Tips from a structural engineer that could save architects time and money: Doors opening out onto gardens

Industry Professionals - Posted on August 4, 2021

We know all too well how costly and time consuming it can be to go back and forth with revision after revision of drawings. As the architect generally begins the process of a client’s home improvement project, there is all the more chance they will come up against roadblocks and change requests as other contractors and consultants are brought onboard. We wanted to share a few pointers from a structural point of view that might save you time and money!

Assuming no Grand-Designs-style ambitions, when a client wants to open out the back room of their house, or a garden room / orangery, onto the garden there are usually only a couple of options:-

  • Large bi-folds central to the wall
  • Multiple French or smaller bi-fold doors / windows

But which is the most efficient in a structural sense?

The problem with multiple openings

When you have multiple full-height doors or windows side-by-side, you usually need wind posts in between the windows to satisfy the building regulations:

Figure 1: Plan showing a double bi-fold arrangement along a rear wall opening out onto the garden.
Figure 2: Elevation on double-bi-fold arrangement showing structure (red lines indicate steel beam / post, blue line indicates lintel)
Figure 3: Plan showing steel beam (B5), wind post (COL1), and lintel (L1).

So… don’t do multiple openings!

In our view, the best way to approach this is to do a single bi-fold central to the wall, making it as large as is needed. That’s because it usually means a more efficient structure.

With central longer-spanning bi-fold doors, although the lintel may be a bit bigger (depends on the size of the doors), there is no wind post and the structure is less fiddly to build – so probably more cost effective.

Figure 4: Plan showing single beam (B5) over larger bi-fold doors – Note that wind posts are not needed here!

It’s down to the client’s preference of course! but in our view with the single bigger opening you get more light and a greater feeling of continuity between inside and outside when the doors are fully open:

Why this might help you…

One of the things that we notice is that when clients initially go for the multiple openings / French doors option and then realise a wind post is needed, they often revert to single bi-folds anyway! This creates more work for the architectural consultant when they need to make a change. If you suggest the single larger bi-fold then this might not happen!!

We hope you have found this article useful! If you have any thoughts, questions or tips you’d like to share we’d love to hear from you. We believe it is invaluable for contractors and consultants to connect and share their perspectives so we can all streamline our workflows and make life easier for us AND our clients. Follow us, drop us a message on instagram and let’s connect @porthousedean_engineers.

Also, if you need a hand with structural calcs or drawings for any upcoming projects, please don’t hesitate to get in touch. You can request a free, no obligation quote on our website or send us an email and let’s arrange a time to chat.  We specialise in providing structural calcs and drawings for low rise residential projects.