surely it depends on what the self build is for.
If you building your private residence then I'd say no way, if you claim your ppr or part of your ppr as business asset then claiming ppr ie exempt from capital gains tax at later stage would be impossible on part of building you declared as business
If your building an office which you intend to use for business purposes and get invoices from registered builders then i'd say yes.. only if invoices are from vat registered individuals, and if this is the case and vat at 13.5% you should be stopping35% and returning it to revenue as rct as you are classed as using subcontractors