The part of the sentence "are necessary to construct" is correct and usable in written English.
It is used to express that something is needed in order to build or create something. For example: "Strong supporting beams are necessary to construct a sturdy bridge."
What steps are necessary to construct the probe?
Around $90 of components and materials are necessary to construct the machine.
Among these are the binocular cells in the visual cortex that are necessary to construct a sense of depth from retinal disparities.
Hopkins saw an opportunity to answer a big question: what genes are necessary to construct a vertebrate embryo from a single fertilized egg?
That study also found that two slow variables are necessary to construct the folded bifurcation plane on which these complicated bursting trajectories arise.
Apart from the grammatical cases, ergative and absolutive, which are necessary to construct meaningful sentences, an entire range of semantic cases occur with very high frequency, even when their meaning can be expressed without using case.
One way to characterize this position is that in order to show that a mathematical object exists, it is necessary to construct it, or at the very least, provide a method for its construction.
In some structures, this is due to the omission of bases during construction of nucleic acid scaffolds, and these omissions may have been necessary to construct homogeneous TECs for crystallization.
Creativity was necessary to construct methods for blinding capsules and the dietary soy intervention.
Hence it is necessary to construct an insulated field termination where voltages up to 5 kV can be applied.
Recently in Japan, it has often been necessary to construct tunnels under more severe conditions and to develop new techniques.
