Screws for stud walls

[Jupiter01]

Hi All,

I was wondering what type of screw I should be using for the above. the wooden studs are 93mm CLS's and I was planning to use 70mm silver screws. Are these adequate?

Thanks in advance

 

[geraldthehamster]

Yes. In fact almost anything is adequate. Plasterboard screws are adequate (and self-drive well).

Cheers
Richard

 

[Deleted member 174758]

For framing (building the studs) you should use 5.0 x 90mm (#10 x 3-1/2in) countersunk head screws such as Screwfix Gold. 70mm is a bit on the short side TBH. Never use drywall screws for framing because they can shear (break) under shock loading. In any case they are generally too short.....

 

[geraldthehamster]

I'm sure you are technically correct. However I have stud walls assembled with 75mm PB screws that have been up for years. They're not going to shear in a finished wall.

 

[Jupiter01]

would these 90mm suffice?
http://www.toolstation.com/shop/Scr...0/Multi+Purpose+Zinc+Plated+Pozi+Screw/p57363

 

[foxhole]

Better not to have fully threaded screws as they pull in better, with full thread they can hold the timber apart if not firmly held.

 

[big-all]

10 or 8s by 3 1/2"
http://www.toolstation.com/shop/Scr...d850/Twinthread+Countersunk+Pozi+Screw/p86794

 

[Deleted member 174758]

I'm sure you are technically correct. However I have stud walls assembled with 75mm PB screws that have been up for years. They're not going to shear in a finished wall.

Twice in the last five years I have dealt with situations when what you imply is impossible has actually happened - drywall screws used to frame new stud walls have sheared and/or pulled out. In one case the building was subjected to sudden partial subsidence caused by an underground sewer collapsing, in the second case it was a jobber who hadn't sufficiently propped an RSJ which dropped (it went straight through the floor in fact because there was no pad to spread the load) and the stud wall upstairs ripped itself apart.

So, drywall screws are far more prone to shearing if driven with an impact driver than conventional wood screws, the threads are smaller so they have poorer pull-out characteristics, the heads are smaller so they don't hold as well either, and in any case you really need 90mm screws (or at a pinch 80mm) to frame out softwood studding at 3 x 2 or 4 x 2in cross section - 70mm is too short - and they will shear well before a 5.0mm wood screw will when subjected to loading. If you are a carpenter, they teach you this at college. For a reason.

 

[Deleted member 174758]

would these 90mm suffice?
http://www.toolstation.com/shop/Screws+&+Fixings/d90/Single+Thread+Countersunk/sd760/Multi+Purpose+Zinc+Plated+Pozi+Screw/p57363

Better not to have fully threaded screws as they pull in better, with full thread they can hold the timber apart if not firmly held.

As foxhole says, particularly if you are a DIYer with a limited toolkit, a screw which isn't fully threaded is a better bet on softwoods. On 90 x 44mm (4 x 2in nominal) framing I'd be using something like these Goldscrews. (sorry, but for some reason the SFX site won't let me find 5 x 90 - the 5 x 80 look the same, and that's the link)

 

[geraldthehamster]

Twice in the last five years I have dealt with situations when what you imply is impossible has actually happened

Fair dos, though it seems to me that in the catastrophic situations you describe, the stud wall was probably the least of the householder's worries. And we don't actually know how well those walls were constructed, or what would have happened to a stud wall constructed by any means.

Cheers
Richard

 

[Deleted member 174758]

From experience if you use the correct size, type and length of fixings they are far less likely to fail even when stressed and when over stressed the failure tends to be progressive rather than instantaneous

 

[big-all]

a wooden structure will settle move spring creak bend with the overloaded component bending bowing and compressing distributing the load to other timbers that will in turn bend bow and compress a bit less until they are happy in turn redistributing the load further till it settles
now a join between timbers designed for the working load in one direction will happily work overloaded in other directions but off course if the fixing have no built in redundancy to cope with unexpected loads they are more likely to fail as things bend bow and compress a bit with the extra loads

 

[geraldthehamster]

All fair points, chaps. OP, listen them, not me