Sorry if I'm being confusing. It actually is confusing. Back to the OP's original post, if the kitchen was put in prior to a first letting it cannot be claimed under the rule of prior letting expenditure not being allowed.
Under the depreciation rules furniture & fittings can be claimed under wear & tear currently 12.5 percent per year (for 8 years). This also applies if you buy furniture later etc.
What is not clear is whether a kitchen/windows is allowed under the wear & tear - some say not as it's capital appreciation, enhancement expenditure, which is not allowed to be written off. Sometimes you replace something that is rotten but it could also be seen as increasing the value of the property. Revenue are not clear on this. See SamH's post (and I have personal experience of it myself).
Also just to make it more unclear there is the Countrywide Rural scheme (only learned about this myself this week) which seems intended to prod landlords into doing up old properties (new kitchens/bathrooms/windows etc) to bring them to year 2007 standards and is allowed at I think 15 % for the first 6 years with 10 % in the last year = 100% write off. (This scheme is being phased out.
If the OP cannot get his kitchen to be written off under any of the above he can write it off under CGT when selling.
Just to add that the revenue guide to rental income does not as far as I've noticed point out the Countrywide scheme, nor does it clear up enhancement expenditure versus wear & tear.
Samh wrote a letter to the revenue outlining what he had done. He's been open and honest and if he was incorrect surely the revenue should write to him saying it was disallowed.