re-enforce stair riser

[joe webb]

Hello all,

My staircase was covered w/ carpet and I am replacing it with oak wood treads and mosaic tiles on the risers. It has few steps w/ curved front. The tread is 44" wide, and the middle point is pushing out about 2" further than the ends.

The risers are made of 1/2" OSB so that they can bend to follow the tread's curve. If I put my knee against it, it flexes, and I am concerned once tiles, the grout lines will crack. I am thinking of re-enforcing them and I see 2 options.

1) Glue another 1/2" OSB in front of it
2) trace the contour and transfer it to a 2x4. put such block behind the riser. One at the top, one at bottom.

Please let me know if there are better ways to re-enforce them.

Thanks much

[Bill Carey]

I would take the second option of fitted 2x4 blocking, glued and screwed. I assume the OSB on the straight treads is sufficiently strong and does not bend when pushed? Some folks walking up the stairs are going to kick the risers so they need to be rock solid so the tiles don't loosen up. And I have no experience installing tile on OSB. Others may want to chirp in on that, or have you satisfied yourself that it's a do-able procedure. Looking forward to the final pics.

[Bill Dufour]

I would think just use silicone caulking to hold the tiles so they can flex a bit, Use silicone grout with a color to suit.
Bill D

[joe webb]

I would take the second option of fitted 2x4 blocking, glued and screwed. I assume the OSB on the straight treads is sufficiently strong and does not bend when pushed? Some folks walking up the stairs are going to kick the risers so they need to be rock solid so the tiles don't loosen up. And I have no experience installing tile on OSB. Others may want to chirp in on that, or have you satisfied yourself that it's a do-able procedure. Looking forward to the final pics.

Thanks Bill. On the straight treads, 3/4" plywood was used for risers and they are solid. I placed a 1/4" hardi board in front of them before tiling.
Given I can't bend the hardi board, i will add Ditra before tiling. My concern is the flexing of this OSB riser.

[joe webb]

I would think just use silicone caulking to hold the tiles so they can flex a bit, Use silicone grout with a color to suit.
Bill D

Good idea Bill. I hope I can find silicon grout matching the grout used on the straight treads. I am using a thinset that have some flexing. But usually given these are small 1x1 mosaic, they won't crack. The grout line will give up first.

[Bradley Gray]

I don't see a downside to doubling the riser AND adding blocking. You only get one shot at this before you tile.

[George Bokros]

Given that some people may kick the risers I would not ceramic tile on the riser bive the tile would be prone to cracking or loosening it kicked. Just $ 0.02.