Sounds like raft and beam...
I take it the fill is less than 350mm(or there abouts)
Re: slabs 61Mar 31, 2010 6:37 pm Sounds like raft and beam... I take it the fill is less than 350mm(or there abouts) Where you are coming from is where you are going to... Re: slabs 62Mar 31, 2010 7:22 pm onc ,almost their the footing layout plan mentions that the fill is to be compacted to a max of 150mm using a compactor.Type 1 modified is the footing layout plan no mention of piers under the slab at all. waffle height -225mm slab thickness-85mm internal rib width -110mm external rib width-300mm stem width-150mm Slab depth -310mm Reinforced with : SL82 -fabric instead of sl72 internal rib -1-N12 BTM external Rib -1-L12BTM Re: slabs 63Mar 31, 2010 7:58 pm http://img62.imageshack.us/img62/6922/p1000082e.jpg picture taken of Form works Re: slabs 64Mar 31, 2010 8:04 pm http://yfrog.com/6gp1000084j another angle taken on the 30/3/10 ,Iam guessing the styrofoam and chairs not in place will be fixed Re: slabs 65Mar 31, 2010 8:25 pm Well there is a setdown and likely why the foam is on an angle... but I don't understand the minimum cover where the mesh/fabric will not have much if any concrete cover. But don't get me wrong it is just me questioning the practice, though it would be good to have some conclusive info on whether there is a need for minimum cover Where you are coming from is where you are going to... Re: slabs 66Mar 31, 2010 8:36 pm andy onc ,almost their the footing layout plan mentions that the fill is to be compacted to a max of 150mm using a compactor.Type 1 modified is the footing layout plan no mention of piers under the slab at all. waffle height -225mm slab thickness-85mm internal rib width -110mm external rib width-300mm stem width-150mm Slab depth -310mm Reinforced with : SL82 -fabric instead of sl72 internal rib -1-N12 BTM external Rib -1-L12BTM Do you have any plans at all (other than floor plans)? Where are these specs from (a drawing or tender doco, or somewhere else)? These are fairly standard, we have very similar specs (except we don't have L bars and our fabric is the thinner one). My signature is distracting people from my wise posts ... Re: slabs 67Apr 01, 2010 3:55 pm The plans,I presume your referring to are the "footing layout plan"from which I am getting all the info.Should I be concerned not as yet because work on slab is still in progress.If the form works ,doesnt look satisfactory at the time of the pour,then its time to worry. Re: slabs 68Apr 02, 2010 1:22 pm Andy - I think the reason why they didn't put piers is because your fill is under 300mm, I think most of the time when piers are required is when the fill exceeds 300mm, or the land had been disturbed eg. knocked down old house and rebuild, or it's built close to easements. If you look at the ready reckoner site cost thread I think most P class falls in the above mentioned categories but not sure why yours is, could it be a mistake eg. should be H class but mistype as P? I think there is no need to be concern about this as I don't think the engineer will put his reputation and business on the line for the builder. In addition, why they haven't poured the concrete yet, I was told by my ss when I ask to defer the slab pour because of the predicted rain on that day he said that the reo's shouldn't be expose to the weather for a long period of time because it will rust and the reo will lose it's strength, he said it's best to pour the next day after formwork is completed. I think you should contact the building surveyor and ask them for their opinion and to check it. All the best with your build. Re: slabs 70Apr 02, 2010 7:03 pm I suspect It would take a long time for the reo to rust enough to lose significant strength. The structural integrity of our first home depended on reo that had been exposed for about 10 years, sticking out of the top of an underground garage built by the previous owner of the block. The structural engineer pronounced it fine and the house didn't move in the 30 years we lived there. Cheers zeke Re: slabs 71Apr 02, 2010 8:12 pm andy The plans,I presume your referring to are the "footing layout plan"from which I am getting all the info. Should I be concerned not as yet because work on slab is still in progress.If the form works ,doesnt look satisfactory at the time of the pour,then its time to worry. Andy, I was asking if you have any plans at all. I cannot refer to a plan when I don't even know if you have it in the first place. So, would be good to actually see a plan, but again, it all sounds pretty standard. Not sure why are you having this 2 week delay - do you know? Isn't the formwork finished? If not, ask them what is left to do. When are they pouring? You could have organised someone during this time to have a look and then you'd be (hopefully) sure. If you are in Melb, you'd be fine, as there are a few good inspectors there. I am still sceptic about you not having any piers in the ground (if that's the kind of piers what you're talking about, and not those above-ground ones). What's your soil type, is it more sandy or more clay-ey? You could also organise your own soil testing to rule out any mistakes. If you end up doing that, I strongly suggest that you use a qualified (residential) structural engineer right from start, and not just an independent building inspector. The engineer can at the same time inspect your formworks (it's actually preferable that an engineer inspects this part of construction). BTW, our soil testing was done by the same structural engineers who "designed" our slab for the builder. Why not give a few of engineers a call and explain the situatation. Sometimes you could figure a few things out just through