why H3? I'd use H2 70x45 on the flat as bearers, 90x45 joists with a 15mm packer at intersection points.
I'd use ultraset with a few hammer in masonry anchors for the bearers and skew nail or batten screw the bearer joist connection.
Ripping 190x45 is a PITA and will have a few kickbacks thrown in.
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