I'm renovating my old stairs and landing. I was hoping to replace the old floor with new T&G boards but I've discovered that some of the old boards run under the wall (not stud) on the left. I've cut a hole to confirm. Have you ever seen the likes of it? Thinking now of laying new boards over the top. Have a look at the two images below and this video: http://www.declanworld.com/Boards.mp4
Yes it is very common in old houses. If you put T&G boards on top of the existing floor, it will mean that the last step onto the landing will be taller than the other steps on the stairs. Whilst it could be as little as 18 mm it can cause problems with people stumbling. It may be difficult to cut the floor boards at the wall edge because the joists are running parallel with the wall and there may not be one underneath the wall giving it support - so it may be the floor boards holding the wall up ! It may be easier to sand and repair the current floor or go for a thin laminate.
As sospan has said above, my own property (approx 100 year old) has the same. Looks like all the first floor joists and floorboards where installed before any walls then lightweight (straw in them) blocks built on top. I know most of my upstairs walls aren't sat on joists from taking down ceilings downstairs.
I'm thinking of either that or veneered board, in tandem with putting new treads on the old staircase.
I have the same issue. What did you do after? I have central heating pipes that are banging under them as well.
I had this problem, so I took off the skirting then cut through the floor close to the wall as I could get. Laid the T&G, then fitted new skirting boards that covered the joins.
Gummo, Whilst I had the whole floor up, I fully insulated the floor, & the water pipes. Made good a couple of bits of electrics, ie Maintenance Free 3 Terminal Junction Box. Foamed up all the gaps round the edges. Used 22mm T&G boards. Put in 5 extra 4x2 floor timbers to strengthen up the floor for the water bed. Fitted a double panel Rad. Full decorate, carpet, & feature wallpaper, plus lights.
Made a feature wall with black glitter paper, LED lights. Black carpet with 9mm underlay & black curtains. New window blinds.