Got a strange one here. In the past year, one section of my ~13 year old
concrete driveway (roughly 10' square) has developed a couple of cracks and
settled 1/4" - 1/2" in the center relative to the edges. By itself, that
wasn't enough to really bother me (other than a "that's weird"), but this
weekend I noticed that section actually had a noticeable "drumming" sound
compared to the other parts of the driveway when I dribbled a basketball on it.
Not only did that make me lose concentration during a cutthroat game of "HORSE",
it also made me start worrying a bit.

Anyhow, there must be a bit of a hollow under the driveway in that area. No
water, sewer, or sprinkler lines in the vicinity, so I don't think it's water
erosion. Not sure how to go about addressing the problem, 'tho. Just get a
mud-jacker out and cross my fingers, or are there other things that need to be
investigated first?

"Andy Hill" wrote in message
...
Got a strange one here. In the past year, one section of my ~13 year old
concrete driveway (roughly 10' square) has developed a couple of cracks
and
settled 1/4" - 1/2" in the center relative to the edges. By itself, that
wasn't enough to really bother me (other than a "that's weird"), but this
weekend I noticed that section actually had a noticeable "drumming" sound
compared to the other parts of the driveway when I dribbled a basketball
on it.
Not only did that make me lose concentration during a cutthroat game of
"HORSE",
it also made me start worrying a bit.

Anyhow, there must be a bit of a hollow under the driveway in that area.
No
water, sewer, or sprinkler lines in the vicinity, so I don't think it's
water
erosion. Not sure how to go about addressing the problem, 'tho. Just
get a
mud-jacker out and cross my fingers, or are there other things that need
to be
investigated first?

I can't answer your question (no knowledge on my part). However, I may be
able to make a suggestion about what caused the problem. When I bought my
house several years ago, a large part of the concrete drive had collapsed.
It was probably much worse than you described, and I negotiated for a
reduction in price that covered removing a large section of the driveway and
replacing it. When I had that done, I also paid to have the rest removed
and replaced because there was no rebar, and I thought it was best to do the
whole thing. Anyway, I asked about what caused the problem because (like
you) there was no drainage problem or water lines in that vicinity. It
turns out that a *gopher* had burrowed under one side of the driveway, and
the previous owners failed to fill it. As a result, heavy rains continued
to wash out the area, and the concrete eventually collapsed!

MaryL

"Andy Hill" wrote in message
...
Got a strange one here. In the past year, one section of my ~13 year old
concrete driveway (roughly 10' square) has developed a couple of cracks
and
settled 1/4" - 1/2" in the center relative to the edges. By itself, that
wasn't enough to really bother me (other than a "that's weird"), but this
weekend I noticed that section actually had a noticeable "drumming" sound
compared to the other parts of the driveway when I dribbled a basketball
on it.
Not only did that make me lose concentration during a cutthroat game of
"HORSE",
it also made me start worrying a bit.

Anyhow, there must be a bit of a hollow under the driveway in that area.
No
water, sewer, or sprinkler lines in the vicinity, so I don't think it's
water
erosion. Not sure how to go about addressing the problem, 'tho. Just
get a
mud-jacker out and cross my fingers, or are there other things that need
to be
investigated first?

if by mud jacker you mean a company that will pump some kind of material
under your slab to relevel it, supposedly those technologies are affordable
and feasible

don't just cross your fingers, have someone who knows what they're doing
look at your situation if you don't fully understand it

That could be a sink hole forming. I had one in my parking lot - opened it
up and it was large enough to swallow a car. 110 tons of large stone and a
new blacktop job looked good until they dynamited for a sewer line across
the street. Now hole is back and the city has no liability - limestone
county sink holes form w/o notice. David and Goliath fight coming.

"effi" wrote in message
...
"Andy Hill" wrote in message
...
Got a strange one here. In the past year, one section of my ~13 year
old
concrete driveway (roughly 10' square) has developed a couple of cracks
and
settled 1/4" - 1/2" in the center relative to the edges. By itself,
that
wasn't enough to really bother me (other than a "that's weird"), but
this
weekend I noticed that section actually had a noticeable "drumming"
sound
compared to the other parts of the driveway when I dribbled a basketball
on it.
Not only did that make me lose concentration during a cutthroat game of
"HORSE",
it also made me start worrying a bit.

