Browse Forums Owner Builder Forum 1 Sep 05, 2009 12:49 pm HI All will be getting a slab poured soon. Can you please tell me what I should keep an eye on. Its a waffle pod, M class, some bulk concrete for deeper footings. Slight fall at highest 600mm so its surgested a cut & fill of 300mm in some areas. Do they vibrate the concrete on all slabs? Its 85mm thick. Can they get away with out vibrating it? How can I tell if its done well? I have the slab plan, and see some extra reo, do I need to make sure they put it in? Any tips would be great as I have seen some stuff ups and I want to make sure mine is OK. Much appreaciate the help from OB thread. Thanks & regards KW.............. “It's just as unpleasant to get more than you bargain for as to get less” George Bernard Shaw. Re: Your slab, what to look out for? 3Sep 05, 2009 1:35 pm KW- All mesh/reo supplied should go in (though there maybe some off cuts) Re entrant bars should be placed at the internal and external corners.(re-entrant bars are 12 or 16mm x 1500mm) Vibe should be done on the edges to stop honeycombing and the thickenings should be vibed. But I don't expect vibe to be throughout. Ask them what kind off curing they do (ie 'conc cure' a spray or 'wet cure' with flooding or hessian and plastic) You will only know if they have done a good job when the forms are off. The edges should be smooth. Good luck KW Onc_artisan Where you are coming from is where you are going to... Re: Your slab, what to look out for? 4Sep 05, 2009 11:40 pm Hi King Willy, the mesh and trench mesh (same stuff but only 200mm wide, 6.0 m lengths) should run to within 50 mm of the perimeter boxing............the key things to look out for are that the boxing is parallel and square, I'd suggest you check after the boxing is in and after they go home for your own peace of mind. You will need someone else to hold the other end of the tape, your looking for the same measurements at each end from inside of boxing on one side to inside of boxing on the other side. Basicly find a square or rectangle shape within your slab once you have checked for equal parrallel measurements, you can see how square the boxing is by checking diagonally from corner to corner, if that measurement is the same your slab boxing is square, and your finished slab should be as well. To illustrate a simple example get an a4 sheet of paper, with a ruler measure the width at each end, then measure the length each side as well, the measurements should be the same, then measure from corner to corner diagonally, if that measurement is equal (same), your a4 sheet is exactly square............I don't know how difficult this may seem but its relativly easy on the jobsite, youll need a long tape measure (30mtr) of course, the other thing worth a look is the top of the boxing, if they screed of it then you can run your eye down it to get an idea how straight (lumpy) the finished crete will be, for the most part you would expect full time concretors to be pretty good at screeding and finishing, I always check for square even at the very least compare the surveyors string building line with the boxing, they would have set to this line, both longitude and latitude.................if the surveyor gets it wrong the house will be built in the wrong spot, so they take great care when setting out.............hope that's understandable, bye for now Shaun Re: Your slab, what to look out for? 5Sep 06, 2009 12:02 am Shaun you forgot to mention... take the measure from the top only or the bottom only of the tape, and it needs to be tight to be acurate. Also the shop drawings will have a few diagonal measures on them, you need these if you want to know the shape is correct Also, I find trying to translate the setout to a novice impossible, I've tried many times. KW no offense intended, K? But good try anyway Where you are coming from is where you are going to... Re: Your slab, what to look out for? 6Sep 06, 2009 12:08 am onc_artisan KW- All mesh/reo supplied should go in (though there maybe some off cuts) Quote: Re entrant bars should be placed at the internal and external corners.(re-entrant bars are 12 or 16mm x 1500mm) Vibe should be done on the edges to stop honeycombing and the thickenings should be vibed. But I don't expect vibe to be throughout. Quote: Ask them what kind off curing they do (ie 'conc cure' a spray or 'wet cure' with flooding or hessian and plastic) You will only know if they have done a good job when the forms are off. The edges should be smooth. Good luck KW Onc_artisan entrant bars..........I pressume you mean corner lap bars to tie perimeters at a corner......... ask what kind of curing they do..........it's a house slab, the concrete has 3 main components, crushed rock, sand and cement, the cement goes hard (dries or cures) over 30 days after bieng mixed with water...........wet cure flooding hessian or plastic...........what do you mean?????........... these are genuine owner builders risking hundreds of thousands of dollars on their dream home, they joined the forum to increase thier knowledge base and become better informed through the build process, they deserve and need good advice........... Shaun Re: Your slab, what to look out for? 7Sep 06, 2009 12:28 am carpenterforhire onc_artisan KW- All mesh/reo supplied should go in (though there maybe some off cuts) Quote: Re entrant bars should be placed at the internal and external corners.