Browse Forums Building A New House 1 Nov 24, 2009 1:02 pm Anyone else had this issue where the slab has been laid and is smaller than the plans. It is short in width and in depth. Obviously the house to us will be smaller. The builder claims the internal room sizes wont change as they have some space to play with. Apparently the bricks can hang slightly over the edge of the slab as can the timber.
Anyone encountered this potential problem or is the builder on the level. Re: slab size laid smaller than plans, 50mm less width 2Nov 24, 2009 1:22 pm To be honest, I haven't even measured my slab. Even if I lost 5 cm of internal space I think I'd be more distressed at the thought of extra delays or structural compromise whilst they tried to fix it. Maybe its enough to know that you'll pull up the builder about any issues to let him know you won't be a push over. My bricks on the garage side did overhang the slab about an inch because the edge of the slab was chipped away in places, the mortar seems to have covered it up though - but if its a straight line, the brickie might just brick up to the edge unless his told otherwise. Re: slab size laid smaller than plans, 50mm less width 3Nov 24, 2009 1:55 pm Hmmm the set out was wrong by the sounds of it. They probably put the boards on the wrong side of the line. Who did the setout, Builder, grano or surveyor? One day someone with enough clout will reject a slab because it is not what was ordered. I'd be asking for a discount since they didn't do the job properly, and will have flow on effects that you don't want to be paying for... since it wasn't your fault. Around 50% would be a good starting point I'd have thought. What is so freaking hard about getting it right? Just a bunch of numbers Where you are coming from is where you are going to... Re: slab size laid smaller than plans, 50mm less width 4Nov 24, 2009 5:31 pm Are you taking the plan measurements of the inside or outside of the walls? 'A bottle of wine contains more philosophy than all the books in the world.' Louis Pasteur Vegie garden: viewtopic.php?f=19&t=27637&start=0 My Backyard Adventure Re: slab size laid smaller than plans, 50mm less width 5Nov 24, 2009 5:45 pm That would be an error of approximately -0.25% if your slab is 20m wide. I work in construction - not house construction, mine upgrades and depending on where the concrete is, we allow for a +/-2 or +/5% error. So your slab is at least 100 times better than that! Concrete is hard to get exactly, so I wouldn't worry about the 5cm and 2cm at all. Re: slab size laid smaller than plans, 50mm less width 6Nov 24, 2009 6:42 pm Mrs smith - You are kidding right? Concrete hard to get right? 50mm x 100 = 5mtrs that can't be right. You're winding me up eh? mrs_smith I work in construction - not house construction, mine upgrades and depending on where the concrete is, we allow for a +/-2 or +/5% error. So your slab is at least 100 times better than that! Concrete is hard to get exactly, so I wouldn't worry about the 5cm and 2cm at all. 5% +/- over 20mtrs is 1mtr. I guess you alway err on the overage eh? Where you are coming from is where you are going to... Re: slab size laid smaller than plans, 50mm less width 7Nov 24, 2009 7:17 pm Dont know about timber, but if double brick, the outer wall is built on the footing, NOT the slab. There are some pics on annie.s site a ways back and a few others for a good picture reference. Research away... and good luck Timeline Aug 08-Land Mar 09-Demo/Titles Sept 10-Handover No1 Sept 11-Handover No2 April 12-Sold No2 Aug 14-Land/Demo Jan 15-Slabs viewtopic.php?f=31&t=25736 Re: slab size laid smaller than plans, 50mm less width 8Nov 24, 2009 7:42 pm mrs_smith That would be an error of approximately -0.25% if your slab is 20m wide. I work in construction - not house construction, mine upgrades and depending on where the concrete is, we allow for a +/-2 or +/5% error. So your slab is at least 100 times better than that! Concrete is hard to get exactly, so I wouldn't worry about the 5cm and 2cm at all. so should i ask the builder to make my slab 50mm longer without altering the price as its within tollerance ................. i think NOT i would be expecting a rebate of some sort & i am sure the builder will pick it up from who ever made the mistake i wonder if they made all there slabs 50mm shorter than specified how much extra they would make on an anual basis cheers rocket Re: slab size laid smaller than plans, 50mm less width 9Nov 25, 2009 11:14 am onc_artisan Hmmm the set out was wrong by the sounds of it. They probably put the boards on the wrong side of the line. Who did the setout, Builder, grano or surveyor? One day someone with enough clout will reject a slab because it is not what was ordered. I'd be asking for a discount since they didn't do the job properly, and will have flow on effects that you don't want to be paying for... since it wasn't your