Hi all, I wondered if you fine folk could help me with some advice on this one. I have built a small garden room at the bottom of the garden under permitted development. Block built structure with 100mm cavity wall 5m by 3m. I was just curious if I could use a concrete lintel (one for each - inner & outer leaf) instead of the normal catnic? I have only ever used catnic in the past so have never used concrete on a span as wide as 2500. It is to go above french patio doors and will be holding a standard flat roof above so nothing too heavy but was unsure on using concrete for a span that long. I could just go with catnic but that will push the whole 2.5m high rule very close and may even exceed by the time the rafters and roof are on. Its an awkward one because I will be way within the 2.5m height rule at one end but the other end is touch and go because the garden slopes away, which is why I was curious about using concrete lintels to save on height. As always guys any advice is much appreciated.

