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Mason only used about an inch of gravel before pouring concrete slab

ktimes2

Member
Joined
Jun 26, 2013
Messages
4
Location
New Jersey
So my mason decided to cut some corners and save himself some money by using dirt and sand with only about an inch of gravel before pouring a 4" concrete slab for a garage. He did lay 6x6 welded wire mesh with a 6mil vapor barrier. The garage measures about 29' wide by 21' long. The plans called for 4" of gravel and 4" on concrete.

He claims it did not need 4" of gravel and that he guarantees his work but i can't get over the fact that he tried to pull a fast one by me to save a few hundred dollars.

My question is a little difficult considering the different elements across the country, but on average, how long does a properly poured concrete garage slab last for? And how does my Masons bootleg job affect the pour? Should I expect to see cracking a lot sooner?

Thanks
 
No footings?

The garage is over 600 square feet and I know you have a frost depth in most if not all of NJ.

What type of walls will the garage be? Block, framed wood?

Was there a permit and was there an inspection prior to him pouring the concrete? In NJ I assume you had this done.
 
Many thanks for the reply. A permit was taken out and footings were done and inspected. 24"x8" continuous concrete footing with #4 continuous rebar, 3' of 8" block to finish grade, followed by 2 layers of 8" block above grade. the rest of the garage will be framed wood.

I'm guessing no inspection was needed before pouring slab.
 


R506.1 General. Concrete slab-on-ground floors shall be aminimum 3.5 inches (89 mm) thick (for expansive soils, see

Section R403.1.8). The specified compressive strength of concrete

shall be as set forth in Section R402.2.

R506.2 Site preparation. The area within the foundation

walls shall have all vegetation, top soil and foreign material

removed.

R506.2.1 Fill. Fill material shall be free of vegetation and

foreign material. The fill shall be compacted to assure uniform

support of the slab, and except where approved, the fill

depths shall not exceed 24 inches (610 mm) for clean sand

or gravel and 8 inches (203 mm) for earth.

R506.2.2 Base. A 4-inch-thick (102 mm) base course consisting

of clean graded sand, gravel, crushed stone or

crushed blast-furnace slag passing a 2-inch (51 mm) sieve

shall be placed on the prepared subgrade when the slab is

below grade.

Exception: A base course is not required when the

concrete slab is installed on well-drained or

sand-gravel mixture soils classified as Group I

according to the United Soil Classification System in

accordance with Table R405.1.

R506.2.3 Vapor retarder. A 6 mil (0.006 inch; 152 μm)

polyethylene or approved vapor retarder with joints lapped

not less than 6 inches (152 mm) shall be placed between the

concrete floor slab and the base course or the prepared

subgrade where no base course exists.

Exception: The vapor retarder may be omitted:

1. From detached garages, utility buildings and other

unheated accessory structures.

2. For unheated storage rooms having an area of less

than 70 square feet (6.5 m2) and carports.

3. From driveways, walks, patios and other flatwork

not likely to be enclosed and heated at a later date.

4. Where approved by the building official, based on

local site conditions.

R506.2.4 Reinforcement support. Where provided in

slabs on ground, reinforcement shall be supported to remain

in place from the center to upper one third of the slab for the

duration of the concrete placement.
 
ktkimes2,

So basically we don't know your soil type but in parts of Jersey, what he did may be OK. What was on the plans approved by the code official? If the plans showed a 4" sub base and he did not put it in then that is a problem.

The vapor retarder is not even required if your garage is detached.

If he placed mesh on the ground just on top of the plastic with no chairs to lift it into the upper half of the pour thickness, he wasted his money and yours.
 
jar546 said:
ktkimes2,So basically we don't know your soil type but in parts of Jersey, what he did may be OK. What was on the plans approved by the code official? If the plans showed a 4" sub base and he did not put it in then that is a problem.

The vapor retarder is not even required if your garage is detached.

