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I've been researching for some time how to cover a curved stair riser that had been previously tiled. I wasn't pleased with the look of the tile, so I removed it and sanded back the mastic before veneering. However, the veneer was too thin and it left a significant gap between the tile and the riser. I would like to cover it with a 1/4" or bigger plywood (or some such material) so that I can paint the risers to match the rest of the staircase and cover the grout. You can see there is a very sharp turn on the left side of the riser. I tried kerf cutting some 1/4" plywood and found it impossible to get the plywood to bend along such a tight curve.

Does anybody know of a good way of doing this? I've had "bendable plywood" recommended to me, but I don't know what that is or where to get it. Lauan plywood turns up as a result, but it's not available near me.

enter image description here

CcS
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    Not quite sure, but I think the process requires steam and clamps and time. Do not know if it can be bent as much as you are thinking of, unless using very thin plywood/thick veneer. – crip659 Aug 10 '21 at 19:13
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    Along with what SteveSh says you can also use a heat gun to help bend it. The heat will relax the grains. Do a search on "bend wood with heat gun" and you'll see lots of info on it. – Micah Montoya Aug 10 '21 at 19:46
  • @MicahMontoya, you won't bend anything thicker than raw veneer (1/16") with a heat gun. Is that what you're suggesting? – isherwood Aug 10 '21 at 19:47
  • I have never heard of a traditional veneer being used for staircases. I have seen retrofit kits which is basically 1/4" wood/material but never have I seen a traditional veneer. I guess it could be done but seems really difficult to make this look good. Also I don't see veneer lasting in an area being kicked by shoes. – DMoore Aug 10 '21 at 19:57
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    @isherwood that would be incorrect. If you've ever been involved in boat or bow building, you would know you can bend wood thicker than what you specified. Just apply some veg oil first. As for the OP and SteveSh it's thin enough to do so. – Micah Montoya Aug 10 '21 at 19:59
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    Preparing the surface for veneer that is easy to bend seems like an easy approach. You say you tried that and didn't like the gaps "between the tile and the riser". Can you explain that better? Why were there gaps? Why, after reasonably smoothing the surface of the risers, can't you cut and apply a suitable veneer in a way that looks good? – jay613 Aug 10 '21 at 20:52
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    @jay613 the gaps OP is referring to is the grout lines where the tile meets the riser or I should say where the tile is too far away from the riser and there's too big a gap. – Platinum Goose Aug 11 '21 at 02:00
  • @PlatinumGoose ah! Well, on the two upper stairs the gap is easily hidden and on the lower one it's not a gap, it's just a grout line meeting the riser. Is that so bad @Ccs? In some ways it's better. If the riser meets floor tile directly, it will also meet the perpendicular grout lines and you'll have to fill the tiny gaps there. If the riser meets a parallel grout line you can try to mate it perfectly. I think it'll look nice. – jay613 Aug 11 '21 at 12:04
  • It's really that the tile previously used on the riser was installed before the floor tile. So you have a normal sized grout and then ~3/4" of dead space from the removed tile and mastic. I can fill that with veneer and additional grout, but it's a lot of space and looks a bit messy in my opinion. I think I'm going to take one more shot at kerf bending a 1/4" plywood strip (as suggested), and, if that doesn't work, I'll bite the bullet and order bendable Lauan plywood on Amazon for $50 with shipping. – CcS Aug 11 '21 at 14:18
  • Will it be painted or stained? – Harper - Reinstate Monica Aug 11 '21 at 23:16

7 Answers7

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Just about any type of plywood can be bent by cutting slots on the hidden side that leave both clearance for the bend and enough uncut wood on the front to support it. I once made some speaker cabinets that had a "horn" output similar to this:

bent plywood in speaker

Your bend is sharper than the one I did, it looks to be 90 degrees, so you'll need to make more cuts to allow it to bend that far. It does take some work and using Luan is a lot easier but, as you said, there is no Luan where you are.

