Suspended concrete slab integrity ?'s

[sailah]

I can understand nobody's happy unless Momma is happy.

Just make sure she understands this repair is coming out of her shoe budget not your budget!

Put your foot down right from the start.

Let's be honest here. We all like to talk tough when it comes to our wives but they have the final say. To my wife's credit she puts up with a tremendous amount of my **** so I'm happy to build her out a couple bathrooms.

Based on the pics, I would guess the garage was actually the original house on the property, then remodeled into the garage when the new house was built out front. Your 'crawl space' under the slab was the root cellar..... It probably had post and beams in it prior to the slab floor getting poured.

And what did the engineer say when you told him the weights of your woodworking equipment?

I'm almost certain it was the barn, almost every house on this street had/has a barn so it appears unlikely it was a house. I'm guessing the cellar was for mucking out. It def has post and beam construction, I'll post some better pics of the attic where the original work is clear to see. And beautiful.

I wrote out the comments that the engineer emailed to me earlier in this thread. His reply was basically patch it up and contain the damage. I personally do not believe that is the correct fix, either short or long term. I explained my tool weights in numerous phone calls including yesterday and he continues to believe the slab is salvageable. I looked at the same rusted through rebar that everyone else has and there is no way that paint is going to fix that. So I'm going to map out where my tools are going and be sure that there is adequate structure under them and avoid the cancer area. When I've narrowed down to the best/most cost effective fix, I'll pull the tools out and do it.

Here is the engineer that wrote the report (and whom I have been speaking to), he's the first principle listed...

http://www.sde-us.com/docs/principals.htm



And his comments after seeing the photos I posted.

It looks like thru their use the deterioration has progressed. I am concerned about falling concrete and tripping hazards and not imminent collapse or structural failure, although this is a natural progression if it continues to be used as a garage and deterioration allowed to continue. The deterioration at the entrance was there, but has progressed.

The extent of concrete repair and coating of rebar has increased . so the cost of repair has increased.

The steel beam corrosion is natural for this type of system in a garage.
The “fix” would be as follows:

1. Have an inspection just to make sure
2. Chip loose concrete to remove spalled items top and bottom, confirm rebar integrity. Apply sika Armatec coting to rebar and act as bonding agent. Patch concrete with Sikatop 123 or like bag mix. Apply sealer healer to slab to fill cracks, may require caulking or taping cracks below, reasonable effort.
3. Apply epoxy garage floor paint to surface with grit and maintain paint. Epoxy coat steel beams below

The garage does not “scare” me, but does need to have the items addressed to preclude further deterioration. No structured garage is maintenance free, by structured I mean garage floor over occupied space. Particularly one built like this for residential use, and built when the industry did not realize the full impact of road salts.

I can think of many other options, all the way up to slab replacement, but that gets expensive. I think the above is pragmatic and would make me feel comfortable.

 

[tab2]

Here is the engineer that wrote the report (and whom I have been speaking to), he's the first principle listed...

http://www.sde-us.com/docs/principals.htm

I work for construction manager, our office is just up Rt. 3 in Quincy. I could recommend some other structural engineers if you want another opinion. PM me if you want.

 

[wssix99]

First of all, I love the way you did your toenails in the first picture!


There's lot's of jumping to conclusions, suppositions, and misinformation in this thread. In real life, a professional expert still hasn't been with the slab in the flesh to assess what the state is.

Your engineer gives you good advice to get a formal inspection. The advice above to also go get a second opinion is also sound. Treat this more like making a decision about heart surgery - go get the second professional opinion and take the barber shop gossip for what it is.


We see this stuff in the City all the time and you should be able to find companies in Boston who can easily handle the repair for you. (I walked, rode on, and drove under 20 bridges that looked just like this today!) I would not run away from the deal - just plan for the expense. Also - the repair will be messy and is better left to people who have skill/experience doing this work. The time to get it done is now, before you move all your stuff in to the shop. I would expect something like this (without seeing the full inventory of items to be repaired) to come in between $15 and $25K.


Structurally, you look fine. (There is a certain bit of wisdom in trusting an old slab that has withstood the test of time vs. a brand new one where you don't know what the workers really did inside the slab...) Your slab is just damaged and needs repair:

- Rusted through rebar can be cut out and new pieces spliced in.
- De-laminated concrete can be patched with modern materials.
- Rebar lacking adequate cover can be coated. (The concrete outside of the rebar is just there to protect it and does very little for you structurally.)

 

[sailah]

Thank you for that, concise, direct and devoid of hyperbole. Price seems inline with what I was envisioning with my WAG-o-meter.

 

[Diesel Dan]

Structurally, you look fine. (There is a certain bit of wisdom in trusting an old slab that has withstood the test of time vs. a brand new one where you don't know what the workers really did inside the slab...)

Only if used in the same manner.
If the slab only held the weight of a Yugo all its life and then you go and add heavy vibration causing machinery then history is irrelevant, JMO.

