Recently there was a thread regarding the virtues of nails vs screws....with the common theme being 'shear strenght'.
Me, being the engineering technogeek I am, I'm not one to accept the a blanket statement of "Nails are better" without something to back it up...
So...I did a test.
I took 2 2x4's and nailed them together with 16d nails. (edit...ok....wrong pic...this is the screws....but the nails were in the same spot)
I left the other ends about 12" apart. The intent is to take this end, set it on a scale and measure how much force it takes to bring the ends together.
So I rotated the test assembly and put the end on the scale....
The weight of the stud was enough to make it drop down to the position shown. The only measurement on the scale was the raw weight of the wood.
The nails did not give....the wood did.
So...I repeated the test using #8 3" screws.
Basically....alsmost exactly the same results.....
Initial conclusion....all the talk about shear strength....bogus....the softness of the wood negates the shear strength of the nails or screws..I don't think the average DF1 stud is strong enough to put a nail or screw into shear failure.....
To add to that...when I was taking the test pieces apart...the nailed pieces came apart easy...just lift one board, pulled apart with no problem....the screws? Damage to the wood...and significant more effort to pull apart....at least 3-4x more force.
With that said......
I can not imagine trying to do a framing job using just screws......the time to use screws would be an easy 5-10x longer over an air nailer...
Given the way typical framing is done....I see no advantage to screws over nails....few of the forces are in tension vs shear....in tension, screws would be significantly better....but that is why we have so many Simpson hardware choices....
Me, being the engineering technogeek I am, I'm not one to accept the a blanket statement of "Nails are better" without something to back it up...
So...I did a test.
I took 2 2x4's and nailed them together with 16d nails. (edit...ok....wrong pic...this is the screws....but the nails were in the same spot)
I left the other ends about 12" apart. The intent is to take this end, set it on a scale and measure how much force it takes to bring the ends together.
So I rotated the test assembly and put the end on the scale....
The weight of the stud was enough to make it drop down to the position shown. The only measurement on the scale was the raw weight of the wood.
The nails did not give....the wood did.
So...I repeated the test using #8 3" screws.
Basically....alsmost exactly the same results.....
Initial conclusion....all the talk about shear strength....bogus....the softness of the wood negates the shear strength of the nails or screws..I don't think the average DF1 stud is strong enough to put a nail or screw into shear failure.....
To add to that...when I was taking the test pieces apart...the nailed pieces came apart easy...just lift one board, pulled apart with no problem....the screws? Damage to the wood...and significant more effort to pull apart....at least 3-4x more force.
With that said......
I can not imagine trying to do a framing job using just screws......the time to use screws would be an easy 5-10x longer over an air nailer...
Given the way typical framing is done....I see no advantage to screws over nails....few of the forces are in tension vs shear....in tension, screws would be significantly better....but that is why we have so many Simpson hardware choices....