Stair Building Taking Sizes

Taking Sizes

WOODdesigner

by Ness Tillson

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Wood Designer | Taking Sizes

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ContentsLegal Disclaimers 2Introduction 4Minimum play 5The golden rules 5

Always use one unit of measure 5Take more measurements than necessary 5Take plenty of photos! 5

Basic measuring tools 6Meter and/or laser meter 6Spirit levels and laser levels 7Laser level/plumb line 8Long square/laser square/adjustable square 9

Preliminary sketches 11Basic measurements 15Floors are not level 17Walls are not plumb 18Complex stair wells 20Conclusion 23

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IntroductionOne of the most important tasks that faces a stair builder is taking the on site dimensions of the stairwell.

The on site sizes are the foundation of the whole job and the difficulty for a professional is that its not always feasible to return to the site to verify or take a missing dimension.

If youre an amateur you might be able to go back and forth from site to workshop but in all cases a complete and methodical attitude to taking the original sizes is a must and can save endless hours and sometimes make or break a stair project.

The objective in taking sizes is to be able to draw an exact plan of the stairwell at the positions that the stair interacts with it.

The more precise and detailed this plan the easier it will be to design a stair that fits the stairwell. 100% precision is nearly impossible to acquire but one should certainly aspire to get as near as possible.

One should always keep in mind that the stair should be built to a preci-sion of +/-1mm whereas the stairwell will in general be more or less +/- 10mm. And in certain circumstances more like +/-20mm.

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Minimum playAs its impossible to measure the exact geometry of the stairwell, its easier to install a stair slightly smaller than the stairwell and add fillers while it would be almost impossible to cut down a stair thats too big.

With this in mind a stair should be designed smaller that the stairwell dimensions.

In my experience a minimum play across two walls that are fairly regular is 10mm whereas in renovation work with irregular walls 20mm play is often a minimum.

The golden rulesAlways use one unit of measureIf you work in millimetres all measurements must be in milli-metres, dont mix millimetres, centimetres and metres. If you follow this rule youll avoid errors like whether one meter fifty means 1050mm or 1 meter and 50cm.

Take more measurements than necessaryTake the same measurement at least twice and from different angles.

Cross reference your measurements so that one will confirm or invalidate another.

Take plenty of photos!If there are lots of details it will be difficult to remember everything.

In todays world of digital cameras its easy and cheap to take photos so dont hesitate to take a maximum number of photos.

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Basic measuring toolsThese are the tools that I have found over the years to be the most useful when measuring up a stairwell.

I have tried many different high tech solutions and often reverted back to simpler means, after finding that simple when used methodically is often better than complicated.

Meter and/or laser meterOf course the basic tool for measuring remains the meter rule or tape measure. A good heavy duty tape measure is enough for taking most sizes. If you find yourself often taking stairwell dimensions I would suggest that you invest as well in a laser meter. The laser meter is the only high tech tool that I strongly recommend.

It will make it far easier to measure across stairwells, floor heights and a host of other situations that although possible with a traditional tape measure are faster and easier to do with a laser meter.

If possible always buy a laser meter with a pointed or extendable back stop that allows measuring into corners.

A must for stair triangulation!

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Spirit levels and laser levelsThese are the tools you need to verify that floors are level and walls are plumb.

I personally have 2 or 3 of different lengths of spirit levels: 600mm, 1m and 2m.

If you can afford it a digital level can be good way of measuring directly the incline of a floor or wall but it will be necessary to lay it on different straight edges to get the inclination between two specific points. Digital levels usually double up with as spirit levels so you get the best of both worlds, although they are of course more expensive.

If youre only an occasional stair builder a couple of ordinary spirit levels are enough to do a good job.

digital level

traditional spirit level

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Laser level/plumb lineAnother tool that although not indispensable can be of great help in certain circumstances is the laser level/plumb line.

Although used rarely, I use a laser level as a plumb line in complex situations when its necessary to project vertically the position of a specific element. This can be very useful when stairwell walls are not plumb and you have to align different floor sections (see the measuring from a pole section further on).

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Long square/laser square/adjustable squareIts important to measure and verify the angles of a stairwell.

This can be done by triangulation but I have found that in practice it can be easier and more precise to use an adjust-able square.

You can use a sliding bevel but in most cases this tool will be too small to get the overall angle.

As walls are not always very straight youll need a longer adjustable square that will lay across a large surface and not sink into small local hollows near the angle youre measuring.

Its very easy to make a simple adjustable square with scrap wood as in the photo top right.

A more precise version of a simple metallic or wooden square is the laser square bottom right that projects a right-angled cross.

