MJ6

Sorry, as for the lintel, I was referring to the 345cm wall, I know it won't stabilise the long wall. So just saying that one side would have a 90cm (P5) return but the other won't, which as I understood is non-Part A compliant, hopefully I got that right! I spoke with a couple, who advised no WPs are needed, if the 3 points suggested in my original post are followed! But as I wanted to be sure, I asked the question here. Yes they're, but now we know they're not needed for the left wall, only the right hand one. Your suggestion of adding a WP at the bottom right corner would serve both walls I think, but as for the shear wall behind the wardrobe, can't this be replaced with another WP either at the start or the middle of the wall (where I put red "?")? - I understand that full calculations still need to be provided here. Thanks again George, and sorry if it's a lot.

I think I have a better understanding of Part A now, thanks to your comments. So if you don't have a buttressing wall/chimney/pier and/or sufficient returns, then an alternative solution should be explored, which is WPs in our case, otherwise to reinforce the wall. As for the left-hand side wall, this has both 90cm start/return, so this is Part A compliant. But in general, is there a maximum length of the wall to comply with this rule, considering openings are less than 3m? As for the 345cm wall, considering a long lintel is installed over the door and window with stuffiest tying to the other walls, would this provide enough stability? What about the lack of return (P5) in the right hand corner?

I see your point, plenty of other requirements are needed to justify not using a windpost, even then, a windpost might still be needed. Good point. Climate change effects need to be considered. As for point 2, would BCO be ok for not having these in place anyway? And if sufficient returns are applied, will WPs still be required? Also, what are your thoughts on the left hand side wall? Considering it only has a small bathroom window with sufficient returns at both ends.

Yeah found out WPs are suggested by the BCO anyway, so calcs/justification are needed for both options.

I spoke with the architect, the drawings were submitted for approval and it was the BCO who asked to explore the windposts option. I agree with your point about the small wall not being considered as a buttress, that's why I asked the question just to confirm. Any thoughts on the left hand side wall?

Hi All, I'm helping a friend to build a single story 6x3.45x2.6m (LxWxH) extension to their house. The cavity wall consists off bricks, cavity and blocks, 100mm each. The architect wanted windpost design for the extension, now I'm not sure whether it's required by the Building Control Officer (BCO) or the architect asked for it from previous experience. Looking at Approved Document A, there's no clear statement to when a windpost is needed (i.e minimum brick wall length or height). Also, I found that the proposed plan doesn't match the Document A requirements of having a minimum of 665mm return (like in red circles 1 & 2), and the minimum dimension between 2 openings (P2 in the second snapshot). Probably why they asked for windposts?! So far, I more inclined that windposts are not needed, especially that it's a mid-terrace house with fences from both sides, with the left-hand side fence being very close to the proposed extension, but probably the followings should be met: Minimum of 665mm returns are built, with appropriate wall starter system Appropriate wall ties are used between wall leaves & around openings (225mm long, 225mm apart vertically) Appropriate straps to tie walls to roof Therefore; Am I thinking in the right direction? Do you think windposts will be required if the minimum returns and P2 are not met? Is there a rule of thumb to when windposts are required? Does the 3.45m wall works as a buttressing wall for the other two side walls? What are the calcs needed to justify not using windposts? (e.g. Masonry wall panel design to EN1996?) Many thanks! Snapshot from Approved Document A