Preparing a building pad

[rockasawrus]

Hello All,


I'm building a house in NY and naturally the first step is to prep the building pad. It's my first time doing this so I'm feeling a bit nervous about the whole thing. I'm hoping kind, experienced folks can review my plan of action and give suggestions/insight. Much appreciated!


The building is a 32x56' pole barn with a 10' wide patio on the front of the building - 4' deep piers and 5" floating concrete slab - wire mesh and fiber mesh as spec-ed by engineer.

I dug a 24" deep test hole the other day...If I'm reading it right, the topsoil appears to be fairly shallow, about 4-6". It's not too obvious when looking at the layers, but the subsoil is quite a bit yellower.

So the plan is to:
1) Dig out 10-20 stumps under and around the building pad. These range from 12-36" diameter, thinking I'll rent a 30 ton machine for this.
-Is backfilling with subsoil or fill and compacting with excavator bucket enough? Or should I run a vibratory plate over these?

2) Scrape off the top 6" of a 52x66' area and put it in a pile for spreading later. Should be approx 73 CY with fluff
I'll do the same to connect the existing driveway to the new building as well.
- Not sure what the best machine is going to be for this - I can get a 75hp tracked skid steer or a 77hp Cat dozer locally. I've never run a dozer before so not sure how efficient I'll be with that. Would using the 30t stumping excavator for digging and skid steer for moving material be awkward/overkill? I feel pretty comfortable operating excavators but the biggest I've used is 12ton

3) Bring in fill and compact in 6" lifts. Back corner of building is high maybe 12".
-Do I have to bring the rest of the pad up to this grade, or can I make kind of a swale to push water either side? I'm in radon zone 1, so planning to install radon mitigation under slab. Engineer wants 6" gravel/crushed rock under the slab. Would it be worth doing 2" ROB and 4" clean gravel, or just use 4" clean for the whole thing? My wallet is hurting thinking about it.

4) Bring in crusher run to bring driveway up to grade



Thanks for reading!

 

[4570Man]

A 30 ton excavator is pretty excessive to dig 20 stumps. Sure it would work but the rental would be expensive and the transport cost will also be expensive. A 10-15 ton excavator would be plenty sufficient for that work and much cheaper to rent. I’d probably rent the skid steer over the dozer. A skid steer is pretty capable at getting work done and a lot easier to learn to operate over the dozer. Use the money saved on the other rentals to get a good size compactor roller. A plate compactor makes the surface look good but it’s only good for 1-2” lifts. It takes way too long to get anything done at that rate. Just tracking the dirt in 6” lifts or so works pretty good as long as the material is right if you didn’t want to rent the roller. The correct moisture for compaction is a pretty slim range. You can’t compact mud or dust.

 

[paulsharvey]

So, 1st, those 36" stumps, are they within the building footprint/slab? If not, I'd grind them. A 36" stump, in what appears to be a pretty clay heavy soil can be a son of a B to get out, but I'd feel fine with a rental Cat-318/Pc170 or similar; unless you have other specific uses for a 330/300.

I agree that it looks like I'd call top soil maybe 6", but it's not really a mater of the top soil, it's about removing organics, which includes any roots bigger than your thumb.

Backfilling a stump hole, the hole for a 36" stump, at the least, put somw.matwrial in (approx 6-12") and pack it with with the hoe, then add more, pack, add more and pack. Your never going to get to 95/98% density just packing with a bucket, unless we do it in lifts

 

[Rockbadchild]

So the plan is to:
1) Dig out 10-20 stumps under and around the building pad. These range from 12-36" diameter, thinking I'll rent a 30 ton machine for this.
-Is backfilling with subsoil or fill and compacting with excavator bucket enough? Or should I run a vibratory plate over these?

one or the other should be fine, you will need a diesel vibratory plate to compact your gravel under the slab regardless

2) Scrape off the top 6" of a 52x66' area and put it in a pile for spreading later. Should be approx 73 CY with fluff
I'll do the same to connect the existing driveway to the new building as well.
- Not sure what the best machine is going to be for this - I can get a 75hp tracked skid steer or a 77hp Cat dozer locally. I've never run a dozer before so not sure how efficient I'll be with that. Would using the 30t stumping excavator for digging and skid steer for moving material be awkward/overkill? I feel pretty comfortable operating excavators but the biggest I've used is 12ton

I would use the excavator to do this, the skid steer is also a good option

3) Bring in fill and compact in 6" lifts. Back corner of building is high maybe 12".
-Do I have to bring the rest of the pad up to this grade, or can I make kind of a swale to push water either side? I'm in radon zone 1, so planning to install radon mitigation under slab. Engineer wants 6" gravel/crushed rock under the slab. Would it be worth doing 2" ROB and 4" clean gravel, or just use 4" clean for the whole thing? My wallet is hurting thinking about it.

