They all look OK. The paired windows make this a Colonial Revival so don't feel obligated to recreate a Georgian or Federal/Adam style. If you use different slopes at the hip roof the cornices will be difficult to align at the corners unless the wall top plates are at different heights. The cornices seem a bit skimpy. What you call a Mansard is not steep enough for that title but it was common in the Colonial Revival period.

I am not a personal fan of mansard style roofs and though I am struggling with this decision on my house, I really like the hip on yours. Please jump over and throw me an opinion on mine if you have one.

bry, its great to have some company:) Funny, I like the
gable end on yours. I like the consistency of having all gable roofs and as you mentioned the dormers and the windows on the gable will be great when you decide to finish out the
attic. Also you'll have more usable sq footage with the gable.

Renovator, thanks also for the input, I'm not really trying for exact Federal/Georgian but am trying to steal elements from each without making it look too a-historical.

As for my bastard hip, I too am a little concerned about finding a good framer who
can handle it but I guess I'm afraid that the 7:12 standard hip will look to squat.

I agree that my cornices could have a little more substance.

I don't think the steeper slope of the sides of the hip will make a substantial difference. Any roof ridge will appear foreshortened, in other words, the roof ridge will look lower when viewed from the ground unless you take a telephoto shot of it from extremely far away; that's essentially what an elevation drawing is and you will never be able to see that in reality. The apparent ridge height will not be changed by the design of the side parts of the hip except to make the ridge longer left to right. If you want a longer ridge use the gable roof.

The "French" roof is not nearly steep enough to be compared to a Mansard roof. The roof shape you have drawn is a very common Colonial Revival feature that gives the impression of a taller roof because the top of the sloped roof is closer to the viewer and therefore less foreshortened.

I am surprised about the height restriction. Tell me the city, the zoning district and the height of the ridge above grade.

Renovator, the irregular hip may be more trouble than its worth.
The "French Roof" maybe with a 12/12 seem to be what most developers are resorting to in this city since they changed the zoning.

The city is Newton MA and its not the ridge height that is the problem but rather the countable living space (FAR) that a full sized attic would yield. So if I used any slope greater than 7:12 I would have to shrink my house.

I don't think they thought through the change that well because they are now complaining about all the flatter roofs that are popping up.

As for the French roof with membrane top, I'm curious if you have any idea how well they perform. In the past leaks where always a worry but I now see so many of them that the leaking concern may be a thing of the past.

I like the elevations. Its a close call but I would go with a gable. It might look different in real life but on paper the gable looks better to me.
I wonder if you might want to consider a small round window for the front gable for a little extra visual interest. It may look a little blank.

I finally figured out that the French roof end elevation is mislabeled as 7/12 instead of 10/12 and the gable roof shows a hip instead of a gable end elevation.

I live in Newton and know the city lawyer who authored the Gross Floor Area rules. I wonder if the house couldn't be tuned so the pitch could be increased to 8 or 9 in 12.

Renovator, hello neighbor... small world:) I hope the lawyer wasn't my favorite city councilor. He is usually the one voice of reason in the City especially when it comes to Real Estate.

I would love to tune the house to get a steeper pitch (other than narrowing the house depth or reducing sq footage). Do you know of any tuning/solutions.

The lawyer I know is on staff and deals with regulations, etc. so she would know the intent and interpretation of this complicated requirement.

Tell me the outside plan and height dimensions, the zoning district, and lot size. The basement garage is a bit of a wild card since it appears only one side of it is more than 4 ft above grade.

Who did the Gross Floor Area calculation and do you have a summary of them? It good to have all of that information in a chart for the building department.

I prefer the gable. I feel like you either need a stilted arch above the upper door in the front gable, or an oval window. That part seems a little blank.

Also you don't really show a side elevation with the gable roof.

