Spiral Stairs - Technical

Spiral stairs are considered to be space saving, however, if replacing a conventional stair structural work will probably be necessary to change the shape of the opening. Bear in mind a diameter of 1900 is normal for a main domestic stair, this will take up over 2m of floor space on the upper level.

Openings are determined by the stair diameter, usually 50-100mm larger for clearance. In square/rectangular situations, lower treads can sometimes under hang the ceiling.

Support is by means of a steel column around which the components are positioned. The stair is stabilised by bolting down the column base and by fixing the landing to the upper floor.

The start and finish point is determined by the number of risers calculated from the floor to floor height. A clockwise or anti clockwise ascent depends on the position of walls and doors etc. Straight treads can be incorporated at the bottom or top of the stair, for example to achieve headroom under a roof slope.

A guard rail on the outer edge of the stair and one side of the landing will be included in the basic price, matching loose components can be ordered to guard the opening. On most model types with vertical uprights modifications can be made to satisfy the 100mm rule requirement, this is not generally an option on stairs with horizontal rails. It is not possible to attach an inner handrail to the column on any of our stairs.

This is an integral part of the stair usually finishing level with the upper floor, a 60º quadrant landing is standard with triangular, trapeze or square as options. Note a quarter landing is not compatible with a 30º tread due to lack of headroom beneath.

Timber Stairs
The standard angle for diameters up to 1.6m is 30º (12 treads per 360º revolution) from 1.7m the angle is 22½º (16 treads per 360º revolution), alternatives are available for a surcharge.

Steel Stairs
Standard angles are given below, alternatives can be used for a surcharge. Note on diameters up to 1.5m a smaller angle is achieved by increasing the tread overlap.

Circular stairs

• 1m to 1.5m
• 30º
• (12 treads per 360º revolution)
• 1.6m & 1.7m
• 22½ to 30º
• (12 to 16 treads per revolution)
• 1.8m & 1.9m
• 22½ to 25.7º
• (14 or 16 treads per revolution)
• 2m to 2.4m
• 22½º
• (16 treads per revolution)

Square stairs

• 1m to 1.9m
• 30º
•  
• 2m to 2.4m
• 22½º
•  

All stairs are made to order, manufacturing times vary according to demand, typically allow three to six working weeks.

A sheet giving approximate dead weights is available on request.

Stairs are factory assembled, dismantled and delivered in kit form. Notification should be given of access restrictions as timber handrails and circular baserails are dispatched in one piece.

Assembly instructions are provided with a working drawing as appropriate. The stairs are a finished product and should be installed as late as possible in the works taking care to protect from damage.

We can give guidance, but it is the responsibility of the customer or architect to obtain any necessary approvals. Interpretation varies considerably and advice should be sought from the relevant Building Control Office. In accordance with Part K1 of the regulations (Part S in Scotland), the Alternative Approach, BS5395:Part 2 is applicable, technical sheets are available on request. Half risers can be supplied for most model types to comply with the 100mm gap rule.

Timber Stairs
Solid and finger jointed timber is used, beech is standard with options on iroko or oak.

Metal Stairs
Most models are made in 2mm pressed steel up to diameter 1.6m, 3mm bent plate is used from 1.7m to 2m and 4mm from 2.1m to 2.4m. The gauge can be increased on larger stairs for a surcharge. The diameter of the central column on small stairs is 102mm and on larger diameters 168mm. On small external stairs the treads have a raised rib pattern, on larger diameters it is diamond shaped

Timber
A factory sprayed polyurethane lacquer in a choice of colours is standard on beech and iroko, with a clear finish on oak.

Metal
A factory paint finish is standard in the colours below, any RAL shade is available at extra cost. External stairs have a rust proof coat for final site finish or can be hot galvanized.

Standard colours are:

• white RAL 9010
• ivory RAL 1015
• red RAL 3000
• black RAL 9005
• grey RAL 7001
• charcoal RAL 7016
• blue RAL 5010
• yellow RAL 1021
• brown RAL 8011
• silver RAL 9006
• grey graphite
• black graphite

On steel stairs the standard carpet colours are beige, grey, green, rust, blue, black or brown, with an option on black rubber.