
435 S.E.2d 793 (1993)
Wade MILLER and wife, Jonah Miller; and Tony Futch, and wife, Mabel Futch, Plaintiffs,
v.
Kenneth A. TALTON and John Arthur Talton, Defendants.
No. 9211SC611.
Court of Appeals of North Carolina.
November 2, 1993.
*796 Armstrong & Armstrong, P.A., by Emery D. Ashley, Smithfield, for plaintiffs-appellants.
Lucas, Bryant & Denning, P.A., by W. Robert Denning, III, and Robert V. Lucas, Selma, for defendants-appellees.
MARTIN, Judge.
Plaintiffs' single assignment of error is directed to the entry of summary judgment dismissing their complaint. They argue first that the affirmative defense of the statute of limitations, having never been properly pleaded, was not before the trial court and could not, therefore, provide a basis for summary judgment. Secondly, they argue that even if defendants had properly asserted the statute of limitations as a defense, genuine issues of fact exist as to whether defendants are precluded by the doctrine of equitable estoppel from relying on the defense. We reject plaintiffs' first argument; however, because we find merit in their second argument, we must reverse.
The principles of law pertaining to summary judgment are well established. A party moving for summary judgment must demonstrate that there is no genuine issue of material fact and that he is entitled to judgment as a matter of law. N.C.Gen. Stat. § 1A-1, Rule 56; Hagler v. Hagler, 319 N.C. 287, 354 S.E.2d 228 (1987); International Paper Co. v. Corporex Constrs., Inc., 96 N.C.App. 312, 385 S.E.2d 553 (1989). Summary judgment is a drastic measure which should be used with caution, Williams v. Power & Light Co., 296 N.C. 400, 250 S.E.2d 255 (1979); Kessing v. Mortgage Corp., 278 N.C. 523, 180 S.E.2d 823 (1971), and awarded only where the truth is quite clear. Lee v. Shor, 10 N.C.App. 231, 178 S.E.2d 101 (1970). All of the evidence before the court must be construed in the light most favorable to the non-moving party. The slightest doubt as to the facts entitles the non-moving party to a trial. Ballenger v. Crowell, 38 N.C.App. 50, 247 S.E.2d 287 (1978). Where matters involving the credibility and weight of the evidence exist, summary judgment should ordinarily be denied. Burrow v. Westinghouse Electric Corp., 88 N.C.App. 347, 363 S.E.2d 215, disc. review denied, 322 N.C. 111, 367 S.E.2d 910 (1988).
Plaintiffs argue first that defendants' failure to formally amend their answer to affirmatively plead the statute of limitations constitutes a waiver of that defense. It is true that the statute of limitations is an affirmative defense required by G.S. § 1A-1, Rule 8(c) to be set forth affirmatively in a responsive pleading. However, while the failure to plead an affirmative defense ordinarily results in a waiver of the defense, the issue may still be raised by express or implied consent. Nationwide Mut. Insur. Co. v. Edwards, 67 N.C.App. 1, 312 S.E.2d 656 (1984), N.C.Gen.Stat. § 1A-1, Rule 15(b). Moreover, we have held that absent prejudice to plaintiff, an affirmative defense may be raised by a motion for summary judgment regardless of whether or not it was pleaded in the answer. County of Rutherford, ex rel. Hedrick v. Whitener, 100 N.C.App. 70, 394 S.E.2d 263 (1990). The affirmative defense relied upon should be referred to in the motion for summary judgment; however, in the absence of an expressed reference, if the affirmative defense was clearly before the trial court, the failure to expressly mention the defense in the motion will not bar the trial court from granting the motion on that ground. Id. This is especially true where the party opposing the motion has not been surprised and has had full opportunity to argue and present evidence. *797 Dickens v. Puryear, 302 N.C. 437, 276 S.E.2d 325 (1981). "Thus, although it is better practice to require a formal amendment to the pleadings, unpleaded defenses, when raised by the evidence, should be considered in resolving a motion for summary judgment." Ridings v. Ridings, 55 N.C.App. 630, 632, 286 S.E.2d 614, 615-16, disc. review denied, 305 N.C. 586, 292 S.E.2d 571 (1982).
