First off, hello to everybody.
The L shaped stair to my brother’s basement is part concrete (the top landing and first 5 steps down) and part wood (the remaining 11 steps and intermediate landing). When he built it a few years ago he used 3/4 plywood for the treads (with no overhang) and risers, with the intent of covering the plywood and concrete with 3/4″ hardwood sometime in the future. He just had a cabinetmaker fabricate the landings, treads & risers out of 3/4″ edge glued red oak. He intends to glue it all down with liquid nails.
The material is on site and will be used. With that in mind, what steps should be taken to get the best installation, especially over the concrete? I also have the following questions:
1. Would a urethane based hardwood flooring adhesive be more appropriate than liquid nails? (The wood portion is extremely uniform. The concrete has been skimmed with a high strength concrete patch to be as uniform as possible, but might require an adhesive with some filling capability; no more than 1/8″.)
2. Should the back of the hardwood be kerfed or grooved (like casings or t&g flooring)?
3. Should finish nails also be used to attach to the plywood and/or between the treads and risers?
Please note the following conditions:
a) There are no moisture infiltration problems.
b) The basement and first floor are heated and cooled with a heat pump.
c) He is in Tucson. Even though he is in a “wet” area of town, precipitation only averages 14 inches. The only humid time of year is Jul, Aug & Sep when the dew point averages 60 degrees, and that’s still about 15 degrees lower than the South.
HLR
Replies
A couple of points:
1) If the stairs are "legal" now then adding the treads will make them illegal. There is supposed to be no more than 3/8" variation in tread-to-tread height, including the top (but not bottom) step. If the top step is "legal" now, it will be too short by the new tread thickness after the tread is installed
2) Stair treads absorb an enormous amount of force, a good part of it horizontal (especially when someone is going down). Some mechanical anchor is needed to keep the treads from moving. (Pegs between the new and old treads might do this OK. Screws up from the bottom, where possible, would probably be better.)
Thanks for the reply Dan,
1) Actually, the stairs are illegal now, but will be legal when completed, as the 3/4" hardwood treads were taken into account when it was originally built.
2) The screws fom underneath are a good idea, although it probably can't be done on the bottom step as there is only 4-1/2" clearance (my brother loves to overbuild; underneath the 3/4' plywood tread is a 2x12)
HLR
hisboi, welcome.
If I'm understanding the construction, there's no way to screw the new pcs. to themselves from the back or underside. That being the case, I'd be tempted to use urethane glue (PL Premium) and screw and plug the risers and treads to the frame as well as to themselves maybe. Drill the plugs from the backside of the tread and riser for good grain match. Set depth stops to keep from over or under drilling, (a drill press with jigs to speed the process.) You can almost make the plugs dissappear.
Best of luck.Remodeling Contractor just outside the Glass City.
Quittin' Time
Hi Calvin,
I meant to say that just the bottom tread has clearance problems (a screwdriver bit set deep into a Milwaukee right angle drill takes up 5-1/2"). The others are all accessible. Even though the substrate is 2'14" thick, with predrilling and an assistant to act as dead weight above, it should be doable.
I am more concerned with the hardwood stock cupping or splitting, especially the landings, which, because they are edge glued, are basically 3'-6" square slabs. Plus, the top landing and first 5 steps need to be adhered directly to the concrete substrate, which goes against most recommendations.
HLR
L Roi, cabinetmakers are well aware of the problems that are created when dissimilar materials are glued to each other. Solid wood will move due to humidity changes as we all know. Plywood and concrete will not move noticeably. If solid wood is glued to them, the wood will either break the glue bond or split. The wider the wood, the more movement.
The best way I know to attach the treads to both surfaces is with screws. Nails will work loose over time. Making a wood to wood connection can be done with trim head screws. Trim heads leave about a 3/16" hole that can be filled. Attaching to the concrete can be done with Tapcon screws. I have not seen trim head Tapcons but they are available in a flat Phillips head in 3/16". The screws can be countersunk enough to use a plug. The wood to wood treads can also be installed with countersunk screws and plugs if you want everything to match. Concrete is a great conductor for moisture so I would seal it and put down some 15# felt paper before attaching the treads or platforms.
The risers that are connecting to the plywood can be nailed, preferably into the stringers. Any going on concrete will have to be screwed.
I made the mistake of gluing some winder treads to an Advantech (OSB) base with polyurethane. I knew better but I thought the PL glue was going to make things more rock solid. I'm a slow learner, I keep forgetting the basics. Please benefit from my mistake. Screws in treads will restrict movement too but not like glue. Make the shank holes a bit larger and there will be plenty for the change in width as seasons and conditions change.
Here is a picture of my bad. The edge glue was stronger than the wood.
Beat it to fit / Paint it to match
Hi Hammer,
Thanx for the response. Your picture perfectly illustrates my fear. A proper edge glue is always stronger than the wood.
I had assumed that, for the landings at least, my brother's cabinetmaker was going to do something that would allow for movement, like maybe laminate thinner t&g hardwood stock to plywood (sort of a shop built engineered floor), with a solid nosing to hide the lamination. Instead, he has edge glued slabs (The landing platforms are about 3'-6" square). I'm supposed to install it for him, but I'm uncomfortable with the way he wants it done. But, then, there is that sibling dynamic thing that makes it hard for me to give him advice and hard for him to accept it from me. That little .jpg may do the trick. Still, I'm worried about splitting even with tapcons in sloppy holes.
HLR
Worry about it if it is glued to plywood. Sealing the back side can help. Wood is a natural material and the cells in it are designed for moisture transference. They still do their job to some extent, tree or board. I supose a cabinetmaker could make plywood and make the top veneer 1/4" thick but it would be costly and may result in some failures.Beat it to fit / Paint it to match
Re glue splitting the wood, you can help things a little if you simply stall for six months or so, while the treads acclimate (hopefully stored right next to the stairs). Although it's probably better to install them in winter than in summer.It might work out to use a pliable glue like Liquid Nails, combined with pegs, at least on the concrete steps. (The "pegs" can be screws set into shields in the concrete.)
a picture is worth a thousand words....