# Forum Home Renovation Structural Renovation  Adding a basement

## LordBug

Having a conversation with some friends about the lack of basements in Australia got me to thinking how nice it'd be to add one to the home. It's probably not going to happen without a massive Lotto win, but at least dreaming is free. 
My curiosity is whether or not it's feasible to add a basement to an existing home, or if that's a bad idea and that rebuilding the entire house along with the basement is the better course of action. 
Also, does anyone happen to know why there's not much use of basements in Australia? 
Cheers

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## Bloss

You can do most things with enough time and money . . . 
So in sandy soiled Perth (if that's what you have) you could do so, but as a retrofit it would be costly and depends on your house construction type. Can't see what you would gain. 
Basements in the Northern hemisphere are and were a function of climate (cold)  and land shortage - neither of which are an issue here although well sited partial or fully underground dwellings can be a good idea in some parts of Australia (but not there by far the most people live).There are other factors, but mostly they come back to those two. 
Because of the more constant soil temperature a basement is good for storage of wine and some foods such as cheese, but even in Perth for much of the year would outside the comfort range preferred by humans (18-26C or so - humidity and airflow affect that perception, but that's the rough range) as it will range from 12-16 (and only if sealed - if you open it to the rest of the house or the air then it will equalise - as heat always tries to do). 
So maybe a though if building new and you can think of a good use that is worth spending the money on a basement rather than something else, otherwise why would you bother.

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## seriph1

some thoughts .... 
Reasons to not have a basement:  *Cost* *damp*-proofing requirements 
Reasons to have a basement  *soundproof * -  great for Home Theatre and other games-room type stuff *small temperature range* with massive thermal mass as insulation  -  wine storage, summer nights, winter nights *Storage*  -  can put a squillion things in a basement *workshop*  -  or cool store, model railway or other hobby area, study etc. *Footprint*  -  a larger home with lower overall land use

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## Bloss

> some thoughts .... 
> Reasons to not have a basement: *Cost* *damp*-proofing requirements

  Plus--- 
No fresh air (or thermal advantages lost)
No windows
Artificial light
Stairs and access generally  *Cost* vs other better options to achieve what you want 
As to 'pros' -  _soundproof - great for Home Theatre and other games-room type stuff_
Maybe . . .depending on the ceiling and activities above and at higher cost _small temperature range with massive thermal mass as insulation - wine storage, summer nights, winter nights_
If sealed and thermally leakproof - otherwise nope (or at least compromised) _Storage - can put a squillion things in a basement_
And in a well-insulation shed at a fraction of the cost with better access - ladder, stairs or a long ramp or a lift are needed for a basement - at higher cost _workshop - or cool store, model railway or other hobby area, study etc._
All problems in storage plus thermal issues, noise issues, access issues _Footprint - a larger home with lower overall land use_
Can't really argue with that but at higher cost than alternatives unless space/ block size an issue (eg inner city reno). Excavation to 2m or more for a residence is costly and can be technically challenging in a built up area and if there is rock and so on - and in this case we are talking about doing so as a choice, not because the site demands it. 
As I said - if you have the money and know that a basement will suit your intended uses (can't usually be all of the above without great compromise) go ahead. But look very carefully at other options first - especially cost vs utility. On sloped sites many of the disadvantages are mitigated by constructing partially underground, such as at back or side of an area under the dwelling, but always at higher cost than not doing so.

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## seriph1

Advances made with air and heat exchange systems in the USA and Europe have made the 'no fresh air' issue redundant.....that's not to say Australians will adopt the same principles .... we seem to often take the lowest common denominator of good design and merely apply the facade of it. 
No windows is certainly the situation but can be addressed with solar domes and light shafts, or basement windows that are really very funky in my opinion. You can also install an outside access door (code requirement in many US states) that can at least be partly made from glass to allow light in 
Artificial lighting is a fact of our modern lives  -  I feel the function our basement would primarily take is as a home theatre so low light is a benefit. In addition, on weeks like we are having in Victoria (45 here yesterday) being able to walk downstairs and be instantly cool - for free - is a real plus. 
Stairs are a pain to some people, especially as we age. My knees hate me when I make them walk up or down stairs, but again I have to recognize that more and more homes in Australia are two storey, so two + basement isnt really anything new, but it is another factor. 
None of this is intended to negate your position - I just reckon for some negatives, there can be positives .... not a BS sales-spin, rather a positive benefit to many things that are perceived as negatives.  
Building into the sides of hills etc. is what most Aussies do to get the benefits of optimal land use  -  I'd certainly do it if I didn't live on flat land.  
For our extension, we are seriously contemplating going down 2400 in order to put two storeys within a single storey Victorian facade. this will give us some benefits of thermal mass, without overwhelming the site with the height of two storeys ..... still very much in the planning stages but it is a likely scenario. 
Good discussion I reckon  :Biggrin:

