# Forum Home Renovation Structural Renovation  Building under house.

## mrsxtro

Hi all.
I have a 1912 Queenslander on 1970m2. At the road it is approx. 1m off the ground. At the back, due to the pretty substatial slope of the ground under the house, it is approx. 3m high. We have 5 rapidly growing children who are bursting the seams of this 3 bedroom house. We are trying to decide whether it is worthwhile building under our house, or are we better off moving somewhere else. So I am after some ideas and thoughts on the "building in under" process. We would like to add another 2 bedrooms, another bathroom, family room and new laundry under there (approx. 70m2 all up). We will need to consider excavation, restumping (including new steel beams for long spans), retaining walls, drainage, plus all the usual building costs. Any one done this sort of thing that can give me a guesstimate of the cost of the total job? Also I would prefer to have a bearer and joist floor down there. How would that compare in costs and also ease of building to a concrete slab?
Thanks in advance for any advice, thoughts or costs involved that anyone can give.
-mrsxtro.

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## bitingmidge

Three minutes isn't a bad time for a reply! 
I've done heaps of them, it doesn't matter how you do the sums, if you are going to do it properly it will be cheaper to build a new house! 
PM me with your email address (and suburb) and I'll get back in detail. 
In the meantime there's another thread hanging round in which a very similar question was asked! 
Cheers, 
P
(Waiting for all those..."no it's really cheap" replies!)  :Biggrin:

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## leeton

I did it about 10 years ago, but I already had the brick walls around the outside, but built a 6sq runmpus room, toilet and laundry with internal stair case, I found it reasonably inexpensive, however I built it all myself, including puting up massive   steel beams to hold up the rest of the house, that was the scariest bit, knocking out the existing stumps...but its still standing, I also put in a slab, that was the most expense I think...it was a while ago...had to get the concrete pumped in...geez the more I think about this it may not have been too cheap...lol, but worth the experience....Good luck.
leeton

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## journeyman Mick

No it's really cheap! (Only about 50 - 150% more than building from scratch  :Biggrin:  ). Timber floor down below will add substantially to the cost as it will require even more excavation and retaining walls and ventilation may be a problem too. 
Mick

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## Ashore

Have you considered an extension connected to the house at ground level , say two bedrooms with a bathroom between them   
Just a nother option / thought    
Thought for the day   Percentage of Africa that is wilderness: 28% Percentage of North America that is wilderness: 38% ; percentage of Japan that is forest is greater than 70 %

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## bitingmidge

We need more info on the slope! 
If there's a couple of metres of fall under the house, there's a fair chance it falls away rather sharply after that!   :Biggrin:   
A separate "Wing" will definitely be more cost effective (note I didn't say cheaper), but one would have to be careful to ensure that it fitted with the character of the house.  It doesn't have to be a replica, just proportionally right.   (not 2100 ceiling, flat roof, clear aluminium joinery please!). 
Cheers, 
P

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## Rubber

I have just done this so it is all fresh in my mind.  I don't know how big your house is so I have assumed a normal sized one  
Restump, raise and steel work                                  $20k
Slab  (depending if you want concrete under decks etc) $18k
Earthworks (not sure in your case as it sounds like you have alot of slope, dumping costs are almost 1/2 of this)                           $10k?
Retaining wall (sky's the limit, for I assume a fairly tall one) $8k?
Underslab plumbing                                                      $3k
Termimesh                                                                 $1k
New stairs                                                                  $1.5k 
You will probably need to disconect the power, gas, water etc so if any of these are out of date ie your switch board will probably be too high once rasied so it will need to lowered. So if it no longer meets the code it will have to be replaced.  Same for gas applicances. 
And then you can start actually building something. 
Don't forget to get it surveyed before you start. In Brisbane you need to be <8.5m from the highest point of your roof to natural ground.  ($600)  And then you need a Hight Certificate on completion.  It is always a bit iffy where natural ground is.  And in your case as the ground slopes away it could be your rear gutter.

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## mrsxtro

Thanks for all the input.
Just to clear up the confusion....
Yes there is quite a drop of land under the house but then it flattens out quite a lot (ie. the rest of the block is useable). Because of this we will not need to raise the house at all, just excavate a bit. The height under the house where we will build ranges from 2.6m high to approx. 1.8m high. I'll attach some photos so you can better see what I am dealing with.
Keep the ideas/experiences coming!
-mrsxtro.

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## Pulpo

The cost factor would depend on whether you intended to undertake any of the work yourself or had some mates helping. 
If you had a builder coming and doing most of the job I would be rather surprised if it was reasonable priced, in a relative sense. 
Liability is such a big factor, very concerned about changing existing footings, potential for a stuff up is greater than building a new or just extending. 
I have found a slab on ground to be cheaper than a steel sub-flooring system, piers, bearers, joists, however if you have your own engineered design it maybe cheaper. 
Other than helping a cousin re-stump his house I really have not had any experience in this area. 
Maybe you could hire a building consultant [builder who consults] for a couple of hours who could offer many ideas and suggestions. 
You would want to be concerned about over capitalising as well. 
Good luck 
Pulpo

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## Wildman

That looks like a relatively easy job, Personally I would do it all myself (I have a Civil engineering background from a previous career and access to professional concreting and welding equipment as well as to friendly plumbers and sparky's to cover regulations). You have plently of access to put in a couple of big concrete pads and steel colums in the corners and it would be simple to put in a few steel RSJ's to sit the house on. You might want to get them engineered though but there is not much excavation to be done and drainage should not be too difficult (drainage on a slope is easier than drainage on flat land). If you shield it from the street, you might even be able to get away with not telling the council, I dont bother if it cannot be seen from the street or the air (did I say that out loud?), it saves a lot of red tape and costs and as long as you are in there for a while, who is going to find out? Make sure you do it properly though, they will notice the house falling down. 
Cheers
Ben 
PS, advice is free but taking it may cost you. I will also deny I wrote this if the council turns up on my door.....the previous owner did it Officer...