(re-entrant bars are 12 or 16mm x 1500mm) Vibe should be done on the edges to stop honeycombing and the thickenings should be vibed. But I don't expect vibe to be throughout. Quote: Ask them what kind off curing they do (ie 'conc cure' a spray or 'wet cure' with flooding or hessian and plastic) You will only know if they have done a good job when the forms are off. The edges should be smooth. Good luck KW Onc_artisan entrant bars..........I pressume you mean corner lap bars to tie perimeters at a corner.........are you referring to trench or mesh lacework??nNo I meant re-entrant bars ask what kind of curing they do..........it's a house slab, the concrete has 3 main components, crushed rock, sand and cement, the cement goes hard (dries or cures) over 30 days after bieng mixed with water...........wet cure flooding hessian or plastic...........what do you mean?????...........Well to cure a slab properly you need to reduce the rate of de-hydration these are genuine owner builders risking hundreds of thousands of dollars on their dream home, they joined the forum to through the build process, they deserve and need good advice........... Shaun I agree to increase their knowledge base and become better informed and is the reason I am here Actually it is the only reason I am here Where you are coming from is where you are going to... Re: Your slab, what to look out for? 8Sep 07, 2009 1:30 am HI KW - good advice from both Shaun & o-a, but let me just reinforce another thing - communicate....talk with the people who are going to do the pour - talk to them about what they intend to do & how. square at slab stage is the future of ur build - if its not square everything is harder from then on. check all set out with diagonal measurements - no offence to the ladies, but do it with another chap so that u can really pull the 30m or 50m tape if its f/glass or cloth - steel tapes r easier as u dont have to pull so hard. IMO realistically with non steel tape there should be no more than 5mm difference over 30m & that 5 mil could be tension or stretch variation- its important to really keep tape tight while u do this & smaller areas less variation. also check that shower setdown is in the right place & at right depth!!!!! very expensive to change after. i see a few different views re curing of slab - this is a good time of the year to pour - shouldn't get too hot & dry out too quick. curing has become a issue in more recent years - never used to be, but now different operators achieve different "curing / setting" rates by having batching plant add "accelerents" to the mix - talk to ur man doing pour about this. "wet cure flooding hessian or plastic.." referred to r different ways to "hold" or "slow up"the cure - a lot of operators don't worry about it over here & we r getting more & more hairline cracks in slabs that i've ever seen b4.i'm no chemist but it appears to me this problem has only occurred since the accellerants have been used - never had this 20 year ago. again talk this through, cos where we used to hose slab for a week or so after pour, now some say u should'nt do that as u wash to curing agent off????? ponding or flooding is where u build a temp dam around the edge of slab & keep it under water, hession is kept damp to stop drying, plastic similar idea. i don't know about these practices - talk to ur grano worker. if u search this forum with words "slab" u will see the troubles that kristo & i had last year - trying to do the very best & both ended up with some cracking - mine has ended up only being "cosmetic" and "fixed" with paint on poly filler - but caused me days of worry & an engineering inspection. i've put down probably 20 slabs in my life - this latest, with all the technowlogy available has been the worst ever result...! hope i haven't worried u too much, but please talk to ur grano chaps & discuss what replys u have had from ur thread..... get as much info as u can then make ur best choise with what u know - very best wishes with it - cheers tony Re: Your slab, what to look out for? 9Sep 07, 2009 1:45 am Tony Thanks for the reply. It seems its importaint to get this right, as you said. Ive got a 50m tape its got a bit of stretch in it, but will use your formual to add a bit to it. Will check the shower depth also. Yes it will have an additive to set it faster ???? Not sure but thats how its dont now days. They told me they could be on it in a week with the frame. Not sure what to think about that. Yes, it should be a good time of the year Spring for the slab. I hope all goes well. Thanks again & good to hear from you. Cheers KW........... “It's just as unpleasant to get more than you bargain for as to get less” George Bernard Shaw. Re: Your slab, what to look out for? 10Sep 