Any Concrete Experts On Here?

[Evolved]

I have been getting bids to remove and pour a new patio as well as pour an RV pad for me. The more bids I get the more confused I become... The bids I have received so far range in price from $5200 to $17,000. I figure the 17K guys bid it extremely high because he doesn't want the job. So, I can just toss that one out. The next highest bid was $9500. Almost all bids were by licensed contractors and all of the reviews I have read were (almost) all positive. I understand there are people out there that just want to blast people so I keep that in mind when reading reviews.

One of things the high bid people say is that they will need remove a lot of dirt (6 inches or so) and bring in road base and gravel to "do it right". The most weight my RV pad will see is maybe 5K lbs at the most.

My question is this, are they really thinking about my best/long term interest or are they just driving the price up? I am looking for totally unbiased feedback and not so much a bid. If you do want to bid it out you're more than welcome to contact me (Private message) but, that's not my goal here.

Can anyone help with my confusion?

 

[Kevin B.]

I've been researching concrete for my future shop. My understanding is that you do need several inches of base to be sure you don't get settling/slumping.

/not an expert

 

[Evolved]

I've been researching concrete for my future shop. My understanding is that you do need several inches of base to be sure you don't get settling/slumping.

/not an expert

One of the guys mentioned this... sort of. He asked how old the home is (4 years) and said "Ohh, you'll be fine. The ground should have settled by now.". I should also mention I live in Syracuse. I have been told the ground here is mostly clay (by the highest bid). But, when the landscaper finished our yard I remember his saying how sandy the ground was. This is another thing that adds to my confusion.

 

[Caleb]

When I had my RV pad poured, the guy didn't use much base/gravel, etc. I questioned him about it. He said the only thing that does is allows the concrete to move separately of the ground for freezing and thawing. I've now had my RV pad for several years, stored a 10Klb trailer on it, now have my enclosed motorcycle trailer on it and have had zero issues. Not an expert by any stretch but based on my experience, it doesn't seem like it's really needed. It also does;t make much sense to prevent settling or slumping, if the ground is going to settle, it'll still do it with base on it and the base will still follow the ground. Not sure how it would help prevent the settling.

 

[Spork]

My experiences with concrete were growing up, it's been 20 years since I've done cement so ignore me if I'm full of it. The gravel helps with drainage, if you're not in an area that collects water it also helps stabilize soil, think driving truck in mud vs driving on gravel road. Some soil types are significantly easier to drive on when wet and would not need the support of others that are bad when wet. Back on the farm we would add rebar/wire mesh to cement to make it stronger and prevent cracks/movement. Thicker cement also helps but cement is a lot more than gravel/backfill so that's why they usually don't do it.

With that out of the way, I think 6"+ is a little excessive most gravel under cement I've seen is in the 2-4" range. I don't think the extra hurts but it's more material required.

 

[ichi-san]

A stone base is the "proper" way but not absolutely necessary. It makes it easier at get a uniform slab thickness and gives the bleed water off the concrete somewhere to drain. It will not help span over soft spots in the ground. I would want the "28-day compressive strength" of the concrete mix is 4,000 PSI. That the concrete mix is "air-entrained", air entrained concrete is more resistant to freeze/thaw cycles. I would want the slab to be a MINIMUM of 4" thick through-out. I would want wire mesh reinforcing in the slab (WWF6x6-W1.4xW1.4) or fiber reinforcing. The wire mesh should be suspended at mid-depth in the slab - if it's not properly supported it ends up on the ground where it does no good. I would want "control joints" tooled or cut into the slab dividing the slab in close to square panels with the maximum spacing between joints about 10 feet - concrete shrinks when it cures causing cracks, this is normal and the control joints give the concrete somewhere to "want" to crack hopefully preventing random cracking. I would want the edges of the slab to rounded or chamfered, a hard sharp corner will chip and break over time. I would want a "broom" finish on the surface to keep from being too slippery when wet. If the concrete is placed on a hot, sunny, dry day, I would want the contractor to do something to prevent the concrete from drying too quickly like cover it burlap, soak it with water and cover it with plastic. If concrete dries too quickly it will have a lot of surface cracks and have a tendency to spall (have pieces pop out).

