i'd guess because general opinion is that screws hold
stronger than nails. when you break off a few just
tightening them by hand, you realize that they
are made from low stength material that is
unsuitable for any important holding task.
my experience is with roberson wood screws available
in canada at hd and cdn tire. there may be better
but i can't find them.
I've never seen 1.5" hot-dipped galvanized spiral nails. In any event,
it's unnecessary. Spiral nails, like screws are meant to keep the
fastener from backing out. If you use the 1.5" joist hanger nails,
they're not backing out. There's not enough embedded length, and if
you've ever tried to pull one of them you know the galvanzing might as
well be glue.
Sometimes you don't have room to swing a hammer but you can get a driver in
Sometimes the vibration from hammering can knock other stuff loose (like
plaster) particularly in remodelling.
Screws allow for (easy) disassembly if you goof or just change your mind.
(the main reason I use them inside)
More holding power particularly in soft woods
Use steel screws labeled for general carpentry use. I use 3" #8 screws for
most interior joining (I am a homeowner not a contractor). Drywall screws
are made of a weaker alloy and with less metal since they only need to hold
up a modist load.
Screws are a little slower to use than nails though and cost a bit more
It is the diameter of the fastener that is most important factor for
installing hangers. That is why they require the special 10d x 1.5" nails.
An 8d common nail is not the same and does not meet the design criteria for
sheer strength. Simpson is very clear on this. If you use screws then the
core of the screw (the center part, without grooves) would need to be the
same diameter as a 10d nail, which means approximately a 3/16" lag bolt.
You'd then have to drill out every hole in the hangers, because they are not
big enough. A joist hanger can reach it's design loading only when every
nail hole is filled. That is why cheap hangers have so many holes. You might
be able to get an engineer to certify that the screws you are using have an
equal sheer strength as a 10d nail.
Regular joist hangers are designed to support vertical loads. They are not
specifically designed to handle horizontal forces of any magnitude. There
are special hangers and connectors made by Simpson and others to do that.
Which would totally change the load capacity of the hanger and expose
bare steel. Extremely bad idea, and I'm sure you're not recommending
Why does the hanger quality or price (not sure which cheap you mean)
have anything to do with the number of holes? A certain number of
fasteners are required to develop the rated load capacity - that's the
only determining factor on the number of holes in a hanger.
No, not recomending it. Anyone crazy enough to drill out every hole in every
joist hanger probably can't read.
The quality of the hanger, and it's price, is determined by the type and
gauge of steel they use to manufacture them. Cheaper, weaker steel would
fail sooner with 6 nails in the hanger than a hanger that was made with
stronger, thicker steel. The manufacturers compensate for this by increasing
the number of nails in order to receive the same design rating as the
competition. Unfortunately, most framers do not/will not fill every hole in
a hanger with 12 holes so the hangers will not deliver full design loading.
Fortunately, these things are way over-designed, so we don't see any
buildings falling down. But they over-design because they compensate for
real world factors like framers not putting all the nails in.
I had an inspector fail a frame once because of the joist hanger nails,
citing the info above. That when I checked it out and found him to be
So too would be a good building inspector! When we built our home, our
inspector checked that the proper nails were used for the joist hangers.
Mind you, the special nails on Simpson hangers are for holding the hanger
on the ledger board. The two (or four, depending on size) angled nails that
hold the joist onto the hanger may be regular common or spiral nails.
"Never ascribe to malice what can equally be explained by incompetence."
Only the shaft of the screw is bearing the shear load...if it is of
equivalent diameter and and strength, the shear strength at the hanger
will be as high as the nail. It wouldn't be out of the question to use
a SS screw that would have higher shear strength at the same diameter...
The screw / nail bears some of the shear force - the clamping force of
hanger against joist (both faces) also bears some, and probably this
clamping force is higher if using modern twin helix screws tightened
The hole in a hanger is just big enough to fit a 10d nail. The screw would
have to be twice that size (assuming the threads account for half the
diameter). Stainless screws or screws that are made of (more) hardened steel
could be smaller. But you still need to find the design data to prove this.
The diameter of the shank is all that is actually resisting the load in
shear--not the threaded portion. it's inside the beam or joist...I never
did nor am I claiming it has been approved, only that it isn't anyways
near a 3/16" lag to get an equivalent area for the shear load...
Are either of you Jesuits? "How many angels can fit on the head of a
I still don't know why you'd want to use screws in the first place.
I've never found a situation that I couldn't nail and nails are
cheaper, faster and there's no arguments about angels and pins. ;)
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