Just got back from one of my units and it appears that the finished floor level of the unit is below that indicated on the plan. Bit of a worry as it means the floor level is below ground level. Someone has messed up but as I am unsure of how the slab heights are established, could anybody tell me what the process is?
I think what happens is that the surveyor using his groovy machine establishes how high the slab height should be above sea level. He then pegs it out and the slab is poured under the supervision of the builder. A brick footing then surrounds the slab to the finished floor height and the actual floor is poured to the correct height as marked out, again, by the surveyor for the actual floor height. Does that sound right?
Any advice would be really appreciated as it looks like war is about to commence!
All the best
AndyletParticipant@letJoin Date: 2007Post Count: 10
hi andy, not sure if this will help. we have just completed a slab via building inspectors instructions (owner builder). it had to be at least 600mm (edge beams) into natural earth. i think this depends on the type of land too (volcanic, clay). your builder should be able to explain. if the land slopes it can meen that the sit cut one end will be deeper than the other. im sure someone with more experience in this area will respond. good luck.mackarMember@mackarJoin Date: 2006Post Count: 106
you are close… after measuring out the footings are poured once reo steel is in place… then build up as you outlined in brick & finally the slab is poured after clean fill has been compacted… this is a very simplified version not allowing for extra engineering etc etc but the initial pour is footings only not final slab. also the brick build up can be more than the normal couple of brick courses…
final slab heights are determined by council either approving heights marked on plans or approving subject to changes as outlined by he Australian Height Datum (AHD).
what stage are you at… at the moment??
also, …how do you know the FFL is below that marked on plans??Scott No MatesParticipant@scott-no-matesJoin Date: 2005Post Count: 3,856
Andy, there is usually no issue of a slab being below the ground surface providing that the outside wall has been tanked to prevent water hitting the wall below ground (there are many houses still being built on sloping sites).
AHD is simply a reference point. A good residential builder will use a surveyor sparingly – boundary, 1 m above FFL & recovery points (possibly setout of the external corners if it is a complex site, lift shafts, all levels above first floor on multi storey buildings etc) and final survey (for strata subdivision). A builder is trained to work from the survey marks and to set out.
The answers to your questions are:
1) The finished floor level (FFL) is marked on the plans as 35.35 above sea level. From the contour lines on the overall plot layout plan, the highest gradient intersecting with the unit should have been somewhere around 35.2. Therefore, as the FFL should have been at 35.35, at no point should it have been below ground level. However, it clearly is. You can see that it is about 400mm lower.
The problem with the FFL being lower than the 35.35 is that the FFL is now lower than a sewerage inspection pit lip. The pit is only 1.5m from the front door. So, if the sewer overflows, the sewerage will flow directly into the front door of the house.
2) We're right at the end of the build. So, it's going to be hard to do anything about it too. I should have noticed it before but then again that's why I used a builder and did not do an owner build.
3) As the plot is only very slightly sloping, it hasn't been tanked.
Anyhow, I'm meeting the builders with the architect on site on Friday. If they are solution providers – as opposed to excuse men – we'll hopefully be able to sort things out. Let's hope so as I really don't want to start getting shitty with them.
Thx for your help.
AndyScott No MatesParticipant@scott-no-matesJoin Date: 2005Post Count: 3,856
Ensure that the builder/architect bear any costs with regard to lowering the pit, these are not your problems to rectify and the responsibility of the arch/builder.
Raise and discuss the problems with the architect – get them to clarify the problem and present the solutions. If the levels have been stuffed up find out what is going to be done.
Check what your position is legally with regard to handing over final payments before sighting the occupancy certificate (from council/certifier) and plumbing compliance (water board/council).
Is the pit an inspection pit or an overflow? (big difference). Insist on a gas tight lid to prevent overflow if it is an inspection pit.
(PS: 35.35-35.2 is only 150 mm not 400mm.)
Thx for the advice SNM.
I don't intend to pay for anything and will be discussing the problem with the Building/Plumbing Inspector once everybody has got the joint plan of action together. I still owe over a $100k to the builders so that should be a fair incentive for them to get everything fixed.
As for 35.35 minus 35.2 being 150mm and not 400mm, the actual slab is even lower than the 35.35 on the plan. About 400mm's lower. My point was that's how I know the slab should have been above the surrounding ground. The FFL should have been 150mm above highest actual ground height before excavation. It's hard to explain without physically seeing it.
All the best, and thanks again.