Construction Contract Law

1. The Theory of Immixtion
Presented to:
Simret Tesfaye(PhD)
May 14th , 2023
Prepared by:
Habtamu Anteneh GSE0104/15
Eleni Endalkachew GSE
Edomgenet GSE
Bedaso Gemechu GSE
Derartu GSE
Dagmawit GSE
SCHOOL OF CIVIL ENGINEERING & ARCHITECTURE
MSc In CONSTRUCTION TECHNOLOGY &
MANAGEMENT
CONSTRACTION CONTRACTS & LAW

2. The Theory of Immixtion
 “Immixtion” is a French word translated as “Interference”
 Legal principle that permits an Administrative authority to make changes to a
construction contract with out the contractor’s consent in certain limited circumstance.
 The theory of immixtion is, therefore, related to an unacceptable interference of the
employer or his representative when the contractor is performing his contractual
obligations.
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3. The Theory of Immixion……Cont’d
Why Changes? ( PPA 2011.94 , FIDIC_2017.65 , Civil Code 1960 522,567 )
 PPA 2011, GCC clause 15.1 : The Engineer shall have power to order any modification
to any part of the works necessary for the proper completion and /or functioning of the
works. Such modifications may include additions, omissions, substitutions, changes in
quality, quantity, form, character, kind, position, dimension, level or line and changes in
the specified sequence, method or timing of execution of the works
 The Civil Construction Law of Ethiopia has provisions that variation is allowed
whether or not a clause to that effect is incorporated in the contract. While establishing
the right, however, it imposes certain restrictions on the right of exercising and
implementing changes or variations to the work.
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4. The Theory of Immixion……Cont’d
 The 1960 Civil Code of Ethiopia , established provisions to what extent variation may be
permitted.
Articles 3283 -85 provide thus :
 Art. 3283.----Unilateral Modification of Contract---1. Right of Administrative Authority
1. (1) During the currency of the contract of public work, the administrative authorities may,
notwithstanding any stipulation to the contrary, impose unilaterally upon the contractor
changes in the original conditions of the contract as indicated in the specifications.
2. (2) Such changes may affect only the Provisions which concern the arrangements of
the public works.
3. (3) They may not affect the financial conditions of the contract.
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5. The Theory of Immixion……Cont’d
 Art. 3284.----New works.
 (1) The administrative authorities may, against payment of an additional remuneration,
require the contractor to perform works which were not mentioned in the contract.
 (2) They may not, however, require him to perform a work which by its object would be
totally different to the work mentioned in the contract or which would have no relation to
such work.
 (3) Nor may they require him to perform a work under conditions entirely different to
those which have been mentioned in the contract.
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6. The Theory of Immixion……Cont’d
 Art. 3285. ---- Rights of the contractor.
• (1) Unless otherwise provided in the contract, the contractor may cancel the contract
where the increase or reduction of the works as a whole required by the administrative
authorities involves a variation of more than one-sixth of the cost mentioned in the
contract
• (2) In the case of reduction of the works as a whole, he shall be entitled to a
compensation equal to the loss suffered by him and profit of which he is deprived by
reason of the variation of the contract.
• (3) The court may limit the amount of compensation for deprivation of profit where it
appears that the variation is due to extraneous circumstances and not to the default of
the authorities having made the contract.
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7. The Theory of Immixion……Cont’d
 PPA Version 2011, GCC provisions on the Financial bounds of variation
 GCC Clause 15.7: Where on provisional acceptance an increase or reduction in the total
value of the works resulting from a change order, or from some other circumstance which is
not caused by the Contractor's default, exceeds 25% of the initial contract price (or as
modified by addendum), the Engineer shall, after consultation with the Public Body and the
Contractor determine any reduction from the contract price as a consequence of the
application of GCC Clause 15.5. The sum so determined shall be based on the amount by
which the increase or decrease in value of the works exceeds 25%. The sum shall be
notified by the Engineer to the Public Body and the Contractor and the contract price
adjusted accordingly.
 GCC Clause 15.8: The total value of the works resulting from a change order shall not
exceed 30% of the total value of the initial contract price.
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8. The Theory of Immixion……Cont’d
 PPA 2011.pdf (94-96) )
 Civil Code of Ethiopia (English).pdf (522, 567)
 Civil Code Ethiopia(Amharic).pdf (658, 660, 719)
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