In a nutshell, you cannot deduct the amount that increased the value of the remodel. For example, if your bathroom was sort of out of date and you totally adapted it for accessibility at a cost of $30,000, you would compare the value of your house before to the value after and the increase cannot be deducted.
That said, I just moved into a new condo. All three bathrooms were of good quality but far from top of the line. While I was waiting for my general contractor to start on my master bath, I put in a BathFitter low threshold shower with grab bars and slip resistant flooring. The total cost of the unit installed was just under $10k. I don't think it increased the value of the condo unless someone disabled bought it. I'm aggressive when it comes to deductions. I deducted the entire $9,600. I put in three high toilets into the three bathrooms. They replaced perfectly good toilets. They cost $650 each. I deducted $500 each. I've never had appraisals done but I do scan all receipts and document them. I also make sure contractors or installers write something on the receipt that proves that they were installed as an accommodation for a disability.
My new bathroom will increase the value because I'm using high-end finishes. I'll probably deduct 50-75% of the cost. Things like ramps, door widening, tracks are fully deductible, IMO.
Disclaimer: I'm a CPA and this is NOT tax advice. It's how I do things. If I get audited, I'll be able to represent myself to the IRS, in court, if necessary.