Footings ideas for granny flat build

[Jade3]

Hi Bunnings world. 

I'm considering building a granny flat. ( Yes will amend my current DA)

The issue I have is a wonderful one to have, I have a backyard full of lovely 50+ year old trees which I will not be removing

I was wondering if there are any alternatives to the current DA requirements for footings.?

Maybe something out of the box so I can have the 2 bed granny flat and keep the tree roots in tact?

I will most probably visit the council at some point to ask them this question too. It won't be happening for several months as I'm venturing on a few holidays. 

Any ideas would be wonderful 

[EricL]

Hello @Jade3

Welcome to the Bunnings Workshop community. It's fabulous to have you join us, and thank you for sharing your question about footings for your granny flat build.

There are a few options when it comes to structural footings, you can use steel, wood or concrete. Where the footings will be placed depends largely on the size of the granny flat. The best person to answer this will be your builder or draughts person. If the tree roots are in the way of the footing the position of the granny flat will need to be changed.

If you are building the granny flat from scratch, then an engineering plan will need to be provided. Your engineer will calculate the optimal position for the footings. But if you purchase a granny flat kit, it will come with an engineering plan and the position of the footings will be pre-determined.

I imagine that you have a very particular place in mind for the granny flat, but I suggest having a second and third position handy just in case your first choice is not accepted.    

Please keep us updated with your progress, we look forward to seeing the start of your granny flat build.

If you have any other questions we can help with, please let us know.

Eric

[diygrannyflat]

Hi Jade, 

Great questions and completely understand about wanting to keep those old trees.

There are 2 main options for the footings or foundation of your granny flat. Both of which require digging holes in the ground to fill with concrete.

You can have your granny flat built on a concrete slab which still means earthworks needs to occur. This is to dig out footings which are filled with concrete. These sit under, what will be your concrete slab. The design of these footings will be from drawings done by an engineer. In short - this keeps the slab in place, without any major cracking.

The second option is to build your granny flat on piers. Generally these piers will be sitting on 'pad footings' which are, holes dug into the ground and filled with concrete. Creating a base for a product such as 'uni-piers' to rest upon. (These are steel posts)

However, before committing to the best option regarding your tree roots, you will simply need to take your plans and have an conversation with an engineer on which option will be less evasive.

I hope this helps.

.The two common options

[Dave-1]

Morning @Jade3 

I have seen these advertised in facebook land. They are metal footings with 4 diagonal bars driven into the ground at angles to give structual support.

https://surefootfootings.com.au/ 

They certainly look doable. I would definently talk to your drafstman/builder about them. I have seen other companies in Aus that do the same type of deal.

Dave

[diygrannyflat]

Yes, @Dave-1 these are a great solution as well. Great suggestion.

I have spoken to the founder of this company and he explained how it all works. He did mention to be sure you have a trusted source to install them for you. (Someone who has done this many times before). Just to ensure everything is true and plumb.

When installing the multiple posts as part of the "sure foot" system they do spiral out under ground just like tree roots do, so there could also be a slight issue of them hitting existing tree roots.

[MitchellMc]

Welcome to the Bunnings Workshop community @diygrannyflat.

I'm sure you have plenty of great information to share with our members. There is plenty of interest out there in granny flat projects.

Mitchell