
416 S.E.2d 597 (1992)
106 N.C. App. 365
SHIELDS, INC., Plaintiff/Appellant,
v.
METRIC CONSTRUCTORS, INC., Equitable Variable Life Insurance Company and the Equitable Life Assurance Society of the United States, Defendants/Appellees. and
METRIC CONSTRUCTORS, INC., Third-Party Plaintiff,
v.
AI GROUP, INC., Third-Party Defendant/Cross-Appellant.
No. 9121SC488.
Court of Appeals of North Carolina.
June 2, 1992.
*599 Hendrick, Zotian, Cocklereece & Robinson, by T. Paul Hendrick and William A. Blancato, Winston-Salem, for plaintiff appellant/cross-appellee.
Moore & Van Allen, by William E. Freeman, Durham, for defendant appellee Metric Constructors, Inc.
Carruthers & Roth, P.A., by Grady Shields, Greensboro, and Lightmas & Delk, Atlanta, Ga., by Glenn A. Delk, for appellee/cross-appellant AI Group, Inc.
WALKER, Judge.
Plaintiff brings forth eight assignments of error for this Court to consider on appeal. Of these, we find it only necessary to address the issue of the trial court's jury instructions, which is the focus of six of plaintiff's eight contentions.
The issues submitted and answered were as follows:
1. Was the plaintiff, Shields, Inc., in making this bid on the Duke Hotel Project damaged by the negligence of the defendants, Metric and AI Group, in providing an engineering design for the roof trusses in any one or more of the following manners:
ANSWER: Yes
1(a) Did the contract documents provided by the defendants consisting of drawings and specifications fail to comply with the North Carolina Building Code as it relates to the required gauge construction of material and wind load conditions for the roof trusses in this case?
ANSWER: No
1(b) Did the contract documents provided to Shields, Inc., prior to its bid on the Duke Hotel Project fail to present sufficient instructions on bridging, bracing and connections in order for Shields to bid and build roof trusses as designed and described in all of the original contract documents?
ANSWER: Yes
2. Did the plaintiff by its own negligence contribute to its own injury?
ANSWER: Yes
3. What amount, if any, is the plaintiff, Shields, Inc., entitled to recover of the defendants?
ANSWER: 0
Under the second group of issues submitted, the jury awarded damages to plaintiff for the services of Gene Farach in reviewing the work performed on this project.
Pursuant to plaintiff's amended complaint asserting a claim in negligence, the issues framed by the trial court for the jury focused on the theories of negligence and contributory negligence. Plaintiff contends Metric was negligent in supplying it with drawings and designs which were either incomplete or in noncompliance with the North Carolina Building Code, knowing that it would rely on said documents when calculating and submitting its bid. On the other hand, Metric argues plaintiff was contributorily negligent in failing to use reasonable care by independently verifying the accuracy and feasibility of the plans submitted by Metric.
Since plaintiff does not dispute the trial court's instruction on the issue of negligence we do not consider it on this appeal. With regard to the contributory negligence issue the trial court instructed:
The defendant contends and the plaintiff denies that the plaintiff was negligent in submitting a bid for the construction of the roof trusses on the Duke hotel project as designed by the contract documents without having sufficient information in order to make an effective bid and that in so acting the plaintiff failed to use reasonable care in submitting its bid.
The defendant further contends and the plaintiff denies that the plaintiff's negligence was a proximate cause of and contributed to the plaintiff's own damage.

*600 Finally as to this contributory negligence issue, I instruct you that if you find that the defendant has proved by the greater weight of the evidence that the plaintiff in making its bid was negligent in any one or more of the ways which I have indicated to you and if the defendant has further proved by the greater weight of the evidence that such negligence was a proximate cause of and contributed to the plaintiff's own damage, then it would be your duty to answer this second issue "yes" in favor of the defendant.
This instruction, while stating the contentions of defendant, fails to adequately set forth the relevant standard of care to which a subcontractor such as plaintiff should be held in submitting a bid under these circumstances. Additionally, even if the instructions as to contributory negligence were proper, the answering of this issue in favor of defendant Metric would not be a complete bar to plaintiff's recovery, since the negligence issues only bear upon whether plaintiff satisfied its duty under the contract to independently verify the accuracy of the plans and to submit its bid accordingly.
Plaintiff contends that when Metric was informed that the new drawings prepared by Gene Farach specified 18 gauge material it advised plaintiff to go forward with this work and waived the provision requiring a written change order. We agree with plaintiff that an issue arises from this evidence as to whether or not plaintiff and Metric entered into an agreement, either express or implied, that 18 gauge material would be substituted for the 20 gauge material specified in Metric's drawings and designs. It is undisputed that the roof with 18 gauge is structurally more sound than a roof with 20 gauge material and that Metric received the benefit thereof, yet plaintiff has not been compensated for its work. Furthermore, quoting from J.R. Graham and Son, Inc. v. The Randolph County Board of Education, 25 N.C.App. 163, 212 S.E.2d 542, cert. denied, 287 N.C. 465, 215 S.E.2d 623 (1975), this Court stated in W.E. Garrison Grading Co. v. Piracci Construction Co., Inc., 27 N.C.App. 725, 729, 221 S.E.2d 512, 515 (1975), disc. review denied, 289 N.C. 296, 222 S.E.2d 695 (1976):
"The provisions of a written contract may be modified or waived by a subsequent parol agreement, or by conduct which naturally and justly leads the other party to believe the provisions of the contract are modified or waived.... This principle has been sustained even where the instrument provides for any modification of the contract to be in writing.' (Citations omitted.)
Insofar as the evidence would support a claim in contract or quantum meruit, the trial court had a duty, without any specific requests by the parties, to instruct the jury on the law as it applies to the substantive features of the case arising from the evidence. Millis Construction Co. v. Fairfield Sapphire Valley, Inc., 86 N.C.App. 506, 358 S.E.2d 566 (1987). " `This means, among other things, that the judge must submit to the jury such issues as when answered by them will resolve all material controversies between the parties.' " Bare v. Barrington, 97 N.C.App. 282, 285, 388 S.E.2d 166, 167, disc. review denied, 326 N.C. 594, 393 S.E.2d 873 (1990). (Citations omitted). Since the inferences from plaintiff's evidence support theories of recovery under contract and quantum meruit, the failure of the trial court to so instruct the jury on these substantial features of the case constitutes prejudicial error warranting a new trial. Mosley & Mosley Builders, Inc. v. Landin Ltd., 87 N.C.App. 438, 361 S.E.2d 608 (1987), disc. rev. denied, 326 N.C. 801, 393 S.E.2d 898 (1990); Hood v. Faulkner, 47 N.C.App. 611, 267 S.E.2d 704 (1980).
Vacated and remanded for new trial.
HEDRICK, C.J., and ORR, J., concur.