Not sure what this mean in red ...

No, follow engineer recommendation I would used 3/4 inch minus crush gravel.

 

[Rockbadchild]

A 30 ton excavator is pretty excessive to dig 20 stumps. Sure it would work but the rental would be expensive and the transport cost will also be expensive. A 10-15 ton excavator would be plenty sufficient for that work and much cheaper to rent. I’d probably rent the skid steer over the dozer. A skid steer is pretty capable at getting work done and a lot easier to learn to operate over the dozer. Use the money saved on the other rentals to get a good size compactor roller. A plate compactor makes the surface look good but it’s only good for 1-2” lifts. It takes way too long to get anything done at that rate. Just tracking the dirt in 6” lifts or so works pretty good as long as the material is right if you didn’t want to rent the roller. The correct moisture for compaction is a pretty slim range. You can’t compact mud or dust.

when we did culvert we did 4'' lift for 3/4 inch crush and 12'' for sand with heavy diesel plate and proper moisture (1 to 2 inch is not much at all maybe for a mini gas vibratory plate)

 

[rockasawrus]

Thank you all for your replies, feeling like I'm almost ready to tackle this!


I got confused about the excavator size. I meant to say a 30,000# machine or 15T, so looks like I'm in the ballpark. I think I may rent the excavator for one day, so I'll see how many stumps I can manage to dig out, the rest I can grind or otherwise deal with down the road.

That's interesting about the vibratory plate, I have seen many people use them for more than 1-2" lifts, but from doing some reading, it does seem like the more official rule of thumb is 1" per 1000# force. Oddly enough, my local rental place has a 20" plate and a 1 ton roller and they both put out 3000# eccentric/centrifugal force. Guess I will need to get a larger machine if I want to do higher lifts. Getting proper moisture is going to be a bit tricky as there's no water on-site yet, might have to figure about getting an IBC tote up to the site or wait for some rain.


About the grading around the building, I wasn't too sure what I meant either but after thinking it through, I guess my question is can I do a combination of cut/fill (Option 2)? I think bringing more fill (Option 1) is probably the better way to go to keep water away from the building. It looks like I will have to cut a little swale either way to direct water away from the building, as I'm not at the highest part of the property. Am I thinking about this right? See attached pics below (blue is pole barn)

So my strategy will be to scrape off topsoil, spread and compact ROB up to 6" below highest side of grade (if needed, probably only on left side of building), and then spread and compact 6" crushed rock to match highest side of grade. Finished floor will be 8" above grade.

How much extra material should I add to what I need to figure for compaction?

 

[rScotty]

It almost sounds like the "engineered design" was done before the test holes were dug and subsurface conditions were considered. Maybe I'm just reading it wrong. But if they didn't do much investigation, you may want to get your money back and get some design work done in the proper order. Probably not much will change - and now you have the pits dug to look at. Getting a real engineer involved might save money in the long run....& it's generally better a few years later.

 

[Quaffer]

I think I may rent the excavator for one day,

What do they charge for rental?

 

[Rockbadchild]

It almost sounds like the "engineered design" was done before the test holes were dug and subsurface conditions were considered, If so, you may want to get your money back and get it done in the proper order. Probably not much will change, but getting a real engineer involved might save money in the long run....& it's generally better a few years later.

lol a real engineer ??

for ops post #1

''The building is a 32x56' pole barn with a 10' wide patio on the front of the building - 4' deep piers and 5" floating concrete slab - wire mesh and fiber mesh as spec-ed by engineer.''

''3) Bring in fill and compact in 6" lifts. Back corner of building is high maybe 12".
-Do I have to bring the rest of the pad up to this grade, or can I make kind of a swale to push water either side? I'm in radon zone 1, so planning to install radon mitigation under slab. Engineer wants 6" gravel/crushed rock under the slab. Would it be worth doing 2" ROB and 4" clean gravel, or just use 4" clean for the whole thing? My wallet is hurting thinking about it.''



Ops said he has engineer slab drawing that comes with sub base... I have never heard of test holes for a residential floating slab, they usually simply ask sand or clay. I got my design for my slab which was structural footing and slab and they ask location, soil type (which is clay) and they did the design.... Ops soil look like more sandy then clay but still most likely sandy clay.

 

[rScotty]

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

 

[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.