Um, yes it is.
WTH you talkin’ bout? The hardening of a room to acomodate SCI data IS NOT classified. My friend actually builds these and DID NOT have to receive a clearance in order to do it.
The SCIF is basically a Faraday cage - the technology of which has been around for say AT LEAST 100 years. Hardly a national secret ...
OTOH, after my friend has built a SCIF, it has been accepted, and SCI material has been placed within - THEN he IS NOT allowed inside ...