Preparing a building pad

[4570Man]

There are lots of ways to build things. The OP says he wants to float a large slab on what is probably unevenly expansive clay soil - "expansive" meaning the soil changes shape and strength with different levels of moisture and pre-compaction.
I've never heard of a foundation design where the engineer didn't first take a look to see what kind of substrate he was dealing with - especially when using 6" lifts.

There was a time when I just charged ahead. But I'm old enough now to recognize when I would want more information. The OP might too.

I hear him on the expense. But knowing the choices is worth something too.
rScotty

It’s more common than you would think. I’ve had plenty of house plans with the foundation details engineer drawn. Most of the time it’s pretty bland details. The engineer almost never makes site visits for residential projects at least in my area. Which the soil here is hard and rocky. It really doesn’t take anything extra to build a foundation here and the county actually doesn’t even require engineer approval for residential buildings plans. If the OPs priority is doing a good job my recommendation would be to use a dozer and strip off all the topsoil, renting a pad foot roller to compact the fill and bringing water to the site to ensure proper moisture for compaction. But the roller is overkill in my opinion. Tracking in the fill is usually good enough.

 

[rScotty]

It’s more common than you would think. I’ve had plenty of house plans with the foundation details engineer drawn. Most of the time it’s pretty bland details. The engineer almost never makes site visits for residential projects at least in my area. Which the soil here is hard and rocky. It really doesn’t take anything extra to build a foundation here and the county actually doesn’t even require engineer approval for residential buildings plans. If the OPs priority is doing a good job my recommendation would be to use a dozer and strip off all the topsoil, renting a pad foot roller to compact the fill and bringing water to the site to ensure proper moisture for compaction. But the roller is overkill in my opinion. Tracking in the fill is usually good enough.

I hear you. Towns and counties vary widely on building requirements. Builders vary too. And some areas don't have any real requirements at all. Some just have a simple form for the builder to fill out so they can collect a permit fee. Those permits don't mean that any standard has been met.

Just because there are no requirements doesn't mean that everything is going to work right.
None of us would choose our doctor on that kind of basis; we'd want a more educated approach.

More knowledge can help. Sometimes the subject is not so simple. Judging by the information the OP gave in his initial message - and then by the questions he was asking - it was my opinion that he should consider getting some more professional help. Engineers are good; so are old experienced builders.

rScotty

Another way is to get any old $20 copy of the International Building Code and study up. It is written for builders, not engineers. And it has chapters on compaction, clay soils, posts. It even has a section on wattle and daub construction.

 

[EddieWalker]

Compacting soil is an extremely difficult thing to do. The more you build up a pad, the harder it is to reach compaction.

A vibratory plate compactor is for home owners doing small patios. It is NOT used for a structure of any kind.

A six inch lift if huge. You will need a full size vibratory roller for that, along with a water truck to get proper moisture in the soil.

For me, when I build something, I build up the pad in one inch lifts, and I compact it with the front tires of my full size backhoe, with a yard of dirt in the bucket. I go over ever inch of new soil, then dump the bucket, spread it out, then load up the bucket with another yard of dirt, and go over the fresh spread soil. This would never pass any sort of test for compaction, but it has worked for me on my projects.

Wire mesh is one of those big red flags that scare me when talking about concrete. The biggest lie told in concrete is that they will pull it up when spreading the concrete, and that it will remain in the middle of the concrete while they walk on it. This is 100% impossible to do. Usually they pull it up when the pour starts for pictures, but ten minutes into it, they stop pretending to do this, and focus on getting the concrete spread as fast as possible so they can get a good finish.

Proof that this is a bad idea is that wire is never used in any commercial, city, county or Code Inspected type of concrete work. It does not replace rebar. It is a waste of money that bad contractors lie to people about so they can do less work and get paid the same amount of money.

Fiber doesn't really do anything either. It is designed to help with small cracks that appear when the concrete mix has too much water. It's very limited in what it achieves. It does not replace rebar. It is a cheap, easy, simple extra that you can add, but it's never really needed.