07, 2009 11:01 am KW, I'd recommend having an expert examine the formworks, reos and set-outs before the pour. It may cost you approx $400, but would be money very well spent. Discuss the curing method with your granos. Nowadays they spray concrete with a compound that's supposed to break down with time. I'd prefer plastic foil cover and watering. Ponding's OK but labour intensive - you need to build a clay/sand dam around the perimeter of the slab, provide for difference in levels and then add water as it evaporates. Whichever method you choose, be prepared, curing should start almost immediately. Keep tabs on the delivery trucks and DON'T LET THEM RINSE THE SHUTES INTO THE MIX GOING INTO THE PUMP (that's what they did on my slab and it started to crack almost immediately ). Ostentatiously wander about with a camera and snap everything. One of my acquiantances had her slab finished off in waves, no wonder, her concretor arrived at 7 AM reeking with booze. Maybe you should have a discreet sniff before they start on yours Chris My father rode a camel, I drive a car, my son flies in a jetliner, his son will ride a camel.Saudi saying Re: Your slab, what to look out for? 11Sep 08, 2009 2:02 am I have to go away soon, but want to be there for the pour. What do you think, just leave it to them or be there every day. Frankly I dont know too much about slabs, good or bad. Same for the site scrap or cut I dont want the house in a bloody hole. I only want the minimum cut, some Ive seen just go for it, then put the house in the middle of a deep hole. I think its best I stay for the whole thing and as you said get an expert to have a look. Problem is not too many guys like to point out stuff ups in others work as most of the locals know each other. Cheers KW............. “It's just as unpleasant to get more than you bargain for as to get less” George Bernard Shaw. Re: Your slab, what to look out for? 12Sep 08, 2009 6:08 pm KW, the slab height is pre-determined already, the surveyor will put in a height peg indicitave of top of slab, based on height above mean sea level, eg (55.65 mtrs amsl) the concretors will remove only what they have to to finish the slab to that height.................. Shaun Re: Your slab, what to look out for? 13Sep 09, 2009 12:29 pm We had our slab poured on Sat and we were away, now we have a heap of cracks all over the slab. M is having it tested today and they have stopped the frame from going up. They are testing the Reo so not sure what will happen now. Hoping it is fine and we can get on with it. But we were hoping to be there when it was poured, not possible for us!! Good luck with your slab pour and hope you don't get what we got!! Forum thread viewtopic.php?f=31&t=22300 Re: Your slab, what to look out for? 14Sep 09, 2009 1:09 pm KW, If your within 1/2 an hours drive of Patterson Lakes, I'll check the boxing with you, I have a long tape, it only takes around ten minutes, no charge and will give you peace of mind, contact details on the website........... Shaun Re: Your slab, what to look out for? 15Sep 12, 2009 12:41 am Hi King Willy! I will ask our grano worker what he put on our slab as he did a FANTASTIC job, we have about 550m2 of concrete (both normal and polished) and we have not one crack not even hairlines. We were warned that due to the amount of concrete that hairline cracks were a given but not to stress about them, but as i said he did such a wonderful job there is not a single one - slab has been down since easter, and and internal bricks have been laid and still none have appeared - i do know they used a better grade mesh in the floors to help and they did "paint" something over it to help with the curing. Like Tony said this time of year is better cause of the cooler weather, we were ready to have the concrete poured and put it off till easter so at least it would be a little cooler. Will email him tonight for you and ask what he used, hopefully it might be of some help to you Nicole Re: Your slab, what to look out for? 16Sep 14, 2009 5:31 pm onc_artisan KW- All mesh/reo supplied should go in (though there maybe some off cuts) Re entrant bars should be placed at the internal and external corners.(re-entrant bars are 12 or 16mm x 1500mm) Vibe should be done on the edges to stop honeycombing and the thickenings should be vibed. But I don't expect vibe to be throughout. Ask them what kind off curing they do (ie 'conc cure' a spray or 'wet cure' with flooding or hessian and plastic) You will only know if they have done a good job when the forms are off. The edges should be smooth. Good luck KW Onc_artisan I think AS2870 has crack control/re-entry now at 2/N12 or n16's @ 2000 long vibe should be on all EB's & IB's and any step down's/formed changes in level..in QLD you'll need an RPEQ to inspect and sign off (Form 15) to say all reo including any additional (pier caps/bored pier/starters etc) is per slab design Re: Your slab, what to look out for? 17Sep 14, 2009 6:18 pm Yep 2 at each site yes keepitgully, quite correct Where you are coming from is where you are going to... Re: Your