Anyhow, there must be a bit of a hollow under the driveway in that area.
No
water, sewer, or sprinkler lines in the vicinity, so I don't think it's
water
erosion. Not sure how to go about addressing the problem, 'tho. Just
get a
mud-jacker out and cross my fingers, or are there other things that need
to be
investigated first?

if by mud jacker you mean a company that will pump some kind of material
under your slab to relevel it, supposedly those technologies are
affordable
and feasible

don't just cross your fingers, have someone who knows what they're doing
look at your situation if you don't fully understand it

A few caveats:

1) Determine why the cavity has formed. If this is a result of significant
re-grading of your property before construction and subsequent settling
of the soil under the concrete, then this is generally a one time problem.
If it is from rodents burrowing, a sink hole situation, etc. - then you must
address the cause before addressing the void.

2) Mud-jacking slab-jacking techniques are generally temporary fixes.
From my observations in our neighborhood, such repairs may degrade
in 5 years or so and need to be repeated. I haven't had a chance to
observe a driveway which has been jacked, but the load-bearing
requirements for a driveway will severely tax the slab-jacking. Note
that slab-jacking will create a small number of mud-cement pillars
under the slab and most of the void will still exist after the procedure.
The small area of soil under those few pillars will now support all
of the weight of the driveway and whatever is upon it.

Gideon

Lucky for you your house wasn't built on that sink hole site! I can just
picture the house going down upon detonation of that dynamite.

"Evon" wrote in message
news
That could be a sink hole forming. I had one in my parking lot - opened it
up and it was large enough to swallow a car. 110 tons of large stone and a
new blacktop job looked good until they dynamited for a sewer line across
the street. Now hole is back and the city has no liability - limestone
county sink holes form w/o notice. David and Goliath fight coming.

I'm with Gideon on this point.
You might investigate the history of your lot. Was there another structure
before your driveway was poured? Suppose there was a basement, etc. Then
inadequate soil compaction would explain your problem...and portend of a
greater threat.
Do you live in Florida? (Sink-hole territory?)
"Gideon" wrote

1) Determine why the cavity has formed. If this is a result of
significant
re-grading of your property before construction and subsequent settling
of the soil under the concrete, then this is generally a one time problem.
If it is from rodents burrowing, a sink hole situation, etc. - then you
must
address the cause before addressing the void.

"John B" wrote:
"Gideon" wrote

1) Determine why the cavity has formed. If this is a result of
significant
re-grading of your property before construction and subsequent settling
of the soil under the concrete, then this is generally a one time problem.
If it is from rodents burrowing, a sink hole situation, etc. - then you
must
address the cause before addressing the void.

I'm with Gideon on this point.
You might investigate the history of your lot. Was there another structure
before your driveway was poured? Suppose there was a basement, etc. Then
inadequate soil compaction would explain your problem...and portend of a
greater threat.
Do you live in Florida? (Sink-hole territory?)

No known prior structures. AFAIK, the area was just being used as horse
pasture before being built on. It's old river bottom (lots of river rock,
mixed with sandy areas and the usual river deposits). The area used to flood
every few years, so it wasn't a great area for living structures. It hadn't
flooded since dams were placed upstream in the mid-40s, so I would've thought
that any organic muck left over from floods would've had 50 years to decompose.
Maybe not.

Grew up in sinkhole territory back in the midwest (along with the occasional
collapsing coal mine). Nothing like that around here.

Once the weather warms up a bit, I might just have to **** off my wife and dig
myself a bit of an inspection hole. The problem area's close enough to the edge
of the slab I should be able to get a look-see without displacing more than a
few dozen yards of dirt :-) . Nothing like a little idiot stick work to make
me appreciate a desk job.

As long as you don't hit yourself with the pick, the exercise will be good
for you!

"Andy Hill" wrote
Nothing like a little idiot stick work to make
me appreciate a desk job.