fault. Around 50% would be a good starting point I'd have thought. What is so freaking hard about getting it right? Just a bunch of numbers I'm sorry but I find this a bit ignorant. I'm not sure what profession your in but every profession has mistakes, just for some professions the consequences of those mistakes are a little more severe than others. Firstly we don't know that this wasn't caused by a discrepancy in the plan (quite common), we don't know how hard the slab was, perhaps it had angled walls all over the place, we don't know the size/volume this is over. If you think this is some big saving for the builder your horribly mistaken, he will still be charged the same by the concreter, no one wins from this, it creates headaches for other trades along the way. As far as the slab is concerned they may plant some timber on edge to the side of the rebate and then average that out over the rooms of the house meaning you wont lose any room. Re: slab size laid smaller than plans, 50mm less width 10Nov 25, 2009 12:00 pm I said I DIDN'T work in housing. I work on major mining projects. I'm currently on a $6 billion project, so perhaps expectations are different. But still, a 0.25% error is nothing. 5% is allowed for "non-essential" and 2% for "essential". This allows survey and concrete problems. And there's still been mistakes past those tolerances. We had a height of some steps (1000x400x400) that were 50% off. I'm not kidding. The base was 250mm lower than expected due to a survey error and they made it 50mm thicker to try to make up for it. With the temperatures too some things have dried warped. We have to pull up a 30m section of concrete 4 times in one area because it wouldn't set properly as it was done in summer up here as was very warped. I hate the allowance as we only have a +/-2mm tolerance for mechanical items, and with a large variance for concrete, and another slightly smaller one for structures, we something get things that are a meter off. But it's appears to be standard in our industry - never seen anything different on the projects (except for highly specialised equipment but this post is longer enough and I'm not going into that). Re: slab size laid smaller than plans, 50mm less width 11Nov 25, 2009 12:52 pm Hi guys, First off i don't work in housing or mining, i'm a systems engineer so this isn't a professional opinion. In all honesty on a Slab of concrete 20m long, i'd personally consider +/- 15mm on each measured side, considering that it is timber edges held in place by timber stakes and holding a measuring tape isn't that hard. So even 30mm of variation i'd consider reasonable. At 50mm yours is outside that range but that said in the grand scheme of things it isn't that huge, depenind on where the short end is in relation to other fixed points, where walls cross etc it may be the case that its say 30mm short at one end and 20mm at the other. Try measuring to the nearest fixed point on the plans and see exactly where its short? In terms of getting the builder to fix it, based on what i've read around on here it seems bonding wet concrete to set isn't the easiest thing in the world to do without using an epoxy repair instead, so perhaps adding 50mm isn't going to be that easy. I think if it was 500mm out you'd definately have a case against the builder to fix it. Personally i'd look closer at exactly where your losing the length apart from just overall and seeing how it effects your room dimensions before taking it up with the builder. You may want to find out what if any effect it will have on framing, roof trusses, roof tiling, guttering as any of those may be effected. Good luck with it. Our Build - Places Fairhaven 23+ - https://forum.homeone.com.au/viewtopic.php?f=31&t=28045 Our Landscaping - Belial's Backyard - https://forum.homeone.com.au/viewtopic.php?f=19&t=45375 Re: slab size laid smaller than plans, 50mm less width 12Nov 25, 2009 1:43 pm I did sound ':butterflies: ish'. Yes... Yes it is my trade... you could check my profile if you were interested or the siggy below ....still there really is next to no reason for a set of forms being placed in the wrong spot ...there is a saying that everyone has heard... 'measure twice cut once' we call it thrice, because 3 times is better than making a boo boo. When you do a set out and cross check, the numbers don’t lie, an error can be noticed by a cleaver grano instantly during, and get confirmation to proceed with an alteration to the set out schedule if needed, why else would you deviate from a plan . If the plan is wrong then that is the problem and it takes a long time to to learn to be able to pick up an error ... The plan in this case reflected an error on the finished size of the actual product. Therefore the set out was incorrect, and is why I ask who did the set out. A tolerance of 10mm +/- each measured side is more than adequate.