We are getting ready to install our pex manifolds for the loops in the 1st and 2nd floor living space. We are installing the pex on top of the OSB with 1.5" gypcrete slab. Any suggestions for installing these manifolds or pictures of what you have done would be greatly appreciated. My initial thought is to create a space in the wall by installing a header in 2-3 stud spaces to create enough room for each manifold. I would prefer to just install in-wall manifold boxes but have not had any luck sourcing them here in the USA (or options for them that are not $250 ea). In the basement we mounted the manifolds onto the stud walls in the mechanical room. Thanks! Scott

You are on the right track,
Depending on the manifold you may need about 5 1/2 " deep cavity.
Lower manifold wants to be about 12" above top of pour. header off a couple studs.
We typically will design manifolds into back of closet, or laundry room wall.
Someplace central to pipe distribution and out of sight.
Dan

Thank you Dan. I'll be calling you guys to rent the stapler for attaching the pex on the OSB.

Do you have a local sheetmetal shop? They could probably fold you up a flanged box to fit whatever opening you size for not too much money.

These 24x24" access doors work quite well for hydronic radiant manifolds installed between 24’ OC 2x6” stud walls:

Acudor Access Door from SupplyHouse

Karp Access Door from SupplyHouse

Both Acudor and Karp manufacture a wide selection of these type of access doors for very reasonable prices. Full disclosure, SupplyHouse is one of our affiliates.