Bottom stair riser creaking and floating

[Curryracer]

Hi all,
I've just had a nice new laminate floor laid in my hallway and now the small creak from the first step has changed to a big creak and more movement about 5mm when stepped on.
Unfortunately for me there is no easy access from under neath as instead of plasterboard, there is a wooden strip over a wood panel on the underside of the stairs, then a vertical tongue and groove piece behind the first riser. Very involved to remove!
I can get behind the first step as the newel post is fitted to the second stair leaving an angled edge.

How can I support the first riser to stop movement and noise?
Would it work to insert a suitable thickness strip under the riser from behind, then poly glue in place?

Thanks
Chris

 

[Deleted member 174758]

Unfortunately to do an effective repair job on a closed riser stair you need access to the underside of the treads. I think you'll have to bite the bullet on this one. At least you'll understand why the Victorians often just had plastered under drawings

 

[Curryracer]

Cheers for that. About what I thought.

 

[bobasd]

OP,
you say, the creaking only bigged up after the laminate installation which would imply the laminate is the major factor with the creaking?
a movement of 5mm is significant - if the 5mm is entirely new then i'd suspect that you've done something to the joinery at, or surrounding, the first step.

can you post photo's?