Help with staircase top riser gap

Hi, I'm new and hoping someone can help. Having removed the nasty carpet on the wooden stairs of the maisonette we recently moved into, there has been found to be a gap between the top riser and tread at one side. The staircase/riser & tread is fully enclosed - walls either side, appears ok (solid) and the damage appears old as someone sometime has caught the exposed screws when painting the side uprights.

The gap is roughly 1/4" at the widest point - where it meets the wall and tapers to nothing by the time you reach the other end, which is still tight and absolutely fine. Looks almost as if someone has kicked the riser end where the gap is at some point.

2 questions really - is this a major deal or cosmetic damage? Plus importantly as a maisonette I cannot access the underneath of the staircase to attempt a repair, it would have to be done from above on the landing above the damaged riser. That raises th issue of armed with hand saw and basic tools and little DIY knowledge where do I begin?

Thanks to anyone who has the time and patience to read all this and reply.

heeelllooo and welcome CatDIYnovice

trying to work this one out lol

are the gaps between riser and string or between riser and tread or tread and string!!

big-all
the gap is L - shaped if that helps if starts very small mid way along between riser & tread and increases in size to wall side bit (string?), gap all the way up string but no sign of any movement/damage beyond that or at other end of tread or to other string on opposite side of staircase.
Hope that helps.....

This photo may help, hope I have uploaded it properly LOL

No show on the photo but it sounds like the staircase was fitted poorly, are both the strings fixed through to a wall at either side, maybe when it was screwed into such walls, by doing this has pulled the staircase apart, measure the distance between the strings where the problem is and compare that with the distance further down the staircase, this may lead to a clue for what is happening here, also from what you are saying about the gaps there may be a twist in the staircase maybe caused by the floor either at the bottom or at the top not being level.

Yes there is a slight difference having measured the gap between the strings at the bottom tread compared to this to one, the top is slightly narrower by a few mms. The picture has been uploaded to this site but can't work out how to post it actually on the question, I presume if you go to my profile it will show there?

An ill-fitting staircase would explain why it all appears solid and the damage appears old but the staircase is OK.

Could I fit another piece of wood over the existing riser and nail to string and tread to improve appearance as I really didn't want to fully re-carpet it but wanted to use a carpet runner or similiar.

Thank you again for your assistance, it is truly gratefully received!

It may be better to bond a thin sheet of ply rather than anything else. If the staircase is sound with no creaks or groans I would guess the problem has been there from the start.

The staircase has got a few creaks here and there and cracks in treads but so has the rest of this maisonette! It was built in the 50's and sadly it has and does suffer a few 'aches and pains' it seems.

Agreed something not too heavy to cover the riser sounds best.
Thank you again

No probs and good luck....

Cheers me-dear