Here is a photo that gives you an idea how this works:

bent plywood

jwh20
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    You beat me to the ans with a picture. The picture in this answere is how to kerf the plywood. It can be done easily and I have done this with both plywood and on a dry walls to create a round corner for a wall.– Also you do NOT have to fill the backside kerf with filler – Programmer66 Aug 10 '21 at 22:31
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    You don't _have_ to fill it, but few use cases are subjected to more abuse than a stair riser. I would. Even a drizzle of wood glue would add substantial impact resistance. – isherwood Aug 11 '21 at 12:57
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    And wood glue mixed with the sawdust left from cutting the kerfs would be even better! – FreeMan Aug 11 '21 at 14:29
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    This is the right answer and I have upvoted. But the wood on wood isn't going to make it look any better. And the plywood grains are not going to take anything but stains well (paint will look terrible). But now OP knows how to make a curve out of plywood... but after redoing many a stairs... he shouldn't be doing this. You don't spend time on something that doesn't solve the issue. The curved wood piece can look good on its own but not with the existing (different wood) stairs. – DMoore Aug 11 '21 at 17:56
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    I was thinking about your answer and something seemed off. Your picture is the OPPOSITE of what you described. The wood wasn't scored either you can see the manufacturing marks. (just update picture so heads don't spin) – DMoore Aug 11 '21 at 20:26
  • @Dmoore I don't understand your comment. These pictures match the text as far as I can see: the first one shows the visible effect; the second one shows "behind the scenes" how to accomplish that effect. – Tim Sparkles Aug 13 '21 at 23:14
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There are plywood products made for radius situations.

Bendy plywood and Wacky Wood are a few names it goes by. Options are available from several manufacturers like Radius-bending Plywood or Flexi Ply.

The layers are oriented in one direction making it easy to bend around pretty tight radius like yours.

enter image description here

isherwood
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Kris
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Take some 1/4 inch plywood, and, with a circular saw, cut vertical slices in the back side ~3/16 inch deep, every half or quarter inch or so in the area where the bend is. This may give you enough flexibility to bend the plywood around the curve. Try it with some scrap wood first, and maybe use a gallon paint can to form the wood.

SteveSh
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    Then, once it's bent into shape, press construction adhesive into any gaps to strengthen and stiffen the assembly. – isherwood Aug 10 '21 at 21:02
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    The method in this answer is correct. 1/2" distance is too much, 1/4 " between the kerfs will provide good flexibility for the bend. Start the kerf at the beginning and the end of the bend. Use a string to measure the correct length of the plywood to use. – Programmer66 Aug 10 '21 at 22:23
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    @DMoore it's similar to blowing glass in that many (most? well, myself at least) people do not succeed at their first attempt, but cutting through all but one layer in plywood seems pretty common. The kerfs are usually glued up in their final position, and that adds a lot of strength back. – Eike Pierstorff Aug 11 '21 at 07:46
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    You can buy MDF already scored this way (in the UK anyway), for precisely that sort of use. But if you're doing it yourself you just need a good depth stop - and some spare material for practice. – Chris H Aug 11 '21 at 08:35
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    The key is to properly support the thing once the kerfs are made. As I said, fill it with glue, or back it with level boards cut at a radius. It's not rocket science and it's a well-proven technique. Poo-pooers need not reply. – isherwood Aug 11 '21 at 12:56
  • @EikePierstorff - the point is you would never do this with 1/4" plywood. 1/2" would be the absolute minimum. Unless the plywood was made flexible (and then you wouldn't need to score as much or at all). – DMoore Aug 11 '21 at 17:59
  • @DMoore ah, you got me there. I have to admit I had to look up how thick that actually is, and I assume you are right (btw. never give up on imperial units - it's just amazing to see american woodworkers calculate fractions without calculators. No European ever hat to substract 3/16 of an inch from one and a quarter feet, and it shows in our math skills). – Eike Pierstorff Aug 11 '21 at 20:16
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The problem you have here is you are trying to solve an aesthetics issue. You could tackle this 10 different ways but what can you make look good? This could be done with just plaster or some lightweight concrete blend (how they do a lot of stairs in europe). But can you make that look good?

You can certainly have someone create a piece of wood for you to use too... But can you make it look good? Can you secure it so it won't pop back out? Is it worth it?

