*Concrete guys here NOW need question answered ASAP

Okay, garage pad is being replaced today. Here is the stone they plan to use as a base. Is this the right type of stone? They're here now. Please reply ASAP. Thanks.

Without an object of familiar size with which to compare the size of the rocks, it's hard to tell their size... But it's probably fine. Make sure they compact the rock base EXTREMELY WELL and lay down a plastic sheet before they pour![/b] Are you having them put in rebar? How deep will the haunches around the perimeter be? Are you having them set J-bolts for your walls? If you're not absolutely sure where your walls will be, don't - use anchor bolts later. Congratulations on this exciting milestone! (No pun intended!) --Keith :mrgreen:

Keith, I knew I could depend on you- thanks. I am off work today to make sure the job is done correctly. They're putting wire on the bottom and rebar at the top- the haunches will be as deep as I need them to be- I told him about a foot wide around the perimeter, I'll probably say 10-12 inches deep. I asked them to dig down to give me more ceiling height. No J-bolts, I need some flexibility with the floor plan. They're here right now- this is happening in real time, so I appreciate the input!

Well, I'm very upset today. Concrete truck was on time, but the contractor was late. They started pouring the concrete and didn't even set the rebar first. They just laid the loose rebar down over the stone and poured the concrete on top. WTF?! I pulled the guy aside, and told him that everything I've read states that the rebar has to be in the top 1/3 of the concrete. He said he was "pulling it up" as they went along. They weren't going to tamp the stone either until I made an issue out of it. I also asked for a vapor barrier but didn't get that. Also, they used 4000 psi concrete. I'm feeling very frustrated right now. All my instructions have been verbal, though, so I don't have proof of what I asked for specifically. I haven't paid them any money and I won't until I can be assured the concrete won't crack, and it's safe to build on. Any ideas?

surley if you dont have a vapour barrier then ou will get damp riseing through the slab. in the uk you would put down your hard core/crushed stone, sand to protect the vapour barrier from the stones, then the vapour barrier. then the rebar mesh raisers i think there called chairs to hold the rebar at the correct height. and then the concrete.

Yep. I'm screwed.

Seems like if they didn't do something that's considered "standard construction" you could work something out with the concrete company. Did you have them to STOP at some point to voice your concerns over how they were doing it? That alone may be a beginning to working something out. I know Keith has spent a lot of time in the concrete area of construction. Hopefully he'll chime in again soon to give you some advice. Hey man, here's hoping it's not as bad as it might seem... :wink:

I guess the question I'd like answered now is: when will I know if I have a problem? If 30 days go by and no cracks...does that mean it's safe to build on?

Studio Drums I am cautious of posting here becuase if you say something against these guys you tend to get flamed. But cant help it in this case. 99% of garage floors are poured with 3000 PSI concrete 99% of garage floors do not have a vapor barrier 99% of garage floors are installed with zero re-bar 99% of garage floor have cars parked on them 99% of garage floors have cracks in them And guess what! They are still functioning And many a studio are still standing on these floors 75% of commercial builds have vapor barriers 100% of commercial builds have re-bar installed 50% of commercial builds do not use chairs for the rebar (they pull it up in the pour) 99% of commercial builds HAVE CRACKS 50% with vapor barriers HAVE MOISTURE ISSUES There are topical moisture barriers that can be applied if you have a moisure problem. But that is only needed if you cover the concrete with a non breathable floor covering ie;vinyl,tile,epoxy If you have french drains around the perimeter of your footings this will divert much of your water away from your garage. Adding rebar at any depth will help shrinkage cracks. The crack runs through the entire slab depth. NOT JUST IN THE TOP 1/3. The problem here is the curing process. If your slab cures too quickly you tend to get shrinkage cracks. Keep it wet for 7 days minimum. A double mat of rebar will increase your chances of zero cracks but it still depends on the curing process. The water to cement ratio, compaction, too much wind and 100 other variables You and many others are not trying to build structural slabs here. Structural slabs are for heavy machinery and or containment of liquids from the top side. Waste of time waste of money Vapor barriers are only as good as the install. As you pour the concrete with sharp rock , walk through it while its wet and have metal tie wires with your rebar your chances of punture are 100%. Ask any General contactor I am so tired of this ( I have crack in my slab :answer: Oh you better rip it out and start over) If its a trip hazard or you notice a slope in the slab or building. YES you have a problem. But not a crack :roll: Here is a good read http://findarticles.com/p/articles/mi_m ... _114818845 Show me a piece of concrete and I will show you a crack S BTW: if you dont pay your installer he can put a lien on your house in most states. And I am sure the concrete company already sent you an intent to lien certified mail. Verbal contracts are still binding but take a while to settle

