Have an attached 12 x 15' workshop with a concrete floor. It used to be a carport which was walled in 1990. There are large cracks in the floor and the floor slopes down almost 3" on one side. It is not part of the house slab which is in pretty good shape. There used to be a water problem in the wet season ( I'm in the Pacific Northwest) but we have added drainage around this addition so the floor is now dry. It would be cost prohibitive to use floor leveling compound ($900). I was thinking of leveling with thin set then a mixture of sand and portland cement as advised by a concrete tech, but our contractor is inclined to shim it with treated wood and create a plywood floor. The advantage of plywood is that the floor would be warmer in the winter. Any thoughts?

I'm looking for solutions for water sealing. Problem- Recently moved into a house and upon more in depth investigation to a water problem I noticed the sill and joice header are rotted (7' tore out so far of the sill). This is located on a wall where previous owners had then built on an additional foundation wall to pour a small sidewalk entry to the main door. The new concrete poured is only barricaded against the house with foam. The walkway does have a roof over but still gets wet and apparently just soaked down into the sill over the years. The outside house wall is vinyl sided, can I just use a sealant along the bottom of where the j type molding meets the concrete walkway? Also, if the 2x4 sill is replaced, and the header joist is only rotted on the bottom, will this be okay later on for resale? I plan to also put in 2x10 pieces in between the joices to restrengthen everything. Any input would be greatly appreciated!! The close pic of the joice header rotted half way up is the worst spot, most others are only maybe 1 1/2'' up from the bottom.