How to fill large crack above staircase skirting board

[Safeer Ahmed]

Hi - I moved into a new build a couple of years back

Since then these large cracks have been appearing. I want to fill them in and have tried to use the Polyfilla Deep Gap - however the crack is so large that I can't seem to get a layer thick enough to sit in the crack. When it dries, it just sinks through and falls into the storage space underneath.

I've attached a picture of part of the crack - any ideas how i can fill this up? Should I use a different product? Or a different technique?

Appreciate your help

 

[Tigercubrider]

Try a silicone sealant or decorator's caulk (applied with a gun) then the filler could go over the top

 

[Robbie uk]

This is one place that will crack forever more, whatever you fill it with. Get some small wooden quadrant and glue it to the wall. make sure its touching the timber of the stairs. As people walk up and down the stairs, the stairs will flex and move. The quadrant will not move as its stuck to the wall.

 

[Dazza Jones]

Could you not use expansion foam to fill the hole, cut off the unwanted but once cured, then fill over,?

 

[misterhelpful]

If the gap is wide enough, you could wedge some 6mm foam backer rod in there, followed by a flexible filler/decorator's caulk. That said, stair strings are notorious for movement and cracking,and may still open up, so a small quadrant bead to cover the whole area might be a better option.

 

[opps]

Hi - I moved into a new build a couple of years back

Since then these large cracks have been appearing. I want to fill them in and have tried to use the Polyfilla Deep Gap - however the crack is so large that I can't seem to get a layer thick enough to sit in the crack. When it dries, it just sinks through and falls into the storage space underneath.

I've attached a picture of part of the crack - any ideas how i can fill this up? Should I use a different product? Or a different technique?

Appreciate your help

Your stair stringers are dropping down. They may drop slightly more.

You can use car jacks and props to lift them up to close the gap and then use more screws to hold the stringers in place.

If you don't want to do that, or don't have access to the underside of the staircase, you can use expanding foam in the gap and then cut away the excess (once cured) and back fill the gap using a sandable filler.

I you don't use extra screws to prevent the stringers dropping further, you will probably find hairline cracks will appear in time. It might be advisable to use a MS polymer "caulk" after the filling. They are more flexible than standard caulk but unlike silicone they won't repel paint (see CT1, stixall, PU40 etc).