Getting accurate measurements is the single most important step when ordering new stair parts. Whether you're replacing a few worn spindles or overhauling an entire balustrade, the wrong numbers mean wasted time, wasted money, and a frustrating trip back to square one. The good news? Measuring a staircase isn't complicated once you know what to measure and where. This guide walks you through every key dimension, from handrails and spindles to newel posts and treads, so you can order with confidence.
What You'll Need Before You Start
Gather a few basic tools before climbing the stairs with a notepad:
- A retractable tape measure (5 metres is ideal)
- A pencil and paper or your phone's notes app
- A spirit level for checking verticals and horizontals
- A sliding bevel gauge (useful for capturing the rake angle, which is the angle of your staircase's incline)
It helps to sketch a simple diagram of your staircase as you go. Label each measurement clearly. If you're ordering multiple components, a labelled sketch will save you from second-guessing later.
Measuring for Spindles (Balusters)
Spindles are the vertical posts that sit between the handrail and the baserail (or tread). If you're looking at how to replace stair spindles, precise length measurements are essential because spindles on the rake (the sloped section of the staircase) are longer than those on a flat landing.
For rake spindles: Measure from the top of the tread (or the top of the baserail, if one is fitted) to the underside of the handrail. Take this measurement at several points along the staircase, as older houses can have slight variations.
For landing spindles: Measure from the top of the landing floor to the underside of the handrail. These are typically shorter and all the same length.
Note the cross-section size too. Most standard spindles in the UK are 41mm x 41mm or 32mm x 32mm square at the ends. Check your existing spindles or the grooves in your handrail and baserail to confirm which size you need. At Stair Crazy, our oak and softwood spindles are available in both standard sizes, so matching your existing setup is straightforward.
Spindle Spacing and UK Building Regulations
While you're measuring, it's worth checking your spindle spacing. Under Part K of the UK Building Regulations, the gap between spindles must not allow a 100mm sphere to pass through. This is a child safety requirement. If your current spacing is wider than 99mm, you'll need to add extra spindles when you renovate. Measure the clear gap between each spindle (not centre to centre) to confirm compliance.
Measuring for Handrails and Baserails
Handrails and baserails are sold in set lengths (typically 2.4m, 3.6m, or 4.2m), so your job is to measure the total run and choose the nearest length above it. You can always trim to fit, but you can't stretch a rail that's too short.
Rake section: Measure along the slope from the centre of the bottom newel post (the sturdy vertical post at the foot of the stairs) to the centre of the top newel post. This gives you the rake length.
Landing section: Measure horizontally from the centre of the newel post to the point where the handrail terminates, whether that's at a wall or another newel.
You'll also want to note the handrail profile. This is the cross-sectional shape of the rail. Common profiles include "mopstick" (a simple round style), "colonial" (with a more ornate moulded profile), and "contemporary" (a clean, flat-topped design). If you're matching an existing rail, take a cross-section measurement or, better still, photograph the end grain and compare it against product listings. Our handrail range at Stair Crazy includes all the popular UK profiles in oak, pine, and hemlock.
Measuring for Newel Posts
Newel posts are the structural anchors of your balustrade. They take the most load and set the height for everything else. When measuring for replacements, you need two key figures:
- Overall length: Measure from the floor (or the side of the string, if the newel is mounted on the outer stringer) to the very top of the existing newel, including any cap or finial.
- Cross-section: Standard UK newel posts are typically 90mm x 90mm, but some older or grander staircases use 115mm x 115mm. Measure yours carefully.
Don't forget to check how the newel is fixed. Some are bolted through the floor or tread, while others are housed into the string (the long diagonal board that supports the treads). Knowing this helps you choose the right newel length and plan your installation.
Measuring Treads, Risers, and Strings
If your renovation extends to the structure of the staircase itself, you'll need a few more measurements:
- Tread depth (going): Measure from the front edge (nosing) of the tread to the face of the riser behind it. Part K requires a minimum going of 220mm.
- Riser height: Measure from the top of one tread to the top of the next. The maximum allowable rise under Part K is 220mm for a private staircase.
- Tread width: Measure the full width of the tread from wall to outer edge (or wall to wall in an enclosed staircase).
- String width and thickness: If you're replacing a stair string, measure its overall width, thickness, and the total raking length from ground floor to landing.
These structural dimensions are less likely to vary within a single staircase, but always measure at least two or three treads and risers to check for consistency, especially in older properties.
Top Tips to Avoid Common Mistakes
- Measure twice, order once. It sounds obvious, but a surprising number of returns come down to a single mis-read measurement.
- Always measure in millimetres. It removes ambiguity. A measurement of 867mm is far more precise than "just under 87 centimetres."
- Account for trimming. Handrails, baserails, and spindles often need cutting to length on site. Order slightly longer rather than risk being short.
- Photograph everything. Photos of your existing parts, joints, and fixings are invaluable when comparing products online or speaking to a supplier.
- Check for consistency. Older staircases can settle and shift over the decades. Use your spirit level to confirm that newels are plumb and treads are level before assuming all dimensions are uniform.
Taking the time to measure properly transforms the rest of your staircase renovation from a headache into a genuinely satisfying project. With accurate numbers in hand, you can browse our full range of oak staircase parts, softwood components, and metal balustrade systems knowing that what you order will fit. If you're ever unsure about a measurement or need help choosing the right profile, our team at Stair Crazy is always happy to help.