Thanks for the information Spidrez. Yes, expect some strong opinions to the contrary... Unfortunately, I'm not building a garage, I'm building a studio and that's the problem. They built it like a garage! So though it might be common, for a garage, it's not appropriate to my needs. So...now knowing that all concrete cracks, can I deduce that the purpose of rebar and/or wire is to control and contain that cracking? Ever crack a cymbal? The way you stop the crack is to drill a hole in the cymbal where the crack ends. I'm picturing a piece of rebar or wire in that drilled hole. Is it the same principle? I guess at this point if I see a crack I shouldn't be surprised. It just blows my chance of having a very cool looking designed concrete floor like this: http://www.ourcoolhouse.com/images/cons ... idetch.htm Maybe I should be more worried about the pad "shorting out" to the garage foundation walls due to poorly placed concrete forms... Keith knows what I'm talking about... In everyone's opinion, when should I make payment for this job?

Sorry for the delay in responding. I'm actually on a mini vacation in San Diego right now. Those contractor deficiences are unacceptable in my opinion. The purpose of your building this new slab is that you didn't want a garage floor anymore! You specified a slab suitable for building upon, and clearly you didn't get that. If you wanted a garage floor, it would be fine... But that's not what you wanted! If you have an oral agreement and you didn't get what you ordered, then I personally would insist that they jackhammer up what they put down and do it again correctly. If they don't, then they don't get paid. Although you could end up with a lien on your house until everything is settled. You really should have pushed the big red button to stop what was going on before the damage was done, I'm afraid... :roll: I'm not an expert on this... I just know how meticulous I was in my slab prep and pour. It took me months, working mostly alone, to get the results I wanted. I resisted the temptation to turn the whole thing over to a contractor, in part due to the lack of control. --Keith :mrgreen:

Hello! First post on this most awesome website. Just wanted to chime in quick regarding your intentions on acid staining your concrete. If you get some cracks in your floor don't worry about it detracting from the overall look of your acid stained floor. Sometimes cracks can actually enhance the aged marbled look staining provides. Also, if possible, wet cure your new concrete instead of using sprayed on curing compounds. Hopefully they didn't already! Any curing compound applied to your floor will have to be removed before you can stain it. You can read about it here: http://acidstainletter.com/archives/080304.html Chris (I'm not the same "Chris" referenced in the article)

spiderz wrote:

Studio Drums I am cautious of posting here becuase if you say something against these guys you tend to get flamed. But cant help it in this case. 99% of garage floors are poured with 3000 PSI concrete 99% of garage floors do not have a vapor barrier 99% of garage floors are installed with zero re-bar 99% of garage floor have cars parked on them 99% of garage floors have cracks in them And guess what! They are still functioning And many a studio are still standing on these floors

You missed the fact that the majority of garage slabs are only 4" thick. Actually I can't disagree with much said above - although I would point out that if you are building a true room within a room - thus a ceiling bearing on the walls - that the slab does not by code constitute a bearing footing as required.

75% of commercial builds have vapor barriers 100% of commercial builds have re-bar installed 50% of commercial builds do not use chairs for the rebar (they pull it up in the pour) 99% of commercial builds HAVE CRACKS 50% with vapor barriers HAVE MOISTURE ISSUES

ALl of the commercial projects I have ever worked on have vapor barriers beneath the slab.... and that's over 30 years of construction........ a vast majority of commercial projects use 6x6#10 mat in lieu of rebar - in fact - I have to change almost every project from mat to rebar...... so that 100% nuber is way off. 100% of my project use chairs (with rebar) (But I will admit I've only got about a billion dollars in construction behind me - as compared to the thousands of billions performed in the US every year) I must be lucky when it comes to cracks - actually the majorty of cracks you see in commercial construction can be traced to problems relating to re-entry corners at columns. I wonder where you derivesd your statistics from? Would you share your source? So you're saying that 37.5% of all commercial project have moisture problems - I really do want to see where you get your numbers from. Of all of the projects I have been involved with in my entire career - perhaps 1% have exhibited water problems - and most of these were dealt with during construction - and the few that we after the fact were due to conditions that changed during the project (i.e.: blasing opening up ledge to allow for water flow where there previously was none).

Adding rebar at any depth will help shrinkage cracks. The crack runs through the entire slab depth. NOT JUST IN THE TOP 1/3. The problem here is the curing process.

Sorry - but this is in error - drop rebar in the bottom 1/3 of a slab and it will NOT help with shrinkage cracks - shrinkage cracks are caused by concrete releiving tension as it dries - and it dries on the top first - ALWAYS- impossible for it to dry any other way - thus the bar HAS to be in the top 1/3 of the slab to work properly (I am a structual engineer BTW). Rebar in the bottom of a slab is required for structural actions only........

You and many others are not trying to build structural slabs here. Structural slabs are for heavy machinery and or containment of liquids from the top side.

Bearing walls require either footings (which the sab can be poured over) or a thickened haunch poured monolithicaly with the slab - your choice - but it's a code requirement.