Although neither defendants' answer nor their motion for summary judgment referred to the affirmative defense of the statute of limitations, the record reflects that the issue was clearly before the trial court. In the order granting defendants leave to amend their answer, entered more than a year before summary judgment was granted, the court ordered that "defendants' Answer be amended to plead the defense of Statute of Limitations in bar to the trial of this cause." Plaintiffs were not surprised by the limitations defense and made no argument that they were prejudiced. The various depositions and affidavits offered in support of, and in opposition to, defendants' motion indicate that the limitations issue was before the court. Plaintiffs' affidavits also raised the issue of equitable estoppel indicating that they perceived that a limitations defense was before the court. Thus, the statute of limitations was before the court by implied consent, and the pleadings are deemed amended.
Plaintiffs argue next that the doctrine of equitable estoppel raises genuine issues of material fact as to whether defendants should be permitted to rely upon a statute of limitations defense. We agree.
The doctrine of equitable estoppel may be invoked to bar a defendant from relying upon the statute of limitations. Duke University v. Stainback, 320 N.C. 337, 357 S.E.2d 690 (1987). Equitable estoppel arises when an individual by his acts, representations, admissions or silence, when he has a duty to speak, intentionally or through culpable negligence, induces another to believe that certain facts exist and that other person rightfully relies on those facts to his detriment. Carter v. Frank Shelton, Inc., 62 N.C.App. 378, 303 S.E.2d 184 (1983), disc. review denied, 310 N.C. 476, 312 S.E.2d 883 (1984). Neither fraud, intentional or unintentional, bad faith nor an intent to deceive are necessary to invoke the doctrine of equitable estoppel to prevent a defendant from relying on the statute of limitations. Hensell v. Winslow, 106 N.C.App. 285, 416 S.E.2d 426, disc. review denied, 332 N.C. 344, 421 S.E.2d 148 (1992); Duke, supra. When estoppel is based upon an affirmative representation and an inconsistent position subsequently taken, it is not necessary that the party to be estopped have any intent to mislead or deceive the party claiming the estoppel, or that the party to be estopped even be aware of the falsity of the representation when it was made. Meacham v. Board of Educ., 59 N.C.App. 381, 297 S.E.2d 192 (1982), disc review denied, 307 N.C. 577, 299 S.E.2d 651 (1983). Estoppel principles depend on the facts of each case. Mayer v. Mayer, 66 N.C.App. 522, 311 S.E.2d 659, disc. review denied, 311 N.C. 760, 321 S.E.2d 140 (1984). In determining whether the doctrine applies, the conduct of both parties must be weighed in the balances of equity. Peek v. Trust Co., 242 N.C. 1, 86 S.E.2d 745 (1955). If the evidence in a particular case raises a permissible inference that the elements of equitable estoppel are present, but other inferences may be drawn from contrary evidence, estoppel is a question of fact for the jury. Meacham v. Board of Educ., 47 N.C.App. 271, 267 S.E.2d 349 (1980), appeal after remand, 59 N.C.App. 381, 297 S.E.2d 192 (1982), disc review denied, 307 N.C. 577, 299 S.E.2d 651 (1983).
In their deposition testimony and in their affidavits offered in opposition to defendants' motion for summary judgment, plaintiffs asserted that defendants repeatedly promised to remedy the surface water drainage problems, that plaintiffs believed that defendants would keep their word and fix the problems, and in reliance on defendants' promises, plaintiffs delayed instituting legal action. If a jury were to believe the plaintiffs' evidence concerning these promises, defendants' assertion of *798 the statute of limitations in defense of the action would be wholly inconsistent with their previous representations, and the law of equitable estoppel would prevent them from relying on the statute of limitations as a bar. See Parker v. Thompson-Arthur Paving Co., 100 N.C.App. 367, 396 S.E.2d 626 (1990). Additionally, the parties presented conflicting evidence, creating an issue of fact, as to when the actions complained of began to occur, and consequently, when the statute of limitations began to run. Therefore, summary judgment based on the statute of limitations is not appropriate. Snyder v. Freeman, 300 N.C. 204, 266 S.E.2d 593 (1980).
Reversed.
ARNOLD, C.J., and ORR, J., concur.
