Soil test came back H1 and now I'm nervous

HazzaB-QLD

Got the soil report back for our block in Ripley and it has come back H1.

I understand the basic idea is reactive clay and more movement risk, but im trying to work out how much I should actually worry.

Does H1 usually mean a slightly beefier slab and move on, or is it the sort of thing that starts turning into piering, drainage changes, extra engineering, and a much uglier site cost number?

Keen to hear from anyone who built on H1/H2/M class sites and whether it ended up being a big deal or just another line item.

gumleaf_88

H1 is half of SEQ mate, its not a death sentence. Most volume builders down here just price a stiffened raft or waffle pod with deeper edge beams and get on with it.

The thing to actually chase is the number. Ask what slab design the site cost allowance assumes. If the allowance was written against M class and the engineer comes back wanting H1 spec, you wear the difference, and thats where the ugly surprises live. Ive seen that jump land anywhere from 8k to high 20s depending on the house.

Get the engineering drawings before you sign anything, not after.

plot-twist-77

We built on H2 in Adelaide northern suburbs a few years back. It turned into screw piers under the slab edge plus articulation joints in the brickwork, and the plumber had to use flexible connections where the services enter the slab.

All up about 22k over the original site allowance which hurt at the time. Five years on there is one hairline crack above a window and thats it. The neighbours who went with the cheapest quote have doors that stick every summer.

H1 is a step down from what we had. Take it seriously but dont panic.

micko73

The slab gets all the attention but water management is the bit people stuff up on reactive clay. Keep stormwater and downpipes piped away properly, dont build garden beds against the slab edge, and dont let the site bake dry on one side while the other stays wet.

Most of the movement drama I get called to is moisture change around the perimeter, not the slab design itself.

HazzaB-QLD

cheers all, this is exactly what I was after. asked the builder today and turns out the site cost allowance was written against M class, so having that conversation now rather than at slab stage.

engineer drawings are getting sent over this week. feeling less like the block is cursed haha

rusty-nail-22

Concreting side of it: H1 pours are honestly routine now. Deeper edge beams, more steel, sometimes piers if the engineer is nervous about a corner. The crew does not treat it as exotic.

Where owners get stung is when the slab design changes AFTER contract. Get the engineered drawings priced into the contract, not floating beside it.

FairGo-Frem

Fremantle side note: our H1 job ended up with a waffle raft and a proper site drainage plan before the slab went down. Builder wanted to skip the ag drains to save a few grand. We pushed back after reading how many H1 slabs crack when water sits under them.

Soil class is only half the story. What they do with water around the house matters more than the letter on the report.

slab-happens

Late to this but for anyone finding it on google: ask whether the price includes the H1 slab design or just allows for it. Our contract said allowance for H class and the actual engineered slab still cost 6k over the allowance.

Words matter in these contracts more than the numbers do.

JenW88

Adelaide H1 update from ages back: drainage detailing around the slab edge mattered more than the class letter on the report. Once the landscaper finished falls away from the house, the hairline stuff we fretted about stopped being a weekly panic.

If you are staring at an H1 result, ask about water management in the same breath as the slab upgrade dollars.