You must ave stable compacted ground for an patio. the old must be removed.

Aloha,I have had one of these for a few years and like it for the compact size.

Make sure to compact. 

So it is labor intensive... but if you mix baking soda and bleach together to make a paste, then scrub that on the grout with a toothbrush, let sit then rinse.

LG has a new stack model that is very nice and fits in a compact slot.https://www.lg.com/us/washer-d...What's nice is that they are good sized. 4.5cuft on the washer.

If they turned off some/all utilities (assuming they were at some point in the tenants name), AND there is nothing but trash left in the unit (no useable furniture, no current groceries, no clothes in closet, no shoes, no toothbrush in the bathroom or meds in the cabinet), check local law but that IS abandoned...not allegedly abandoned.

Otherwise if you put your smaller 1 inch to 1.5 inch and filler (dust and smaller parts), directly on top o the 3 inch rock without compacting the 3 inch first, it will mix together.

-Thickness 4 inches concrete- crushed concrete or grit substrate, compacted 4 inches-PSI 2,500; with 3,000 recommended.

@Troy TakamotoI would absolutely speak to local authorities as we looked at one in my area and it would have been easier to knock down and start over.Remember it’s more than just electrical and plumbing - foundation compaction, concrete strength, framing etc.I would not touch them

What make a house structurally sound are a compact structure of the foundation framing and the roof.