Don't think of it in dollars. Think of it in terms of kicking your self for not doing it. It will be less expensive doing it now that later.

We are tending towards getting it but have to get the price negotiated and want to be reasonable / fair during negotiation as I read many threads where people have posted its costs around 50% to get bonus done

OK so as I understand, they quoted you for custom home $120/sq ft, but for bonus room they gave you a discount -$4/sq ft. So if let's say bonus room is 16x16: Your total discount is $1024. A whole $1000 off the custom home price.

@Brian - yes you are correct. any idea what it really costs and what would be a fair?

You should talk further with the builder. I'm guessing, but I'd suspect that the unfinished attic space above the garage is to be enclosed and roofed using the most economical 2X4 roof trusses, not designed to carry either a human occupancy live load or dead load (or both). To make the space habitable, it's very likely that either the roof trusses will have to substantially strengthened or abandoned entirely and the roof framed with conventional floor joists, sheathing and roof rafters. Depending on the size of the garage, a column inside the garage could be required or joists which will clear span and carry the combined live and dead loads of the new habitable space.

@virgil - its a 200 sq ft bonus space on top of a 2 car garage

In 2009 the builder charged us 12k for a 275 sq ft bonus room with full bath. That is $43 a square foot. Builder grade carpet, linoleum and formica counter.

For safety and comfort include the cost of spray foam on the bottom of the bonus room floor sheathing even if it is only an inch or two.

The "bonus" in bonus room refers to the contractor's potential benefit not yours. The only way you could have received a competitive price was to include the bonus room finishes as an alternate in the original bid which IMO should be standard procedure. To get a fair price now you would need to put the bonus room work out to bid. Of course, there might be additional costs and time involved but it would be a net savings.

If you want to play hardball, write up a detailed description of the of work and include the original builder in the list of bidders to whom you give it. You don't actually have to give it to other contractors unless your contractor declines or offers another "unresponsive" bid.

@JDS there is no contract yet. We only got the first draft of numbers and were given a $XXX,XXX with out any detailed breakdown . $X for the plan as is and $x + ( 120 x 200 sq ft for finished bonus = $x + $24K )

I can't imagine a more ridiculous way to price a house project. Is this part of a developer owned sub-division? Can you finish the bonus room later?

In other words, will the garage attic floor and roof strucrure need to be modified in order for the space to be habitable or is it structurally ready for finishes? Would insulation and windows be added? You haven't actually told us the complete scope of the work.

@JDS no.. a custom home in a lot - not a new sub division development

Many of the costs of bonus rooms above garages are measured long term: energy, comfort and health. It's tough finding contractors or designers proficient in making these spaces healthy and efficient. There's a lot more to it than finishes and cost per square foot.

Will the HVAC system need to be extended to the space? Will that increase the size of the equipment?

Luv Mann, you are making this hard on yourself. Have a meeting with your builder and ask him what extra work is required to make the above garage space habitable. You've received some good explanations here of the range of possible extra materials and labor.

After your meeting, you will have a much better basis for making your decision.

Is you post here simply a way for you to fish and try to find ways to negotiate with your builder?

@JDS the house is 2 floors - so 2 systems will be used - 2200 on first and 800 including bonus room on the second..

@Vigil I just want to make an informed decision rather than blindly negotiate

@liv mann, I would recommend to look at what else changes, for example, how will the roof line change, will there be need to run plumbing to that room, is it brick exterior, how many windows would be added etc. Based on what it will take to do the change you would be in better place to negotiate and talk to builder about the price.

@jimpats - Plan / house structure allows for bonus - no need for plumbing as the bonus shares a bathroom with one of the bedrooms like a jack and jill bath. 2 windows per the plan - ballon price quote provided is for all brick exterior

To what does 2200 and 800 refer?

I an having a terrible time understanding what we are talking about. I dont think anybody can tell you what a fair cost per square foot of your bonus room should cost without a TON of additional information. Even then, what we think is "fair" may not be what your builder is willing to do it for.

A sq ft cost is derived by dividing the total cost of a house (without land or site improvements) by the habitable floor area. It will vary greatly with the design of the house and can only be used to compare houses of similar size and configuration. It cannot be used to predict the cost of a portion of the original house.

Your builder should not be discussing the average cost per s.f. at this stage of the project. If there are design documents, he should be able to do a take-off of the labor and materials required and add his OH&P. It sounds like you are dealing with his marketing staff.

Who designed the project? Are the drawings his or yours?

@JDS 2200 sq ft on first and 800 sqft on second in reference to your post on HVAC needs to bonus room ( 800 sqft on second includes bonus )

@schreibdave thats why I have given how much the rest of the house was quoted for to compare with the cost of bonus. Builder may not be willing to, hence i can make an informed decision to walk away or negotiate the cost or negotiate upgrades in other areas.

There are too many variables to discuss this as a "CPSF for this" vs a "CPSF for that." For example, will your builder have to beef up the framing that supports your bonus room? How much additional exterior brick will be needed, if any? How many windows? And of what quality? Does finishing that space create special challenges for the insulation sub contractor?