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## mrsxtro

Thanks for all the advice.
If we go ahead....
We intend getting someone in to do the restumping, excavating, drainage, retaining walls and slab. We will probably do most of the building ourselves. My father is a very handy man and between him, my husband, my brother and myself we have completely ripped out and replaced 2 bathrooms, 2 kitchens, built 3 decks(including the one on the photo) and numerous other building tasks. I'm pretty sure we could manage the building stuff once all the hard work has been done. 
Am I being overly ambitious?
-mrsxtro.

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## dallas

FOR SURE BUILD UNDER... TONNES OF ROOM!... 
i'm currently in the process of building in under my house (built on piers, so removing piers and excavating under house), and i'm getting piers removed and excavated for $9K.. prob alittle pricier than DIY, but it'll be done in 2wks, and peace of mind as well... that includes eng. inspections, sizings etc, etc..  
i'lldig up some piccies of it shortly to give you an idea... cheap way of adding serious floorspace to your place....   
D

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## dallas

Ok, here are some before piccies of my underhouse (when viewed from garage) http://i17.photobucket.com/albums/b9...rhouseb4_1.jpg
and anotehr http://i17.photobucket.com/albums/b9...rhouseb4_2.jpg 
Some progress shots as of sat arvo with the piers removed, adn beams in place.   http://i17.photobucket.com/albums/b9...molition_1.jpg http://i17.photobucket.com/albums/b9...molition_2.jpg 
I'm gonna get the slab done and do the retaining wall mysefl (require small retaining wall up far end where level rises), and will knock in some windows for light.  
Slab is getting laid to 55mm below the existing garage slab level, to allow for 35mm battons and 19mm recycled timber floorboards...  
The only frightening part i reckon is to remove piers and install RHS members, so if you can get this done professionally, you should be right to do the majority of the work yourself!  
D

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## mrsxtro

Thanks Dallas for the photos.
Did you do that work yourself? 
Here's some photos of under my house.   http://groups.msn.com/AussieChicks/k...o&PhotoID=2066
This one is from the back looking towards the front of the house.  http://groups.msn.com/AussieChicks/k...o&PhotoID=2067
This one is from the front looking towards the back of the house.
The blue steel pole in both photos is where we intend to build from.
Hope that shows a little more clearly what we are working with.
-mrsxtro.

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## Theremin

See here for more discussion on raising Queenslanders: http://www.woodworkforums.ubeaut.com...ad.php?t=15387

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## tcns

> Ok, here are some before piccies of my underhouse (when viewed from garage) http://i17.photobucket.com/albums/b9...rhouseb4_1.jpg
> and anotehr http://i17.photobucket.com/albums/b9...rhouseb4_2.jpg 
> Some progress shots as of sat arvo with the piers removed, adn beams in place.   http://i17.photobucket.com/albums/b9...molition_1.jpg http://i17.photobucket.com/albums/b9...molition_2.jpg 
> I'm gonna get the slab done and do the retaining wall mysefl (require small retaining wall up far end where level rises), and will knock in some windows for light.  
> Slab is getting laid to 55mm below the existing garage slab level, to allow for 35mm battons and 19mm recycled timber floorboards...  
> The only frightening part i reckon is to remove piers and install RHS members, so if you can get this done professionally, you should be right to do the majority of the work yourself!  
> D

  Dallas, 
just a few questions - your situation is very similar to mine, I have a stack of 
brick piers with a brick surround. How much did your steel cost and did you just work out the span between the brick walls and buy the right size so no additional supports were necessary ? 
Thanks mate
Tom

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## ian

One thing to keep in mind is the living comfort in the old part of the house.
Queenslanders are on stumps to allow air to circulate UNDER the house thus keeping it relatively cool, especially in summer.  Closing in this space may mean that you need to factor whole house air conditioning into the cost.   
In Sydney, you'd split the block into two, sell one and use the cash to build a new house

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## dallas

No sweat guys, 
No, i got the piers removed and RHS members installed by a builder. I could have prob done this myself, but the hassell vs the cost vs the completion time just made more sense to get a builder... and like I said, i'm paying for peace of mind, speedy turn around, and not giving myself a hernia by lifting and digging! LOL! 
Span was worked out for each end, and additional piers were bricked and tied in to the existing piers at the beams end to give it additional support. Think about it... the end pier used to only support the outside of house and some floor load (whilst other piers took the rest of the floor load).. now i've removed the piers, that floor load is transferred to the outer piers, so they carry more weight, hence being strengthened by new piers tied in.  
After seeing the work progress (it's still going as you can see), I would 100% recomend getting the piers/RHS done professionally, (and also quickly!) and then allowing you to save $$$ on the other things like organising the slab/retaining wall, installing windows, plasterboards and fitting it out...   
D

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