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Residential Concrete Deck on Steel Beams
6

Residential Concrete Deck on Steel Beams

Residential Concrete Deck on Steel Beams

(OP)
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?



RE: Residential Concrete Deck on Steel Beams

2
I can't see that being repairable. Knock it down and start over.

RE: Residential Concrete Deck on Steel Beams

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

RE: Residential Concrete Deck on Steel Beams

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

RE: Residential Concrete Deck on Steel Beams

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.



RE: Residential Concrete Deck on Steel Beams

(OP)

Quote (Ingenuity)

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...

RE: Residential Concrete Deck on Steel Beams

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

RE: Residential Concrete Deck on Steel Beams

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.

RE: Residential Concrete Deck on Steel Beams

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.

RE: Residential Concrete Deck on Steel Beams

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

RE: Residential Concrete Deck on Steel Beams

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.

RE: Residential Concrete Deck on Steel Beams

Quote (StuctPono)

Are you out here or behind a VPN?

No VPN. Local haole (via Australia), braddah smile

RE: Residential Concrete Deck on Steel Beams

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.

RE: Residential Concrete Deck on Steel Beams

Quote (SPono)

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.

RE: Residential Concrete Deck on Steel Beams

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.

RE: Residential Concrete Deck on Steel Beams

(OP)
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.

RE: Residential Concrete Deck on Steel Beams

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.

RE: Residential Concrete Deck on Steel Beams

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

RE: Residential Concrete Deck on Steel Beams

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.

RE: Residential Concrete Deck on Steel Beams

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.

RE: Residential Concrete Deck on Steel Beams

I’m all for “friends hat” when called for, but vouching for this crazy thing is quite a stretch.

RE: Residential Concrete Deck on Steel Beams

Legally, your friend can indeed toss you under the bus if you say all is well. In that respect, it depends on how much you trust your friend.

That said, I wouldn't be saying thst all is well. I would be saying:

1) this is what I can prove.
2) this is what I can't prove.
3) this is my my gut feel for performance and risk in this situation.

Basically the same engineering opinion that I'd offer a paying client.

RE: Residential Concrete Deck on Steel Beams

That's my point KootK. The OP is saying he'd recommend a complete rebuild to a client but not his friend. I don't see how you can justify such a drastic difference in recommendation. I can see turning down this project due to liability with a paying client but I also wouldn't provide recommendations for free to a friend on something like this.

I've always said "families get along until there is money involved". I've seen it time and again that siblings get along great until it comes time to divy up their parent's wealth. It'd be a pretty rare friend that wouldn't throw you under the bus if sh*t hit the fan.

I also don't like the view that a "deal" could fall through if we are too hard on the condition of this thing.

RE: Residential Concrete Deck on Steel Beams

Ah... okay, I understand your perspective now Rabbit.

RE: Residential Concrete Deck on Steel Beams

Another thought to add to your collection:

The slab thickness cannot be determined from your photos, but the photo from the top side shows that the slab is jointed. I would conclude then that the concrete is not structural, and rather that the corrugated steel deck carried the load. Since the deck essentially no longer exists, the slab could collapse locally without much additional loading. The shadows at a couple of the joints indicate there has already been some differential deflection.

RE: Residential Concrete Deck on Steel Beams

The first line the Op says it all IMHO.

KootK is right up to a point - it's still standing (somehow) and shows no clear signs of distress as far as we can see from the limited amount of information. Please tell me it's not a cantilever at the edge....

However, the issue for me is that you have no control at all over what the new owners will ever use it for.

Get a birthday party out there in the sun and bit of dancing and down she goes. Quite steep drop by the look of it.

Is some of that concrete under the wooden decking? Did they build the wooden decking to hide the cracks in the concrete?
I would be telling your friends that it is essentially structurally unsound as it sits now and you wouldn't feel comfortable with any more than 4-5 people on it and collapse might be very sudden. To fix it to get it semi decent might be ~$20,000?? $40,000? but then they will have a proper deck. If that's a deal breaker then so be it - their money and health

The only thing that tells you the deck might be a bit stronger than it looks is that the "formwork" which has all the appearance of corrugated roof sheets, hasn't collapsed and the concrete may well have some re-bar in it. but you need to destroy part of the patio to find out.

Fix the missing column, double up on the timber beams and turn them the other way around and limit the numbers on the deck to no more than 15.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Residential Concrete Deck on Steel Beams

(OP)
Ingenuity, not a chance that this was permitted!
KootK, Thanks for all your input.
Hokie66, The joints appear to be steel screed rails that they left embedded in the concrete. They run parallel with the deck flutes.
LittleInch, there is a cantilever on the ends. Surprisingly, the corrosion of the steel beams can be considered mild to medium. I am essentially telling them something similar to what you suggested but a bit more conservative on the condition as it stands. I think the cost of the critical fixes would be lower than $20,000. My estimate for a brand new deck is $75,000.

