Residential Concrete Deck on Steel Beams 6

[STrctPono]

The longer you look, the worse it gets....

I'm helping a colleague as they are in escrow to buy this house. I'm headed out tomorrow morning to take a look at it in person.

This portion of the outdoor lanai is a concrete topped metal decking (however, I don't think that is a metal deck and looks more like corrugated roof panels??)

I am certainly going to have a punch-list of things to do, based on priority, however the one thing I keep coming back to is the metal deck itself. It is going to continue to get worse and I have no idea how much concrete topping is poured above, therefore I have no idea if the metal deck is necessary or if it is more of a stay-in-place formwork. Given the quality of construction, I would think this Contractor didn't pour an ounce more of concrete than was absolutely necessary... What do you think?

Either way, I'm thinking that to stop the progressive corrosion of the underside of the metal deck it should be abrasive blasted and then repainted. Additionally, I am thinking that the top of the concrete should be sealed with an epoxy flood coat or something similar to slow moisture infiltration. Any thoughts?

 

[hokie66]

I can't see that being repairable. Knock it down and start over.

 

[Ingenuity]

I agree with hokie66, that kama'aina lanai is all pau and ready for the opala.

 

[dik]

Start with a backhoe... I assume the wood product has dryrot... beyond repair IMHO.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Tomfh]

Customorb is often used as sacrificial formwork, but who knows what's going on with this crazy structure!

The steel framing is bad too, rusted and missing in places.


I agree with the others. Demolish and start again.

 

[STrctPono]

I agree with hokie66, that kama'aina lanai is all pau and ready for the opala.

This had me laughing! Are you out here or behind a VPN?

You guys are a tough crowd. The craftmanship is certainly atrocious but it is sadly enough pretty par for the course out here. I actually believed that this was salvageable to the point where they could have squeezed some more years out of the deck.

Knocking it down is the easiest solution (for me) but my guess would be that if I say that it will kill the whole house sale. In this market, not sure if that is the best thing.

I could always suggest to make only the critical repairs (i.e. replace wood transverse joists that are all destroyed by termites and replace section of steel column and bracing that is missing) and then live with the rest until the service life of the structure is up. Could be another 10 years down the road? I think they could do those simple repairs for less than $5,000 and may even be able to get it as a credit from the sellers.

I will know more when I head out there tomorrow...

 

[dik]

As an engineer, there is no way that you could suggest that this is salvageable. If you do otherwise, you are doing them a great disservice... they can buy the house fully realising that the deck is unworkable.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[hokie66]

I really don't see anything there that deserves salvaging. Another word of caution...make sure your colleague gets a thorough termite inspection. It is highly likely the little blighters have found their way to the interior of the house, not just that deck.

 

[3DDave]

That doesn't look from the picture like corrugated metal. OTOH, the missing diagonal connection and incomplete portion of that column also happens to not look like metal either, so perhaps there is a pattern.

If the corrugated material or that cross beam were critical to supporting the concrete they stopped doing that job a while ago. Either unneccessary or just not recently challenged.

Best of luck. Wear a fluorescent hard hat in case they need to know when to stop excavating.

 

[dik]

Thanks hokie... that's termite damage? I've never seen termite stuff before... I thought it was dryrot (brownrot).

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[hokie66]

3DDave, it looks exactly like corrugated steel to me. What else would corrode like that?

dik, that is what severe termite damage looks like, and the OP said the joists were destroyed by termites.

 

[Ingenuity]

Are you out here or behind a VPN?

No VPN. Local haole (via Australia), braddah

 

[3DDave]

It's the lack of rust stains on the wood beams that leads me to believe it's some sort of cellulose/resin material made for this purpose. I admit I could be wrong, but where there is rust there are often rust stains running down from them. If its cellulosic then termites would do as much damage as corrosion would to metal.

I'm more concerned with the air-gapped structural connections.

 

[KootK]

Could be another 10 years down the road?

Obviously, your response here kinda depends on whether you're wearing your engineer hat or your friend hat.

If you're wearing your engineer hat then, yeah, definitely do not take responsibility for this thing as is and recommend a rebuild.

Wearing a friend hat, I'd be a little more optimistic/pragmatic:

1) My money says you could not touch a thing and it'll be fine for another ten years.

2) Wood purlins look pretty easy to replace based on the detailing.

3) Beams and columns are rusty but I'm not registering a lot of meaningful section loss.

4) Even that missing steel column might be viable if the remaining brace is connected suitably to hold up the beam above, like a knee brace.

5) That looks like non-composite form deck to me. Ideally, that would mean reinforcing in the slab and no reliance on the metal deck. What it probably means is no reinforcing in the slab and total reliance on the metal deck even though it's non-composite. Still, depending on the slab thickness, you may get some decent arching out of the concrete with the deck being sort of a tension tie through some voodoo friction. It doesn't take much deck section to do the tension tie job. Lastly, I'd think it a pretty easy thing to install some new purlins at a tighter spacing than the old ones to improve matters with the deck.

 

[Brad805]

My concern would be if they did such a poor job here, what else is buried where I cannot see it. I would be very careful having done a lot of residential work long long ago.

 

[STrctPono]

KootK, thanks for jumping in! You hit the nail on the head with your response. I was also thinking about tightening up the joist spacing to help mitigate any issues with the deck. If this were for a random client and I were signing off on this, no question it would be a demo job. As a friend, I can take a step back from my day-to-day conservative tendencies and look at this a bit more pragmatically without dropping a $75,000 bombshell on his lap. The goal is to get it safe now and then look toward replacement in the near future.

The multi color (green and yellow) paint on the joists tells me that cheapskate contractor probably cut this wood out of an old house job and reused them here. If so, they are (at best) borate treated, and not properly CA-C treated which makes sense why they are destroyed by termites.

hokie66, duly noted. Termite inspections and fumigations are pretty standard for all house sales out here since they are so bad!

Brad805, you're right. My first thought goes to the foundation (or lack thereof) work.

 

[KootK]

I bought a house last spring with the following features:

1) Big deck with stupid, "elephants foot" footings that are not frost protected at all (Canada).

2) Several pre-engineered trusses with pulled apart connector plates (I was once a truss engineer).

3) Fake architectural rafters made out thin of sheets of wood assembled into boxes.

4) 2x floor joists everywhere with no connector hardware at all, just toe-nails and such.

5) Windows and doors that were clearly chainsawed into the original wall construction.

6) I have a few feet of repugnant, foam, brick substitute on the outside that woodpeckers are poking holes through.

I love it because the yard's big, the location is stellar, and my family thinks it's the best thing ever. But I have to put my "friend hat" on for my own benefit in order to endure it.

 

[BridgeSmith]

As others have noted, it matters alot whether the slab is adequately reinforced. For the purposes of making an offer to buy, it should be assumed to be unreinforced, so either total demolition or stripping the corrugated, replacing the wood beams, cleaning the steel beams, and possibly isolated strengthening of the steel beams.

When and if the sale is completed, then some minimal concrete removal would seem to be in order, to ascertain what reinforcing, if any is in the slab.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[Ingenuity]

The other non-structural aspect to consider - was a building permit obtained for the lanai.

I assume not. So the pending new owner may have an illegal structure to deal with. Oh so common in Honolulu.

 

[Rabbit12]

Is it really possible to "remove you're engineer's hat" in this situation? If this was your house it's one thing, but this is a "friend". If something happens down the road is this friend going to keep you out of any litigation if it comes to that? That'd be some friend if he did.

I don't see how you can say this is salvageable for a friend but not for a client. IMO you're always an engineer and it'd be pretty easy for a lawyer to say you should have know this was garbage.