
289 S.E.2d 145 (1982)
FEDERAL REALTY INVESTMENT TRUST
v.
BELK-TYLER OF ELIZABETH CITY, INC.
No. 811SC548.
Court of Appeals of North Carolina.
March 16, 1982.
*147 C. Glenn Austin, Elizabeth City, for plaintiff appellant/cross-appellee.
Leroy, Wells, Shaw, Hornthal & Riley by Dewey W. Wells, Elizabeth City, for defendant appellee/cross-appellant.
ARNOLD, Judge.

PLAINTIFF'S APPEAL
Federal Realty's sole assignment of error concerns the trial court's failure to submit to the jury the issue of quantum meruit. In support of this assertion, plaintiff cites evidence that defendant Belk received the benefits of maintenance services rendered by the landlord during the period in which payments were withheld. It argues that even if its performance was insufficient to fulfill the terms of the express contract, it should be permitted to recover the value of the services under an implied contract.
Quantum meruit recovery is based on the amount by which one party is benefitted as a result of the other party's performance. Pilot Freight Carriers, Inc. v. David G. Allen Co., 22 N.C.App. 442, 206 S.E.2d 750, appeal after remand 25 N.C. App. 315, 212 S.E.2d 699, cert. denied, 287 N.C. 465, 215 S.E.2d 625, cert. denied 423 U.S. 1055, 96 S.Ct. 786, 46 L.Ed.2d 644 (1974). We find nothing in the record from which the jury could have quantified the value of defendant's benefit from plaintiff's services here. Moreover, plaintiff failed to show that defendant "accepted" plaintiff's performance as required for quasi contractual recovery. Hood v. Faulkner, 47 N.C. App. 611, 267 S.E.2d 704 (1980). Finally, there can be no implied contract covering the same subject matter governed by an express agreement of the parties. Snyder v. Freeman, 300 N.C. 204, 266 S.E.2d 593 (1980). Plaintiff's own evidence shows that such an agreement was in effect between these parties.
In plaintiff's appeal, accordingly, we find no error.

DEFENDANT'S APPEAL
Belk's first assignment of error is that the trial court erred in submitting the issue of "waiver" to the jury as a possible defense to Belk's claim for the number of parking spaces allegedly called for in the parties' agreement. Belk notes that plaintiff's plea of waiver had been stricken by *148 court order and that only the defense of estoppel was set forth in the amended reply.
We have carefully examined the jury instructions and have concluded that the court's instruction on this issue was, at best, a highly confusing one. The court may have intended, as plaintiff claims, to instruct on "estoppel." However, the term it used was "waiver," a related, but unquestionably distinguishable defense not raised by the pleadings. We hold, therefore, that the court's instruction was inconsistent with the pleadings in violation of G.S. 1A-1, Rule 8(c).
Ironically, our review of the record has led us to the conclusion that the defense of waiver more nearly conforms to the evidence presented at trial than does the defense of estoppel. We are unable to determine, as a matter of law, whether there exists sufficient evidence of either defense for submission to the jury. However, plaintiff should have been permitted to amend its pleadings to raise either or both defenses and to present such evidence as it may have had available in proof thereof. We hold, therefore, that Judge Brown's order striking the plea of waiver was error.
Belk also assigns as error the court's failure to submit to the jury the issue of Federal Realty's failure to provide a rear driveway to the mall. Federal Realty argues that the court correctly relied on the general rule of contract construction that ambiguous terms should be construed against the party who prepared the contract. While we acknowledge that such a rule exists, and is properly applicable where the intended meaning of a contract term cannot be ascertained with certainty, we find the rule inapplicable here.
The very heart of contract law is that a contract should be construed, wherever possible, so as to give effect to the intent of the parties. Adder v. Holman & Moody, Inc., 288 N.C. 484, 219 S.E.2d 190 (1975). In ascertaining the parties' intent, courts may consider the language, subject matter and purpose of the contract, as well as the situation of the parties at the time, and may even read into a contract such implied provisions as may be necessary to effect the parties' intent. Lane v. Scarborough, 284 N.C. 407, 200 S.E.2d 622 (1973). Courts also must give consideration to evidence of the parties' own interpretation of the contract prior to the controversy. Goodyear v. Goodyear, 257 N.C. 374, 126 S.E.2d 113 (1962); Shoaf v. Shoaf, 14 N.C. App. 231, 188 S.E.2d 19, reversed on other grounds 282 N.C. 287, 192 S.E.2d 299 (1972).
In the case at bar, it was error for the court to decide the issue relating to construction of a rear entrance as a matter of law. The jury should have been permitted to consider evidence of the parties' communications and conduct, as well as the written terms of the contract, in determining whether an ambiguity as to the meaning of contract terms in fact existed. If an ambiguity had remained after all of the evidence had been weighed, then and only then would the court have been justified in resolving it against Belk as a matter of law.
We hold that the errors noted above require that we reverse the judgment and remand for a new trial on the issues of plaintiff's liability for construction of additional parking spaces and for construction of an access road from Halstead Boulevard.
Defendant's argument that specific performance would be the appropriate remedy for breach of these alleged duties since money damages cannot be estimated with accuracy is well taken. However, since plaintiff's liability has not been established, we find it unnecessary to reach this issue.
In plaintiff's appeal there is no error.
In defendant's appeal on its counterclaim judgment is vacated and remanded for new trial.
CLARK and WHICHARD, JJ., concur.
