UK Slate Sizes

In British practice the length of the slate is typically twice the width, each of the most popular sizes having a traditional name. Thus Imperial slate sizes range from 12″ length by 6″ width (Small Doubles) and 14″ by 7″ (Narrow Ladies) up to 24″ by 12″ (Duchesses) and 24″ by 14″ (Princesses). Popular sizes are:


Duchesses: 24″ x 12″

Small Duchesses: 22″ x 12″

Wide Countesses: 20″ x 12″

Countesses: 20″ x 10″

Wide Viscountesses: 18″ x 10″

Viscountesses: 18″ x 9″

Wide Ladies: 16″ x 10″

Ladies: 16″ x 8″

Clearly when modelling it is necessary to assess the type of slates used on the building in question and allow for the overlap which takes up a lot of the length.

The N Gauge table is:

Size	Length (inches)	Width  (inches)	N Gauge  Length (mm)	N Gauge  Width (mm)
Duchesses	24	12	4.1	2.1
Small Duchesses	22	12	3.8	2.1
Wide Countesses	20	12	3.4	2.1
Countesses	20	10	3.4	1.7
Wide Viscountesses	18	10	3.1	1.7
Viscountesses	18	9	3.1	1.5
Wide Ladies	16	10	2.7	1.7
Ladies	16	8	2.7	1.4

Information from John Williams Roofing.