Standard Slab or Dropped edge Beams

Hi

Hoping to get a builders or site supervisors advice on am I better sticking to just a standard slab or going dropped edge beams. Reason is we have a slight fall and the builde ris cut and filling. On the fill side we are 1350mm away from the fence and after building need to do a retaining wall approx 11 metres long most probably to contain the fill. Have been quotes approx $1500 extra for dropped edge beams which I think will be cheaper than getting a retaining wall down however I have no idea on retaining wall cost. Are drop edge beams more prone to problems or slab cracking etc? Only reason I ask is my other house which is built in a clay ridden area has cracking on the slab and its only at the spots where the drop edge beams are. The soil wer are building the new house on is reactive also and builder is specifying a h1 class slab. Whats my best option going drop edge beams or just doing a retaining wall?

Thanks

Only one of the structural engineers who frequent this forum could give you an accurate assessment of one vs the other unless you opt for a cheap retaining wall ( with the obvious caveats that entails ). I don't think there is any reason for a slab with an incorporated drop edge beam to crack vs a standard slab with a turndown as long as all the reo is the correct size and placement and the correct strength concrete was used it should be the same deal. How much are you talking about for the height of the retaining wall if you went down that path ?

Stewie

I think it hs to be 11 metres long not sure on height I think maybe 600mm? I dont know which way to go Im thinking of just going a standard slab and building the retaining wall? Im not even sure how much a retaining wall in timer this size would cost though

I am not a engineer but if you have fill you will need deeper edge beams anyway unless the fill is compacted which if the fill is currently unretained near the edge then very hard to compact properly.
So after saying all that I think you will find your design engineer will deepen you edge beams so you
won't have to decide.

Me thinks Insider could be right. Our engineer specified our slab to have 1 metre beams plus 350mm piers at the back where the fill was deeper. We also retained our boundary

HI

Im not sure if they will as its a fixed price tender couldnt imagine this builder making a mistake that would cost them. I know the fall across the buildiing envelop is 1.2 metres so they are cutting 550mm and filling 550mm. I have no idea how they compat it either as its pretty clay/silty soil.... I guess they know what they are doing I just dont want cracking slab like our other house I just have a fear of dropped edge beams now.

Deepened edge beams or piers should reduce your chance of cracking.If it was my slab I would like the design engineer to deepen the beams into natural ground so that your footings are consistently on natural ground rather than part on natural and part on questionably compacted fill which is your cut and fill situation.

Interesting they have now advised me to just move the house over 500mm from the boundary and advised I shouldnt need a retaining wall now. Hope they have it all sorted legit as they are a high volume builder..... They were quoting $2000 for drop edge beams? What to do