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## sundancewfs

Having lived in Chicago for 5 years.... basements were a part of our life.
Building codes state that there must be an alternate exit route from a basement. windows are the way out and let light in. They are usually well types. Some of the older basements don't meet today's codes. We lived in a 3 bedroom one bath, house which was almost identical to what we now live in in Australia....but.... it had a full basement. We had a home theatre, workshop, laundry and computer/music area down stairs. It effectively doubled the size of the house. As far as drainage and waterproofing, If you can build a swimming pool to keep water in, you can build a basement to keep water out. having said that basements in the midwest have a sump and pump in the floor of them and a battery backup pump in case of power failure. Chicago isn't exactly hilly, being as its in the middle of prairie land, so drainage can be a real issue. They seemed to have worked it out...
Having said all this, a friend of mine, who has lived in Chicago all his live said "Its not a matter of if your basement will flood, just a matter of when."
Oh and there a great place to be if there is a tornado.

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## GraemeCook

Sundancewfs Chicago experience is pretty much the same as out Boston experience, except we let the Mid-Westerners keep their tornados. 
Watching a new house being built, first the excavator arrived and dug a 12 foot deep hole, then they started with the dampness control and insulation that went below and around the basement, then they built the basement and finally they built the house on top. 
Putting all that underneath an existing house without undermining the footings sounds daunting.   Digging such a hole without and big excavator is frightening. 
Years ago we looked at building a new house in Hobart with a basement but there was solid (geologist called it massive) dolerite about a metre below the surface.   Costs would have been prohibitive, and as builders /architects rarely build basements in domestic buildings they would have been learning at our expense. 
Cheers 
Graeme

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## intertd6

Every job I did in sydney had basements or basement carparks ranging from sandstone to sand. With rock saws mounted on 30 t excavators nowadays, its not a big slow deal anymore & grout injected bored piles handle the messy foundation materials.
For years they tried to keep the water out with tanking but it leaked almost evey time
now they seal with filter cloth, mesh & shotcrete or similar & catch the small inflows with spoon drains piped to pumped sumps
For a better finish a wall is placed on a hob giving a cavity between the internal space & the sometimes wet walls
Regards inter

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## GraemeCook

> Every job I did in sydney had basements or basement carparks ranging from sandstone to sand. With rock saws mounted on 30 t excavators nowadays, its not a big slow deal anymore & grout injected bored piles handle the messy foundation materials.
> For years they tried to keep the water out with tanking but it leaked almost evey time
> now they seal with filter cloth, mesh & shotcrete or similar & catch the small inflows with spoon drains piped to pumped sumps
> For a better finish a wall is placed on a hob giving a cavity between the internal space & the sometimes wet walls
> Regards inter

  
Correct me if I am wrong, Inter, but weren't all your projects large scale commercial buildings.   The economies of scale of such structures and the exorbitant CBD land values would justify the cost of of a basement. 
It would be much different doing this on a single occupant house.  
Cheers 
Graeme 
PS:   Dolerite, aka bluestone, is much harder than sandstone.

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## intertd6

Yes mostly units but a couple of houses as well, mind you they were at the upper end of the scale, one house excavation was 13 meters deep & took 10 months.
Land is a scarce commodity in sydney so you nearly always have to go down before you go up.
regards inter

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## GrahamC

In my new house I am kind of getting a basement - really just an oversized garage with the same foot print as the house. It is built into the side of the sloping block. It only goes down 2m so there will be windows /  all around. I hope I will be getting the best of both worlds.

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