I've always taken a serendipity view of screw gauge when doing rough
stuff as in "hey, I'd better use a bigger screw for this." I need to
cobble together some two bys for a frame for a basement storage rack.
I've got a box of number 9 2 1/2 inchers that ought to do the trick.
Question: Is there a formula for determining the minimum gauge for a
screw if you know the load?
My favorite screw for that application is a "Spax":
I prefer them for attaching cabinets to walls these days because of the
superior shear strength.
That said, most engineers will tell you that for many
construction/structural projects nails will provide more shear strength
than screws, so it really depends upon the application.
I never thought about it. Just that so many screws today are absolute crap.
If you shear off a screw while driving it into the wood, it is a bad sign.
And it depends where you buy them too. I have had terrible luck with deck
screws and lag screws from the local home depot. But the local ace hardware
store gave me screws that were higher in quality, stronger and a few cents
If I got any kind of basic repair outside or in the garage these days, I
just use their deck screws. It ain't art or furniture. But it is strong.
They don't shear off and they don't rust outside.
The old standby rule about strength for fasteners is to estimate how many
will do the job. Then put twice as many in there. I have always been
accused of using too many screws anyway.
What you also need to ask is if there is a way to determine the quality
of the screw you are using. I know of #6 screws that are stronger than
All things be in equal, McFeeleys.com has the specifically information
that you are asking and IIRC their catalog has a chart of this also.
On Friday, April 6, 2012 12:05:36 PM UTC-4, Gramp's shop wrote:
Those will do. If you are concerned, smear a little construction adhesive in
there too. Up here in the Northeast, if we are framing a house, we cannot use
screws. Must use nails or you will not pass the framing inspection.
That seems a little strange - what's the rational given, if any?
I learned the hard way that any carpentry (as opposed to ww) work I do,
someday I, or someone who comes after, will have to take it apart again.
I use screws for all that now.
Intelligence is an experiment that failed - G. B. Shaw
Used to be that framing had to be toe nailed...
Now I see nails used from top and bottom sil to studs. Not as strong.
The toe nailing really locks it in from both sides.
straight nailing will not withstand storm forces as much.
But then again, most roofs will easily lift before the framing gives.
On 4/11/2012 7:37 PM, Swingman wrote:
If you google "strength of wood screws" you will find
Download the PDF and read it. You will find out all you ever wanted to
know about wood screws, their strength and application. (and likely
even MORE than you wanted to know). A good read.
on wood: mechanical fasteners.
www.awc.org/pdf/ndscom97.pdf will find you my first reference to "Part
XI: Wood Screws" in secion XI. All you ever wanted to know about wood
screws (particularly in construction) from the American Forest and
Look up "fasten master" structural screws. They are approved for a LOT
of general construction use - and their "timberlok" screw can be used
in place of hurricane straps to fasten trusses to double top sills -
as an example - replacing the tiedown strap and 12 nails with ONE
And put on earth quake straps on the foundation and sil board.
That will work in other cases of strong wind. A force trying to
flatten a house.
Another thing we did in earth quake country was to put in shear walls.
Often the outer boards are 1x tongue and grove but they silip and slide
in wind. On the inside put sheet ply It doesn't have to be all walls,
but some of the side on all sides. Keep that side from laying over.
On 4/11/2012 7:15 PM, Leon wrote:
On 12 Apr 2012 01:17:25 GMT, firstname.lastname@example.org (Scott Lurndal)
toe-nailing USED to be pretty well a requirement in the days of plain
nails. Ardox nails help. TimberLok screws can be used in place of
hurricane straps to connect trusses to sills. Fully code compliant,
and you won't mistake them for a common screw or lag bolt - and you
don't need to remove them or X-Ray to know how long the timberlok is
(they are clearly marked on their black hex heads)
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