wood floor over irregular dock subfloor

[kcalvin]

I am going to be installing a 2 x 8 T&G recycled douglas fir wood floor over somewhat irregular thickness 2 x 12 RS planking on a renovated dock in Southeast Alaska. This will be a new 2,500 sf retail showroom. We are insulating below with 4" of XPS insulation between joists and sealing all gaps with Enerfoam. Despite being directly over water, the area stays dry as long as the roof doesn't leak. The XPS will serve both as an effective air barrier, and vapor barrier due to it's thickness.

I was intending to trim-head screw the 2 x 8 flooring perpendicular and directly onto the 2 x 12 planking, using constuction adhesive to back up some of the inevitable voids between floor and subfloor, as well as lock the floor down to prevent squeeking. I was also told we should apply wood glue to the T & G joints, and end match material with a 1/4" spline.

I read on this forum that 30# felt was highly recommended below wood floors. Obviously a slip sheet of felt would not allow the construction adhesive to do the job I had intended. It is not practical to level this floor--it is an undulating dock almost 100 years old.

Should I not worry about using the felt, as perhaps the XPS below is doing the job? Any comments on my installation plan?

Thanks!

[Outfoxed]

Whew. I dunno, this job might have its own appeal. If you live out of state and the terms were COD.

I was sorta hopeful until that whole undulating dock thing . . .

[dgbldr]

A couple of suggestions:

It may make the job easier to get a floor sander to shave the high spots to be closer to flat. If it's too "undulating" for that, you might want to use a leveling filler material. Construction adhesive may or may not make a good "filler" for this application, depending on the gaps.
If you screw and glue everything together real tight, you better not have any expansion and contraction. So you want to seal every board well on all 6 sides before installation. And if you cut any of the boards during installation, the end grain needs to be re-sealed. This would not be my installation choice. I would give it some room for movement and put the slip sheets to facilitate that movement.

[Bill S]

I would not glue the T&G edges together. That will make the floor act as one big board. The expansion buy the end of the summer would be huge. The 2 x 12 sub floor will be moving at 90 degrees to your finished floor, again why glue. You should check the moisture content of the sub floor and the 2 x 8's. Check with local lumber suppliers for the correct MC. If you are installing the floor in the winter, you needed to leave expansion joints so the individual floor boards will have room to grow. If you gauged it right, the floor will be tight by the end of the summer when the boards reach there maximum size. There are charts online that will tell you the expansion per foot for doug fir as it goes from say 8% to 12% MC.

[davenorthup]

I would not glue either. Glueing 2X to a floor sounds pretty scary as you watch it all move. I would be especially careful to allow for summer expansion as mentioned above. You guys are still getting quite alot of rain now though?

Felt should never be relied on (completely) as a flooring moisture barrier; especially after you blow 10,000 small holes through it with your nailers. I would rely on your underside MB.

Flattening the floor may not be practical and as long as the client knows and accepts that there may be variations and creaks - Your fine. I would still get it as flat as possible. Using the felt in this case will aid in moisture protection and help keep the floor a little quieter. Construction adhesive will not bridege the gaps. Use a floor leveler or something else that will set up.

Where in SE are you?

[kcalvin]

Great comments! thank you. Project is in Sitka and we get over 100 inches of rain a year--30 of it in October & good deal throughout rest of winter. Your ideas of measuring moisture content and predicting potential expansion are excellent and I should have thought of running such calculations myself as I am a timber framer in Oregon, but also the manager/developer/part owner of the dock in Alaska.

In using reclaimed fir planking salvaged in Oregon, I assumed I would not have to worry to much about movement due to the material having basically stabalized long ago. But--as you rightly point out I did not take into account seasonal variations and the consequential expansion and contraction. I don't actually know the change in ambient humidity between the seasons--seems like it is always pretty damp regardless of the time of year! I will both get the average moisture content of the material we are shipping up (currently stored in my shop in Sisters, OR) and see if I can find how to accurately predict the result of it being relocated to the Alaska climate.

Nixing the glue joint at the T & G makes good sense. Complete leveling the subfloor would be an excercise in futility because leveling across the area would cause significant floor height tie-in problems where the the floor meets other spaces and doorways. Also, we periodically have to replace rotted piling below, and even with tremendous care cannot reasonably peg a precise resulting height of the floor--hence the undulating dock. My intent in using the 2 x material was to be able to bridge the variations in planking below (no more than 1/4" between planks) so we would not have to use any kind of filler type floor leveler material, other than possible globs of construction adhesive in a few of the longer spans between contact points. We have replaced many of the most irregular subfloor planks to get some semblence of a reasonable subfloor, so that contact points with the subfloor would not likely be more than 18-24" apart.

This is meant to be a rustic-looking floor and as I am essentially the client, If it doesn't work as expected I know exactly who is responsible. But having never laid or finished a wood floor, I'd like to try to do it right and use this as a learning experience on other future projects.