slab, what to look out for? 18Nov 02, 2009 12:26 am We just poured our slab a fortnight ago. I am an owner builder but my brother and father are professional builders. First of all I stayed right through the poor, helped out when I could and watched. A couple things to watch for: Before Pouring: *check the weather before they start digging the trenches. If it pours down with rain the sides of the trenches will fall in. This material then has to be removed from the trenches by hand (hard work) and the width of the trenches will increase which means more concrete!. Unfortunately rain poured down between our trenches being dug and before the foundations were poured. We had to delay for 1 week due to the rain and a second week to clean up the mess made by the rain. *check the plastic - you dont want holes in the plastic as it will let moisture through. Tape up the holes. Note - in South Australia the engineer must inspect and sign off on the foundations before any pouring can commence. *make sure the appropriate plumbing is in place. If you have an island kitchen then make sure all the services have been run to the island kitchen spot - not just plumbing but also electrical conduit. *check the reputation of your concrete supplier if you are able to do so (its not an easy thing to do). Not all concrete suppliers are the same. We ordered the concrete from a supplier that has a tendency to exceed the specifications - ie request 20mpa concrete and it turns out closer to 25mpa. On commercial jobs they will take samples of the concrete and send it away for testing. So my brother was able to advise which suppliers sail close to the margin and wish suppliers dont. On a residential job you wont take samples so you have to rely on the suppliers reputation and your concrete workers. *practice your OI scream. Pouring foundations is noisy and if you want to get attention then saying a polite "excuse me" will get you nowhere and no one will listen. You will need to be vocal and the concrete workers wont be offended by it. You will find they will be pretty abrupt and loud towards each other. "Oi - stop adding water - Oi Oi Oi - stop adding water" *buy yourself a pair of rubber boots so you can walk around the concrete as the pour is in progress. It is pretty hard to do very much from the sidelines and the rubber boots will make you look the part. During the Pouring: *watch for the adding of water to the concrete as it goes into the concrete pump. The concrete pump operator will tend to tell the concrete truck driver to add water because it reduces the stress on the concrete pump. Adding water decreases the strength of the concrete. However it can be legitimate to add water if the concrete has spent a bit of time in the concrete truck. *watch for the concrete driver cleaning his truck. If you have a soil driveway (most likely) the water will end up turning the soil into slush and the concrete trucks will make an absolute mess and may end up having difficulty getting in and out. * one option to reduce cracking is to use 20mpa concrete for the foundations and then use 25mpa for the floor. This is what they will do on commercial buildings. The concrete workers dont like it though - its tougher on the concrete pump and harder to finish/screed. *we planned to use 25mpa on the floor but the concrete workers quickly poured the foundations and floor in one in one hit in the first section with 20mpa - so we stuck to 20mpa throughout. *make sure their is sufficient cover of concrete over the mesh. Check with your engineer for the right level of cover - you dont want the mesh too close to the surface. *keep the concrete workers moving - if they are too slow the concrete will start to go "off" (ie get hard) and it becomes quite difficult to work, screed and apply any finishes. *beer and concrete workers are best friends. Try to stop them drinking while the work is underway. Dont bring out any beer before the job is finished. The moment beer is brought out the job will slow down. However it is quite common to buy the concrete workers a slab of beer once the job is done (however a professional builder will not do this). *keep an eye on any complex sections of the foundations such as stepdowns. There may be a stepdown to the garage - there will be a small stepdown for the bathrooms. (if you can you may want to double check the bathroom stepdown dimensions are correct). The concrete workers have a disposition to simplifying things particular if it involves a lot of boxing (putting in borders). *make sure you know what sections are to be tiled, what sections are to be smooth and what sections are to be "footpath" finished. Keep an eye on the concrete workers to make sure they apply the correct finish and also apply any edging. *when the boxing is removed go around and remove any remaining metal pegs sitting in the concrete. The concrete workers may leave them in place and the concrete will set and then they cannot be removed. You have to use a grinder to cut the pegs. *if you have any exposed foundations and you want them to be finished nicely - ask