This is a long answer. What the IRS will accept can be very subjective depending on your auditor, should it come to that. With that in mind I have not been forced to pay them an extra cent since my first audit in 1981 taught me a valuable lesson in keeping or constructing impeccable records. You can construct a record for fair market value, assuming you have photos and/or an inventory of your loss items. Photos do not have to be pre-loss, because it might be photos of your belongings as you pulled them out of the flood muck. It may not be worth your time to do this with every nit-picky item so pick your price threshold and here goes. Take your inventory (or construct an inventory from your photos) and pick the items that are above your threshold valuation, say $5.00. Then one item at a time find a like or very comparable item in a thrift/resale shop or on eBay (eBay has worked best for me). At the shops take photos of the item with price tags or take computer screen shots of eBay items and this will establish the current value of your items. If you had some high dollar irreplaceable items, you may want to talk with an appropriate appraiser to find what the item may have been worth. Total the values for your form 4684 entry. Keep all photos/screen shots (both of damaged items and your current valuations) together with your inventory at least 5 years beyond the tax year of loss. Now lets discuss the possibility that you do not have photos/inventory or even that the ones you had may have been destroyed along with your possessions. From your own and family members memories, write down an inventory of everything you can remember you owned that was destroyed. Document this list as what it is, a reconstruction of your possessions from memory. Now follow the same process as previously explained and construct a current valuation list. As long as you are not making things up that are obviously well beyond your means to have owned in the first place, an auditor is probably going to let it go through. Now for the kitchen cabinets, if lower cabinets cannot be obtained which will match upper cabinets, an insurance adjuster would replace both upper and lower, so deduct the costs for them. The flooring? Clean, repair or replace it, whatever it needs and deduct it, it's a loss. One caveat with all this is, if you had insurance that is going to pay for most of your losses, don't bother with the tax deduction. It most likely will not be worth the enormous hassle because you will have to subtract your insurance reimbursement from your loss total before claiming it on the tax forms. However, on your tax form, deduct your your insurance deductible. That insurance deductible itself is a loss to you and if it is a large one, it could save you some tax money.