Soooo... sounds like the use of felt couldn't hurt, and drop the edge glueing and construction adhesive to allow for more unrestricted and inevitable movement. Celebrate the gaps that open up as a sign that the wood is alive and well, and attribute any creaks to the ghosts of long-dead cannery workers.

The good folks at McFeelys recommended against a trim head screw due to lack of holding power--felt I should go to a #10 head. As we will be sanding out the 2 x 8 (having previously been lightly planed) I suppose we therefore have no choice but to countersink and plug screw holes. What kind of screw spacing/pattern would you guys recommend?

Perhaps I will look more at a leveler product between some of the more irregular subfloor boards--I am familiar with the powdered product--Durobond, but this would be a very big job if the goal were to create a smooth--(but not level) surface over the entire 30 x 80' area. What other leveler products should I consider that wouldn't require so much mixing--and is reasonably priced?

I am also trying to figure out what kind of an epoxy filler product I should use to deal with chip-outs and knot holes. Any thoughts?

Thanks! You're all invited up to visit!

[davenorthup]

Yeah your in a rainy place for sure. I may just stop by in 2 summers from now when we kayak SE. Thats the plan - ferry - kayak - ferry - kayak. Never been to Sitka, closest I've been is Ketchikan.


RE moisture content - just let it acclimatize in the building when it arrives. I am sure it will suck up some moisture on the trip up. If your 'subfloor' and new floor are within 2-3% you are good to go.

The 2x should do a pretty good job at bridging some of the gaps. I would suggest adding in some shims here and there as your going for gaps that exceed 1/8" or start using them at a 1/4". The construction adhesive will not act as a shim holding the flooring up as well as an actual shim would.

Felt will help in a little noise reduction (squeaks) and you can double or triple up felt in low spots to help bridge those gaps.

The 2X T&G flooring will never stay completly together unless you have little moisture change and constant Rh levels. Your older DF probably stands a better chance than some of the pine 2X floors I have seen.

I agree with using a #10 head screw vs. trim head. As far a screw pattern I would go ramdom especially since it is supposed to be rustic.

If you are going to site finish your floor I would install and wait as long as possible before sanding and finishing - giving it time to move, then before sanding you could add a fill for the gaps and screw heads.

My favorite floor ever was rustic hickory we did. Installed the 6" boards, threw everything metal on it and then laid 4' X 4' plywoods squares on the floor and jumped on the plywood, then hit it with a chain. You rarely get to do that to a finished product.

Again I'd level with shims ect and use any normal floor filler before sanding.

Good luck...

[Bill S]

"RE moisture content - just let it acclimatize in the building when it arrives. I am sure it will suck up some moisture on the trip up. If your 'subfloor' and new floor are within 2-3% you are good to go."

Make sure you sticker the pile of 2 x 8. The boards need to be exposed to the air on all six sides. The stickers need to be inline from top to bottom to so the load is directed down and not trying to deform the stock. If you dead stack the lumber, the boards in the middle will not acclimate and the ends of the boards will bell out since they take on moisture the quickest.

[kcalvin]

Hey Homer, you definately have a place to launch and store your kyaks when you get to Sitka. Just contact us at www.fishermansquay.com before you get to town. Hopefully you will approve of our floor installation.

We were intending to sticker, heat and fan-dry as recommended for at least two weeks in area prior to installation. Sure hope this is enough time. Current moisture content of material is 15-18 percent at core--adjusted for temperature. Higher than I had expected, but it has only been under good cover for past 2 months and we've had an unusually wet winter here so I'd be surprised if it picks up much more moisture on the trip up.

With a #10 screw, the great folks at McFeely's think I should be countersinking and plugging--not trying to fill the large hole with putty. I've never done this on such a large scale so we will just have to see how it goes. They also recommended having pairs of screws across from each other on the same plank, rather than an offset alternating pattern.

Screw pattern--when you say random, do you mean completely random? Roughly how many screws/ LF on average would go you suggest? As you know, anything special order is at least two weeks out or more in Alaska.

Kris

[joseph]

I did a random plugging on a floor ,i figured i would just do the squeeky areas and high spots and be done faster and have less screws . In hindsight it would of been better to have some pattern to follow .stopping to think where the screws need to be as i go is a time killer .

[davenorthup]

Hey there - after thinking about it more I think a regular screw pattern is best. I've only done random patterns on wide plank boards that were both nailed through the tongue and also top nailed. Since you are dealing with 2X I bet you'll have to at least screw 2 per each board that are intersecting the 2x12 (running perpendicular?). You'll know if that is enough as you get going.

Your probably right about the plugging - that is alot to plug but would look better than filling. Depends on what you want the finished product to look like.

Let your moisture meter dictate when the floor is ready - as you know. We've had floors ready in a day and 3 1/2 weeks - you never know.

Good luck