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I want to expand my house upwards by adding another 1000ft2 level. I'm told that knocking the house down and build from scratch would be easier than dealing with all the issues. In my area I've been told construction costs 200/ft2 which would be rather expensive for a new 2000 ft2 house. What do people think?

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This is something you should discus with an engineer and/or architect. Without actually seeing the site, there is no real way to tell you if what you plan can be done. –  Tester101 Jan 25 '11 at 21:49
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Yeah, the knock-down suggestion actually came from a friend who is an architect. But they have their own view point. It is understandable that they would prefer starting from scratch. –  Peter Q Jan 25 '11 at 23:29
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You should talk to a structural engineer, they would be a better source to tell you how much work is involved in adding a second level. Keep in mind when your house was designed it was designed to carry the loads of a single story, adding a second could require major structural changes. –  Tester101 Jan 26 '11 at 13:15
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Have you considered buying a new house? –  Tester101 Jan 26 '11 at 13:32
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No. Maybe I should consider starting to make more money first. :-) –  Peter Q Jan 26 '11 at 22:02
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I've thought about doing the same thing (adding on an upstairs to my house). One of the simple problems is permits; the inspection offices want to deal with things they know, and building above an unknown.

Basically, your support comes from below; the new floor rests on the floor below, and the floors below on the foundation. If you need stronger walls, you need to start tearing things out (eg, drywall) so you can bulk them up, and you can't just add new load-bearings walls without putting some sort of footing in below them; that's near impossible in most construction.

There are typically tables of how much load a room has to be able to support in a given area; 30lb per square foot is pretty typical, but you have to remember that an unevenly loaded area often requires heavier duty walls to deal with the torsional and lateral forces.

I still haven't given up on putting a second floor on my house, but I know that to be able to do it, I'm likely going to have to strip the walls back to see what there is, which means either from the inside (plaster walls) or outside (wood siding), either of which is going to suck to replace.

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Joe, I've been told that supporting columns (whose footings are in the basement) can be added. –  Peter Q Jan 26 '11 at 4:43
    
@Peter : you'd probably be looking at a couple of grand to have an engineering firm take your existing plans, get them into whatever software they use, and then determine what additional support would be required, and give an estimate of effort and cost. –  Joe Jan 26 '11 at 13:20
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I'd have to agree with @Tester101 that without actually seeing the site, there is no real way to tell you if what you plan can be done, but one data point: my brother looked into adding a floor to his house, and the estimate he got was a lot more than he paid for the house 5 years earlier. I can easily believe that it would be cheaper in the long run to knock it down & rebuild, and would probably have much higher resale value.

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You could build over, rather then upwards using a metal frame, then just connect the two independent structures at the stairs. You will need a very good engineer, but at least there will be very few unknowns as the new frame could even sit on separate foundations outside of your current foundations.

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Yeah, I've been dreaming of the same. But I guess there would be the engineering and cost considerations. Do you have any stories to tell on this subject (I see that you're in the UK, not the US but still interesting) or are you a professional by any chance? –  Peter Q Jan 27 '11 at 17:21
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@Peter, given the land cost in some UK city, and the regs on listed buildings etc, buiding cost is not always an issue! In most of the UK 2/3 of the cost of a new home is the land cost. –  Walker Jan 27 '11 at 17:41
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That's sounds normal to me. Here in the US not necessarily so though. Around Washington DC that's true for some areas. I assumed that's the case for the area where I bought (upper middle class) but contractors and developers are asking outrageous money when they see where the house is. –  Peter Q Jan 27 '11 at 20:13
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