What kind of screws for attaching metal brackets to treated lumber?

[Stephen Tashiro]

What's a good kind of screw for exterior use to attach metal brackets to treated lumber?

I like Deckmate brand screws for exterior use, but I think all their screws have tapered heads, so they don't sit flush if you use them in a metal bracket. I'd like a screw with a non-tapered head. It woujld be nice to find one wtih a "square drive" head like the Deckmate screws, so I wouldn't have to change bits to use them.

[Bruce Page]

Mcfeeley's sells good quality SS square drive screws.

[Rich Engelhardt]

There's washers you can get for the bugle head screws.
I can't recall exactly what they are called though - except for washers.
They come in chrome plated, brass and stainless steel.

[Erik Loza]

Rich, are you thinking of "finish washers"?...

260399

Erik Loza
Minimax USA

[Jamie Buxton]

When you say "what kind" there's two issues. One is the head design. The other is the screw material. Pressure-treated lumber quickly eats some materials often used for fasteners, like straight steel. Google with "ACQ fasteners" to learn more.

[David Helm]

I am wondering what kind of brackets you are talking about. If they are structural (joist hangers, etc.) screws are not allowed. What is generally required is the appropriate sized hot dip galvanized joist hanger nail (hardened steel and must fill every hole). Only heavily galvanized can withstand the corrosive affects of the wood treatment.

[Rich Engelhardt]

Erik,
Yep - those are the ones.

[steve joly]

Would kreg pocket hole screws work? Variety of lengths and square drive

[Lee Schierer]

Why not just countersink the brackets so the screws will fit. However, I don't think countersinks or screws meet building codes for structural brackets.

[Andy Pratt]

You just need an exterior rated screw from a reliable manufacturer. McFeely's has a lot of options for this in square drive and they usually have $1 shipping so that is the first place I would check. Most of their offerings have a variety of head types available, so I think you will find what you need there.

Not sure if Stephen is using this for a structural application or not, but Simpson makes screws that are rated for use with their structural hangers. They have a design that looks like lags but they are actually #9 and #10 screws. I only know this because they came in a bag attached to each of the large joist hangers we put onto a recent addition. You can look up load data for them on their website under "structural connector screw".

I would match my screw type based on what the bracket is made of (i.e. don't bother with stainless screws if the bracket is just galvanized for example), but don't drop the screws quality below any "exterior" grade.

If your lumber is ACQ treated then you need an ACQ rated fastener: some treated lumber is done with ACQ some is not. I have received both types in the last two years depending on who I ordered the lumber from. It is hit and miss which screws meet this rating, so you need to check the box/description for each one. Kreg Blue-kote for example does not meet ACQ rating even though you might think it should based on their descriptions.

[Jim Matthews]

Hot dip galvanized or stainless steel should be adequate.

If you're concerned about electrolysis between the ACQ PT board and the metal hanger, lay in a stip of water and ice membrane between them.
The screw will pull the elastomer into the threads and should be sufficient to prevent moisture migration.

(No water, no electrolysis)

[Stephen Tashiro]

lay in a stip of water and ice membrane between them.


I'm not familiar with "water and ice membrane" -another thing to browse at the hardware store!

I don't have a particular bracket (structural or non-structural) in mind yet. I was merely curious what people like deck builders use when they have to attach metal components. I'd think that would be a common job.

Now that cordless impact drivers have been invented, I much prefer screws to nails and I think of them as better fasteners than nails. But, as David Helm points out, structural brackets beg for nails. In many of them, the holes aren't big enough for a typical deck screw - and common nails don't have a head that sticks up.

[Bruce Page]

Deck screws are too brittle and do not have the shear strength that joist hanger nails have. Thus, they are not allowed for use in joist hangers. Just an FYI..

[Steve Losing]

I bought some cabinet screws at the Local hardware store they were torx head. They also come in various lengths and sizes they have about a 1/2" head on them I used them to fasten bathroom privacy stalls to wall. With the gold heads I drilled my oak frames and then ran the screws in with impact driver they really HOLD!!!

[Mark Bolton]

Hot dip galvanized or stainless steel should be adequate.

If you're concerned about electrolysis between the ACQ PT board and the metal hanger, lay in a stip of water and ice membrane between them.
The screw will pull the elastomer into the threads and should be sufficient to prevent moisture migration.

(No water, no electrolysis)

Yikes!! Are you serious? Thats a roll of the dice at best. Is the screw guarnateed to be coated? Fully, Partially? What mechanism guarantees the screw gets adequately coated?

This is all to say that a coating of ice and water is an approved coating to protect the screw in the first place.

The ACQ issue depends only on whether your source is supplying ACQ. If they are supplying CA, or CA-b, or something else the issues are all different.

Im not trying to nit pick here but the issues of hangers and fasteners in exposed areas (if the OP is exposed or not) above 19% moisture content, are critical. The wrong fastener choice with ACQ, in a wet location, is a nightmare waiting to happen.

*EDIT* - Speaking to the screw protection, not the hanger protection. The ice and water for joist, and hanger, protection is fine (though TV overkill to me) but the membrane will likely to nothing for the screws

[Mark Bolton]

What's a good kind of screw for exterior use to attach metal brackets to treated lumber?

I like Deckmate brand screws for exterior use, but I think all their screws have tapered heads, so they don't sit flush if you use them in a metal bracket. I'd like a screw with a non-tapered head. It woujld be nice to find one wtih a "square drive" head like the Deckmate screws, so I wouldn't have to change bits to use them.

