises alternating courses of headers and stretchers with quarter lap.  Inserting a quarter bat or Queen closer in the middle of the wall would destroy the quarter lap and create straight joints. So we use a half plus a three-quarter instead of one plus a quarter.

The other two cases are more straightforward.  The column of 3/4 bats is plain to see when I colour it green, but in real life it’s much harder for the uninitiated to spot.  A header, placed in the middle of a stretcher course stands out more obviously, but as long as the broken bond is maintained as a vertical column the effect is quite regular and pleasing to the eye.

The cardinal sin for a trained bricklayer, is to let the broken bond wander around from course to course.  Our eyes much more easily catch this irregularity.  

 

I should mention that I am creating these patterns from memory and by reference to basic principles.  There may be alternative versions in some cases and I am interested to receive comments from anyone with a different view. 

My own approach to bonding has always been to absorb the principles and to tackle problems afresh when I come across them.  Memorising rote solutions has never held much appeal.  I’m much good at doing things that way, and as I get older my memory weakens but problem-solving still holds my interest.

I should mention that Broken Bond can sometimes by pushed to the end of a wall.  This could be in a short panel between openings for example.  In the example below, the alternate version of a stopped end is used on the left.  This is a simpler solution than introducing broken bond in the middle of the panel.  In the case of a panel between windows, the solution chosen will usually be dictated by following the bond below. This will normally mean placing any broken bond next to the window frame, as shown here.

 

 

So far I have been using elevation views, which might as well have been drawn using a 2d CAD application, but of course Revit gives us other capabilities, including axonometric views and rules-based view filters.  These allow the same objects to be coloured differently in different views.

In the final image I have used more subtle colours in the hope of allowing the underlying logic of English Garden Wall bond to shine through, while still identifying the cut bricks.  I am colouring the bricks according to their shape rather than picking out the broken bond as a vertical column.

I will close this account with an observation.  I find bonding patterns endlessly fascinating and a great source of challenges to sharpen my intellect.  Bricklaying is a craft that challenges both mind and body.  It has taught me, by experience, that mind and body are two sides of the same coin, and I have never regretted devoting a large portion of my twenties to pursuing that trade.