an introductory talk (since things get mentioned and then you sometimes get enough info to connect the dots). I really haven't heard that anyone has a slab with no piers. Have you taken any pictures of the site just before the formworks started? My signature is distracting people from my wise posts ... Re: slabs 72Apr 02, 2010 10:00 pm Hi all, My slab was done 2weeks ago. Today I found too may narrow cracks across the slab. Is this a normal problem or serious? My site is E-D category, single story brick veneer home, single pour grillage raft, 100mm thick SL82 slab 250x900mm deep. Anyone can say something about this? Re: slabs 73Apr 03, 2010 7:18 am Hi dream home1, looks like you're talking about hairline cracks?? How about posting some pictures? It's hard to say anything without looking at the issue. Also, have a look at http://www.buildingcommission.com.au/resources/documents/S+T_GUIDE_07.pdf in regards to cracks in slabs. If they are under certain widths, most likely nothing will be done about them. My signature is distracting people from my wise posts ... Re: slabs 74Apr 03, 2010 7:26 am zeke I suspect It would take a long time for the reo to rust enough to lose significant strength. The structural integrity of our first home depended on reo that had been exposed for about 10 years, sticking out of the top of an underground garage built by the previous owner of the block. The structural engineer pronounced it fine and the house didn't move in the 30 years we lived there. It's good to know that, zeke !! I was also told many times that it's actually better for the reo to have just a bit of rust as it 'bites' better to the concrete Andy, in regards to the delay, I'd be more worried about the moisture protection plastic sheeting, as this material (at least ours) should not be exposed to UV rays for more than several weeks (I think 4, can't remember) - after that, its moisture barrier properties start to be affected. When is your pour happening? Have they tidied up the formworks that are not horizontal and any other bits and pieces? Have you had a site meeting with the builder to inspect the work together and explain all the questions for you (I'd put them in writing to the builder + pictures when requesting the site meeting). Or even better a separate email as a record of your concerns and what they did (or didn't do) about them, but definitely in writing. Let us know what's going on. My signature is distracting people from my wise posts ... Re: slabs 75Apr 03, 2010 8:06 am lex , the builder outsources the slab work to a engineering company called "structural works " they have done the soil test and based on that prepared what sort of slab is best suited for the site . The building surveyor is a company by the name of "DJM surveyors " who issued out the building permit (which is standard practise these days) it states that the following inspections are mandatory 1.steel for slab inspection 2.pre slab inspection 3.frame work report this puts my mind at ease . Any stuff ups and their heads on the chop/chop. The reason the pour has taken so long ,it rained ,plus the easter break .From the 18th its been approx 14 days. I have attached a photo taken prior to the form works being prepared ,give us your opinion . http://img87.imageshack.us/img87/7637/p1000079u.jpg Re: slabs 76Apr 03, 2010 8:38 am OK, here's a quick checklist for Andy of what can be quite easily checked, even by yourself. As you can see, some things are very trivial. Moisture barrier Has the plastic moisture sheeting been overlapped and ends securely taped (wherever there are end rools)? Taped around pipe openings within the formworks? Extend to the end of the outer-most timber formworks and preferably go over it? There must be no (untaped) tears or holes in the plastic. Fabric (also called mesh) Has the fabric been tied at regular intervals? Have the ties been turned down (so they don't stick up vertically)? Fabric should always overlap by 1 full square and the bars on the 2 overlapped fabrics should align, and not being moved by any distance. Have they used the 82 fabric, as specified? There should be no more than 2 layers of fabric overlapping (not a good practice to have more than 2 layers stacked on top of each others). No piece of mesh (or top placed reo) should be higher than the rest, ie. your mesh should not be tilted etc. They say the weight of the concrete should weigh it all down, but it doesn't take much to tie any protruding areas to the lower placed reo. Basically, the top surface should be pretty much horizontal and tidy. Not sure why they placed that top mesh just to slide to the lower height slab. I would have thought they should set out those 2 different levels clearly via creating formwork that steps down. Reo bars Take your slab plan (or whatever it's called) and compare to the f/works. Have ALL the reo bars been placed and where they are indicated on the plan? Your internal ribs should all have 1 N12 bar at the bottom (must be sitting on chairs). Your external ribs should all have 1 L12 bar (I think this is for the corners only). (I must say it's a bit odd to me to have only 1 N12 bar at external ribs - are you sure there are not 3 of them?) Overlap of bars should be 600mm (from memory) and should be tied securely. Corners should have L bars (you do mention them). Also must be properly overlapped. Does all reo and all mesh sit on chairs? (Also, sometimes a few chairs are just sitting there, supporting nothing. The reo or the mesh has to sit inside their grooves - easily adjusted.) Have you got those reo bars placed at re-entrant corners? They are not visible on your pics. Clearance (cover) of all steel All reo bars and all mesh should have 50mm clearance