Ok, this is way off from Explorer, and no one will probably read this but,

In my house, I have a crawl space under the garage, and it had a plastic vapor barrier on the dirt under there, to stop moisture from leaving the ground and condensing on the underside of the house. I had it sprayed for bugs and they removed the vapor barrier (it's basically a big black trashbag piece of plastic)

Some people say that you can remove the vapor barrier and just cut some ventilation in the foundation to keep the moisture out; others say you just need the vapor barrier; others say BOTH!!
Anyone have any experience with this? If so can you share, help a fella out?

Is the garage conditioned?

If conditioned, I would run just a vapor barrier (well sealed along the edges), and forget the foundation vents. Also, if you have mechanicals (elec, hvac, gas, etc) under there that may require work in the future, it is always nicer to work on plastic than it is on dirt. It is also a lot easier to lay plastic then it is to install proper foundation vents in an existing foundation.

If it isn't conditioned and there isn't much of a reson to go under there, vents will work fine. Make sure to use good vents though, and not just some "holes" punched in the foundation. Any opening big enough makes a great entry way for spiders, snakes, rodents, etc.

Yes you should at least have a moisture barrier. I am an engineer who normally gets paid to give these recommendations. I believe that the most recent building code requires it. The moisture barrier should extend throuout the floor, no breaks. Ventelation is also a good idea. In most cases the vents should be open in spring and fall and closed in winter and summer. Of course I am assuming that you have insulation in the floor. If you have a bad moisture problem you can put in a ventilation fan with a timer or humistatic controller.

State of the art heating and AC systems are insulating the exterior walls and placing a thick seamless moisture barrier on the ground. The floor insulation is removed. Then the ventalation system includes ducts into the crawlspace, conditioned crawlspace.

I do the conditioned crawl spaces when I install a new system, so I second unclemeat's opinion.

What those guys said.
I always put two layers of heavy poly (overlap seams ) in crawl spaces.
Im not so sure about venting- if you have humid summers and dont close the vents you invite problems.
Ill reiterate what Uncle said - vents closed summer and winter , open in fall and spring

The local climate is the greatest controlling factor here. From an east-coaster that has been in the home-building industry for what seems like forever, I have had the best luck in the following manner :

A vapor barrier over the dirt is an aboslute must-have. The best way to control humidity and temp in the crawl space is to condition the crawlspace enviornment just like the coditioned space above (assuming you have full-time heat/AC in the space above).
In other words, insulate the perimeter of the crawlspace foundation walls and provide a means of heating/cooling air exchange below the floor as if it was living space (cut a register or two in the trunk line, if forced air, for example).
If the space is conditioned, no foundation vents are necessary. In fact , it would be good to make sure all penetrations through the foundation are sealed, and the inside of the access panel ( or door) to the crawlspace is also insulated /sealed.
Insulation between the floor joists will eventually come apart, sag and prove a worthless heat barrier as it absorbs humidity in the air of a unconditioned crawlspace.
If the space above the floor isn't conditioned full-time, then put in lots of closable foundation vents and look at installing some fans to move air through the crawl.

Either way, you need the vapor barrier on the dirt.

The crawl space appears to be climate controlled (conditioned); although I have not yet entered the space to verify this. A duct enters the crawl space through the access panel. This crawl space is only accessible via a basement access panel and is sealed to the outside.
I'll get a layer of poly to replace the old vapor barrier, which is old (from mid-1970's) and has holes in it.

Well, if you have a supply line going through the crawlspace, you are miles ahead. Unless the perimeter walls of the foundation are insulated AND there are some registers supplying conditioned air, however, your crawlspace is not conditioned.
I might also mention that there needs to be a means of air return in addition to supply. If practical, sounds like the easiest way would be to remove the access panel around the trunk line between the basement and crawlspace area.. this will probably allow full circulation of the conditioned air ( don't do this if the perimeter walls are not insulated).
Maybe a screened panel could be fabbed to replace it with.

I will have to get in there this weekend; I don't like the idea of getting that dirty but it has to be done. I also have this fear of getting jumped by 500 brown recluse spiders when I get in there (heheh). If this happens, one of you guys can have my truck.

I have to measure the crawl space so that I have some idea of the size of vapor barrier to roll out in there. The old moisture barrier is probably unusable due to holes, etc.