It is very neat for measuring some angles but I have found that it cant replace a simple square for measuring stairwell corners.

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My favourite tool for measuring angles is the adjustable square that has a mechanical or digital read off of the angle. This neat tool is really a square, a protractor, a sliding bevel and a spirit level all in one.

It will measure the angles, and as it has an integrated spirit level you can measure slopes as well as use it as a simple spirit level.

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Preliminary sketchesBefore taking the sizes its good to have an approximate idea of where you want the stair to start and arrive.

Heres how I set up the basic sketches to write down the stairwell sizes.

First section that shows the lower floor.

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Second sketch that shows the upper floor.

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Third sketch that shows the elevation section.

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Fourth sketch that shows the left view section.

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Stairwell length and width Floor joist depth

Basic measurementsHere is a very basic checklist of on site dimensions:

Floor to floor height Maximum base floor length and width

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If youre making a stair in a recently built stairwell, taking the sizes may well be very simple. But even for a simple project I suggest strongly that you verify these basic points:

Are the walls plumb? Are the floors level? Are the angles of the walls at 90?

If any of these points are not perfect you will have to measure their deflection and mark it on your sketches.

In renovation work taking on site sizes can become very complicated and its more than likely that none of these points are true.

The following are some tips for the more common difficulties that can arise...

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Floors are not levelBe careful if the floors are not level as this will change the total height of the stair.

Its common to measure the total height by pulling a tape measure from the lower floor level to the upper floor but if either floor is not level the total height will have to be adjusted.

The example below shows a slope on the upper floor. If the height is measured from the left the real height of the stair will require subtracting the level deflection from the measured height.

Of course it can often be the lower floor thats not level and as often as not its both and youll have to note all the level deflections to calculate the real height.

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Walls are not plumbIf walls are not plumb you must be aware that the stair size will vary accordingly.

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Note as well that if the walls are not plumb though the angles of the walls may be at 90 measured on the level, when measured at the slope of the stair this angle will vary.

For small differences in the wall vertically, angle variations may be insignificant and easily absorbed in the 10mm play,

but for larger differences it can be useful to measure wall angles approximately on the slope of the stair and include this in the stair design.

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Complex stairwellsIn renovation work stairwells can get really complicated.

Difficulties often arise due to irregular walls, floors not level and often obstacles that make precise measure-ments difficult to take. When a stair rises up through several different floors heights, getting accurate measure-ments that enable the exact overlaying of different floor configurations can be a real nightmare.

One way to simplify measuring a complex stairwell with irregular walls and different overlaying sections is to use the central pole method.

This method can be used using a standard tape measure but is far more effective using a laser meter.

The idea is to create a central reference point and refer-ence plane in the stairwell. To do this I fix a central pole perfectly plumb approximately in the middle of the well. The pole is held with boards screwed or clamped onto each floor. Note that I have also drawn the centre line on each board.

For the pole you can use a 30mm dowel, tube or any round object.

If you are measuring with a laser the easiest option is use a thick rope that you can hang from the upper board with a weight at the bottom to keep it tight. The boards with their centre lines must form a perfectly vertical plane so

make sure that the boards holding the pole are perfectly plumb with each other.

This is easily done by hanging a plumb line or laser plumb referencing the centre line on the support boards.

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Once set up its possible to triangulate the shape of each level and get a precise measurement of the angles and the relative overlays of each floor.

Heres the measuring sequence for each floor.

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With this method all points are measured from the same vertical plane and its easy to align all the different sections.

Although this method gives precise measurements, I always suggest that you measure also the angles with an adjustable square and the walls and floors with a spirit level as a double check.

Note that these measurements give the shape and relative positions of horizontal sections of the stairwell but not the vertical sections that give the eventual slopes of the floors.

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ConclusionI can never stress enough the necessity for precise measurements of the original stairwell.

I have built many stairs for renovation work and for many taking the sizes has been the most challenging part of the project.

Renovation projects can get very complicated and its often necessary to invent a specific tactic for the situation at hand.

One must always keep in mind that a bit of thought and preparation to put together an organised method will always save a lot of time and avoid errors in design and installation.

Please make sure you check out the rest of our stair building resources in the members area of WoodDesigner.org.

Happy woodworking.

Ness Tillson

Legal DisclaimersIntroductionMinimum playThe golden rulesAlways use one unit of measureTake more measurements than necessaryTake plenty of photos!

Basic measuring toolsMeter and/or laser meterSpirit levels and laser levelsLaser level/plumb lineLong square/laser square/adjustable square

Preliminary sketchesBasic measurementsFloors are not levelWalls are not plumbComplex stair wellsConclusion

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Stair Building Taking Sizes

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