When the ladies arrive at Barton Cottage at the start of Ch. 6, we read

As a house, Barton Cottage, though small, was comfortable and compact; but as a cottage it was defective, for the building was regular, the roof was tiled, the window shutters were not painted green, nor were the walls covered with honeysuckles.

My Norton Critical edition of S&S makes this note:

The cottage later in the 18th century was increasingly glamourized and sentimentalized, seen no longer as a laborer's dwelling but as a site of rustic simplicity and retirement from the debasing pleasures of the city. Tiled rather than thatched, symetrical rather than irregular, yet a far cry from the affluence of Norland Park, Barton Cottage s not the elegantly quaint abode then becoming fashionable.

There will be more to discuss on attitudes towards cottages later, but I can well imagine Marianne's head being filled with thoughts of the type of cottage Cowper describes in The Task:

Once went I forth; and found, till then unknown,
A cottage, whither oft we since repair:
‘Tis perch’d upon the green hill top, but close
Environ’d with a ring of branching elms,
That overhang the thatch, itself unseen
Peeps at the vale below; so thick beset
With foliage of such dark redundant growth

Especially when Barton cottage has a prospect that commands the whole of Barton Valley and beyond!

Ch. 6 is quite specific about the dimensions of the cottage. It strikes me that the size would not be dissimilar to Chawton itself. However, the two sitting rooms that are 16 Ft2! Surely they are not 4'X 4'!! Jane Austen must surely have meant 16 X 16, don't you think???