# Forum Home Renovation Sub Flooring  Questions about attic conversion floor

## paddyjoy

Hi, 
We have a semi Californian bungalow with a 30 degree roof pitch. I'm  putting together some conceptual plans to see if it would be feasible to  put two small kids bedrooms upstairs. I don't know much about attic  conversions and would appreciate if anyone can help out with some basic  questions. 
I'm assuming you would typically need to put in new floor joists upstairs? 
How much space would you typically lose when you put new floor joists above the existing ceiling joists? 
Can the new floor joists be put in between the existing ground ceiling joists to reduce lost height? 
Could you remove the existing ceiling joists and put a combined ceiling/floor joist in there? 
Thanks.

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## Bloss

Not as simple a new joists. For example, the new floor and whoever uses it imposes more loads on wall structures (the ceiling joist loads are transferred to the ground through the walls . . . via floor joists, bearers and piers and footings). This needs professional design, plans & approval and to minimum standards required for the Building Code (BCA) for habitable areas. 
A couple of basic rules: going up is almost always more expensive than going out and renovations are always harder to do and more complicated than they first seem and will cost double your estimate in time and money.  :Eek:  
Not enough info - if you can upload plans or a sketch or pics of what the house is now and then we can give some ideas about what might be possible.

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## paddyjoy

Thanks for the comments. 
Here is the full story, would really appreciate any opinions  :Biggrin:  
Understand this will cost more than the cost of building a brand new  house somewhere else but due to so many reasons we are willing to  overcapitalise a little bit if we have to as we want to be here long  term. 
House is on 160m2 so due to council restrictions/practicality can't expand out in any direction. 
Currently house has small kitchen and two bedrooms.   
Would like to remove one downstairs bedroom and add two small bedrooms upstairs for the kids. 
Proposed downstairs plan.  
I have spent literally months playing around with different stair locations and have come to the conclusion that the only way it can work is if the stairs is in the middle of the ground floor with one room at the front and one room at the back like this.    
I can make the front room conform with BCA regulations to be habitable but the back room is an issue as it has two sloping sides. With the back room every 10cm of height makes a big difference. So for this reason I'm trying to get an idea of how much height I'm going to lose with new floor joists. To be honest I'm not even sure if the back room will be too pokey, even it does comply, which would be a show stopper! 
Here is the actual attic.   
Have a structural engineer lined up to do all the calcs and engineering drawings. 
In terms of approval I have: 
One DA approved for a one bedroom attic conversion (dome by previous owner). Plan to submit modified drawings when we go for building cert.
Just recently got another DA approved for the ground floor modifications and back deck (did this myself, was fun/interesting/time consuming!) 
My stab in the dark at cost is $150k-$180k..............

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## Bloss

That makes more sense! More info is better! As to the new floor joists - they can sit in beside the originals or replace them, but if you want to stay living in the house the construction process needs to allow for that - so to minimise disturbance to the current dwelling. But you should get compliance with that back sloped roof bedroom - your architect and/or engineer can offer a few options - one obvious one is a dormer window (ie: and upright window on a sloping roof - this link shows heritage windows http://www.heritage.nsw.gov.au/docs/...d_sunhoods.pdf) rather than the roof line Velux style your drawing shows (you might get away with balcony windows Cabrio balcony system | VELUX. You might be able to gain a little more in both rooms by raising the low wall a little or stepping it. 
Going way out there you might also look at stairs for tight places such as these alternating stairs (Karina attic stairs loft stairs - not sure of their status re BCA or availability in Oz - I have seen and walked on them in EU and USA). These are quite common in industrial use and they do have quite a few drawbacks (can't turn around on them, they are very steep and so on, and take a little practice for most people to master. This guy has installed a set and covers the caveats very well bottleworld.net - not least that they probably would not get approved! 
But that was really a bit of fun for those who like to see innovative building ideas (as I do) - there are a range of BCA complaint stair systems and designs for tight access situations.

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## cherub65

Spiral stair case could be an option for an attic conversion, takes up way less space

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## paddyjoy

Thanks Bloss, going to have to work with the back room and find some creative ways of getting compliance. The federation dormer window would be nice but I think we have no chance with the council due to privacy issues. 
So with the new floor joists is it safe to assume they would sit on the wall plate the same as the current ceiling joists? So to calculate the new floor height in the attic I would just use wall plate height + height of new joists (possibly 200)?

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## paddyjoy

> Spiral stair case could be an option for an attic conversion, takes up way less space

  Thanks yes spiral is definitely an option, or maybe even a stepsure StepSure Winder - Spiral Stairs, Staircases, Balustrades, Balustrading - Slattery & Acquroff Stairs Australia

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## Bloss

You might have to double up under the existing top plates if they are single now (as is likely) or use some steel reinforcing, but you should be bale to do what you say and regain the current ceiling joist depth.

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## paddyjoy

Thanks I was having a good think about this over the weekend and I think a dormer window is the way to go if we can get approval. Will give stacks of more floor space and will have no problem complying with BCA.

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## Bloss

There are all sorts of possible variations on a dormer window too which can help get around various restrictions on heights and neighbour site line impact etc.

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