Increase crawlspace area?

Question

i have crawl space at 16-24". I would like to have 36"

Answer 1

In the first place if you have 16 to 24 inches and you want to go to 36 inches I have to assume you are talking about the distance between the bottom of the floor joists and the probably dirt floor of the crawlspace.  This would be increasing the depth not the area.  Secondly, unless you are talking about a mobil home I would not even consider raising the "house."  While a mobil home is internally supported a normal house sits on the foundation.  To raise it you would first have to support all of the floor joists.  Then you have to lift all of the temporary supports uniformly.  It is done when houses are moved and it is a huge undertaking.  

With that put aside the normal foundation does not go much below the grade at the bottom of the crawlspace.  You have to find the footing  Dig straight down on either the inside or the outside of the foundation.  The footing is wider than the foundation wall. If the footing starts at or below your 36" mark you can simply dig out the dirt.  If it is shallow then you will first have to install another wall inside the perimeter of your existing foundation.  This should not be done lightly.  Soil conditions, existing weight of the house, possible temporary shoring may all have to be considered.  Give us some more details and we will see what can be done.

Answer 2

Well.... how is the house supported?

You've got 2 options, or a combination of them...

1)  Raise the home

2)  Dig out the crawlspace

Your home's foundation has to have a certain amount of support... you cannot dig to below the level of the foundation footer, and not create problems.  So that's the first thing you need to find out, the depth of your foundation and footings.  I'd speculate you wouldn't even want to expose all of one side of the foundation, i.e., dig out the inside to the bottom of the foundation, as this could cause a problem with hydrostatic pressure on the outside of the foundation, and with no support on the inside, I could see them buckling at some point in the future.

Raising the home would probably be the easiest method to gain the space you want.  I'd suggest you consult a structural engineer.  I know its done to homes in flood prone areas, to protect them.

Good Luck