Not to mention climate matters a decent amount when we start talking insulation. I think we can guess that you are using some stock plan and that there are zero exterior changes for this bonus room. We can also guess that the hvac changes are modest. So we are potentially beefing up floors, insulating and finishing space. Lots of educated guessing of course.

More guessing - southern US climate, carpet, no cabinets, modest trim, 8 ft ceilings, flat paint 2 coats, same color as rest of house?

See how much guessing is involved?

But I like to guess. $30 a sqft or $6k. But I'm going to guess this is a potential huge profit item for your potential builder. I really do like to guess!

Guessing is fun as long as you don't have to explain why it was wrong later, or worse, pay for it.

If I am forced to guess, I imagine what I would be willing to pay for the work and then double it.

I'll play along, my builder charged us $50 a sqft to extend a basement closet by 14 square feet. This involved taking out the previously studded back wall, moving it by 2 ft and then it required a few extra 2x4s, maybe a sheet and a half more of sheetrock, a litle extra mud, and paint, 4 more ft of baseboard trim and an additional 14 sq ft of carpet. I know that the carpet alone cost about $5.50 a sqft.

Didnt involve any electrical, plumbing, cabinets, light fixtures, architect drawings, insulation, windows, siding, roofing, etc. Also pretty unlikely to require any warranty work since it's a closet.

By comparison if I divide the cost of the rest of the house by its square footage, I get $163 per square foot. That does include the building lot, base layer of driveway, no landscaping, no appliances or light fixtures.

That's just one example of what is involved in comparing CPSF for one thing to another. Change some of my variables above and you would get different outcomes.

Recently a builder slipped and told me(complaining about appraisals) that it only cost him $40/ft to do the bonus room but the banks gave him same price/ft value as the rest of the house for it.

Whoever thought of the term "Bonus Room" was a marketing genius. It implies to the consumer "free space", yet it's anything but free. Online plans list the bonus space separately, leading consumers to think the house plan is smaller /more affordable than it actually is. If the consumer hasn't read /educated himself, one of two things is likely to happen:

- He mentally counts on that space being used ... and then -- after buying the plan -- he discovers that building will be more expensive than he thought, leaving him with the uncomfortable choice of over-spending or not getting the room he'd anticipated.

- In trying to save money, he says to the builder, skip that for now --thinking he will finish it himself later -- and he doesn't realize that this means the builder won't complete the flooring to the point that it is a habitable room, so it's not a realistic, affordable project later.

"Bonus room" is more than a little misleading.

This is also why I've come to the conclusion Cost Plus is a better way to go than Fixed Priced. Transparency in the cost.

@David Cary

southern US climate, carpet, no cabinets, modest
trim, 8 ft ceilings, flat paint 2 coats, same color as rest of house -- Yes , Yes and Yes

using some stock plan and that there
are zero exterior changes for this bonus room. , hvac changes are modest. So we are potentially beefing up floors,
insulating and finishing space. Lots of educated guessing of course. - Yes

Another point about Bonus Rooms is they really do change what you envision about the size of a home. A 4000 sqft home in which 300+ sqft of the home is the Bonus room will never seem as big as a 4k sqft older home before the 'Bonus Rooms' trend came about.

If you are comfortable paying based on a SF number, why don't you simply total up the habitable square footage, with and without the bonus room, and pay the builder's SF cost for which ever option you prefer?

After all, it's just more or less square footage at the same price per overall SF...

Are you paying a higher SF cost for the kitchen and toilets, and a lower SF cost for the garage...or a single lump-sum cost for the entire house?

Do you see how a SF cost makes no sense at all? As for negotiating with the builder, do you have any leverage to negotiate?

The Fixed Price Math I've been given(NC market):
$110/ft for Main Floor

$100/ft for Second Floor

$40/ft to Frame Bonus Room

$60/ft Garages and Covered Porches

$25/ft for Basement

Do you buy the house by the square foot? Or by a lump sum? Or like a roll of salami--just give me a half-pound please! :-)

I'd like to meet the contractor that would come out to my house and frame the bonus room for $40/ft.

My guess is that person doesn't exist, because no part is done indepently of any other part without completely up ending the calculations.

Mrs. Pete is right on. Marketing genius!

Good luck with your build. Looks like it's going to be a bumpy ride.

no that was included in overall house. i.e. framing the entire house including the bonus but NOT finishing the bonus like the rest of the house.

@jpniner Cost plus is a huge nightmare for first time home owners as many things needs to be monitored . If the builder wants to , he can add extra costs all along and the owner would have no control? I am saying in general though ..and not by experience.

Since the bonus room is already framed, HVAC and elect is installed, that price is COMPLETELY insane. All you need is sheetrock, trim and carpet and lighting. That shouldn't be ANYWHERE near where the GC is pricing. The GC is trying to make insane profit here!!!! Not unusual! Because at least 99% of the people have NO idea what it costs to build a house. I personally would have it done later after the build.