Quick answer: A UK staircase balustrade is built from four main timber parts: newel posts (the heavy vertical anchors), the handrail (top rail you grip), the baserail (bottom rail holding the spindles), and the spindles (vertical bars between them). Standard sizes: 90 x 90mm newels, 32mm or 41mm baserails and handrails to match spindle width, and spindles at 100mm centres maximum to comply with Building Regulations Part K.
Whether you're renovating a Victorian banister, installing a new staircase, or upgrading a tired pine balustrade to oak, this guide covers the four core timber parts you'll need, the UK standard sizes, and how they fit together.
The four main parts of a UK staircase balustrade
Every staircase balustrade in the UK is built from the same four timber components, regardless of style or property age:
| Part | What it is | Standard UK size |
|---|---|---|
| Newel post | The heavy vertical post at the start, end, or turn of the staircase that anchors the balustrade. | 90 x 90mm interior, 100 x 100mm decking |
| Handrail | The top horizontal rail you grip when walking up the stairs. | 32mm, 41mm, or 55mm to match spindle width |
| Baserail | The bottom horizontal rail that holds the foot of each spindle. | 32mm, 41mm, or 55mm to match spindle width |
| Spindles | The vertical bars (also called balusters) between handrail and baserail. | 32mm or 41mm square, in 900mm or 1100mm lengths |
Get any one of these wrong — particularly the spindle-to-rail width mismatch — and the whole balustrade fails to fit.
Newel posts: the structural anchor
Newel posts are the heaviest part of the balustrade and do the structural work. They bolt through the floor or stair stringer and resist the lateral load of someone leaning on the handrail.
UK standard newel post sizes:
- 90 x 90mm — interior staircases (the default for almost all UK homes)
- 120 x 120mm — decorative box newels for grand staircases
- 100 x 100mm — decking and exterior balustrades
You need a newel at every direction change: start of stairs, top of stairs, half-landings, and any winder corner. A straight flight needs two; an L-shaped staircase typically needs three; a U-shaped staircase needs four or more. Browse the full newel posts range for plain, stop-chamfered, turned, and contemporary styles.
Baserails and handrails: the horizontal pair
Baserails and handrails are the horizontal rails that span between newel posts. The handrail is the top rail; the baserail is the bottom rail. They almost always come as a matched pair — same timber species, same profile, same groove width — so the staircase reads as a coordinated design.
The most common UK profile widths:
- 32mm — slim, modern profile, used with 32mm spindles
- 41mm — the most common UK standard, used with 41mm spindles
- 55mm — heavy traditional profile for grand staircases, used with 55mm spindles
Both rails have a fillet groove that the spindle ends slot into. The fillet (a thin strip of timber that fits in the groove between spindles) sets the spindle spacing automatically — typically 100mm centres to comply with the UK Building Regulations Part K "100mm sphere rule."
Browse baserails for the bottom rail, and the matching handrails for the top.
Spindles: getting the spacing right
UK Building Regulations Part K requires that no spindle gap can pass a 100mm sphere. In practice this means:
- Maximum spindle spacing: 99mm clear gap between spindles
- Standard fillet sets the spacing at exactly 100mm centres
- Standard spindle length: 900mm for landings, 1100mm for tall staircases
Spindles come in plain square sections, turned profiles (decorative beads and shapes), or twisted/barley sugar profiles for traditional designs. Always pick spindles in the same timber species as the rails and newels for a coherent look.
Choosing your timber: pine, oak, or hardwood?
Pine — the cost-effective standard for painted staircases. Easy to work with, takes paint and primer cleanly. Use this if the staircase is getting a white-painted finish.
Oak — the premium choice for natural-finish staircases. European oak takes a stain or wax beautifully and matches oak floors and oak doors. Significantly heavier and harder to drill — expect to pre-drill all fixings.
Other hardwoods — sapele, ash, walnut, and mahogany available to match existing joinery in period properties or specific design schemes. These are usually special-order rather than off-the-shelf.
Match all four parts (newels, handrails, baserails, spindles) in the same timber for visual consistency. Mixing pine spindles with oak rails looks half-finished.
Replacing a Victorian banister: the order of work
Most period banister replacements follow this sequence:
- Remove the old balustrade — handrail first, then spindles, then baserail, finally newel posts. The newels are usually the deepest fixings.
- Install new newel posts — bolt through the floor or stair stringer. They must be plumb and rigid before anything else goes on.
- Cut the baserail to length between the newels (subtract 6mm for clearance).
- Mark spindle positions on the baserail at 100mm centres.
- Glue and pin the spindles into the baserail groove with PVA wood glue and 40mm panel pins.
- Drop the handrail over the spindle tops, glue, and pin.
- Fix the assembled unit between the newels using hidden fixings.
- Paint or stain as a final pass once everything is fitted.
FAQ
What's the difference between a baserail and a handrail?
The handrail is the top rail you grip when walking. The baserail is the bottom rail at floor or step level that holds the foot of each spindle. They usually come as a matched pair in the same profile.
What size spindles for UK stairs?
32mm or 41mm square is standard. Match the spindle width to the rail groove width — 32mm spindles need 32mm rails. Length is 900mm for short balustrades or 1100mm for taller ones.
What's the maximum spindle gap in UK regulations?
UK Building Regulations Part K says no gap can pass a 100mm sphere. Standard 100mm centre spacing with a 41mm spindle leaves a 59mm gap, which is comfortably compliant.
Can I mix pine newels with oak spindles?
You can but it almost always looks wrong. The most common compromise is paint everything white — that hides the species mismatch. For natural finishes, all four parts should be the same timber.
Do decking balustrades use the same parts?
Yes — same four parts, but heavier. Use 100 x 100mm pressure-treated newels, exterior-grade rails, and stainless steel fixings to prevent rust streaks.
Browse the full staircase parts range: newel posts, baserails, handrails, and spindles. Or call 01656 745959 with your staircase dimensions and we'll put together a complete pack.