Order, Supreme Court, New York County (Milton A. Tingling, J.), entered August 26, 2011, which denied defendant RSUI Indemnity Company’s motion for leave to amend its answer, unanimously affirmed, with costs.
Defendant waited more than one year from the date on which it received notice of the claim against its insured to assert a disclaimer based on the policy exclusion for residential projects. This unexplained delay was unreasonable as a matter of law (see Insurance Law § 3420 [d]; Agoado Realty Corp. v United Intl. Ins. Co., 260 AD2d 112, 118 [1999], mod on other grounds 95 NY2d 141 [2000]). Thus, although leave to amend a pleading “shall be freely given” (CPLR 3025 [b]), the residential project exclusion “[canjnot be used as an affirmative defense because of its late assertion and the strictures of Insurance Law § 3420 (d)” (Agoado Realty Corp., 95 NY2d at 146 n). Concur — Mazzarelli, J.P., Catterson, DeGrasse, Manzanet-Daniels and Román, JJ.