If you have a new slab poured it is very easy to know what was done inside the slab, engineered drawings, material list, concrete slump tests followed up with Photo documentation.

OP, if you get a second engineering opinion that concurs with the first then a repair sounds like the way to go. Just make sure you get a qualified contractor that is familiar with these kinds of repairs.

 

[pstnbly]

If it were me, I would cut the suspended slab out, grade the crawlspace floor, make provisions for a sump pit, place a moisture barrier, and pour a rat slab. Then I would repoint the rubble wall foundation and coat the interior with Dry-Lok. I would then form and pour a new slab.

 

[sailah]

If it were me, I would cut the suspended slab out, grade the crawlspace floor, make provisions for a sump pit, place a moisture barrier, and pour a rat slab. Then I would repoint the rubble wall foundation and coat the interior with Dry-Lok. I would then form and pour a new slab.

I had to look up what a rat slab is, makes sense. The dirt floor under the deck is def wet and there is a lot of moisture down there evident in corrosion of joist hangers etc. That's one area the inspector told me I need to work on.

So let me see if I understand this. You grade the floor to create a gravity drain path to the newly formed sump pit. Vapor barrier on the ground to stop moisture from coming up, rat slab on top of that. Repoint the foundation and drylok to help from getting water through foundation walls. any water hits the rat slab and goes to the sump and out.

How does a rat slab get formed since it's so thin? Do you have to actively work it in place since the floor is pitched towards the sump?

Thanks

 

[coldh2o]

There's lot's of jumping to conclusions, suppositions, and misinformation in this thread. In real life, a professional expert still hasn't been with the slab in the flesh to assess what the state is.

Your engineer gives you good advice to get a formal inspection. The advice above to also go get a second opinion is also sound. Treat this more like making a decision about heart surgery - go get the second professional opinion and take the barber shop gossip for what it is.

This is very good advice...then you go on to jump to your own conclusion:

Structurally, you look fine. (There is a certain bit of wisdom in trusting an old slab that has withstood the test of time vs. a brand new one where you don't know what the workers really did inside the slab...)

What are your qualifications for such a broadbrush statement, based on the few available pictures? Flies directly in the face of what you said above. And that old slab has hardly withstood the test of time

Only if used in the same manner.
If the slab only held the weight of a Yugo all its life and then you go and add heavy vibration causing machinery then history is irrelevant, JMO.

If you have a new slab poured it is very easy to know what was done inside the slab, engineered drawings, material list, concrete slump tests followed up with Photo documentation.

+1

 

[sailah]

What are your qualifications for such a broadbrush statement, based on the few available pictures? Flies directly in the face of what you said above. And that old slab has hardly withstood the test of time

All indications are that the slab was done in the late 70's. Speaking to the engineer he said that, at the time, industry wasn't building these slabs with foresight to corrosion etc that they do today.

He has 2 cars parked in that garage, a brand new Suburban and a brand new Toyota Highlander, for the last 8 years. That's 10,000lbs parked right in the middle of the span. And dripping salt water down those cracks 5 months a year. I'm going to be parking my stationary, non salt-dripping machines over the supports and using the mid span areas for things like the outfeed table/workbench on my table saw. I figure with running new timbers underneath to halve the span, my gut tells me I'll be fine until I redo it.

I have a hard time believing with my intended use, with my planned fix, and thinking logically about tool placement, that I can't extend the safe life of that slab into a reasonable time frame to come up with a permanent fix. I simply have other priorities in this old house to tackle to keep my wife happy and I'm the kind of guy who likes to do things myself.

I may be wrong, everyone else may be right. I'm man enough to admit when I'm wrong and I will be sure to document the results.

 

[gregtwojeeps]

If you are so sure of your solutions having the outcome you predict, then why put them on the internet to be dissected ? Just do them and move on to better things. I only ask for advise on GJ if I truly have doubt in my own judgment... then I post for advice from the guys "in the know" on GJ, and I have learned a LOT from them by doing so. Any project that I take on that I am sure of my own skills to do, I just go with it. JMO

 

[sailah]

2 days ago I wasn't sure at all. It was all new to me.

One of the best pieces of advice I ever got in life came from some nerd I went to school with. He was the smartest kid in the class and went to MIT. I remember asking him how he got to be so smart and he said "I ask a lot of questions and read everything I can get my hands on"

I've followed that advice throughout my life and it has served me well. So to your question why did I ask? I asked because I want to hear all sides. I've spoken to the structural engineer with letters after his name, who has seen the slab and wrote the report. I've heard differing opinions from people on the internet. I've spoken to a friend of mine in Pittsburgh that did a lot of concrete work and who is now an explosives/demolition guy. I've read online about slab construction. And most importantly I'm using my own sense of what feels right to make my decision.