One of the ways I've been told to determine is the ground is firm enough for sidewalks/driveways is to push a piece of #4 rebar (solid steel rod 1/2" diameter) into the ground. You probably want to do this in a pretty tight pattern over the area, say a 12" or 18" grid. If you can push it in more than 1" with your body weight, the ground is too soft.

If you have any inside corners (called "re-entrant" corners) I would want two #4 rebar say 3 or 4 feet long placed centered on the corner at a 45 degree angle (not sure if this make sense but a good contractor should know what it means). Cracks want to form at inside corners.

 

[Evolved]

A stone base is the "proper" way but not absolutely necessary. It makes it easier at get a uniform slab thickness and gives the bleed water off the concrete somewhere to drain. It will not help span over soft spots in the ground. I would want the "28-day compressive strength" of the concrete mix is 4,000 PSI. That the concrete mix is "air-entrained", air entrained concrete is more resistant to freeze/thaw cycles. I would want the slab to be a MINIMUM of 4" thick through-out. I would want wire mesh reinforcing in the slab (WWF6x6-W1.4xW1.4) or fiber reinforcing. The wire mesh should be suspended at mid-depth in the slab - if it's not properly supported it ends up on the ground where it does no good. I would want "control joints" tooled or cut into the slab dividing the slab in close to square panels with the maximum spacing between joints about 10 feet - concrete shrinks when it cures causing cracks, this is normal and the control joints give the concrete somewhere to "want" to crack hopefully preventing random cracking. I would want the edges of the slab to rounded or chamfered, a hard sharp corner will chip and break over time. I would want a "broom" finish on the surface to keep from being too slippery when wet. If the concrete is placed on a hot, sunny, dry day, I would want the contractor to do something to prevent the concrete from drying too quickly like cover it burlap, soak it with water and cover it with plastic. If concrete dries too quickly it will have a lot of surface cracks and have a tendency to spall (have pieces pop out).

One of the ways I've been told to determine is the ground is firm enough for sidewalks/driveways is to push a piece of #4 rebar (solid steel rod 1/2" diameter) into the ground. You probably want to do this in a pretty tight pattern over the area, say a 12" or 18" grid. If you can push it in more than 1" with your body weight, the ground is too soft.

If you have any inside corners (called "re-entrant" corners) I would want two #4 rebar say 3 or 4 feet long placed centered on the corner at a 45 degree angle (not sure if this make sense but a good contractor should know what it means). Cracks want to form at inside corners.

Thank you for the advise. You were right, I didn't understand the last paragraph but 45 seconds on google and I knew exactly what you were saying. So, for a best long term result some sort of stone base is worth the extra cash. I was talking to my pops and he said something to effect of "quality will be remembered long after price is forgotten" or something like that.

At what size of pad would you recommend the use of rebar or a mesh reinforcement be used? Is there a common width/length that it becomes necessary?

 

[SLC97SR5]

I'm following this, we have an area that we would like poured as well as redoing our driveway.

Please keep this updated, good luck!!

 

[BlueWolfFab]

I prep this stuff all day every day for work. I'm actually technically still at work now so I don't have a lot of time to go into full detail yet but without having seen the job myself; the 6" of excavation is most likely in order to get the proper elevation/drainage. If elevation is not the issue, then they are likely thinking its a sub-par material to base/gravel on. If it's good, clean hard dirt that has been there a long time then there's no reason you can't clean up the grade a little and base/gravel on top of that.

If if you in fact are on clay, I guarantee you it needs to come out for a quality product, or else that 5k lbs of weight WILL crack your concrete sooner than later.

As far as base / gravel goes its circumstancial to the conditions to say what is best and the proper thickness.

 

[ichi-san]

Thank you for the advise. You were right, I didn't understand the last paragraph but 45 seconds on google and I knew exactly what you were saying. So, for a best long term result some sort of stone base is worth the extra cash. I was talking to my pops and he said something to effect of "quality will be remembered long after price is forgotten" or something like that.