If he placed mesh on the ground just on top of the plastic with no chairs to lift it into the upper half of the pour thickness, he wasted his money and yours.
But, Senor Jeff, I've been doing this for 40 years and always raise the mesh when pouring. It's tradition and I saw Bob Vila do it on TV.
 
Are you the homeowner that is paying for this? If so I would at a minimum demand that he pay for an engineer to determine if it would be a problem given your particular soil condition. An engineer that you have selected. I would also look to reduce his contract sum as he took the cheap way out.
 
I agree with uncle and the only mesh that lift is the part being lifted as the weight of the concrete will keep the other areas on grade, as far as cracking moist curing it will helpbut basically only 2 types of concrete slabs, cracked and gonna crack
 
ktimes2,

Welcome again to the Building Code Forum.

I'm guessing no inspection was needed before pouring slab.
Yes, an inspection was needed and "required" before the concrete was placed. See Section R109.1.1

from the 2006 Edition of the IRC.

R109.1.1 Foundation inspection = Inspection of the foundation shall be made after poles or piers

are set or trenches or basement areas are excavated and any required forms erected and any

required reinforcing steel is in place and supported prior to the placing of concrete. The foundation

inspection shall include excavations for thickened slabs intended for the support of bearing walls,

partitions, structural supports, or equipment and special requirements for wood foundations.

.
 
A permit was taken out and footings were done and inspected.
R109.1.1 was met. This sounds like it is just the interior slab which does not require an inspection per the IRC if it is non-structural or does not have any interior footings

We do not see welded wire on garage or driveway slabs around here. Contractors use #3 rebar at 24" OC to control cracking.

All concrete slabs will crack over time due to the shrinkage of the concrete
 
The plans called for 4" of gravel. That is what the inspector approved. He basically used the dirt he dug up to fill about 3" and only a 1" layer of gravel. His thinking i believe was to save money on discarding of the dirt that he dug up, as well as the gravel. For all i know the slab could last just as long, but mentally, it's driving me nuts that he tried to pull a fast one.

To top it all off, when pouring the concrete slab, he must have not ordered enough concrete and ran out. So he had to finish about a 10 sf area off by mixing his own bags. So now this brand new slab looks like crap because it is a completely different color in one section. Really makes me want to make this guy rip the whole thing back up and redo. but i know that's not realistic.
 
ktimes2 said:
The plans called for 4" of gravel. That is what the inspector approved. He basically used the dirt he dug up to fill about 3" and only a 1" layer of gravel. His thinking i believe was to save money on discarding of the dirt that he dug up, as well as the gravel. For all i know the slab could last just as long, but mentally, it's driving me nuts that he tried to pull a fast one. To top it all off, when pouring the concrete slab, he must have not ordered enough concrete and ran out. So he had to finish about a 10 sf area off by mixing his own bags. So now this brand new slab looks like crap because it is a completely different color in one section. Really makes me want to make this guy rip the whole thing back up and redo. but i know that's not realistic.
You are the owner, you are paying him and you are not getting what you paid for or an installation that meets the minimum standards. Your answer is to contact the building code official and tell him the story and he may be able to pull rank and have the slab repoured. The permit and fee was for a reason.
 
you are absolutely right and i think that is the way to go. I really appreciate all the feedback and advice. i shall keep you posted to the outcome.
 
jar546 said:
You are the owner, you are paying him and you are not getting what you paid for or an installation that meets the minimum standards. Your answer is to contact the building code official and tell him the story and he may be able to pull rank and have the slab repoured. The permit and fee was for a reason.
I wonder what dream world you live in?
 
Originally Posted by jar546 View PostYou are the owner, you are paying him and you are not getting what you paid for or an installation that meets the minimum standards. Your answer is to contact the building code official and tell him the story and he may be able to pull rank and have the slab repoured. The permit and fee was for a reason.
Yankee said:
I wonder what dream world you live in?
I thought the same thing and then I noticed that Jeff told him to contact the building official.

I'm just an inspector.

An inspector who would like to have his new office manager get that call.
 
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