Architecture

Although the Spanish were sophisticated in architecture, they decided to create their own styles to differentiate themselves from the English who had built house in the accustomed styles.

Glass

Glass-making was already known to the English and Spanish settlers and was allowed to advance by the Priestesses as it was beneficial to them and the Cregans. There was a tax on glass for other people so it is less common.

Glass-pane sizes

Building	Max pane width	Max pane height
Ordinary house	8–10 in	12–16 in
Merchant / prosperous house	10–12 in	16–20 in
Wealthy / important building	12–14 in	20–24 in
Cregans	14–18 in	24–30 in

12 × 20 inches is a very typical large pane, with 18 × 30 inches being about the largest you'd commonly encounter.

Window sizes

For an architectural stone mullion:

4–6 inches wide — elegant, relatively fine 6–8 inches — substantial and probably most appropriate for your buildings 8–12 inches — massive, fortress/temple appearance

I'd favour 6 inches for ordinary architectural mullions and 8 inches for imposing Priestess buildings.

Example: a large arched window

Say you have an arched window 4 ft wide × 7 ft high.

You could divide the lower rectangular portion into three bays, approximately:

1 ft 2 in wide each, separated by 6-inch mullions.

Then subdivide each bay vertically with lead cames into panes around:

12 in × 20 in

The arched section above can use progressively smaller panes following the curve.

This gives you a window that looks large and impressive from outside, while no individual piece of glass is particularly large.

A useful rule for your Altierra designs

I'd establish this as part of the world's architectural convention:

No ordinary sheet of window glass exceeds approximately 18 inches in its longest dimension.

Exceptional temple glass might reach 24–30 inches, but would be expensive and prestigious.

That would also make large arched windows visually distinctive. The arch isn't a single expanse of glass; it's a framework containing perhaps 20, 30 or even 50 individual panes.

Arches

Not wishing to use semi-circular or pointed arches because of their association with the styles of Earth (and Christianity), the Spanish created the Altierran or Divaran arch. It is more simple arch, harking back to primitive designs, but with elaborations to distance itself from Anglo-Saxon arches.

Altierran arch

Arch with boss

Arch construction