the concrete workers to finish it as soon as the boxing comes off. I grabbed an old sack and used that to finish the exposed foundations. It was surprisingly effective. Once pour is finished: *cure cure cure - if you want to avoid cracking. Go to the site 2-3 times per day and water the foundations as if they were plants. The warmer the weather the more important and the more frequently you should do this. Do this for at least the first 4 days. Alternatively the foundations can be wrapped in plastic. *get some non shrinking, waterproof, grey mortar. Make it very watery and go around and fill any peg holes in the foundations. It is quite likely the peg holes have been made right through the plastic so you want to fill them and you dont want moisture seeping through. *finally - think about applying a waterproof coat to any exposed sides of the foundations particularly if soil fill is going to be placed against the foundations. The most important place to put this stuff is around the front of the garage (driveway into the garage) and the tiled portico/entrance/rear veranda (if it has a concrete floor). The waterproofing coat is like a grey concrete slurry, its applied with a heavy brush and then you may need to water it 2-3 times a day for 3-4 days. The reason you do this is to stop moisture travelling through the concrete and coming through the surface in the form of a white salt damp like powder. Sometimes this happens (maybe 1 in 10 jobs), frequently it doesnt. If it does happens it is a pain. The cost is around $70 for 4kg (enough for a garage, portico and veranda) or $150 for 10kg (enough for a standard house). You can get it from Bianco's in South Australia. Empathy: *foundations are very very hard work. Walking around the mesh carrying the concrete pump hose is not for the faint hearted - it is unbelievably heavy and I just dont know how they can do it for hours. Screeding (the process of levelling) is backbreaking work. More recently they have introduced screeding machines - but many concreters will do it the old fashioned way. So have some empathy for your foundation workers - they may be a little rough, a little tough and a little rude/crude but they do work very very hard and its not something most of would want to do for a living. I am no engineer so dont take this as gospel. Rather just outling some of the steps that I went through. Re: Your slab, what to look out for? 19Nov 02, 2009 1:41 am Interesting post Webzone... Just wondering what line of work you do I guess you are not with the family business, but then you could be. I would be checking to see if your Dad as a buillder, would allow the owner to swan around in the mud like you suggest. I would be tipping you would have a walkout of your/my granos if you tried that on any of our sites. Buy a pair of rubber boot(s) to look the part WTF ??? Control the added water?? how would a novice know what is which? Keep the workers moving??? Why not just pour it yourself Sorry mate you lost me and I am in the business and only recently too... about 20+ years as an owner operator. You did make some good points, but I am a Rum drinker PS With all those conditions you just doubled the cost of building the slab Where you are coming from is where you are going to... Re: Your slab, what to look out for? 20Nov 02, 2009 4:22 pm onc_artisan I would be checking to see if your Dad as a buillder, would allow the owner to swan around in the mud like you suggest. I would be tipping you would have a walkout of your/my granos if you tried that on any of our sites. Its my site and I shall do as I please. I just did it and no-one complained. Who are you to tell an owner-builder what they can do on their site. onc_artisan Buy a pair of rubber boot(s) to look the part WTF ??? What you suggest turning up wearing running shoes or maybe thongs? WTF??? onc_artisan Control the added water?? how would a novice know what is which? Thats what you have two eyes for in the front of your head. Its pretty obvious to see them pouring water into the concrete. onc_artisan Keep the workers moving??? Why not just pour it yourself Maybe you are just so good that you dont need any gentle prodding. But not all concrete workers are as good as you. onc_artisan Sorry mate you lost me and I am in the business and only recently too... about 20+ years as an owner operator. You did make some good points, but I am a Rum drinker Of course I lost you. You want to do the job your way. In contrast the owner builder wants the job done the right way. Again you may be so good that your way is the right way but that is not the case with all jobs. onc_artisan PS With all those conditions you just doubled the cost of building the slab [/quote] Absolute rubbish. No the fireplace doesn’t work. It’s been enclosed. I’m not sure what was removed, as it was done quite some time ago - well before what I can see with photos online… 2 11584 Interested in getting either the Polytec Boston Oak or Palace Peak for kitchen cabinets. Looking at the Boston Oak ones, it appears that the colour varies significantly… 0 9169 4 14297 |