Well, there are a number of items that can contribute to increasing your basis when calculating the gain on the sale of your cabin that you purchased in 1993.
1. Any expenses from the original purchase escrow statement that you did not deduct on prior years tax return.
2. Any major improvement expenses incurred to date, that were not deducted on prior years tax returns as repairs.
3. Any repairs or improvements that were incurred prior to the sale of the cabin, known commonly as fixing up expenses.
4. Any commissions paid to a real estate agent for the sale of the cabin. Of course this is not part of the basis calculation but is reflected as a reduction of sales price.
5. Any amounts spent on fixtures that were permanently attached to your cabin.
6. Any amounts spent on painting, roof repairs and fixing windows of the cabin over the years. Usually a reasonable estimate would suffice usually.
Clearly, the above list is a sample of items and it is quite possible that you may have spent additional amounts that are deductible. I would urge you to consult your tax advisor to ensure that you have not missed out on allowable deduction.