Estimating construction costs

We’re considering a house that will need a bit of construction done to be suitable (to us). Since any work would be far off, and even then it’s only one factor in the decision-making process, we don’t feel right calling in a contractor to give us an estimate. But we still need an idea — even a rough idea — of what kind of costs we’re looking at. I’m sure lots of people are in similar situations, and am hoping the loose nature of IMHO will give us some food for thought.

We’ve heard about $100-$150 per square foot, but have no idea if that’s a reasonable number to work with, or if it’s applicable to what we want to do (basically add an addition to house a staircase).

Here’s a description of what we’re looking at:

It’s a two story home in Staten Island, New York.

On the ground floor, there is an existing exterior door.

On the second floor, there is an exterior door that opens onto an un-enclosed terrace. The terrace runs the length of the wall. The entire interior terrace wall (i.e., the exterior wall of the upper floor) is made up of about three feet of brick (almost wainscoting-like) at the floor; to the ceiling is glass. If we took all the windows out of the second floor, we could walk from the living room onto the terrace at any point along the wall (save stepping over the bricks).

The second floor’s door is directly above the first floor’s.

The goal is to connect the first and second floor with a staircase that replaces/takes up the same basic footprint as the terrace. As far as we can tell it will require:[ul][li]moving the second floor door to the opposite end of the wall; []building a staircase; []enclosing the staircase/insulating it; [] putting footings/foundation down; []building a vestibule/entryway on the ground floor; and installing a new exterior door on the ground floor. [/ul][/li]
Since both floors already have an exterior door, we’re hoping this isn’t going to require significant work to the house itself (i.e., no knocking through walls). There is the movement of the door, but since the brick ledge isn’t substantial, we don’t think (hah!) it has any structural component.

So, barring wasting some poor contractor’s time, how the heck do we think of this job?

Call up a couple of contractors, maybe an architect or two. Let them know the situation upfront, they’ll be able to ballpark a figure. Add about 30% to that. A lot of contractors wouldn’t waste their time, in fact, I wouldn’t, but you might get lucky.

Really no other way, sorry. There are way too many variables.

Your estimate of 100-150 per SF is probably low, you are moving stairs and doing foundation work. Both of them are involved projects. Unless the house is a complete steal, find a different property.

fisha-contractor

I agree there is no way to get an accurate estimate without having someone look at it. An experienced eye will be looking for things that you don’t even know to ask. For example:

Perhaps your proposed addition puts you too close to the property line or,
Covers too much of the lot or,
Will require relocating the weather head or electrical panel
Means replacing all the siding on that side of the house
Will require taking out a tree, which takes a special permit application
Is the 2nd floor terrace roofed?
Are you in one of those frikkin hysterical preservation zones?

That’s why the most you will get from photos is a loose guess. However if you’re OK with that, it is possible to get an idea. I’ll assume the balcony has no roof. In the big picture, the balcony is likely not worth the trouble to work around it and would be demolished. Thoughts on scope of work:

Permit. You’ll need one, so skip through the denial phase and go right to acceptance.

You can usually get free pipe location service from your local utilities which will give you a real good idea what you’re looking at. Search for a ‘call before you dig’ number.

I assume from your description you want to take out the 2nd floor windows but leave the wainscoat wall with any existing posts (no new headers or framing).

Demolition of terrace & 2nd floor windows.
Excavation & forms. Poured concrete foundation wall to below frost line. Assume no impact to buried utilities.
Wood joist / plywood floor.
New 2 story stud wall w/ exterior door tied in to existing structure (demolish as needed).
New roof structure, shingles, gutter. Assume OK to extend existing roof line and splice in to existing shingles.
Demolition of existing 1st floor exterior siding.
Demolition of existing 1st floor exterior door. Finish as interior doorway (no door).
Demolish existing 2nd floor door, wall over existing doorway, frame & finish new interior entry (no door).
New stairs & upper landing.
Trim out existing 2nd floor wainscoat wall where windows were removed.
Drywall & paint, insulation, porch light, exterior siding. Assume OK to splice in to existing siding.
Finish floor (Vinyl? Carpet?), finish molding as needed.
New exterior window(s)?
New exterior walkway, steps, landing?
Remove / relocate landscaping as needed. Assume no buried sprinkler system.
Enclose understair area, exterior door for garden tool storage?

That’s all I can think of from here. Finally, this here looks like a half decent rough cost estimating spreadsheet. Note that Staten Island is the 2nd most expensive place to build stuff. So solly. Luck!