Manual of Purpose-Made Woodworking Joinery

122 Designing and making stairs to current building regulations

blocks to present a more visual finish to the underside

of the stair. The fretwork risers were drilled and coun-

tersunk at approx 200mm centres on their lower faces

for eventual gluing and screwing to the backside edges

of the adjacent treads.

Bullnose- ended step details

Figures 6.51(a)(b)(c)(d)(e): The easy way to produce

the segmental- rounded face- edges on the tapered,

bullnose- ended tread was to use a solid timber board

of 22mm thickness, as seen in Figure 6.51(a) – the

face edges and end grain of which could easily be

shaped to form the nosing. But, I chose to do it the

hard way because 18mm softwood ply had been used

enable the narrow tread widths to be checked for
the required regulatory minimum of 50mm – the
quadrant- shaped outer wreathed- string was drawn
from the riser’s centre point.
To develop the shape of the strings, the points of
the risers and nosings that met the string- faces in
the plan- view rod were extended out (as indicated by
broken lines) onto the elevational- view rods and the
riser heights were added to plot the wide ends of the
steps. Once these wide- ended steps were drawn, top
and bottom margin- marks were pencilled in tangen-
tially to the assumed string- shape at 40mm above
each nosing and 25mm below each step’s underside
corner. A flexi- curve lath of narrow hardboard strip
was then held to the marks and the curved easings
were drawn. Note that – because the underside of
this stair was visible – the steps (as shown) were only
housed in to their exact thicknesses; no tread- or
riser- wedges were used. However, to compensate for
this omission, each tread had two tenons which were
through- mortised and wedged to both of the strings.
The approximate positions of these 25mm- wide
mortise- and- tenon connections are indicated on rods
(b) and (c) above.

Tread and riser details

Figures 6.50(a)(b): The tapered treads were of 18mm-
thick softwood exterior plywood, with 22 × 12mm
redwood lipping glued on as nosings and shaped with
an overhead router. The fretwork risers were also of
similar plywood, but 9mm thick. These were grooved
into the underside of the treads to a minimal depth of
4mm. As shown in Figure 6.50(a), the positioning of
the groove created a recess to accommodate the 19 ×
10mm scotia mould, between the riser- face and the
backside of the lipping. To complete the construction,
continuous lengths (rather than individual blocks) of
28 × 28mm cavetto- shaped mould were used as glue

28 × 28 mm cavetto

mould used as full-

lenght glue blocks

19 × 10 mm scotia

mould

22 × 12 mm

segmental

lipping

Figure 6.50 (a) Vertical section of the tread- and- riser
construction.

64 mm

Ø

Figure 6.50 (b) Elevation of the simple fretwork pattern

pierced through the riser- faces, emanating from a line of

64mm Ø (diameter) holes drilled with a holesaw. The

radial triangular shapes were drilled for saw- entry and

carefully formed with a jigsaw. This view also shows the

step’s nosing above the scotia mould and – at the base –

the extended and pilot- holed riser- allowance for connec-

tion to the back- edge of the tread below.

Solid timber tread

Scotia board

Framed-up

bottom

riser

Figure 6.51 (a) By using a solid timber tread for the

bottom, bullnose- end step, the additional work involved

with a plywood tread requiring a lipped, gluelam nosing

would have been avoided.