Show me a piece of concrete and I will show you a crack

I'll show you a 12.000 s.f. pour and give you a magnifying glass and you won't be able to find a crack in the entire 12,000 s.f. - and that is in an 11 year old slab. Actuall I can find you quite a few commercial / industrial slabs that you couldn't find cracks in......... There are best construction techniques and products that make certain that cracks don't occur. PLease share the source of your statistics with us...... Sincerely, Rod

I've been watering the top of the slab since I got home from work, every half hour or do. I'm doing what I can that's in my control. Man, I can't believe how much heat the concrete gives off. But I can't do this through the night... Here are some pics from today:

Drums, save yourself work and aggravation - wet the slab down and then cover it with poly - the poly will help to stop the evaporation that's taking place........ Then it's the edges that will want the most water...... and it will be easier for you to keep up....... You can also purchase some concrete curing agent - which will maintain the moisture levels in the concret without the need for you to keep watering it........ this is how commercial projects are generally dealt with (you can't stp the flow of work to allow for concrete curing - and you can't safely work on poly with wet concrete below - it ends up like ice....... Here's one type of curing agent: http://www.seichemical.com/products/GCC-31S.html Rod Rod

Sorry , missed the stain - Chris is 100% corret in his post - don't use a curing compound if you're going to stain......... in practice you should not use it without verifying with the manufacturer of the adhesive even if you are gluing down a floor - just to make certain that it's comatible with their product. They will often list products that they have no problem with...... Rod

Rod, Many thanks on the advice. Going to make a run to home depot to get the poly. What do you suggest I put in the gap around the perimeter? Should I take the stone out? They're taking out the forms and chipping away the spillage right now...

Okay, no sealer then- just poly.

studio_drums wrote:

What do you suggest I put in the gap around the perimeter? Should I take the stone out?

If you can get the stne out to the bottom ofthe slab easily - then fine - otherwise - don't kill yourself. I woulduse a cheap foam in a can - like the crap they sell at home despot - it has no real density to speak of - so it won't act as a bridge - tape off the edge of the concrete s o you don't get any n it - and then foam away - go back after it cures and cut away the excess - and then trim it down about 1/2" - use a good (picture sikaflex) quality caulk to complete the edge. Rod

Thanks Rod. I know what you mean. I know they have the softer white kind and the stiffer yellow kind. I guess I'll go for the yellow. So no poly in the gap before spray foam? I wonder if that will be enough to keep the termites out. Maybe I should treat the area first like Keith did?

studio_drums wrote:

So no poly in the gap before spray foam?

Nope- that stuff never leaks - it's a great vapor/water barrier.

I wonder if that will be enough to keep the termites out. Maybe I should treat the area first like Keith did?

Wouldn't be a bad idea........ Rod

Rod, did you catch the post (and my reply) about the wa the concrete contractor didn't follow the agreed-upon directions/specs? If it were I, I'd have 'em jackhammer it up and do it all over again... I'm interested in your take on that. Perhaps I'm overreacting, but I somehow think if it were one of your projects, you'd insist the contractor does it right or does it over until they get it right. --Keith :mrgreen:

Keith, you're right I would - but then again - on my projects we have writeen contracts - with clearly defined scopes of work - we have superintendents that are up to speed on my requirements watching over their sholders - and we have testing labs whose people come to me the second the slump is 1/4" outside of tolerance to find out if I'll accept that. In this case if it goes to court it's a ' "he said" - "no he said" ' sort of a thing -and it can get nasty.......... At the very least there should be a written scope of work signed by each party spelling out clearly what is intended. Rod

To be honest, I made the unfortunate decision of hiring a close relative to do the job, having too much confidence in his abilities, and not putting my demands in writing. So I can't be the a-hole I would like to be. They just started pouring and I was shocked, but still hopeful he knew what he was doing. Then I pulled him aside and he said he was "pulling it up" as he went along. I got so upset I just left. I guess I'm not good at confrontations. I've marked the wall where the top of the slab rests so I can see if it settles. I'm also going to wait until the last minute to pay for the job. I still need to beef up my outer walls, so that will allow more time to see if the slab cracks or settles. If it does, I'll deal with it then. On the upside, the slab seems very, very solid. The resonant frequency is below the threshold of human hearing and absolutely no vibration is being transferred to the surrounding walls. I've been slamming my heel into it as well as a 2 x 6 and the only thing that vibrates is the board. The previous slab transmitted vibrations to the house very clearly. I'm trying to be optimistic now.

There is a non-destructive (magnetic) testing process that can tell you exactly where in the slab that rebar ended up if you're really concerned - on the down side of the bottom 1/3 of the slab - is the problem with shrinkage cracking - BUT - cracking doesn't mean settlement in and of itself - The upside is that the slab becomes more structural in nature - and would more easily span small voids without having settlement problems. Just picture the cup as being 1/2 full....... Rod