from the timber all around the external perimeter of the slab. All reo bars and all mesh should have around approx. around 20-30mm clearance from the pods and timber inside the slab. Chairs Typcially should be 45mm high (it should say on your plan). Should be spaced at 800mm distances. Waffle Is it of the correct size (it should be documented on the plan, eg. 1100x1100 mm). Is it of correct thickness (eg. yours is 225 for the main slab; it's possible it's 150 for your garage, verandah etc - you didn't mention it, but may be different in your case). Your internal rib width should be 110mm (it's the distance between pods inside the slab). Your external rib width should be 300mm (it's the distance between the perimeter pod and the outer timber formwork). Your stem width should be 150mm (it's the distance between the perimeter pod and the inner timber formwork). External rib width and stem width are checked around all of the perimeter of the slab. Slab thickness It relates directly to the waffle thickness, but should also relate to slab class. Your slab thickness should be 85mm (it's the distance between the top fabric to the top of future concrete). I don't think you can really measure this now for sure, since they could use any type of timber planks around the slab and you can't be sure how high it's going to be poured. Your slab depth should be 310mm (it's the distance between the very bottom, ie. from the lowest point inside the slab (from moisture barrier) to the top of the future concrete on the main slab). One way to measure this is to measure from the moisture barrier to the top of the fabric and then add 85mm in your case. Same as for slab thickness, you can't really ensure this right now. Levels (Step-down areas, ie. where the slab will of different finished heights) This is hard to explain and even harder to see/measure. Basically, wherever your future slab needs to be of a different finished height (as, for example, for a typical 75mm (or as documented in your case) garage step-down), the top mesh needs to be by that much lower positioned than on the main slab. And similar for porch step-down etc. (I think you don't have different levels within the house itself?) Mesh should overlap by 225mm typically (should be shown on your slab drawings/plan). Slab will be thinner at Step-down areas by the step-down height (typically 75mm) because the pods are typically 75mm different in height (your pods in main slab are 225, and it's probably 150mm in your garage, porch, etc). And there could be mo re, but I have to get going ... I will add later if I remember something else. Just saw your pic of the site, with no piers My suggestion at this point is to get it all in writing. My signature is distracting people from my wise posts ... Re: slabs 78Apr 03, 2010 3:17 pm I figure that will extend from an internal corner to the side of the slab?? Lex... Where the slab heights differ, the should be an allowance for this in the dig out. The slab should be NO thinner than the minimum thickness ANYWHERE. Set downs(step downs) for wet areas will have a variation from the 'normal' slab height to the 'set down' in concrete thickness. What makes concrete crack : variations of thickness, variations of mass(shrinkage), too rapid hydration, too rapid cure(no cure method), too much water in the concrete, a larger mass joining a smaller mass, cold joins(where the previous truckload finished poorly compacted concrete. Where you are coming from is where you are going to... Re: slabs 79Apr 03, 2010 5:34 pm Hi dream home1, Well, that's quite a well defined crack! I guess the first thing to do is to measure its width and compare to the tables in that doco I attached earlier. Then you can figure out what's the most likely answer you will get from the builder. Hi Onc, as you can see from my post, the slab thickness should be 85mm - and that's it (based on the specs provided by Andy). This includes the step-down areas, which are typically the 75mm step-downs into a garage or onto a porch, veranda, alfresco and similar. On slab plans (drawings), step-down areas are detailed (drawn) separately and clearly, just like any other section of the slab. The difference in the finished floor level is achieved simply by using waffle pods that are thinner by 75mm in those step down areas (and I already wrote that slab thickness relates directly to the waffle thickness). (I can't believe how simple this concept is !) Obviously, I have not mentioned any internal recesses in the slab for bathrooms etc. because it is not specified in Andy's post and many builders don't do them at all. If Andy's slab is supposed to have recessed wet areas, it obviously needs to be accounted for (and not just "shave off" some of the slab's thickness). From the specifications that Andy provided, this seems like a typical slab. There are hundreds of examples of such slab (technical drawings) in various documentation and web sites. I would still like to hear if anyone else out there didn't have any piers under the slab. My signature is distracting people from my wise posts ... Re: slabs 80Apr 03, 2010 5:45 pm Thank you very much for the reply. My slab was done 2weeks ago. Today I found too may narrow cracks across the slab. One end to the other end more than 5 places( pics in theabove post). Is this a normal problem or serious? My site is E-D category, single story brick veneer home, single pour grillage raft, 100mm thick SL82 slab 250x900mm deep. Is it need to make any complaint to the builder? http://yfrog.com/5bdscn5833j my suspicion - some builders, they do usually make 'odd' settings in their site plan / pricing as their standards - being hopeful that first - the initial price is… 9 2508 |