Some information on Irish Genealogy Toolkit "1901 census forms are crammed with information about your Irish ancestors"
https://www.irish-genealogy-toolkit.com/census-forms.htmlBy enlarging a form slightly on the National Archives site I was able to read the headings.
Form B1 House and Building Returns
Columns 1-11 are headed HOUSES
Column 1. No. of House or Building
Col. 2. Whether Built or Building
Col. 3. State whether Private Dwelling, Public Building, School, Manufactory, Hotel, Public House,
Lodging House, Shop, &c.
Col. 4 Number of Out-Offices and Farm-steadings as returned on Form B 2
Col. 5 Is the House Inhabited.
Yes or No as the case may be
Columns 6-11 are headed Particulars of Inhabited Houses
Col. 6 WALLS
If walls are of Stone, Brick or Concrete, enter the figure 1 in this column;
if they are of Mud or Wood or other perishable material, enter the figure 0
Col. 7. ROOF
If Roof is of Slate, Iron or Tiles, enter the figure 1 in this column;
if it is of Thatch, Wood, or other perishable material, enter the figure 0
Col. 8. ROOMS
Enter in this column: -
For each House with
1 Room only - the figure 1
For Houses with
2,3, or 4 Rooms - 2
5 or 6 - 3
7, 8, or 9 - 4
10, 11, or 12 - 5
13 or more - 6
Col. 9. Windows in Front
State in this column the exact Number of Windows in Front of House
Col. 10. Tot the figures you have entered in columns 6, 7, 8 & 9 and enter the Total for each House in this
column
Col. 11 CLASS OF HOUSE
When Total in col. 10 is:-
1 or 2, enter "4th"
3, 4, or 5 "3rd"
6, 7, 8, 9, 10 or 11 "2nd"
12 or more "1st"