This ritual is not required, but if celebrated, follows the blessing of the site. If this option is skipped, the rite proceeds to the conclusion (I, 26). The red-n-black (27-29):
27. The bishop goes to the place where the foundation stone is to be laidand, taking off the miter, blesses the stone, saying:
Let us pray.
Father,
the prophet Daniel spoke of your son,
as a stone wondrously hewn from a mountain.The apostle Paul spoke of him,
as a stone firmly founded.Bless + this founation stone
to be laid in Christ’s name.You appointed him
the beginning and the end of all things.May this work begin, continue,
and be brought to fulfillment in him,
for he is Lord for ever and ever.Then the bishop may sprinkle the stone with holy water and incense it. Afterward he receives the miter again.
28. When he has finished, the bishop lays the stone on the foundation in silence or, if he wishes, saying these or similar words:
With faith in Jesus Christ
we lay this stone
on which a church will rise.May it be a place of sacrament
and a source of grace
to the glory of the Father
who with the Son and Holy Spirit
lives and reigns for ever and ever.29. A stone mason then fixzes the stone in with mortar. Meanwhile, if the occasion demands, the following antiphon is sung.
The house of the Lord is firmly built on solid rock (alleluia).
Commentary:
Old Testament and New Testament allusions in the prayer.
If the text at number 28 is optional, I’d almost prefer a sung text. That text could be with the assembly or without.
No psalm given with the antiphon at number 29. What do you think? Not repeat either psalm 84 or 48 from the earlier part of the rite? If not, perhaps a section of Psalm 118. Or maybe Psalm 95.
Your thoughts?
Catholic Sensibility 
It’s the chant for vespers for the dedication of a church: Haec est domus Domini firmiter aedificata: bene fundata est supra firmam petram. Alleluia.
It traditionally preceded Psalm 122.
good verses
it helped me