I did get a chance to inspect it for myself. It really is a monstrosity. The craftmanship is very poor and there was an improper use of materials right from the get-go. There is also very poor drainage in some areas which is exacerbating some issues. With all that being said, I have come up with a list of critical fixes that IMO actually salvage this lanai for a bit more time with annual inspection. My gut feeling is that this could still be used for approx. another 10 years until the section loss in the steel beams gets too excessive. Current major section loss of steel beams and columns is limited to only 3 select locations. Wood joists need to be replaced, redetailed, and closer spaced to account for an assumption of plain unreinforced concrete deck. Concrete deck varies from 3.5" to 5.5" to bottom of flute. Several column bases need to be fixed.

I do appreciate the insight from everyone. I understand that it seems that I am taking a path that not many agree with but based on my observations I do not feel as if this lanai is in danger of imminent collapse. Although tempting to take the easy route and just condemn it outright that does not feel like I will be doing them a service. I am certainly taking care to document my findings and write it in such a way that helps protect myself from the brunt of the initial liability. Thanks to all!

RE: Residential Concrete Deck on Steel Beams

I would note very heavily that they shouldn't have a party on it....

E.g. and numerous other examples in the failures and disasters forum....

https://www.sacbee.com/news/california/article2512...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Residential Concrete Deck on Steel Beams

anymore when a friend/family or a friend of a friend asks for engineering help, I always refer them to a competent engineer in town if possible.

RE: Residential Concrete Deck on Steel Beams

Quote (LittleInch)

I would note very heavily that they shouldn't have a party on it....

Exactly! I would also make sure they don't put planters with soil, water, and plants (110 pcf) -- nothing more than a lightweight table and four metal chairs. You'd be amazed at what owners will put on a deck.

Quote (STrctPono)

salvage this lanai for a bit more time with annual inspection

What is the cost for annual inspections? Or will you do the annual inspections, casually, while visiting? What happens if you are no longer visiting this friend? At what point do you say, "Put up CAUTION tape and Do Not Enter signs and stop using this deck immediately"? What if your friend refuses to stop using it? For that matter, do you have to sign anything saying that the deck is in useable condition right now? I would not put my name on anything related to this deck.

Quote (STrctPono)

Concrete deck varies from 3.5" to 5.5" to bottom of flute

Do you mean that there is at least a 3.5" slab everywhere, but it goes deeper, to 5.5" at the bottom of the flute? Is there any evidence of reinforcing?

Quote (STrctPono)

Current major section loss of steel beams and columns is limited to only 3 select locations

What happens when one of those becomes a point of failure? What will the progression be?

I would stay far, far away from certifying the viability of this structure, and I would also refuse to step foot on it.

RE: Residential Concrete Deck on Steel Beams

@STrctPono:

Your attempt to wear your "friend hat" has inspired me to post about my recent attempt to wear my "neighbor hat": Link.

The nature of this space is that we tend to hear conservative viewpoints more loudly than others (often that's me). And, for the most part, I think that's healthy. At the same time, I feel that it's useful to hear from other risk-dummies from time to time so that we have an accurate perception of what's actually taking place out in our profession. So count me as a data point in that respect.

Butchering Einstein: Do not worry about your quandries in professional risk taking. I can assure you that mine are greater.

RE: Residential Concrete Deck on Steel Beams

This deck does not look too big. How could it possibly cost 75k to replace?
I'm with the majority here - tear it down before someone gets hurt.

RE: Residential Concrete Deck on Steel Beams

Quote (XR250)

How could it possibly cost 75k to replace?

'Cause it is Honolulu and that house probably sold for more than $1M

RE: Residential Concrete Deck on Steel Beams

(OP)
XR250, The deck is 750 sq. ft. Approx. $100 per sq ft construction cost for that type of deck. That doesn't even include demolition of the existing deck.

Everything is expensive where I live. Same reason why I just paid $5200 for a KX65 when MSRP is $3700.

Ingenuity, $1.9M. Nice cul-de-sac up in Nuuanu.

KootK, I have been enjoying following your post about your charity work. That was a ton of effort on your part to stick with that thread and address everyone's comments.

RE: Residential Concrete Deck on Steel Beams

Wow, that is amazing

RE: Residential Concrete Deck on Steel Beams

An owner who pays $1.9 million for a house should be happy to pay $75 thousand for a deck without structural defects.

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