Stair treads installation and humidity

[highup]

Keep in mind this is the Oregon coast, not New Mexico or Arizona. We don't get hot, we don't ever have 25% humidity.

Here's a data-logger graph of the place these oak stair treads are stored, and of the place they will be installed.
His shop is heated, the home is always kept on the cool side.
The treads are 1 inch by 11 1/2 inches, by 40. Stairs will be 35 inches wide.

I moved the logger upstairs in the heated garage (where treads are stored on stickers), on Thursday at noon, then on Friday and for the rest of the week, it was inside the home in the living space in the area by the stairs.

(pay no attention to the "Noon Wednesday shop floor" box where I started the logger)

The finish will probably be a waterborn poly like Benjamin Moore's Stays Clear.

I'm curious what the difference in temp and humidity will do to something the size of a stair tread................... especially if I seal all sides of the tread before installing them.

They never keep the house very warm, and in the summer I suppose it will be a little bit warmer. The home is shaded a lot and we live near the coast, so early morning temps are rarely above 65. Daytime temps can reach mid 70's later in the summer.
With the house being two stories tall and pretty shaded, not a lot of warming will occur from the daytime temperatures.

Anyway, here's my graph................ what's your take on sealing all sides of the treads and installing them in this place? Does it really need a lot of acclimation? The poly will certainly dry a lot better if the treads are coated in the garage.

 

[DarisMulkin]

I don't know about the wood but those are ideal temps for me.
Looks to be pretty consistent to me. Just thinking, would you really want to seal all sides and edges. To me if you did that the wood wouldn't expand and contract with the rest of the house.

Daris

 

[highup]

I don't know about the wood but those are ideal temps for me.
Looks to be pretty consistent to me. Just thinking, would you really want to seal all sides and edges. To me if you did that the wood wouldn't expand and contract with the rest of the house.

Daris

House was built in '23 ........it can move around the stairs.
Walls have MDF skirt boards and the walls are wavy and move a little when you push on them.......... maybe just the skirt boards move. Not sure.
Sealing them in my own mind, would stabilize them and keep humidity from getting into the bottom side.

 

[highup]

I don't know about the wood but those are ideal temps for me.
Looks to be pretty consistent to me. Just thinking, would you really want to seal all sides and edges. To me if you did that the wood wouldn't expand and contract with the rest of the house.

Daris

The "upper level of the shop" reading section is only a 24 hour period, but it would be stable in that range had I recorded longer. The treads have been up there for over 6 months.

 

[Floorist]

I wouldn't seal them. I would think they should keep acclimated to the rest of the house.

 

[Nick]

Cut your treads a 1/8" short at the crotch Hi to allow for expansion and contraction. the rise will hide the gap. I would just top coat them to with a lambs wool pulling in one direction only .

 

[highup]

Cut your treads a 1/8" short at the crotch Hi to allow for expansion and contraction. the rise will hide the gap. I would just top coat them to with a lambs wool pulling in one direction only .

The home is 1923 and still has the old fir flooring. I was thinking of sealing the tread all the way around so moisture coming up through the floor and inside the enclosed stairwell cavity couldn't cause it to warp.

I don't think the floor is sealed all that well because of a prior issue I had with MDF crown molding that had been laying on the floor in the living room. It shrunk a lot after being installed. It had been stored inside and laying on the floor for quite a few weeks.
If there's moisture coming up through the floor, then I assume it could possibly stagnate under the enclosed stairwell cavity.
I'll pin the floor tomorrow for kicks and giggles and see what it reads.

I'll hit it with my infrared thermometer too, especially the gaps to see if they read different.

 

[Nick]

Not a good idea Hi. The technical term for wood is sponge.

The moisture has to go somewhere , and that is into your new treads .

Cut them a 1/8" shy at the crotch . they are going to shrink and swell for the life of the flooring from changes in Temp, & RH. The shrink swell coefficient for wood is 1 x 4 , so it is going to expand 4 times as much in the width of the step . Thus the 1/8" gap.

 

[highup]

Not a good idea Hi. The technical term for wood is sponge.

The moisture has to go somewhere , and that is into your new treads .

Cut them a 1/8" shy at the crotch . they are going to shrink and swell for the life of the flooring from changes in Temp, & RH. The shrink swell coefficient for wood is 1 x 4 , so it is going to expand 4 times as much in the width of the step . Thus the 1/8" gap.

I haven't looked at the edges of the treads. Do they have a "finished" side? Cupping is a concern to me if only one side is sealed. I mean, even prefinished wood floors have some sort of sealer on the back side.

