We just spent our evening discussing how to handle our dirt crawlspace with a salesperson and want to weed out the facts. Can anyone help. His advice: Dig trenches for 3 downspouts and use pipe to take water away from foundation. Install sump pump and dehumidifier. Lay a cover on the dirt and bring it up the sides of the foundation. Put a new "door" on access space to seal it completely. add a small window well in front of access door. approximately half of space would not be accessible for the ground cover due to the height of the crawlspace. The accessible crawlspace is about 14x14. I use the term "accessible" very loosely. It is not easy to access, there is little head room. Price quoted to do it all was about $10,000. Could really use your expertise to make sure we are getting the right advice.

I'm troubled by the fact that you can't get a vapor retarder on half of the crawl space floor, and I can't really see $10,000 worth of work there, although prices can vary widely between regions. Where are you located?

If you're thinking of spending that kind of money, it might be a thought to dig out the rest of the crawl space so there is enough headroom to get a vapor retarder in there too. It's that important...more important than piping the downspouts, for example.

The vapor retarder should be turned up all walls and all penetrations usch as posts or pipes, and taped. All joints should be lapped 6 inches and taped. Then, and this is important, the space should be either ventilated or conditioned.

Ventilation should be by vents located three feet from each corner, with a total net free vent area of 1/150th of the crawl space floor area.

Conditioned means at least heated, or mechanically ventilated. There is a system which steals a small amount of the conditioned air from your home and ducts it into the crawl space. Home Care Club knows what it is...I haven't got time now to search for it.

The crawl space, under no circumstances, should be simply sealed. It is not permitted by code.

Ok, need some more info

Bases on what your saying you have a small crawl that is accessed from the outside of the house.
the contractor is suggesting that he dig down and install a window well in front of the door to allow for easy access to the opening.

Extending the downspouts away is a good idea but will do very little to correct any major water issues within the crawl space. It will slow water entry down however.

Sump pump in crawls is not a very good idea, Unless the area is heated. Which I assume its not?

If you want to stop any water from getting into the crawl space you must dig around the outside down to the footing and properly water PROOF the walls. Install a drainage tile system and devert it away from the structure. Back fill with pea gravel and cover the top with soil.
However my thought on this is do not bother. Unless the soil level is lower then the outside level and water puddles inside due to leaks, Its under the soil why bother? Its not harming anything.Just cap it with plastic and install vents.

As far as the dehumidifier. Why? If you seal the space with plastic. Where is the moisture coming from? Let me clarify this.

If its a damp crawl. You must put in a vapor barrier on the exposed soil. Once that is done you should, assuming its not a crawl accessed from the inside of the house. Install vents on the side walls to let any moisture that does creep in out. You must insulate the ceiling properly and be sure that the vapor barrier on the insulation is facing the heated side of the house. In otherwords if your in the upper half of the country, You should see the pink stuff not the paper.
If there are water pipes in this crawl you need to properly insulate them as well. Be sure to install heat tapes on them if your area gets real cold during the winter to protect them from freezing.

That is it. Most of this can be done by you for simply your time and material cost. If its a block foundation installing crawl vents are easy. they are sold the same size as one of the blocks. Simply hammer it out and cement the vent back in.