Setting out and making a simple Stair

For our first steps (sorry for the pun, couldn't resist) in setting out I will be using a single straight flight stair as an example.

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The overall height

Stair marking out - Open riser flight of stairs

What we are going to be talking about here is the actual marking out of the stair strings.

1. The most important thing to do first is to check the actual measurements on site.  Make sure that if an error has happened in the building process that you find it and use the correct overall rise.
2. The most common mistake is to measure what you have, floor to floor and forget to add for the floor finishes.  That is you have to add to the measured height for say, ceramic tiles that will later be added to the top.
3. For instance, on the left is a flight going up to say a deck.  It is quite possible that you will be measuring for the stairs before the decking timbers are fixed.  Don't forget to allow for them.
4. Another potential problem shown at the right is a sloping floor or ground.  Don't just assume that floor is level.  Check it!  The total height is from the position of the first riser to the position of the last one.  It is not measured directly below the the top landing unless you are sure that the bottom floor is level.
5. Another point on the sketch here, is that if a concrete landing is being poured after the stairs have been fixed, the make it big enough so that it is a definite landing.  The reason for this is that although we keep the landing to the first step the correct rise, rarely is the landing to the ground the same.  It is usually a lot less and it could be a trap if it was little more than another step.

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Find the slope distance.

Stair marking out - The slope distance.

On A previous page we covered the basic of design and we finished up with a step triangle that had a run of 275 and a rise 0f 178.

Here its is again, but this time I have shown the length of the third side of the triangle which is the hypotenuse.  For simplicity I'll call it the slope distance

A reasonable way to get this distance is to draw it out on a piece of board very accurately with a sharp pencil, and then measure it.  I prefer a pocket calculator for speed and accuracy.

Using the calculator we use Pythagoras theorem, so it is:-

Stair marking out - Getting the slope distance with a calculator.

If we want to be super accurate we could put that distance in our calculators memory and use it for the next stage.

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If in doubt draw it out.

Stair marking out - A steel square with two battens screwed on, used for marking out individual steps and top and bottom angles.

Stair marking out - A home made ply pattern made to the stair triangle, with the offset from the edge of the stair string added.

Stair marking out - Using the home made square for marking out closed string.

It is quite easy once you have the correct rise, go and slope distance worked out, to start marking out your strings.  I very rarely do.  I almost always draw part of the stair out full size on a bit of ply, MDF. or something similar.  A couple of saw horses and a sheet of ply.

I am not talking about a big deal here, only three treads or rises, that's all I need.  I pencil in the rise times three on a square end of the sheet, and the go time three on the edge of the sheet and join the points to give me an exact stair angle to set my squares and bevels to.

I mark out the layout at the top, It could be double timber joists, it could be concrete or I might have to fit inside the flanges of a steel beam.   I draw it out, correct, full size, down to the thickness of the floor covering (if any).

I do the bottom the same and gradually draw the lot.  Most times it is very simple, and once it is laid out, it is clear which bits of the strings I have to cut off to fit snug here and there.

I don't physically use this drawing as pattern.  In many cases I don't need to refer too it much at all after doing the sketch.
The actual fact of drawing it out may remind me of something I could otherwise have missed.

Because I have gone to the trouble of drawing it out, when I get to the stage of marking the strings then the details are clear and I can go ahead with confidence.

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Marking the top edges of the strings

Good practise when making any type of joinery or carpentry work is to mark out the pieces in multiples whenever possible for a few reasons.

1. For example if we are making three flights of stairs the same then we would mark out the six strings together.
2. This saves time, measure, check, them mark them all and they will all be right.
3. If you do them separately then errors can appear that may get missed.
4. We mark them on the top edge.
5. If we are working with timber we select the best edge with the bow (if any) up, to be the top.

Stair marking out - Marking the top edges of both strings with the slope distances.

1. Start in from the end enough for the part of the string that goes past the riser and mark a square line across.
2. Stretch out your tape measure the full length and nip it tight.
3. Clamp the tape lightly to the string with the end exactly on your zero line.
4. Run along and put a pencil mark every 328 for 10 spaces.

So why do we do it this way, and more to the point how do we do it?
We do it this way to be more accurate.  In the previous section I said that we could put the number327.58 into the calculator's memory.  By rounding off to the nearest 1.0mm in the ten steps just done we have gained over 4mm.  Imagine what we could gain if we were doing 17 steps and just measuring each section separately.  Maybe we could get 20mm-25mm out.
A lot of texts recommend using a steel square to step it out, similar to the way they use it to step out rafters.  This may be more accurate, but it is still prone to creeping or the odd human error.

So how do we do this chain dimension thing?  Easily, that's how.

If you use Windows, fire up the calculator in the accessories menu.
Punch in "328" and the the "+" button.
Then hit "enter" ten times.

What you have just done when you hit the "enter" button is to add 328 to the previous total.  Talk about easy peasy!

Just about every calculator does this. You just have to find the method for your own calculator.  I have two of them and each is slightly different.

Stair marking out - Chaining dimensions.

If you did't follow that you may be interested in my ebook "Using a Ten Dollar calculator to solve Construction Problems"

This is a useful thing to remember, I have used it heaps of times, not just on stairs.  The last time I did it was when setting out a ceramic tile floor.

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Marking the inside faces of the stringers.

Stair marking out - Marking the inside face of the strings. Note that the strings are not identical, they are mirror images of each other, always!  That is they have a right and a left hand side.

From here on it is a matter of squaring the top marks onto the face, marking any offsets, and marking the tread lines.

Each type of stair has it's own particular design but the main principle remains the same, whether its is a steel stair up to and outside deck, an internal closed string stair or the formwork for a concrete stair.

1. Get the step triangle and the slope distance.
2. Do a full size drawing on a corner of a scrap sheet of ply of the bottom,a middle and the top steps showing all details and thicknesses.
3. Mark out the tops and then square the marks onto the faces.
4. Mark out the faces and mark the top and bottom cuts.
5. Go for it!

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A timber closed string stair

Stair marking out - A routered string

The sketch above shows the few actual setting out marks on the string. The rest is done by aligning a pre-made jig to the marks.

You can see how the jig is made on my router jigs page.

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A steel string

Stair marking out - A steel string with angle supports for timber treads

Here is a quick and easy steel string for an outside stair.  Again a fairly simple set out, very few lines needed.

The steel can be either RHS or PFC.

The main line for the welder to weld the angles on is set back the thickness of the tread.

The treads are fixed later to a string line or straight edge, or just kept in line with the front of the steel,

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