Carpentry & Joinery

Strenghing 4x2 with 9x2 ( do you need a birds mouth)

Anonymous user 09/03/2024 - 2.50 PM

Hi All Can anyone help.The wife wants roof windows in the bedroom. The pitch on the of the roof is 15 degrees. The length ,wall plate to knee high load bearing stud wall is 4.2 on top of 450 thick load bearing stone wall, well will be once purling is proped and taken out in sections.ceiling joists also removed Building control are on board and structural engineer coming out on Wednesday evening for other things going on.so will check with him as well. Getting dizzy from looking up and scratching my head and was wondering if any one on here would be kind enough to enlighten me so I don't sound like a plumb when I'm talking to the bc officer. Now proposing to put 9x2 along side existing 4x2.screwed nailed bolted drilled for airflow ,insulated. Double up around Windows. Now the bit I'm confused with is do the new 9x2 have to have a bird mouth.as that would require taking the roof off and I really don't want to Be doing that. Or would the bc just accept seat cut on 9x2 and bolted fixed to bird mouth cut 4x2. Also for detail could I put a birds mouth on the inner face of the wall plate rather than cutting the seat cut all the way through level. Or would that cause to much pressure on the inner wall. Thank you in advance for any advice