If all wall gaps were the same size life would be simple. A jig tool to make the railing to the size. Quite rapidly you would have a railing panel made.. because its quick to make it would be cheap.
Trouble is railing gaps vary in size, height isn’t really an issue. its just cutting the upright bars to a different length. The real problem is the length, and the spacing between the upright bars.. If you have a railing that is 1800mm long then a space of 100mm between bars means you have a nice even gap. From the brick pier to the first bar will be the same gap as between the first and second bar. All gaps are even and the railing looks pleasing to the eye.
If the rail was for example 1750mm then the 100mm gap just doesn’t work. you now have the choice of keeping the bars at 100mm spacing, but now the gap between the brick pier and first bar is going to be 75mm, with the gap between the remaining bars at 100mm. It doesn’t look as pleasing to the eye and now has a cheap look about it.
The alternative is adjust you bar spacing. Trouble is the spacing jig you have to make the railing quicker is now useless. So its down to hand marking up the bars and welding in place. This can slow the manufacture process down by a factor of 3. Where you could have made 3 railing in a time frame, now you will only get 1 made.. This obviously adds quite dramatically to the cost.
Interesting enough he majority of UK Bricks are 215mm long, and a mortar joint of 10mm is recommended by most brick manufacturers.. (Older imperial size bricks are obviously different) So by counting the bricks you can gauge the size of a railing gap.. One brick with a joint each end is going to be 235mm long. Two bricks will be 215mm twice, so 430mm and a 10mm joint at each end and a joint between the 2 bricks. So 450mm long…
8 bricks will be 215mm x 8 plus 9 brick joints at 10mm, or 1810mm. which is close to 6ft but actually 24mm short (1 inch) which now perhaps makes you wonder why so many manufacturers sell 6ft railings.. This forces the brick layer to use a 13mm joint rather than a 10mm joint. to make up the gap of 6ft..
Bricks can obviously be cut to make up a size but its usual for either a whole brick or a half brick (on a 225mm wide wall, double brick, its often turned sideways) So the table below show sizes and bricks starting from 4 bricks
| 4 bricks | 4 and half bricks | 5 bricks | 5 and half bricks | 6 bricks | 6 and half bricks | 7 bricks | 7 and half bricks | 8 bricks | 8 and half bricks | 9 bricks | 9 and half bricks | 10 bricks |
| 910mm | 1023mm | 1135mm | 1248mm | 1360mm | 1473mm | 1585mm | 1698mm | 1810mm | 1923mm | 2035mm | 2150mm | 2260mm |
Obviously these are theoretical sizes as brick layers don’t usually work to a plus or minus 2mm size but its a good guide to work from.and the majority of garden walls end up with a brick joint of 12mm. so will be slightly larger than stated size
interestingly enough if you take a long look at the sizes, and spend time doing a little maths. you could divide 910mm down so that it has 7 vertical bars or 8 gaps. you end up with a centre spacing of the bars around 115mm.. take the 2260mm size and divide down by 20 gaps 19 bars you end up with 113.5mm gap. in fact it gets progressively smaller, the more bricks there are but only by a small amount.
Note, to work out bar spacing the formula is size plus bar thickness used. so if using 12mm bar 910mm plus 12mm or 922mm, this is because you are working from bar centres as your reference point. So you reference point for you first bar would be 6mm inside the brick pier, and you reference for the last bar gap would be 6mm beyond the railing length.
So assuming you took a bar spacing of 115mm with a 12mm upright bar you end up with a gap between bars of 103mm (4 inches), now this is not building regulation compliant but there are no rules for a garden wall railing unless it is acting as a barrier to prevent a fall.. Obviously if 16mm uprights were used the gap would be 99mm which would be building regulation compliant.
You almost have a one size fits all. bar spacing jig tool. where you are going to end up with a minor difference between the first bar and wall and the first and second bar.. This is a few millimetre and unless you have an eye for such detail, the majority of people wont notice. This will give a more quality look,. without the need to individually mark each bar spacing. Thus adding time and cost to the railing construction.