Renovator, The building is 52 ft
wide by 34 deep with a 2ft bump out for the front gable. It’s in an SR3 zone (old
lot) so allowable FAR ratio is 0.48. The Lot size is 7'934 sq feet sa max GFA is 3,808.

Below are the summary calcs. I am working with a designer but I am doing a
lot of the detailed work including the FAR calc/tweaking myself. (I’m actually
a P.E. and have my MA CSL ... first home though).

I’ve also attached a jpeg of the
spreadsheet. I also double checked it using the autocad areas.

As mentioned. the basement garage is exposed only on the front side, so the basement FAR calc is based on the ratio of 20ft to
the total perimeter.I wonder if the building
department actually goes through each calculation in detail or just does a
quickie sanity check.

Palimpsest, yes I agree on the
empty gable and am debating between a round or oval window or something else I
can steal from pics of old colonials, a plaster casting of the houzz logo
perhaps. I may be missing something but
it seems to me that a 2d side view of a hip or gable roof would appear the same
if they have the same height and the same front and back slopes i.e. the base
width and the height define the same triangle. It would only look different
from an angled perspective.

But the gable end would have eaves and a soffit and fascia up under the peaked part of the roof as well, and probably an attic window or some sort of ornamental gable vent as well. Maybe it's not a finished drawing, but it's missing a lot of detail it seems.

palimpsest, I knew I was missing something. I did the gable option as a quickie just to
see if I liked it better.

One reason I am leaning towards the hip is that there is a similar colonial
across the street with a gable roof. Not a great reason but just a little tilt
on the scale.

Also in theory at least it seems the hip would look more grand but often I see hip roofs
that look rather weak. I am thinking that it is usually because their eaves are
rather shallow and their cornices are typically thin which makes the hip look
strange, like an ill fitting hat. I am hoping a 14" overhang and a 16" cornice (maybe some dentils) will take care of that.

The Dept of Inspectional Services usually expects the dimensional information to be shown on the survey. And the surveyor is required to come back after construction to verify that it was build as drawn.

What is the width of the lot? Is it wide enough for a 52 ft house with a 10 ft setback on each side?

On some of the drawings the first floor appears to be close to 4 ft above grade. Where it gets to be 4 ft or more the gross floor area will be increased.

If the house is the minimum setback from the street, a person standing in the middle of the street would only be able to see a very small part of a 7 in 12 roof. Each additional foot of slope reveals more roof and a higher ridge but although the 10 in 12 truncated roof will show more roof, it will have a half or less height ridge line. True Mansard roofs are full top stories with windows projecting from an almost vertical wall disguised to look like a roof.

Moving the house back on the lot would show considerably more roof.

The lot is 80 feet wide. I have a little over 10' and 12' at the pinch
points towards the back. I’ll need to double check the exposed basement to make
sure no more than 4 feet is showing. The lot slopes left to right so I’ll have
to build up the left hand side with retaining walls to get a flat site and of
course bury the basement.

Not seeing the roof from the curb would be a problem. I can’t really move
the house back as my backyard is already kind of small. Do you think a 7 in 12 gable
would give more presence than the hip?

A house down the street was just built with a truncated roof at 8.5 in 12,
and a flat rubber EPDM top. I wonder if it’s worth the added cost and potential
for flat roof headaches. Any thoughts on the rubber roof option?

My house has that kind of roof but the slope is 12 in 12 and the height is probably over 10 ft. A single-ply fully-adhered synthetic rubber roofing membrane is as good as the detailing of the penetrations. The slope will be a minimum of 1/4" per foot. If you plan to use the attic, a gable roof will have no structure supporting it other than the rafters themselves. A truncated or hipped roof requires additional vertical support to beams in the attic floor. The old roof framing of these kinds of roofs is no longer allowed even though it has worked for over a century.

The height of the exposed basement wall is "measured from existing or proposed grade, whichever is lower, to the top of the subfloor of the first story". That rule is intended to prevent increasing the allowable Gross Floor Area by filling the site. Perhaps you should review that rule with the zoning officer.

