Upright bar spacings for patio railings.

The space or gap between upright bars on a patio railing is an important part of the design. For patio railings it needs to be less than 100mm gap between bars to comply with building regulations. Patio railings usually have to fit a gap. This usually means multiple railings of the same size to cover a distance. You can’t have a patio railing at 6mtrs long at least not in one piece. You would make either 4 railings at 1.5mtrs long or 3 panels at 2mtrs long. How you set the gaps between the upright bars defines how it looks.

Set spacing

Using a set space method of 99mm apart, is by far the quickest method. It allows a spacing tool to be made, this dramatically speeds up construction. The tool holds all the bars in correct place so they are ready to weld. The issue here will be that at the ends of the railing the gap is likely to be smaller than 99mm. There may also not be a centre bar in the railing, which can be an issue when trying to add a centre piece design.

Variable spacing

Here you are not fixing the gap but working to a maximum gap of 99mm. This just means for each size of panel, you do a bit of maths and work out your gap size. It has the advantage of being able to squeeze in an extra bar if needed. Allowing for a centre bar if required.

The maths

The maths for working out a gap is simple enough, its works for almost anything that requires an even gapping. You need to know your maximum gap required and you need to know the thickness of your spindles. For patio railings its usually 12mm or 16mm. But if you were working in wood it would obviously be thicker.

If you maximum gap is 99mm apart you need to add the thickness of your spindles. So for 12mm bar it is 111mm. The reason for this is that we are working to a centre point. Its usual to mark up any bar with the centre line of any bar to be welded. Next you obviously need the length of your panel. As an example i will say 1565mm seems as good a length as any.

Now you have to take you 1565mm and add 12mm to it (using 12mm spindles or add what ever thickness your spindles are), this is because as said you are marking the centre line of where the bar should be placed. So we are marking the point of an imaginary start and end bar, that would touch the edge of the railing, allowing our first bar to be a maximum 99mm away from that point.

So 1565mm + 12mm is 1577mm. Taking that 1577mm and divide it down by 111mm we get a result of 14.2. We were looking for a whole number, certainly not one with a fraction. So we have to round that number up to 15. Back to our 1577mm and divide by 15. This gets us a result of just over 105mm. The centre point for each bar is 105mm apart, taking away our bar thickness we know that the gap or space between our upright is 93mm. That’s less than our 99mm so an acceptable result.

Well it might not be acceptable if we want a centre bar. We divided by 15, which means 15 gaps therefore 14 bars. When you need the centre point of something you divide by 2. Creating 2 gaps and 1 centre point. So we should be been dividing it by an even number. So if we try 16 instead we get 98.6mm for our bar centres or a gap between bars of 86.6mm. A closer gap than we would have ideally liked but it does contain a centre bar which we need for our design.

This can end up very frustrating when on multiple panels because if the panel next to it was 1542mm or less we could have achieved a centre bar with 14 gaps of 99mm. Assuming the two panels are next to each other. Its going to notice, the difference in the bar gaps. Here despite getting a centre bar and a gap of less than 99mm, two extra bars are going to have to be added. This gets the gap between bars closer to the first panel.