Rebar on chairs is the standard that has been proven to work every time it's done properly.

The most important thing about concrete, is to never let them add more water to the mix. Extra water reduces the slump, and makes it easier for them to spread. If you watch YouTube videos, it's very common to see them spreading soup like concrete, which is very VERY BAD!!!!

Do a YouTube search on Commercial Concrete work and you will see the difference between what Home Owners get stuck with, and what the real pros do.

Look up what "slump" is. Be sure that you know what it is when they start pouring. They will try to sneak in extra water, and your slump will turn into soup. The only way to make sure they do not do this is to tell them before hand, and to stand there when the concrete is coming out of the truck!!!!

NEVER EVER trust them to do it right!!!!!!

When the extra water evaporates, the concrete cracks. This is why concrete cracks more then any other reason. If you soil isn't compacted, the concrete will crack five to ten years from now, but not in the first month like it does from too much water.

 

[Rockbadchild]

Come one guys not all deisel plate are created equal

 

[paulsharvey]

So, I don't know how we made it this far down with mentioned compact testing. At first, I wasn't sure if this was a barn, home, shop, or what, and I reread, and it's his home. I would 100% recommend having a proctor pulled, and doing some density testing when you Think it comcpated. Yes, it's going to cost $350 for the proctor, and $80/test, (3 test min), but when we are talking about a $200k+ structure, it's money we'll spent. If you have future cracking, without density test, no way you can go after concrete guy, or anyone else, you have no proof the fill was compacted.

 

[Rockbadchild]

So, I don't know how we made it this far down with mentioned compact testing. At first, I wasn't sure if this was a barn, home, shop, or what, and I reread, and it's his home. I would 100% recommend having a proctor pulled, and doing some density testing when you Think it comcpated. Yes, it's going to cost $350 for the proctor, and $80/test, (3 test min), but when we are talking about a $200k+ structure, it's money we'll spent. If you have future cracking, without density test, no way you can go after concrete guy, or anyone else, you have no proof the fill was compacted.

If such things is even possible (go after the concrete company) then I agree but if not as per experience when these things started to bounce around you have reach max compaction.

 

[paulsharvey]

If such things is even possible (go after the concrete company) then I agree but if not as per experience when these things started to bounce around you have reach max compaction.

Well, it depends on how the contracts work, but if you did the slab prep, and hired a concrete guy, without testing, and it cracks more than acceptable, you wouldn't have much to be able to blame him. If you had passing density tests (generally required as part of the permit around here), you would have some proof that it's on them.

Material testing, for a house (not barn, shop, ect), I would have density tests in footers and slab, as well as test cylinders mafe on the concrete at the pour. Sure, that costs money, but it's maybe 1% of the total cost, and poor density and/or bad concrete, will cost Huge amounts to correct latter.

 

[paulsharvey]

A lot of the "sink hole damage" in FLa is not sink holes at all, (so not an insurance issue), but many times stem from poor construction, no density, adding too much water to concrete, ect, and now for a sink hole claim, they use GPR to get out of the claim, poor construction=owners problem, sink holes=insurance claim

 

[Rockbadchild]

Well, it depends on how the contracts work, but if you did the slab prep, and hired a concrete guy, without testing, and it cracks more than acceptable, you wouldn't have much to be able to blame him. If you had passing density tests (generally required as part of the permit around here), you would have some proof that it's on them.

Material testing, for a house (not barn, shop, ect), I would have density tests in footers and slab, as well as test cylinders mafe on the concrete at the pour. Sure, that costs money, but it's maybe 1% of the total cost, and poor density and/or bad concrete, will cost Huge amounts to correct latter.

I am surprise for use up north all our concrete crack, we do control joints and hopefully it happens there but cracks is fully acceptable just not displacement.

 

[buckeyefarmer]

I would rebar a pole barn slab, and skip the wire.