# What kind of screws for hold up a plywood sign?



## bobbotron (Jan 7, 2010)

I'm helping a community org mount a plywood sign to strapping that we've screwed into a cinderblock wall. I'm wondering what kind of screws you guys would suggest we use - we're currently debating between galvanized, stainless and brass. Brass seems like it would be too soft to hold up the heavy plywood and probably annoying to install... Haven't decided between #8 and #10 screws...


----------



## bobj3 (Jan 17, 2006)

Hi Rob

I would say number 10 stainless screws..


=======



bobbotron said:


> I'm helping a community org mount a plywood sign to strapping that we've screwed into a cinderblock wall. I'm wondering what kind of screws you guys would suggest we use - we're currently debating between galvanized, stainless and brass. Brass seems like it would be too soft to hold up the heavy plywood and probably annoying to install... Haven't decided between #8 and #10 screws...


----------



## jschaben (Jun 21, 2009)

bobj3 said:


> Hi Rob
> 
> I would say number 10 stainless screws..
> 
> ...


YEP - :dirol:


----------



## Phil P (Jul 25, 2010)

Hi Rob

Unless it's a marine (salt water/salt air) environment or the screw heads will be on show I'd go for galvanised steel screws or better still treated decking screws. The reasons are that they are cheaper, more readily available and are less likely to shear off or round over when driven home than the alternatives. Modern passivated screws can always have their weatherproofing improved by dabbing a spot of clear lacquer or gloss paint onto the screw head

Brass is actually perfectly strong enough to hold heavy weights; in fact bank and other high security wooden doors which tend to be thick and very heavy are often specified with brass or bronze hinges and matching screws. Brass screws won't break if subjected to a "jemmy" attack, instead they tend to rip or deform very slowly. Brass was also the traditional choice for use with timbers with a high tannin content (esp. oak, S.American mahogany and walnut) as it doesn't corrosion stain but brass is soft so that it is often necessary to drill, pilot then fix with steel screws first before backing out the steel screws one at a time and replacing them with brass ones to avoid damaging the visible screw head (BTW always remember to align the screw slots..............)

Personally I dislike stainless steel screws. I find the quality very variable with the cheaper ones having no better weather resistance than cheap galvanised steel screws. They are also prone to the heads shearing off and the drive indentations (on Phillips or Pozidriv screws) rounding over when driven in unless you are prepared to pilot and pre-fix with ordinary steel screws first (just like you do with brass screws). Architects specify stainless steel hinges/screws on every building I work in these days so I've fixed thousands of the so and sos in recent years and learned to carry a spare box of stainless steel screws and a pair of pliers in my tool belt whenever I'm working with them. On the up side they can look good in the right environment

Regards

Phil


----------



## TomE (Dec 17, 2010)

Could also go with hex drive roofing screws if the holes in the strapping are correct size. 
The washer head with rubber washer helps seal the attachment and offers a bit of "shock" resistance.
Might also consider through bolts


----------



## bobj3 (Jan 17, 2006)

Hi Phil

Here we go again, we have 60,663 Members and I would say 60,000 are on this side of the pond, we can buy stainless steel cheap in the states, the zinc plated ones will not stand up to the true test of time, most will put black marks on the stock in time.he only needs to put in 4 to 6 screws to hold the sign, the norm.he is not building a deck... 


=======



Phil P said:


> Hi Rob
> 
> Unless it's a marine (salt water/salt air) environment or the screw heads will be on show I'd go for galvanised steel screws or better still treated decking screws. The reasons are that they are cheaper, more readily available and are less likely to shear off or round over when driven home than the alternatives. Modern passivated screws can always have their weatherproofing improved by dabbing a spot of clear lacquer or gloss paint onto the screw head
> 
> ...


----------



## Phil P (Jul 25, 2010)

bobj3 said:


> we can buy stainless steel cheap in the states, the zinc plated ones will not stand up to the true test of time, most will put black marks on the stock in time.


Bob, cheap stainless steel screws here often cost less than Spax or Reisser passivated zinc steel screws, but it still doesn't alter that fact that the cheap stainless steels are often no better than BZP screws in terms of weather resistance and that they are far more prone to heads snapping off and drive recesses rounding out, especially if you use an impact driver

Phil


----------



## bobbotron (Jan 7, 2010)

Hadn't thought about that - I put up a fence a while ago, where the gate hardware used cheap stainless screws. Those screws were quite soft, I rounded out a few of their heads while installing it until I realized I really had to be careful driving them in. Guess I'll see what the local hardware store has in stock. I think I'll either go stainless or #12 brass.