Not to be harsh but the whole staircase looks pretty rough while floor above looks nice and floor below so-so. If I were doing this I would reskirt the right side - (you already have a template with the existing one, just extend it. You can get a 1/2" white pine and have this knocked out quickly). Obviously this wasn't made correct and should end at floor - or some kind of trim/transition piece attached to floor. The left side is missing trim too. You can't have a rounded corner to walk on and an exposed wall. You are going to have to custom cut a plinth there. I would then plaster the bottom and use pine board for the other three. I would then paint them all the same color (this could be white like the trim or a color to make it stand out).

That's as nice/cheap as you can get. No way would I put wood/veneer there because it would have matching issues with the other wood. Wood + wood is hardly ever good.

Your other option if you are replacing floor below it to chop off that rounded corner. The bottom step may not be as functional but will probably look better.

DMoore
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  • I agree that trying to do this with plywood is possible but not the easiest way of accomplishing your end goal (to make it look good). One additional way (of many) to accomplish this goal is to use white laminate (link below). This would require having a flat, smooth surface first. It will bend around your radius. https://www.homedepot.com/p/FORMICA-4-ft-x-8-ft-Laminate-Sheet-in-Brite-White-with-Matte-Finish-004591258408000/202911152 – stmp945 Aug 10 '21 at 21:52
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If it is going to be painted, I would probably do 1/8" or 3/16" tempered hardboard. It will take that curve easily. Just be liberal with brads/staples and use adhesive on the backside. You can fill the staple holes with spackle or your favorite filler. You will need to prime it before painting and definitely sand the smooth side with 150-200 grit before priming.

They also make 1/8" finished veneers for cabinet work like covering kickplates but those are a bit harder to source over 6" wide. Local cabinet makers could help you source the material if you call around.

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I am going to suggest a coopering approach. Several small pieces cut at a slight angle to make the curve. You might be able to glue them up before attaching for long term stability. Visualize how whiskey barrels are made.

If you wanted an exact match to the curve on the lowest riser, once installed, some aggressive sanding could probably get you there.

You'll need a chop saw or table saw (or a friend with one!) to create the pieces. Use extra caution here because the pieces will be quite short.

This quote is from a simple search I did: "Coopering technically refers to the art of wooden barrel making, but cabinetmakers use the term to describe the process of making curved parts of solid wood without steaming or bending the wood."

IMHO, steam or heat bending would require very thin layers of wood, multiple laminations...quite a bit of work and sourcing very thin wood might be tough.

George Anderson
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    This would create multiple seams, Kerfing a piece of plywood is the easiest way to create a curve riser for this stairchase. – Programmer66 Aug 10 '21 at 22:29
  • @Programmer66 To each their own. Like another person posting mentioned, there are probably 10 ways to solve this problem. You're method might be fine. I've had issues trying that with the plywood cracking and splitting. There is nothing wrong with multiple seams, it's done all the time in woodworking. ...just glue them up and clamp. it's very reliable. To attain a matching curve would require some sanding to round it over, but not much. Anyway, just wanted to respond. Take care and DIY on! – George Anderson Aug 12 '21 at 14:57
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You mention plywood here but there's another option that you might want to consider which I don't see mention in other answers. Instead of manufactured plywood, you can laminate thin boards around a curve and glue them in place. This is a process usually used in furniture making. You need a bunch of flexible strips of wood that add up to the desired thickness. You could cut them if you have access to a bandsaw but I think you might be able to get away with commercially available veener. Then you take a strip, wrap it around the curve, and then wrap each successive layer around the last, gluing the surfaces together. This needs to be held in place until the glue dries. At that point the curve should hold pretty much on it's own. You could do this on a jig and put it in place after drying but I'd be tempted to do it in place with a little vertical trim on both sides (do this before the straight section is put in place) should clamp it in place. Something heavy (e.g. boxes of tile) might be helpful as well. It might want to relax a little after the glue is dry. Brads or finishing nails should help and gluing the first piece with construction adhesive might be warranted.

JimmyJames
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