Unfortunately its not really a simple answer any longer unless you can default to the guaranteed solution which is stainless. Most people have to be a little more cost conscious than that.

There are many changes with regards to pressure treated in the last ten years however things were really bad, and then got a little better, but now you still have to think a little. When the old treated was phased out (still available to the commercial market) which was CCA, they replaced it with ACQ. With ACQ they traded out the arsenic in place of copper and de-rated any lumber that would normally be used above ground. This holds true for many of the new treatments. It means anything other than timber/posts will not be rated for ground contact.

To the point, trading the arsenic for copper made the material highly corrosive due to electrolysis. But what you have to remember is electrolysis requires water. This is why the caveat is 19%. Thats the threshold for outdoor/wet condition use. Below that the fastener corrosion issue becomes much less. At that level or above you must use fasteners that are double hot dipped galvanized or better or stainless. You can have no aluminum flashing in contact with ACQ at the 19% level either.

Now,.. they have come out with numerous other treatments. CA, CA-b, CA-c, and several others. All of these are basically to try to combat the highly corrosive (and costly) aspects of ACQ. You have to remember, when a commodity which is so heavily sold, is tied directly to the copper market its not such a good thing.

In the end, if you want to buy "just enough fastener", you have to look to what material your local source is supplying. Your lowest cost choice will be a fastener that meets the double hot dipped spec. Something between a G90 and a G185 coating depending on the lumber in your area. More than likely your only going to find fasteners which meet the G185 or higher.

If your talking structural hangers you will simply want to go with a simpson structural screw. They are available right in the joist hanger isle along side the hangers. Nails are fine too, and are my preference for speed and cost, but if you prefer screwing have at it. Just remember with joist hangers you will have to cross nail anyway which is not really feasible with screws.

[Andy Pratt]

No intent to be argumentative but need to correct repeated misinformation in this thread:

There are load-rated screws that are ok for use with structural hangers, see this link: http://www.strongtie.com/products/connectors/screws-loadrated.asp

[scott vroom]

Lots of advice being given here, some good and some bad.

The PT wood you buy today is absent the anti-corrosive arsenic and chromium used a decade ago. Today's PT wood is highly corrosive, even to thinly coated galvanized fasteners. Stain less steel fasteners will not corrode in the PT wood, but will corrode galvanized connector hardware.

You should follow the manufacturers' reccomendations for the combination of PT and connector hardware you've chosen, particularly for applications where a failed connection could result in injury (e.g., decks). There are some newer epoxy coated fasteners that can be used safely.

Here's a couple of links you may find helpful:

http://www.strongtie.com/productuse/ptwoodfaqs.html#

http://www.deckmagazine.com/decking/fighting-fastener-corrosion.aspx

[Mark Bolton]

The simple fact of the matter is the only reason this thread would even arise is for the mere fact that we had a perfect solution for treating lumber in CCA. The absolute only reason CCA was voluntarily phased out for residential use is because of ignorant and improper handling.

CCA was a completely save and reliable treatment for lumber. The lumber industry knew full well how valuable CCA was and voluntarily took it off the residential market to insure its use in commercial applications where its essential and properly handled. All products were treated for ground contact. You could embed a 2x4 in concrete if you needed to. Easy on fasteners.

The only reason we no longer have this option is for the fact that individuals burned CCA, buried CCA scraps and waste, improperly disposed of CCA sawdust, and so on. This ignorance now has us coating fasteners with more than twice the galvanizing and ITS associated costs. It has no longer allowed aluminum flashing, roof metal, or any other non approved material to come in contact. It has caused builders to come up with the idea of wrapping joists in membrane to protect fasteners and ITS associated costs. It goes on and on.

The lesson in all this is when you have a board that bugs die if they eat. Mold can not decay. Do us all a favor, handle and dispose of it wisely. The idiots who packed scraps home and burned them in their wood stoves, burned them in a pile on a job, shoveled their sawdust into the backfill around pier holes on a deck build, and so on, have cost us all dearly.

Virtually everything to buy at this point that is associated with PT lumber costs 40% more than it did 10 years ago. And you can be rest assured, the PT of today is not going to last like CCA. The PT of the future may, but CA, CA-b, CA-c, no dice.

[scott vroom]

The absolute only reason CCA was voluntarily phased out for residential use is because of ignorant and improper handling.


I'm sure there were those that also disagreed with the banning of asbestos in so many building trade applications, and I'm sure they had the same (invalid) arguments.

[Mark Bolton]

There is no invalidity. The science is there to prove it and is easily found. The material in its intended use is, and was, completely stable. The entire issue arose due to improper disposal. Studies of leachate around structures, and waste, are clear. Its been measured and documented. The waste is the issue.

I personally agree with the removal of the material from the marketplace. However the reason I agree with it is because of the sad fact that even when provided with the information, a large majority of individuals will choose to dump/burn their scraps as opposed to disposing of them properly. It would be akin to sprinkling a healthy quantity of D-Con on your campfire and then handing your children a bag of marshmallows and a stick.

That does nothing for the fact that CCA was better in every way as compared to anything we have today.

The bonus as I see it is the fact that the reduced life of todays treated is having a positive effect on the use of materials like cedar. The extreme increase in cost alone has made many of my customers move to cedar and other naturally decay resistant woods all the while knowing it too will not last.

[steve joly]

I'm sorry I misunderstood your orrigional post, for metal strapping, joist hangers, or other similar items the easiest thing I think is a strap shot gun with nails. There are screws available also but we only use those in the rare occasion that we can not use the gun.