----------



## bobbotron (Jan 7, 2010)

So the sign is 4 sheets of 4x8' sign grade plywood. Each sheet will be hung 4' wide, 8' high, screwed along the left and right side (into strapping), I was thinking 4 screws on each of these two sides, do you think this will be sufficient? It would be nice if there weren't too many screw heads, I know I could hide them with plugs, but I think that's getting a little OCD.


----------



## Phil P (Jul 25, 2010)

That's actually a pretty big sign, especially for only a few screws. When you say strapping am I right to assume that you're talking vertical softwood battens which are fixed in turn onto the wall using good long screws (#10 x 3in or longer) into what we call Rawlplugs? From your description am I also right to assume the sign is 16ft wide x 8ft high? For signboards I normally make up a flat frame from 2 x 1 or 2 x 1-1/2in in or similar with top, bottom and for taller signs middle horizontal battens running the full width of the sign. That gives me the opportunity to fix at something like 16in centres across the top and bottoms of the boards near to the edges as well as get a screw into the middle of the board to prevent it from "popping" when the damp gets to it (as it will over time). Screw spacings I tend to put at 16in centres just like a domestic stud wall (which means 6 or 7 screws up each side) but with more screws you could happily go down to something like #8 x 1-1/4in screws (for 1/2in board) or 1-1/2in screws (for 3/4in board). Plywood signs need edge protection (weatherstripping) at the top and sides and if this is rebated it can be used to hide the screw heads if they are placed right at the edges.

With sign boards and sign boxes it's probably better to err on the side of caution and over engineer it. That way it won't fall off (or get blown off) and injure someone in the future

Regards

Phil


----------



## tdublyou (Jan 8, 2010)

Rob,
I have to agree with Phil here. With an exterior sign that large, more is better. Weather will do a number on plywood, especially the edges and the wind can turn a 4 x 8 sheet into a sail that can do a lot of damage. 
We are all making a lot of assumptions about this project so more information will get you much better advice, such as. 
What size is the strapping? 
How is it fastened to the block wall? Tapcons, rawlplugs, ackermans, etc.?
What is the spacing on the strapping?
What is the fastening schedule for the strapping? 12" OC, 24"???
I'd be more worried about having enough screws rather than how many will show. If the sign is painted, you could simply paint the screw heads to match and they will virtually disappear.
Just my 2 cents


----------



## Mike (Nov 22, 2004)

There is a simple test to determine if the screws are stainless that is rust resistant: simply see if a magnet will stick to them. If the magnet sticks the stainless is a 400 series and will rust. If it does not stick then the stainless is a 300 series and will work fine. 400 series has a very high percentage of chrome in the mix and this can make them brittle. This is also a handy tip when shopping for silverware; test with a magnet before buying.


----------



## bobbotron (Jan 7, 2010)

Thanks for the info guys. Yeah, it's a big sign - it's a mural! 

The strapping is 1x6 red cedar, we used 2 1/2" tapcons to fasten them, as this allowed for more than 1" of the screw in the brick, as per the tapcon instructions. Each board is 8" long, the whole height of the sheet of plywood. The plan was to mount each panel on two vertical strips of cedar. We may end up sticking another piece of strapping in the middle of each panel, I have some unused fence strapping we could use.

Thanks for the suggestion, we were definitly planning on well sealing the sides of the ply. I want to put a flashing cap on the top too.

Would like to write more, but I'm at work, maybe later!


----------



## tdublyou (Jan 8, 2010)

Rob,
I would seriously encourage you to add the middle piece of strapping, 1 x 3 would be sufficient since you will not be joining 2 sheets on that piece.
A flashing along the top can't hurt as long as it keeps water out and doesn't trap it. 
As for a fastening schedule, I would go with 12" - 16" O.C. around the perimeter and 16" - 18" in the field, which in this case would be the middle piece of strapping.


----------



## bobbotron (Jan 7, 2010)

*It's up!*

Thanks for the suggestions guys. It's up now. We did a #10 brass screw every 12" on each side of each panel, and 3 screws in a row down the middle. There's a cap on the top, lots of paint everywhere, the sealer is going on later this week..... Here's a photo of it.


Re-cycles mural is up & on it's first coat of paint... by bobbotron1, on Flickr


----------



## tdublyou (Jan 8, 2010)

Rob,
Looks great, job well done.


----------



## Phil P (Jul 25, 2010)

I agree with Tim, Rob. Looks great!

Regards

Phil


----------

