Expert: Dan Griffin - 5/15/2010

Question
We recently purchased an older home which has a 12X12 room which was added on by previous owner.  We noticed that it feels hollow when you walk into it and found out it was built on wood which is rotting on the outside. Should we have concrete poured after we remove all the tile?  Can we put dirt first so we don't need so much concrete? and should we leave the wood in place and just pour inside of it?  Thank you,  Lisa

Answer
Lisa, I would need a lot more information to answer this well.  

Wood framed floors are quite normal and can be just fine.  They would be installed over a crawl space or basement whose sides will be  on concrete, block, or brick walls.

Slab (concrete) floors are also normal, and they typically sit directly on the ground.

Wood, siding, or sheathing should NEVER be touching the ground outside.

Framing sits on top of the walls.  If it is a crawl space, the wall framing is sitting on the wood joists.  YOu would need to remove the walls and roof or devise some method of holding them up if you intend to remove the joist system.

Ceramic tile can be installed on wood floors.  It will have a bit more of a hollow sound when you walk on it.  This does not mean it is done wrong.

What exactly is rotting on the outside?
You need a footing poured of concrete or layed block.  This will need to go deeper than the frost line in your area which is different all over the country.  Here it is 18" underground.  This footing needs to be about 12" wide.  A concrete floor needs to be about 4" thick.  Fill sand or gravel can be used to reduce the quantity of concrete, but I don't think that is exactly what your problem is. .

It sounds like you need to discuss this with someone who can see it that knows buildings.  I'm sorry I can't give you a stronger, better answer.