Canon information about septs?

[Anthony Appleyard]

What GRRM canon is there about the layout of a sept? Some GOT / SoIaF -derived videogames include ability for the player to build a sept, but such septs as shown in the game seem to me to be much influenced by European cathedrals without reference to GRRM and are not reliable as canon. (Search for the word "sept" is much swamped by "Sept" meaning "September".)

Canon bit of information that I have found are:

(1) A sept built on the Iron Islands had been demolished by the Ironmen, leaving only a seven-sided foundation.

(2) Weddings take place between the images of the Father and the Mother, which therefore must be on adjacent corners of the heptagon.

(3) There is singing in septs, presumably of hymns.

(4) At intervals there is a Festival of the Maiden, where only virgin women and girls are allowed admission.

If each of the Seven gods is an equal representation of a One God, as seems to be stated, that may mean that each of the 7 images and altars in a sept must be equally related to the others and so must be in a perfect circle (or heptagon). That causes a problem providing an adequately wide door to the sept, and (1) seems to prevent making the sept 8-sided with the 8th side being for the door.

I have not yet found canon info even about which of these is true:

(i) The Seven images are at the corners, or at the middles of the sides, of a heptagon, and face inwards. That constrains the amount of space that there is for a congregation, and for weddings (which attract a big congregation) would put the images of the Father and the Mother a long way apart. Compare most real churches and Hindu temples, which are rectangular with the sacred images at one end.

(ii) The Seven images are all together in a small circle and face outwards, at the centre of the heptagonal building.

 

[Tucu]

I don't think there is one rule for that. The sept at Castle Black has 1 altar; the one in Dragonstone had 7. The one in Winterfell had masks on each wall. The Sept of Baelor seems to have benches around the altars.

[direpupy]

These are Catelyns thoughts on it when she is in a small sept .

A Clash of Kings - Catelyn IV
the seven walls were cracked and crooked. God is one, Septon Osmynd had taught her when she was a girl, with seven aspects, as the sept is a single building, with seven walls. The wealthy septs of the cities had statues of the Seven and an altar to each. In Winterfell, Septon Chayle hung carved masks from each wall. Here Catelyn found only rough charcoal drawings. 

And Arya's thoughts on septs.

A Feast for Crows - Arya I

The septs of Westeros were seven-sided, with seven altars for the seven gods, 

[Ser Lepus]

GRRM has confirmed that some of the more important Septs are centers of learning where Septons are trained. He has said that many Septons are locally trained in small Septs and Septries in the countryside, and the Septons trained there can be quite ignorant and poorly trained, but places like Baelor's Sept have higher standards.