How much does the site slope across the house? You should draw the existing and final grades on the elevations. If it is more than a couple of feet you might need to review it with the city or a zoning lawyer.

You can look at the design and zoning calculations of nearby houses in the city records.

I just realized the gable option wont work. It seems, I would need to lower the slope even further than 7 in 12 to meet FAR rules regarding keeping the ratio of the area under a 7 ft plane vs area under a 5 ft plane to under 50%.

So it seems I need to decide between a hip and a truncated roof which I need to look into further as far as additional cost/maintenance etc.

The land doesn't slope too much maybe 2-3 feet and I was able to keep the exposed basement wall will be no more than 4 ft above existing or proposed grading. My civil engineer/ site surveyor will sett the final elevation based on the plot plans.

I didn't see a problem with the gable roof. Are you taking the horizontal measurements to the inside face of the rafters? You would need an accurate section of the structure to be sure. I assumed the rafters and attic joists would rest on the top plate of the exterior wall.

You wouldn't have to reduce the area of the house by much to get an 8 in 12 slope.

Ive attached the 1/2/ story calc diagram.

I may be wrong about the gable but it seems that the problem is that the ratio of the area of the plane under 7 ft goes up relative to the area under a 5 ft plan as compared to the ratio for a similarly sloped Hip roof.

With the hip, the 7 ft rectangle is smaller than the 5 foot rectangle on all 4 sides because of the 4 slopes (see pic). With a gable only having two sloping sides, so only 2 sides (the widths) of the 7 ft rectangle would be smaller than the 5 ft rectangle and the lengths would be the same. In my case this would bump the ratio of the two areas to over 50%.

I thought about reducing the area of the house to allow for a steeper slope, but it is my understanding that once you go over the 50% ratio, your stuck with the whole attic counting against you (at least the 5 ft rectangle). So in my case If I go to an 8 in 12 from 7.5 in 12 I would need to reduce the house sq footage by about 20% (at least 625 sq ft). Unfortunately they don't prorate the 1/2 story calc based on how much the ratio is over 50%.

Of course I may be wrong because I just noticed a 7 in 12 gable being built that is wider than what I am proposing. Am I missing something. I do plan a visit to Inspectional Services to check out some of these permit applications.

I think it only the floor area below where the width of the 7-0 line is more than 50% of the width of the 5-0 line.

The thickness of the exterior wall is important and the detail at the rafter tail can make a big difference. Is the exterior cladding brick or stucco? You did not draw the top plate of the exterior stud wall but I think your placement of the rafter is odd and causes the width dimensions to be greater than they need to be.

The only reason to raise the rafter tail is to create more wall above the tops of the windows and that can be achieved by raising the second floor ceiling height.

By raising the second floor ceiling (if necessary), lowering the rafter to wall connection and making the attic floor framing deeper I think you can make the roof slope 7.5 in 12 and possibly 8 in 12. Taking a foot off of each end of the house might let you have a 9 in 12 roof slope.

The house will be 2x6 with stucco. I recently raised the 2nd floor to 9 feet to give me some more room above the windows so I do have room to play around with lowering the rafters and maybe taking a foot out of the width.

What did you mean by "making the attic floor framing deeper." Do you mean using 2x12s or raising the attic joist framing like in a tray ceiling or vaulted ceilings.

Also am I understanding the 1/2 story calc properly for a Gabled roof and that it would always be shallower than a hip to meet the 7ft/5ft ratio or am I not getting something.

There are two ways to connect the lower end of rafters to a wall. The one you show is not the usual one although it is the one I always try to use because it provides more space in the attic and more wall above the windows. In that design the rafters sit on a 2x6 sill plate mounted on the floor deck of the attic.

The other way is to put the raters on the same top plate as the attic joists and nail them together. That reduces the attic floor area and allows a steeper slope.

