I am quite accustomed and also saddened with the practices of the construction industry where most of the specifications attached to the contract or covenant often outdated. So what is the importance of specifications?

Specifications is the part of the contract instruction which forms the standard requirements in accepting completed job/task or work-in-progress. It is essential to build the accurate and applicable inspection and test plan (ITP). The wrong grading or zoning of course aggregates and fine aggregates will lead to rejection of materials, or worst dismantling of a completed task. This mean the whole stockpile of these materials shall not be accepted for any part of the job. MS 1195:1991 is no longer applicable (as it is based on BS8110:1991 superseded by BS8110:1997 + addendum) and was not replaced by any MS in accordance to BS 8110:1997 onward or BS EN 1992/EC2. Instead, the current standard criteria for concrete is dictate by MS EN 206:2016 which is a direct adoption of BS EN 206:2013; moreover an obsolete specification since the latest one supposedly be BS EN 206:2016.

Secondly, it plays important role in procurement where obsolete specification will make it difficult for contractors to procure materials which are no longer available in the market. Say, you are using the old standard specification for main steel bar, you will not be able to find HT steel bar with grade 460 since the market now only provide grade 500A/B/C, not only increase in strength but ductility capability. Changes to specification also states that mild steel is no longer applicable as nominal links for structural concrete. 
Remarks/Read: BS 4449:1997, BS 4449:2005, BS 4449:2005+A2:2009, MS 144:2006, MS146:2006, MS 144:2014 and MS146:2014.

So, what is the leeway when this occurred in your project? It depends on what kind of contract form you are using. In this case I will discuss about government project and form PWD203/203A. I will leave out CIDB, PAM and FIDIC contract forms.

What happened if specifications are outdated? Most of the government contract forms will annex the Standard Specification for Building Works (SSBW). In case there are addenda or addendum made for specification(s), then any parties can raise up query or queries based on the following clauses available in the annexed standard specification. Nothing is mentioned about precedence of specifications in Condition of Contract form. However, it is clearly spelled in specification where;

SSBW and SSRW (Road Works) clearly stated this in;

SSRW Clause 1.3.1(iii) - "All standards and Codes of Practice referred to in this Specification shall be deemed to be the editions current at the time of Tender. If the Malaysian Standard exists, which the SO deems to be equivalent to the British or other Standard specified, then the Malaysia Standard shall be followed. In provision within the relevant Standards or Codes of Practice as mentioned in this Specification, then the provision of this specification shall take precedence."

SSBW 2014 Clause 3.1 - "Specification together with any addenda issued shall be deemed to be the editions current at the time of Tender. If the Malaysian Standard (MS) exists, which the S.O. deems to be equivalent to the British or other Standard specified, then the MS shall be followed. Other equivalent standards specifying superior material may be used with the approval of the S.O."
At the same time, clarification should be made to fulfill Clause 3.2 where, In the event of any discrepancy between the provision of this Specification and the provision within the relevant Standards or Codes of Practice (CP) as mentioned in this Specification, then the provision of this Specification shall take precedence.

Therefore, it is essential for those who are in QAQC to review the validity of specifications annexed to the contract documents. You have to remember, any changes and removal of work shall be incurred by contractor. If you failed to see the importance of specification in your contract, expect prolonged issues throughout your project physical phase.