Packing for under ply on worn stone stairs

silver50 · 8 Dec 2021

Due to having to shape and cut the ply on the first 5 stairs (where stairs turn) I opted just to use 12mm ply to overlay the old, worn stone stairs. It’s getting done just to be better for new carpeting.

Is there anything that can be dispensed (ie from a sealant gun/spray foam( that would support weight where the worn area is rather than using the packing I’ve used so far?

For it’s purpose (carpeting) what I’m doing will probably be fine but when screwed down the 12mm ply isn’t lying quite as level as I’d like.

Just wondering about any ideas for filling the gap the worn stair treads are leaving. Considering smoothing with some sand/cement but im not sure how ideal that really is either. Bit messy and might still break up..

thanks

cross thread · 8 Dec 2021

Self levelling compound

silver50 · 8 Dec 2021

cross thread said:
Self levelling compound

Do you reckon? I did consider it but in the situation I can see it running down the stairs.

Also whenever I’ve come across it over the years (when other people have obviously used it) it always seem to be broken up into a million pieces

dazlight · 8 Dec 2021

It having carpet it will be ok. Round off the edge of the plywood as well so it’s not a point on the underlay.

but if you must screed it. Use ardex NA or a fibre smoothing compound like Mapei renovation.
Plywood the riser so it’s level about 5mm over the tread and that will stop the screed running.

silver50 · 8 Dec 2021

Thanks. Tbh I don’t really want to screed it.

main reason for posting was wondering if any products out there (likes of something dispensed with silicone gun) that I could use that should offer extra support under the ply/filling any gaps

I’ve got quite a good rounded edge on the edges of the ply

Deleted member 174758 · 8 Dec 2021

If you were going to that level it would have been almost as easy to face the treads with plywood (as shuttering) and fill to the correct level with something like an epoxy-based stone repair material. Anything light enough to spray in a can is probably going to be too soft to give a lot of support although maybe low expansion PU foam might do the job as it sets with higher density - the standard stuff probably won't work

big-all · 8 Dec 2021

will carpet gripper nails damage stone ??
no nails in blobs under the treads will work, but you can't use the stairs until it hardens but you will need to get the stone very clean and free from loose paint

silver50 · 8 Dec 2021

Did wonder if a foam might do it, thanks.

the gripper can be screwed to the ply easily enough. It was previously screwed and looked like on with some sort of no nails.

RandomGrinch · 8 Dec 2021

If the gaps were a few millimeters - maybe Gripfill?

Edit: sorry @big-all , just noticed the 'no nails' comment

big-all · 8 Dec 2021

the trouble with foam is it expands perhaps 20-50 times the volume and flows easilly and a pain to clean up
if the foam is captive it can blow/bulge the tread

Deleted member 174758 · 8 Dec 2021

big-all said:
the trouble with foam is it expands perhaps 20-50 times the volume and flows easilly and a pain to clean up
if the foam is captive it can blow/bulge the tread

Wrong type of foam B-A! You are thinking of the high expansion stuff you blow into holes in masonry round pipework and the like - I was specifically referring to low expansion PU foam such as Everbuild Exact Gap which expands only 5 to 10%.

JobAndKnock said:
...although maybe low expansion PU foam might do the job as it sets with higher density - the standard stuff probably won't work

This is the sort of stuff we've been using to foam-in door casings and windows the last few years as it doesn't bow in the door jambs, etc (and potentially undo all your hard work getting them in straight). I was also assuming that the OP had fixed down the plywood to the stone steps (4 to 5 fixings each?), otherwise that will all go Pete Tong the first time the skid come skidding down the stairs. If low expansion stuff is blown in to 3/4 fill the available space, left for half an hour to expand then "topped up" it won't bulge the plywood. This stuff takes no more than a couple of hours to set and the expansion phase can be accellerated a bit by spritzing the underside of the ply and the steps with a wee bit of water (not a flood). One thing to note is that PU foams never work in very cold weather, so the materials need to be at 5 degrees Centigrade or above for it to set (10 degrees plus is better). Also I'd suggest adding a cut to length timber "leg" under the middle of the plywood treads before foaming-in - it should make for a more rigid repair

silver50 · 8 Dec 2021

The gaps are up to about 5-6mm max, Is gripfill quite a good bet? I'm happy to still go with packers but wouldn't mind using something like that too.

Deleted member 174758 · 8 Dec 2021

In this cold weather GripFill, etc will take maybe a day or two to set. If the gaps are only 5 to 6mm I'd go with the low expansion foam TBH

cdbe · 10 Dec 2021

I would use flexible tile adhesive - it will be perfect for this.

silver50 · 10 Dec 2021

Thanks v much for the replies. I stuck with the packers and screwing down well. Still got first 5 steps to do, where the stairs turn so trickier shapes.

I’m 90% happy with how they are but under the very leading edge of each step could do with a bit extra support. I think I will need to use one of the suggestions here. The flexible tile adhesive sounds like quite a good shout.

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Packing for under ply on worn stone stairs

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