I have an extension that was built outside the original back door and window (please see picture http://63.218.54.74/knockwall.jpg). The wall was originally the exterior wall of a 2-story 4 bedroom house. I want to knock out the middle section and under the window. The wall is about 260mm (10") thick and seems to be two blocks wide with a gap in between. The total distance across the door and window is
3m.I was thinking of supporting the wall with a series of wall supports (e.g. hired from HSS) while I fit a beam over the old window and door.
Do I really need to hire a structural engineer for this ? Note that I won't be doing the work myself, most likely hiring a builder of some sort.
Is there any rule of thumb for calculating the weight of the structure above? The wall supports from HSS are only rated to 340kg which is pretty miserable compared to the "super prop" which supports 12ton.
Any advice appreciated, Chris.