At what size of pad would you recommend the use of rebar or a mesh reinforcement be used? Is there a common width/length that it becomes necessary?

It's not really about the size of the pad but more about the use. The heavier the loads put on the slab, the thicker the slab needs to be and the heavier the reinforcing in the slab needs to be. For a typical driveway for cars and SUV's, your RV weighs less than my pickup, 4" thick with wire mesh sounds about right.

 

[nnnnnate]

My understanding was that anywhere a new pad will butt against a foundation you ought to drill holes for rebar to help the new pad from sloughing down. I'd like to know if this is still correct.

When we had an RV pad and patio poured we cheaped out and it shows. There are really big cracks on the RV pad, it has flaked off, and water pools on a couple spots on the patio. I'd love to extend the RV pad a little behind the fence, pour a bigger patio, and have the main driveway lifted since it has sunk but am also afraid of the cost for all of this, especially to have the main driveway lifted.

 

[ichi-san]

My understanding was that anywhere a new pad will butt against a foundation you ought to drill holes for rebar to help the new pad from sloughing down. I'd like to know if this is still correct.

When we had an RV pad and patio poured we cheaped out and it shows. There are really big cracks on the RV pad, it has flaked off, and water pools on a couple spots on the patio. I'd love to extend the RV pad a little behind the fence, pour a bigger patio, and have the main driveway lifted since it has sunk but am also afraid of the cost for all of this, especially to have the main driveway lifted.

What happens is the backfill area along the foundation or basement walls of your house will gradually settle more than the undisturbed soil next to it. This happens over years. Then if you add something like a patio, the extra weight from the patio will make it want to settle some more. One of the ways to keep the slab from dropping when the backfill settles is to tie it to the foundation wall. Or, if you don't have a basement and the foundation is not too deep, you can excavate down to the footing and let the new slab turn down onto the footing.

 

[Evolved]

Whelp! It's all done now...

I went with a bid that was pretty close to the middle as far as price goes. I was concerned with price but I was more concerned with a guy that seemed honest and easy to work with. It was sort of difficult to gauge this as meeting with contractors was a little like speed dating. If you are a terrible judge of character this idea probably wouldn't work for you . I felt that once we got into the project and if I had concerns or wanted to change anything having someone that either I couldn't communicate with or would not listen to my ideas would be a nightmare. So, a shout out to Frank at First Mountain Concrete. They did a killer job and explained everything to me. AND... did not complain at all when I decided to change a few things during the process.

He did dig down a few inches (my guess was 2-3) and brought in road base for the sidewalk and the patio. Because the RV pad was already covered with gravel (and road base under that) he just re-purposed that and saved me some cash. They demo'd our existing patio and re-used the re-bar that was already sticking out of the foundation for the patio. They also drilled into the foundation and used re-bar along the walkway and the the entire length of the RV pad. I am extremely happy with how it tuned out but, time will tell if I made the right choice and they prepped everything correctly. With that, here is my 10K in concrete work (ouch!)

Here are the before pics


Here are the after


Not sure if this thread helped anyone but someone asked to keep the thread updated.

 

[rholbrook]

Looks good. One thing to remember, there are two kinds of cement, cracked and will crack. All cement will crack, that doesn't necessarily mean it was a bad prep job, it will all eventually crack.

 

[Hickey]

Man, that looks nice. I like what you did with the rocks next to the patio.

Did the contractor me ton anything about sealing the concrete?

 

[Evolved]

Looks good. One thing to remember, there are two kinds of cement, cracked and will crack. All cement will crack, that doesn't necessarily mean it was a bad prep job, it will all eventually crack.

Yeah, I understand that. I am just hoping for cracked in 10+ years not 10 months!

- - - Updated - - -

Man, that looks nice. I like what you did with the rocks next to the patio.

Did the contractor me ton anything about sealing the concrete?

Yes, it has been sealed.

 

[Evolved]

How many yards was the pour, Evolved?

I've been drinking and my memory sucks. Soooo lets go with 22...