My house, built 1988, two story wood frame, has a sinking floor downstairs. The house is built over a crawl space. Downstairs, livingroom, foyer, familyroom at front of house. Back downstairs diningroom, kitchen, breakfast room. With center of house stairway and small hall from the foyer to kitchen. The area the is sinking is the kitchen under the refigerator and directly between the kitchen and breakfast room. This area also had an enclosed wall for the duct work for the heating and airconditioning of which we have 2. We would like to update the 1980's kitchen with tile floors and tile countertops But would like to level the floor first.

Rather than level the floor, it is necessary to find out WHY the floor is sinking, and cure the problem first. If it's anything like the crawl spaces around here, I suspect rotted and failing floor joists. If that's the case, then you must also find and cure the conditions which produce the rot...probably a poor or no vapor retarder on the crawl space floor, and/or poor or no ventilation, or a combination of both.

Consult a contractor who is knowledgeable about crawl spaces, or a GOOD architect.

As Richard indicated in his reply to you it is necessary to find out why the floor is sinking.
If you are contracting out your kitchen remodel perhaps your contractor would provide the necessary pre-remodel inspection for you. He or she may also be able to coordinate necessary inspections with others qualified.
Based on the information you have provided there are several items to consider.
With the layout of your two story home and the area identified as sinking you have considerable loads consolidated in that area.
1.0 Inspect the soil conditions in that area to determine if conditions are dry or if moisture is present. (based on center of house location the conditions should be dry)
2.0 Inspect the supporting members of the floor system such as foundation walls (framed, concrete or masonry, beams, post etc.) Inspection of the floor joist for size, span (length) and inspect for any visual signs of damage such as cracks or splits to include checking for the crown of the joist. Typically with center of home location you should not see wood damaged by moisture (dry rot)
3.0 Inspection of the exterior landscape. Large trees planted near the exterior foundtion may also be considered. Root systems under foundations remove moisture from the soils allowing for settlement.
4.0 The load bearing points described in 2.0 can be checked for settlement with the use of a dry line. Attach a dry line at each end of the supporting structure and pull tight. You should be able to identify settlement, if any, at any location.
5.0 If settlement is minor (you have not indicated the extent of sinking) you may be able to correct the problem with the use of shims, installation of longer support post or perhaps the installation of an adjustable steel post to level the floor. Depending on the level of your experience you may or may not be able to complete the task yourself.
To eliminate all of the guess work it would be wise to consult with a local Structural Engineer. They would be able to accurately identify the problem and provide corrective measures for you or your contractor to follow.
Their would be little or no cost for this service depending on who you contact.
Good luck on your project and enjoy your new kitchen.

This message has been edited. Last edited by: Lee,