How to defy gravity
I heard a wonderful interview with engineer Bill Lawson on a podcast the other day (Richard Fidler’s Conversations) where he talked about how engineering is really the art of defying gravity. I thought this was such a wonderful way to describe a science that’s all about working out how to keep heavy things from collapsing. Which is something that builders are pretty interested in too.
Lots of the work that JD does is replacing doors and windows – it’s a fabulous way of changing the feel and purpose of various rooms in a house. One of the things he most often gets asked about is knocking out a wall and putting in bi-fold doors – a change that really opens up a room. We did it to our old house that previously had no connection to the backyard at all and it was awesome.
However, before you pick up a sledgehammer and start swinging you need to talk to a builder, and probably a structural engineer, about what’s going to support those doors. Most bi-fold doors are top-hung – that means that they “hang” from the top, which must be strong enough to support their weight. A five-leaf bi-fold door weighs approximately 140kg and bricks alone will not be able to support that weight.
To defy gravity and have top-hung doors, you’ll need to install a beam, which is where your structural engineer comes in and also where additional – and necessary costs – come in. A structural engineer will be able to advise your builder on the size and type of beam that will be needed to support the weight of the doors. The builder will then be able to safely knock out the wall, support it with acro props, install the beam, install the doors and finish the job neatly.
Another alternative is to install bottom-hung doors which, as the name implies, have all the weight loaded to the bottom track. Not as many door companies manufacture bottom-hung doors, but your builder should be able to recommend a supplier.
Have you had a wall knocked down and replaced it with doors or windows? Was structural work required? Do you dream of defying gravity – I know I do!