Cob walls for existing shed frame and room

Hi guys newbie here.

I’m 24 years old and are living on a family property.

We have an existing shed that is made from solid wooden posts with a tin roof.

I’m looking for an inexpensive and natural building material and cob really interests me.

Problem is... We have a poinciana tree growing about 2 foot away from where the foundation would start.

We don’t want to have to cut it down, but I don’t see how else we could put in a solid foundation without the roots ruining it in a couple of years?

Also if we were to go ahead with the project what is a realistic time frame be to build walls up to the roof. The dimensions are 5m wide x 15m long x 2.5m height

Most earth buildings in Australia are built as post and beam structures, just as you have now.
I would pour the foundation in a number of ways;
- leave a gap in the footing where the major roots pass through.
- cut the root just short of the foundation.
- put a curve in the wall to give the roots room.
The roots will be seeking moisture, if the floor is covered over the roots may just stop growing since there will be no water for them.
Building time, 6 to 12 months depending on what equipment and labour you have.
You could try earth blocks, it may speed up the process.

Think about using steel poles elsewhere and bury them in the wall for windows and doors.

So you think that the roots won’t uproot the concrete over say the next 10-20 years?

Please see attached picture on how close the tree is to the structure, we will be removing the tin and replace with cob wall.

Is there any reason to be concerned by the tree or if it is trimmed and like you said cut the roots away we would have no issues?

And lastly, could you please just elaborate a little bit of the steel frame and why you suggested that over wood or concrete?

Thanks for the help appreciate it 👍🏼

Steel posts are often lower price, lighter to carry and easy to work with.

An arborist, tree fella, may have more knowledge on the tree and its roots.

Plant a royal poinciana tree in a location where it has enough space to grow. Not only can this variety of tree reach up to 40 feet,
but it can also spread to between 40 and 60 feet wide. While the tree can provide a lot of shade, it can also be damaging if not planted in the proper area.
Keep the plant away from walls, pavement or anything else it might spread into, as the tree has shallow roots and can easily cause damage.

Termites are a significant threat to the Poinciana tree. If you identify any pests, treat the tree to control the pest and termite spread.
Poinciana trees have buttress roots that often extend to the surface.

And last but not least, and similar to the first two on the list, you should avoid planting poincianas because their root system is quite invasive and large. But, that’s not all! Even though they are extremely lovely when in bloom, their wide and low growing canopy requires ‘the right space’ to grow. If planted near any structures, constant directional pruning is needed, which can affect the symmetry of the canopy.