Cimino Construction Company appeals from a judgment entered after a nonjury trial in the Superior Court (Cumberland County, Perkins, J.) in favor of Willis Realty Associates and Maine Printing and Business Forms Company for recovery of property damages resulting from a construction collapse. Cimino contends that the court erred in concluding that (1) the claims of Willis Realty and Maine Printing were not barred by a contractual waiver of subrogation provision and (2) Cimino was not immune from suit as a co-insured under Willis Realty’s and Maine Printing’s property insurance policy. We affirm the judgment in favor of Maine Printing, but because the Superior Court erred in concluding that the contractual waiver of subrogation did not bar Willis Realty’s claim against Cimino, we vacate the judgment in favor of Willis Realty.
Willis Realty, a general partnership, owns commercial property in Portland that is leased to Maine Printing, a Maine corporation. Robert Willis is the managing partner of Willis Realty and the president of Maine Printing. The leased building was originally constructed in 1980 by Cimino and was designed to accommodate a subsequent addition. In 1986, Willis Realty, through Robert Willis,1 contracted with Cimino to build the addition. The parties signed a standard American Institute of Architects (AIA) form construction contract that provides that the owner and the contractor waive all claims for damages “to the extent covered by insurance obtained pursuant to this [contract] or any other property insurance applicable to the work.” Subsequently, by letter, the parties altered the contract to require Cimino, the contractor, rather than Willis Realty, the property owner, to maintain property risk insurance on the “entire work at the site” (commonly known as “builder’s risk insurance”). No change, however, was made in the waiver provision. Cimino did not procure the builder’s risk insurance until November 1, 1986, and, under the terms of that policy, any prior damage to the existing building was not covered. Willis Realty and Maine Printing continued to maintain a general business and property liability insurance policy with their insurer, Royal Globe Insurance Company, on the lot and the existing building.
In October of 1986, the excavation by Cimino in preparation for construction of the addition caused a collapse in the rear wall of the existing building. Royal Globe paid the losses incurred by its insureds, Willis Realty and Maine Printing, respectively.
I.
WAIVER OF SUBROGATION
The construction of an unambiguous written contract, and the terms of such a contract, is a question of law. Hopewell v. Langdon, 537 A.2d 602, 604 (Me.1988). Whether a contract is unambiguous is also a question of law. Id. Only when the language of a contract is ambiguous or uncertain is its interpretation a question of fact to be determined by the factfinder. F.O. Bailey Co., v. Ledgewood, Inc., 603 A.2d 466, 468 (Me.1992).
Under Article 11.3.62 of the contract, the parties waived all claims for damages covered by insurance obtained pursuant to Article 11.3, or “any other property insurance applicable to the work.” Such clauses have been liberally construed. See Village of Rosemont v. Lentin Lumber Co., 144 Ill.App.3d 651, 98 Ill.Dec. 470, 475, 494 N.E.2d 592, 597 (1986); Haemonetics Corp. v. Brophy & Phillips Co., Inc., 23 *1289Mass.App. 254, 501 N.E.2d 524, 526 (1986). Here, “the Work” is defined in Article 1.1.3 of the contract as comprising the “completed construction required by the contract documents.” The construction contract involved an addition attached to the existing building at its back wall. That back wall was therefore an integral part of the project.
By its plain language, Article 11.3.6 bars subrogation recovery between the parties to the contract for damages to the extent covered by insurance. Royal Globe’s complaint seeking recovery for damages paid to Willis Realty should have been dismissed.
II
MAINE PRINTING AS CONTRACTING PARTY
The court did not err, however, in concluding that the contractual waiver of subrogation is inapplicable to Maine Printing and thus does not bar the recovery against Cimino for damages incurred by Maine Printing. The contract bound Willis Realty and Cimino. Maine Printing is not named as a party. Although Robert Willis appended the title “president” after his name, rather than his actual title as a partner in Willis Realty, when signing the contract, the signature line over which Robert Willis signed specifically names Willis Realty as the contracting party. The court correctly concluded that Maine Printing was not a party to the unambiguous contract.3 The fact that Robert Willis was president of Maine Printing as well as managing partner of Willis Realty does not estop Maine Printing from denying that the waiver of subrogation clause applies to it. See Anderson v. Commissioner of Dept. of Human Servs., 489 A.2d 1094, 1099 (Me.1985) (estoppel warranted only when misleading conduct of one party induces other party to rely to his detriment).
III.
CIMINO IMMUNITY AS IMPLIED CO-INSURED
Cimino also contends that it is immune from suit as an implied co-insured under the Royal Globe property insurance policy carried by Willis Realty and Maine Printing. Although an insurer may not sue its own insured for damages covered under the policy, see 16 couch on insurance § 61.133 (2d ed. 1966), the court did not err in concluding that Cimino was not a co-insured under the Royal Globe policy, and thus was not immune to this subrogation action to recover damages Royal Globe paid to Maine Printing.
In contending that it is a co-insured, Cim-ino relies on an endorsement to the Royal Globe policy extending the owner’s property insurance to cover additions and alterations to the existing building. That endorsement, however, allows the named insureds to undertake renovation or remodeling without invalidating their existing property coverage, and does not inure to the benefit of Cimino to the extent of making Cimino a co-insured. Nor does the Royal Globe policy coverage for damage to the personal property of others within the control of the named insured, also relied on by Cimino to establish itself as a co-insured, do any more than indemnify Willis Realty and Maine Printing for damages for which they would be liable to others. It does not evince any intent to indemnify Cimino. The court was not required to find that Cimino was a co-insured merely because payments made to the named insureds under the policy included the cost of replacing some of Cimino’s construction materials and equipment damaged in the collapse. The court’s conclusion that Royal Globe is not barred from asserting its claim as to what it paid Maine Printing in subrogation is not error.
The entry is:
Judgment for Willis Realty vacated. Remanded to the Superior Court for entry of *1290judgment in favor of Cimino Construction Company.’ Judgment affirmed in all other respects.
ROBERTS, GLASSMAN and COLLINS, JJ., concurring.
. See infra Part II.
. Article 11.3.6 reads in pertinent part:
The Owner and Contractor waive all rights against ... each other ... for damages caused by fire or other perils to the extent covered by insurance obtained pursuant to Paragraph 11.3 or any other property insurance applicable to the Work except such rights as they may have for the proceeds of such insurance held by the Owner, as trustee.
. The court further concluded that even if the contract were ambiguous, as Cimino alleges, based on the extrinsic evidence offered at trial, the only parties to the agreement were Willis Realty and Cimino. That finding is amply supported by the evidence.