Home Improvement Today?

I would glue and screw the layers together

 

Yeah I was planning that, but also heard to use Rosen nails, .( like roofing nails) to hold down second layer. Always go with instinct, right. And I use liquid nails as the glue

 

If you do use nails , they should be ring shank

 

Why would it be bad to screw into the joist?

 

This????

 

The screws being pushed out by the joists shrinking/drying out. It really only makes sense in new construction when you are framing with joists that have a high moisture content. I was on a framing job for the state, we did 72 residential units, every one need a second layer of plywood in the kitchen and bathrooms. The architect wanted a screw every 4" and no screws in the joist. That sucked.

 

You don't use Kiln Dried framing material ? WTF

 

Ya i do. Still shrinks. I still screw into the joists especially if its not new construction, but that specific job we didnt. There was 8 units from the first phase of the job that had nail pops like crazy in the subfloor so the architect was probably just paranoid. We had reps from the lumber mill come out to test moisture content, the material sat outside to long and it was over 19%

 

May e they cut trees down and plane them into boards and right to being used?


Never heard of non kiln dried lumber being used for residential framing, or any framing. Except decking lumber which is usually dripping wet with chemicals smell great when burned, smoke clears the sinus's

 

Glue and ring nail > screws on a subfloor IMO

 

The ring shanks were the ones that popped. We started off glueing and screwing, but the job was all about speed. The architect and the state signed off on using ring shanks so we swithed to those. There was a year gap between the first and the sencond phase, by the time the second phase started we had to switch back to screws because off all the nail pops from the first phase. The nail pops resulted in a $450,000 lawsuit, everyone pointing fingers. Thats why a rep from the lumber mill had to come out. The majority of the houses were done with floor and roof trusses, but some of them had to be conventionally framed, those were the ones with the issues because of the wet lumber.

 

Speed and building almost always results in problems. If building our own home, speed would never be the plan. But we allow it to happen to others. ( not pointing at you at all) I sell home improvements, so I understand

 

Nail pops where ?

 

The subfloor. They came up right through carpeting and linoleum. I know its pretty much unheard of, but the nails came up everywhere, whole joists.

 

Nails don't lift from joist shrinkage , they come through the finished surface when the plywood shrinks , unless they were not shot into the joists or there was excessive movement in the joists and the worked themselves up which also shouldn't happen if the floor is glued because the joist shrinkage will be at the bottom of the joist

 

I completely agree. That job was a clusterfuck. People getting hurt, stuff being done wrong. I hated it by the end but now i miss it because the pay was great.

 

I agree there is many other factors but i think joist shrinkage definitely plays a role in it, especially if the moisture content is to high. You would know better than me tho, i just have the opinion because of what happened on that particular job.

 

Well , think about it

The nail gets shot through the 3/4" plywood into a 2x10 joist that because of moisture content is 9 1/2" , if the joist shrinks down to 9 1/4" and the plywood is still in contact with the top of the joist due to glue , how does the nail get further exposed ? The only way for that to happen is if the plywood was swollen at the time of nailing , or the nails were not driven completely , or there was excessive vertical movement ( flex ) and the nail worked it's way up which shouldn't happen with a ring shank

 

It looks cool but I bet it would be a bitch to keep clean...

 

I was thinking more along the lines of the grain tightening and the nail losing its hold due to shrinkage. Then other factors you mentioned like momevent in the joist and the joist or subfloor swelling and shrinking because of changes in humidity would help work the nail out. The houses were framed in the summer and its ushually really humid here in the summer, plus the framing was to wet. The nail pops happened in the winter when everyone turned the heat on and dried out their homes. Im not trying to argue with you, and i am not one of those guys that thinks they know everything, ive been in carpentry since i was 18 and i am still learning new things all the time.