Heavy corrosion at deck attachment points

[Matt Fellman]

PT joists, glue-lam beam (treated?), metal hangers and fasteners.

As I snapped the attached pictures I was literally clinging to a clump of ivy to keep from falling down into a creek. I wish I could have got closer to investigate what type of fasteners and hangers they were but it just wasn't safe.

I know 7-8 years ago the whole thing went around (at least in my area) about needing hot dipped galvanized fasteners with PT lumber but this corrosion seems to be heaviest at the connection to the beam and not at the PT joists (I know the fasteners are missing at the joist). I'll admit I'm not an expert of outdoor treatment of glue-lams but am suspecting there is a bad reaction going on between the fasteners and/or hangers and the beam. The mating of the hanger and the PT seems to be okay (other than missing fasteners)

Any thoughts?

[Jerry Peck]

PT joists, glue-lam beam (treated?), metal hangers and fasteners.

As I snapped the attached pictures I was literally clinging to a clump of ivy to keep from falling down into a creek.

I suspect that is the problem ... the creek and all the moisture 'trapped' under that deck.


I know 7-8 years ago the whole thing went around (at least in my area) about needing hot dipped galvanized fasteners with PT lumber ...

That is a possibility, but I think it is the creek moisture corroding (rusting) the fasteners and hangers from the untreated edges inward. The hangers are made from galvanized metal shipped in large rolls to the hanger manufacturer where the hanger manufacturer stamps the hangers out of the rolls as the metal unrolls ... all the edges are left untreated (including the edges around the punched out nail holes) - and that is where it looks like the corrosion and rusting started.

[Rick Cantrell]

Could be that the nails were not galvanized. Once the nails started to rust it spread to the hangers.
Notice the other end of the hangers to not have been affected as much as the end with nails.

Also, hangers are galvanized after forming, at least the ones I have seen.

[Garry Sorrells]

Matt,
It is exactly what I would expect to see. The nails are making the good connection between the hanger and the wood, like twisting electrical wires together makes a good connection as opposed to the wires just touching.

Without getting on a rant about the changes in types of chemicals used, the new compounds are extremely reactive with steel. Adding zinc only reduces the reaction time. The more zinc just add a little time, ergo hot dipped as apposed to elector plated.

Take some time and read through the manufactures tests and recommendations dealing with fasteners and attachments to the wood. It will be a good exercise and very educational. Also, a little humorous.

Bottom line the use of anything other than stainless steel for long term application is not recommended where the material will be subjected to moist conditions. Meaning, it will get wet. Go figure, PT wood used where it may get wet.

Using SS materials adds cost and many either just didn't understand the ramification, just didn't want to add the expense or possibly just kicking the can down the road. Many, when the change took place kept doing things the same way just not knowing or caring.

[Jerry Peck]

Also, hangers are galvanized after forming, at least the ones I have seen.

One manufacturer does that, the others buy the sheet metal already galvanized on the roll, which leaves the cut edges exposed ... at least it was that way 5-10 years ago. You can order the hangers with extra galvanization, those are galvanized after forming - there are several protection levels available that way.

Materials and Coatings Available ~ Simpson Strong-Tie (http://www.strongtie.com/productuse/coatings.html)

Go down to:
- HDG Hot Dip Galvanized: Products are hot-dip galvanized after fabrication (14 ga. and thicker). The coating weight increases with material thickness. The minimum specified coating weight is 2.0 oz./ft2 (per ASTM A123 total both sides). These products require hot-dip galvanized fasteners or fasteners approved for use with ZMAX.

General corrosion information: http://www.strongtie.com/productuse/corrosion.html

[Scott Patterson]

What you are seeing on the hangers also happens to the fasteners that secure them. Just last year I worked on three cases of decks and railings failing due to fasteners and hangers corroding causing the deck and rails to fail.

[Jeff Zehnder]

We see a lot of hardware along the coast (Wilmington NC & South) that is in poor condition, generally we make a judgement based on the amount of deterioration and either recommend replacement or if in fair shape list it as a maintenance item. Exposed hardware along the coast is a maintenance item and it doe not mater if it is galvanized it will deteriorate.

If i found the same conditions inland i would still likely recommend replacement. We have had too many catastrophic 2nd and 3rd floor decks to sit on the fence.

[John Kogel]

What is the recommended repair? Supposing buddy won't shell out for SS hangers.
Is there a paint that they could use, or a gasket between the glu-lam and the hangers?

[Jerry Peck]

What is the recommended repair? Supposing buddy won't shell out for SS hangers.

Recommended repair:
Option A) Replace galvanized hangers and anchors/fasteners every 3 years.
Option B) Replace hangers and anchors/fasteners with SS hangers and SS anchors/fasteners

Too cheap to use SS? Replace galvanized on a regular basis. Suddenly, SS hangers and fasteners are really not that expensive. :)

[Jeff Zehnder]

Jerry is on the money, they simply need to be changed out when needed, along the coast they may need it in 2-5 years, inland it will depend on the weather and other conditions. I have seen people paint them but they still deteriorate from behind. I have also seen the butyl tape used under them but don't know how much better that will perform over time.

[Thom Huggett]

Thanks for risking your life for such a good picture!

[Eric Barker]

Replace galvanized hangers and anchors/fasteners every 3 years.

And nail back into the same nail holes???

[Jerry Peck]

And nail back into the same nail holes???

One could use nails or approved screws (Simpson makes some) into the same holes with larger nails or screws, or, if one wanted to, through bolt at each hanger hole to facilitate easier replacement.

Otherwise, no, not with the same size nails.

Just one more reason on the list to use stainless steel hangers.

A better was in a situation like shown may be to design in a larger beam that the floor joists mount to, then through bolt fasten on a ledger with stainless steel bolts, washers, and nuts; resting the joists on the ledger and installing solid bridging between the joists.

I'm not the engineer (or even "an" engineer), so let the engineer of record figure it out - they are the party responsible for the design of the deck (if it was even designed by an engineer).