Nothing is 100%. I'm not 100% sure that what I am doing is right. No one is. If we did, we wouldn't have airbag recalls, the Challenger wouldn't have broken up and the Hindenburg might have docked just fine. We do what we believe is best in the interests of time, money and the proper repair. I have gained a level of comfort, based upon my research and the opinions of others, with my prescriptive repair.

And that's why I asked the question. If you somehow feel slighted that I didn't heed your exact advise and took someone else's, please feel free to cast the first stone when I post up the disastrous results of my repair.

 

[Stuart in MN]

It doesn't look very good in the photos, but as was posted above we all probably drive over or under bridges every day that look worse. I'd go more by what your PE had to say about it, since he's the only one here who has actually seen it in person.

 

[gregtwojeeps]

I am not slighted at all and my apologies to you for my reply being an irritant, but you seem to have your solutions thought out, but cannot get settled with them.

After reading your replies thus far my last reply was for you to go for it and do the floor renovation. You have the money, the time, the skills, the motivation. Whatever advice given on the GJ forum is usually good, but for a project like yours with its complexity, you will ultimately need to get ..and as you are doing... a professional structural engineering study and solution.

I don't think if I was an engineer of any field, that I would be giving out my services for free on the internet, so you are probably taking mostly layman's advice on here. Only so much great advice can be given from someone viewing pics on a monitor. JMO

 

[sailah]

I am not slighted at all and my apologies to you for my reply being an irritant, but you seem to have your solutions thought out, but cannot get settled with them.

After reading your replies thus far my last reply was for you to go for it and do the floor renovation. You have the money, the time, the skills, the motivation. Whatever advice given on the GJ forum is usually good, but for a project like yours with its complexity, you will ultimately need to get ..and as you are doing... a professional structural engineering study and solution.

I don't think if I was an engineer of any field, that I would be giving out my services for free on the internet, so you are probably taking mostly layman's advice on here. Only so much great advice can be given from someone viewing pics on a monitor. JMO

I will agree with what you wrote 100%, no need for apologies, I've got thick skin.

 

[wssix99]

What are your qualifications for such a broadbrush statement, based on the few available pictures? Flies directly in the face of what you said above. And that old slab has hardly withstood the test of time

I was not making a statement that the slab was structurally sound. That would take a professional in the flesh to determine. The intent behind that statement was to point out that I do not see anything that is beyond repair.

 

[johninct]

I did not read every post. With that said, that is not just a slab, but one that has a structural element to it. Rebar isn't just put in randomly , it is placed in specific locations for structural reasons. Think factor of safety. It is supporting 2 vehicles now but how much of a factor of safety is left? Can it be ripped out and rebuilt...YES. Should it be ripped out...YES.

 

[Diesel Dan]

I did not read every post...........Should it be ripped out...YES.

The OP posted a report from a certified engineering firm that states the slab is sound and can be repaired for $1-2000.

 

[coldh2o]

The OP posted a report from a certified engineering firm that states the slab is sound and can be repaired for $1-2000.

The idea that slab can be repaired for $1-2000 calls into question the whole engineering report.

I'm anxious to see if the OP gets a second engineering opinion and/or quotes from contractors.

 

[readhead]

The usable life for that slab could end tomorrow. I am having a hard time with the engineers report. He is basing his conclusions on a visual inspection. I think it would be a good idea to have all the information and request that an NDT company come in and do a random X-ray test of the slab to see what kind of condition the rebar and slab are in.

I think there are two options to cure the problem. Complete removal and new slab or new support under the slab and resurface the top. Either way will be costly but supporting the existing slab will be less intrusive to day to day use.

 

[sailah]

The idea that slab can be repaired for $1-2000 calls into question the whole engineering report.

I'm anxious to see if the OP gets a second engineering opinion and/or quotes from contractors.

I agree, I don't see how, in this area, you are getting anything other than a coat of epoxy on that floor for $2k.

I am having a concrete contractor come and give me a second opinion and inspection. I will post up his review.

 

[ADSR]

I agree, I don't see how, in this area, you are getting anything other than a coat of epoxy on that floor for $2k.

I am having a concrete contractor come and give me a second opinion and inspection. I will post up his review.

LOL, for 2K, he'll mix up some non shrinking grout and butter on a nice facade. It wont fix anything, just give you some eye candy to look at while underneath is still decaying.

 

[wssix99]

I agree, I don't see how, in this area, you are getting anything other than a coat of epoxy on that floor for $2k.

I am having a concrete contractor come and give me a second opinion and inspection. I will post up his review.

Not all concrete companies can do this kind of stuff. Especially the areas where the rebar needs to be replaced. An experienced company should be able to show you pictures of jobs that look like your repairs.

Another thing you may want to plan for is having your engineer come out and inspect once all there repairs are made, but before the concrete/grout is poured. It will probably cost you a few extra hundred for the visit, but can spare you from some big headache$ down the road if the work isn't done right.