(15mm if you want) We all make mistakes don’t get me wrong... for the good of the job let’s get it right (FIXED) without being asked to do so. It is not very hard to pass a tape across a finished slab before you leave the site. ...being pleased with you efforts or passing the error message along. The builder will have a mill' things on the go so don't leave it to the last minute. Belial I do agree, though if the short side is a critical area then the 50mm could be the diff between pleasure and pain... and may mean making alterations to the plans to reflect the construction variations of 50mm as you said split the diff is as good an option as poss... and this changes all of the numbers so would need a new set of plans or addenda ... Who is paying for this then...? Not meant to be insiteful. Just asking a question. Sorry to be a boring a&%$ Where you are coming from is where you are going to... Re: slab size laid smaller than plans, 50mm less width 13Nov 25, 2009 6:33 pm The fact its out in two places indicates its more likely the plan than measuring the wrong side of the boxing. Once again we don't know the plan, it could be an absolute mud map we are seeing. I have seen plans where the internal dimensions don't add up to the external dimensions, which can be difficult to pick up before setting the slab out as the external dimensions add up but the internal ones don't. Then again it could be the apprentice having the 'smart' end of the tape. The plan won't need to be redrawn but the builder will need to pass the changes on to the appropriate trades, a copied plan with the amended dimensions works best. Re: slab size laid smaller than plans, 50mm less width 14Nov 25, 2009 6:56 pm Who makes the amendments? Where you are coming from is where you are going to... Re: slab size laid smaller than plans, 50mm less width 16Nov 25, 2009 7:33 pm x ... It is 50mm short in width and 20mm in depth. ... The builder claims the internal room sizes wont change as they have some space to play with. Apparently the bricks can hang slightly over the edge of the slab as can the timber. OK, if my maths is OK ( ), and assuming an external planned wall size of 15m, and according to this document http://www.buildingcommission.com.au/re ... IDE_07.pdf, and assuming that the variable "L" used in the calculation is measured in [mm], it works out that the acceptable tolerance for the assumed size wall is 75mm (you are very much encouraged to double check ). It appears that the max brick overhang can be 15mm, which would only gain 30mm of the lost length (15mm from each side). So, it appears that this can be considered to be within tolerances , but I can't work out how the internal sizes won't be affected ... My signature is distracting people from my wise posts ... Re: slab size laid smaller than plans, 50mm less width 17Nov 25, 2009 7:56 pm Both walls have a cavity 'nominally' of 40mm I know this could be reduced to 15mm as a minimum. So you have your 50mm. This leaves 15mm as an air gap, which to my way of thinking will have the potential to be bridged and allow moisture ingress... and defeats the purpose of the air gap. Hey before I go on... These are moot points but the people paying for these structures have no say and no recourse. Is this fair and reasonable? I have piped up because I know how easy it is to get right. ...the apprentice should be on the dumb end for the second measure and the tradie on the first measure. Nomad does the builder do these amendments ex gratia? Where you are coming from is where you are going to... Re: slab size laid smaller than plans, 50mm less width 19Nov 25, 2009 8:37 pm I think its rather naive to just say its easy, the average house slab is but complicated jobs are by no means easy. These jobs are priced accordingly of course and often commercial jobs but also some architectural plans can be enough to pull your hair out. Do you have any experience with this type of work onc? I don't believe I insinuated this would be kept from the home owner, that is up to the builder how much he divulges to the client. Re: slab size laid smaller than plans, 50mm less width 20Nov 25, 2009 8:51 pm Nomad - I did say this is my trade of the last 30 years and my business since 1991. A few photos for you below... amongst other things http://s670.photobucket.com/albums/vv70 ... ?start=all I have also said previously over 4000 slabs under my belt, would that be considered 'experienced'? Where you are coming from is where you are going to... I had new concrete laid, extended the alfresco and had the sidewalks concreted too. I noticed the concreter didn't put the expansion foam anywhere, there are expansion… 0 8117 Dear Members I have to decide the Facade column size. My custom builder standard is 350mm with rendering, but i asked for 470mm plus stone or tiles and yet to get… 0 7496 All sorted guys. Just needed to buy a blade with the correct bush. 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