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Fred_ 07-17-2012 10:31 AM

Regular floor screws in pressure treated wood

I am posting in the general forum as I could not find one dedicated to decking / outside building. Let me know if I missed it.

I just realized I made a mistake rebuilding my deck and would like the know the real impact of it as well as potential options to mitigate the damage.

The problem: I rebuilt the whole floor of my deck with regular floor screws (I did not know the existence of PT wood screws). From what I read, the water will come in contact with the copper in the wood and cause premature / accelerated rusting.

Here are my questions regarding that:

1. Apparently this starts happening in the first few weeks and you can see staining on the wood around the screws. The deck has been there for 3 months and I don't see any stains despite some major rainfalls. Is this really an issue or just some marketing trick to sell new stuff ?

2. I plan on staining the wood by the end of summer to protect it, given that, I don't see how the water would come in contact with the copper / screws so will this still be an issue ?

3. Are there any other way to protect the screws if staining won't do it ?

4. If it is still an issue, is it worth it to replace all the screws (roughly 1000). There is no real danger of harm here since it's just the floor (the railing is made of metal) and the worst that can happen is a plank becoming loose but the base below it is 100% safe and at worst the garage roof is 5 inches below. I would much rather replace the screws as they fail then replace them all.

5. I am also doing some lattice framing with pressure treated wood. Right now I am using a nail gun and I don't see how doing this with screws would be a good idea but pressure treated nails don't seem to exist, what would be the best course of action here ?

Thanks a lot for the help !

pkrapp74 07-17-2012 10:34 AM

They do need to be replaced, and it would be much easier to do it now versus as needed.

Fred_ 07-17-2012 10:51 AM

Thanks for your answer,

would you mind expanding a little bit on the questions I asked ? I really like to have the whole story when doing something.

danpik 07-17-2012 11:01 AM

Are these galvanized screws you used? Galvanized screws in contact with the copper in the treated wood will have a galvanic reaction weather there is moisture or not. It is the electrical properties of the two dissimilar metals that causes the corrosion

Fred_ 07-17-2012 11:48 AM

No those are regular floor screws - there is a slight plastic coating on them I believe but they are not galvanized.

Here is something interesting though : I am about to build a pergola with PT wood and large bolts to hold it together - Interestingly enough, what home depot suggests for that is - galvanized bolts - I just went there and asked them about a potential reaction between the galvanized bolts and the PT wood and they were not aware of any risk. Apparently it's what they always suggest and never had a problem. There even was a demo structure in their yard built with PT wood & galvanized bolt, it has been there 6 years and seemed totally fine.

Thoughts ?

joecaption 07-17-2012 12:48 PM

There is no such thing as "floor screws" that I know of.
If the box did not say ACQ approved then they have to go.
There going to corrode off inside the wood where it can not be seen.
The best most cost effective ones to use are ceramic coated decking screws.
Big differance between a 1/2 bolt and a tiny screw, it would take about 100 years to corrode through a large bolt.

Fred_ 07-17-2012 01:27 PM


There is no such thing as "floor screws" that I know of.
Well I'm in Canada and most hardware store label screws as such. The box is not very helpful at saying what they are made of. The brand is dura-grip and as you guessed, they are not ACQ approved. For my personnal curiosity, are those ok for indoor use ? Else, what are they good for ?


Big differance between a 1/2 bolt and a tiny screw, it would take about 100 years to corrode through a large bolt.
Agreed but why not use a material that will not corrode in the first place.

Many website state the hot dip galvanized steel is fine even with cooper :
[...] Hot-dip galvanized or stainless steel fasteners, anchors and hardware are recommended by the Preservative Treated Wood Industry for use with treated wood. This has been the position of this industry for years and their position has not changed with the transition to the alternative copper-based products. [...]
[...]Reliance on a “generic” galvanizing requirement may not be sufficient. Currently available information recommends use of hot-dipped galvanized fasteners[...]

joecaption 07-17-2012 02:55 PM

I'm sticking with the ceramic coated ones for several reasons.
You can get them in a number of differant colored heads.
There is no galvinizing finish to knock off and expose the bare steel as there being screwed in.
There really tough heads so you get almost no cam outs.
They come with what looks like a drill point on the tip so there fast to get started.

A stainless steel carrage bolt would just cost at least 5 times the cost as a galvinized one for one reason. A galvinized bolt is going to out live the wood there going into by a long shot.

There's thousands of decks built every year using them with no problums so why reinvent the wheel?

hand drive 07-17-2012 08:40 PM

not changing them now will lead to them rusting inside of the wood and not coming out later, or if you do get them to reverse out later the heads will probably pop off of the screw shank leaving the rusty shank in the wood.

firehawkmph 07-17-2012 08:40 PM

Hot dipped galvanized hardware and joist hangers are fine with the new treated lumber. There is a big difference between HDG and the normal zync plated hardware. I just took a small porch landing apart that was made with treated lumber. The joist hangers were about 5 years old and rusted away to just about nothing. All the compatable hangers will have a Z in their part number. The HDG hardware will have a rough, dull gray coating on them as opposed to the shinier zync. Change out your fasteners now and avoid a mess later on. Next time, read up on the material requirements and save the headache of doing it twice. A lot of things are changing nowadays, some for the better, some for the worse.
Mike Hawkins:)

Fred_ 07-17-2012 11:15 PM

To read about I would have had to know there was something to read about :) I just had no idea I had to pick my screws so carefully.

By the way after reading a lot about PT wood screws I tested both my local hardware store and Home Depot deck screws and there are both worthless. Home Depot's seem only painted and the coat chips away very easily. My local hardware store was even worse, one drill in / drill out in a piece of wood and the coating was 100% gone.

Given the multiple negative comments I am seeing on deck screws and the fact that those I tested were disappointing, I will opt for stainless steel ones. 50$ more, not that much compared to the cost of the project.

When you don't get what you want, what you get is experience !

Thanks for the answers.

joecaption 07-17-2012 11:20 PM

What are you trying to put them in with?
I use at least 5000 deck screws a year and never had the finish come off and have never had the screws rust up later.
I've tryed the stainless screws and at least 10% of them rounded off before going all the way in.

mae-ling 07-17-2012 11:21 PM


Originally Posted by Fred_ (Post 968004)
Well I'm in Canada and most hardware store label screws as such. ]

I have lived in 5 provinces, 10 towns/cities and have not seen this

Fred_ 07-17-2012 11:22 PM

Well there are many qualities - Those are just painted, no epoxy, no ceramic. On the cheapest ones, I can get the coating off with my nails. I am not doing anything special drilling them in and the wood is not specially hard.

Fred_ 07-17-2012 11:27 PM


I have lived in 5 provinces, 10 towns/cities and have not seen this
Well welcome to Montreal, Quebec

And by the way here ACQ means Association de la Construction de Quebec (Quebec Building Association) so I had no idea this sign had something to do with PT wood.

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