A box frame is a structure that is made from two columns and two beams which looks like a typical rectangular or square. This structure is needed to support buildings if walls are removed. Box frame needs to be used if there is no party wall agreement in place.
Portal frames are low-rise structure supported by columns and characterised by a beam or rafter. However, the joints between the beam and columns are 'rigid' so that the bending moment in the beam is transferred to the columns.
This structure is generally attached to the flitch beam. The main reason why these plates are needed is to connect to timber joists at a point where shear and bending occurs.
This type of structure is generally used for rear extensions where the foundations are suitable or where pads for the columns to bear onto can be dug and cast in concrete. The 2 columns transfer this load down to the foundation and also add greater lateral stability. It can also be used if there is no party wall agreement in place.
Box frame with Post and Beam
A post is added when there is no support for the beam and load needs to be transferred to the ground.
Cross beam is a structure where two steelworks are connected at right angles.
Crank with Cross Beam
Cranked beam is an essential part when it comes to loft conversions. Additional cross beam helps to support roof joists.
Box Frames with Cross Beam
When two parallel walls are removed and perpendicular wall needs supporting it is common to use two box frames.