If the walls are not insulated I will do that. I'm an insurance guy by trade but I have some experience with remodeling from when I was younger. Thanks for the information...

If you install the moisture barrier as you go you will be working on top of the plastic. If you want to kill the bugs let of an insect bomb. The crickets are the worst IMO.

My crawl space didnt have a vapor barrier on the floor and had no vents in the foundation. About 10 years ago our dryer vent that runs thru the crawl space broke and we didnt know. All that moisture was being pumped into the crawl space and rotted the main beam and about half of the floor joists. That half of the house basically collapsed. The house had to be jacked up, floor joists replaced, half of the main beam replaced and upgraded (went from 3 2x12's to 5) 2 additional support beams (6x6's supported with concrete footings) running paralell with the main beam were installed, new insulation with a vapor barrier put on the floor joists and vents installed in the foundation. I'm suprised the crawl space didnt have a vapor barrier or vents because it was built in '79. I thought by then they were at least that advanced.

Originally posted by VAHAM
The local climate is the greatest controlling factor here.

This is a very good observation! I'm sure that the codes require this now, but my house was built in 1958. There is no vapor barrier and no insulation, but many vents around the perimeter of the house. It has been doing fine without any vapor barrier, because of our climate. I'm sure if this house were in the south or midwest, I would have major problems at this point.

Ditto on the vapor barrier. I lived in Iowa in my High School years. In my Junior year my dad bought us a house build by a real numnutz. It had no vapor barrier or vents on the ground level. It was only three years old and we ended up tearing out the entire ground floor , flooring and rebuilding it all. Ruined my the entire years for me. The worst part was that the the numnuts builder lived right across the street and was still building more houses to sell and screw over more people.

Yeah get the barrier in and in my paranioah I would also add vents:D

Today I got in the crawlspace, and looked around.
Imagine a big rectangle, which is the concrete foundation walls of my house.

Now, imagine another smaller rectangle attached to the regular foundation. This smaller rectangle is filled with dirt almost to the joists (but not quite). Why they did not simply dig this out and make more basement I'll never know. Probably, the dining room and wet bar above were additions to the house; but I see no change in brick color on the exterior to indicate this; possibly a late contractor change.

The walls are all capped and the joists rest on this; it seems like it would be quite possible to cut open that part of the rectangle, remove the dirt, and have a nice 20' x 15' addition to my basement...

A big air duct, a 1.5" copper drain tube, and 2 copper water pipes (for the wet bar in the dining room) runs from the access panel 20' to the far end to serve the dining room above. For now, I'm just going to level the dirt as much as possible and lay a barrier down.

I seriously doubt the footings for the addition (if thats what it is) go deep enough to be able to dig out the dirt. It probably is possible to cut a doorway in the middle concrete wall, put in a steel header and dig out the center of that area and build a concrete wall around that. I supposed if you wanted to get the whole area dug out you could dig out the center and then jack up the house, dig out the rest and then build a new foundation in that area with footings... but that would be a lot of buckets of dirt for you to carry out. ;)

X24 hit it right... The bottom of the footings in the crawlspace area probably only get down to the frostline-24"-36" below exterior grade ( depends on the local building codes).
It is actually quite a cost to the builder to pay for the extra excavation, extra depth of foundation walls, drain tile, concrete flatwork (slab prep, pour, finish), and provide a complete functioning system to accomodate the change in basement conditions (even the heating and cooling systems would probably have to be upsized) to meet minimum code requirements.
If the original purchaser was willing to pay for it, and the timing allowed for it, I'm sure the builder would have been accomodating.
Generally speaking, builders are not the rich daddy-warbucks con men that they are often portrayed to be.
By and large, builders rely on satisfied customers to sell their homes and keep them in business( there are exceptions, of course !).
They operate on very tight budgets in order to be competitive, assume all of the risks, and make less profit on their homes than do the individual suppliers and subcontractors involved.

Good point about the footings being shallow. That probably explains why the dirt is piled up against the walls almost to the joists. It's probably not worth it to dig it out just so I can have another 250 sq. ft.

I'm a real estate title insurance agent and I know who does and does not get a big piece of the pie in the whole realtor-banker-surveyor-contractor-title insurance chain of events. A contractor who isn't building almost all the time is losing money.