I ask because I don't know if material used for stair treads has a crown, or if there is a specific side that does up pertaining to the curve of the growth rings.
Treads will be net fit to the skirts..... as close as I can get them. There's enough movement in the skirt boards and walls to allow for any movement.
I was planning on using Chemrex 948 on the stringers when setting in the treads. The risers will be 3/4 inch plywood with a surface to be determined later. I was planning on using a bead of Chemrex on the top edge of the riser too.............. along with finish nails of course.

 

[Nick]

I never came across hardwood with a finish on the back side .

are you buying stair treads , or something to make them out of ?
Either way the length of the board should be running from stringer to stringer .

Chemrex 948 is good , But i like PL 400 premium better , and it is a lot cheaper .

Don't over think it . When you pin the treads go with the grain. one pin behind the other But you probably already know that .

 

[highup]

Ever install Junkers 3/4" floating solid? Has a seal on the back side.
Stair treads are on sight in a different area. That area is heated better. Look at the humidity graph on my first post.

 

[Nick]

No, Never even heard of them . I always installed solid nail down.

 

[highup]

No, Never even heard of them . I always installed solid nail down.

Junkers was probably spelled different than I typed it. They had a metal clip system that you installed on grooves in the back. The solid wood was coated with a heavy duty Scotch tape looking stuff.

The oak that is stored in the heated garage pins out at 6...... the lowest my ligno mini reads, and the stringers in the stairwell inside the home are averaging 12. I hit a 14 on the fir flooring under the bottom step.

There are currently temporary 2 by 6 treads and no risers, so there is no air stagnation under the stair case.

I gotta get for tonight and do some house sitting for a friend........... so no computer time till morning.

 

[Nick]

Is there a basement Hi ?
Are you making the adjustment for the different types of wood with the meter ?

 

[highup]

Is there a basement Hi ?
Are you making the adjustment for the different types of wood with the meter ?

No basement. yes I made adjustments to the meter. it only has two settings for different groups of species.
Picture a large garage that has never been below 60 degrees, even when we had a two week cold spell in February.................... lows around 25 and highs just over freezing. Currently with lows 30 to 40, the garage is still hovering in the upper 60's. They keep the home cooler than the garage.. I'm sure once all the work gets completed they will warm it up slightly.
The garage is sealed and kept somewhat constant. The living room, stairway and master bedroom area upstairs has always been cool. Being that the home is pretty old, I don't believe there is tar paper under the fir floor. Not sure, but I don't believe so.
New warm garage, versus old damp house would explain my pin readings and the datalogger graph between those two areas.
I'll pin the floor again tomorrow.

 

[highup]

I have new data from the datalogger.

I put two graphs side by side. The left one is from a week and a half ago. The one on the right ended today.
See the high humidity readings taken on the floor of the house? I'm thinking there isn't any kind of paper between the ship lap and the fir floor where I placed my datalogger. I'm also thinking the vapor barrier under the home is in bad shape.

The oaks stair treads have been upstairs in the heated garage for many months now. They are separated by cardboard strips to provide air circulation.
It stays about 70 degrees with 54% humidity.
What's going to happen when the treads get installed in the house?

I pinned the floor and it's in the 12% to 14% range.
I pinned the oak stair treads and they show 6% or possibly less. My meter only reads to 6%

 

[Ernesto]

Why don't you install plywood and full spread with an all in one adhesive like Bostik Single Step and be done with it already.

 

[highup]

Why don't you install plywood and full spread with an all in one adhesive like Bostik Single Step and be done with it already.

On the floor under the stairs, right?

 

[Ernesto]

On the floor under the stairs, right?

Huh?

On the stairs and under if you want. I've never seen movement in a stair tread or cupped ones.

 

[highup]

Huh?

On the stairs and under if you want. I've never seen movement in a stair tread or cupped ones.

..................and I live on the coast.

Not sure I'm understanding this. Plywood? The risers will be the only plywood on the stringers, the treads are 1 inch unfinished oak. The floor inside the stair enclosure pins out at 12% 14% and 16%, the treads are stored elsewhere and pin out at 6% or less.
Plan is to acclimate the treads in the house bu leaning them against the walls for good air circulation. I was told a week or possibly two to acclimate.

I figure sealing the floor inside the stairwell with something.......... Bosticks, or Aquabar and plywood, to stop air from coming in from under the house.
Once the stairwell is sealed off by installing treads and risers, there will be no air movement inside the cavity.
If the floor under the stairs is not sealed off, the moisture will in my opinion, build up under the stairs once they are finished.
I'm gonna seal the underside of all the treads after it's acclimated.