Making the attic floor joists deeper also helps. You are trying to reduce the floor area of the attic for a given building width.

The 7 ft rule says you can have rafters higher than 7 ft for only 50% of the width at 5 ft above the attic floor. Only where that the 50% limit is exceeded is the floor below it counted as Gross Floor Area. It may seem complicated but its the only way to do it without knowing the roof slope.

I drew the gable slopes and found that you can use a 7 3/8" slope if the rafter is set on the wall top plate (LOW option) or 6 1/2" if the rafter is set on a sill plate on the attic floor deck (HIGH option). The ridges would be the same height but the cornice would be 15" lower for the LOW option. That might not be a problem since the second floor has a 9 ft ceiling but you should to draw the elevation to see for sure. I set the window the same as in my house, built in 1891 with large decorated cornices.

There doesn't appear to be a difference in the roof slope calculations between a full gabled and a fully hipped roof. I don't know about the truncated roof.

One thing I think you might be missing is that all of these sloped roofs will be foreshortened when viewed from the ground and appear to fall away and disappear. But the pediment end of a gabled roof will be vertical and will not appear foreshortened. You will see the full height of the ridge and the true slope of the rake. I would only use a hipped roof to reduce the apparent size of a big roof. You have the opposite problem and the gabled roof seems to be the only reasonable option unless you are willing to cut 200 to 300 s.f. out of the house.

The insulation is shown in the attic floor. If you plan to have mechanical equipment or ducts in the attic or you want to store anything temperature sensitive up there, the insulation should be moved to the rafters. The best HVAC system for this area is hydro-air. It uses a high efficiency gas-fired condensing boiler in the basement, condenser/compressors outside and two air-handlers, one in the basement and one in the attic to avoid vertical ducts, shorten them and create two separate control zones. For this system the insulation must be placed in the rafters whether you intend to seal the attic or not.

Thanks again Renovator,
Is that your house above...I love your cornices. I’ve been thinking about
adding dentils and/or corbels and am definitely inspired. What are the approx.
dimensions of the overhang, cornice and frieze? My overhang is 18" from
the studs. (maybe 14" from the frieze). I like a prominent overhang but
don't want to go Frank Lloyd Wright on a colonial.

Following your suggestions, I dropped the rafters to sit on top of the wall and
used a 2x12 joist which together just barely allows for a 8:12. Unfortunately I
am now at 36' 6" above the lowest grade (4ft of exposed basement). I
am calculating the average grade plane now as a first cut and will soon have my
land surveyor's calc to see if am under 36’.

I wouldn't mind a gable roof but am still confused on the 1/2 story calc.
Based on my reading, it seems that they refer to the area under the 5ft
and 7 ft planes and not just the width. If that is the case it would seem that
a Gable roof would need a lower slope than a hip. I have a call into ISD to
clarify.
"a) Gross floor area shall include:

ii.
Any floor area above the second story, whether finished or unfinished, that
meets all of the following criteria:

1.
It lies below the area of a horizontal plane that is five (5) feet above it and
which touches the side walls and/or the underside of the roof rafters;

2.
Is at least seven (7) feet in any horizontal dimension, as measured within the
area having a wall height of five feet or more;

3.
Has a minimum ceiling height of seven (7) feet on at least 50 percent of its
required floor area; and

4.
Has a floor area of not less than 70 square feet as measured within the area
having a wall height of five feet or more."

From
#1 and #3 is seems to say that the floor area is based on the 5ft area and not just
the 7ft area. I hope I'm wrong though.

I've heard
that hydro-air is great (but expensive) and will look into it. A couple
concerns about moving the insulation to the rafters is that I would have a
large additional and unused space to condition and that I may have issues with
excess moisture in the attic. I will need to do some more research
on this. What is the next best option that doesn't require insulating the rafters.
It seems most developers are putting ducts and a secondary HVAC system in an
unconditioned attic and a primary HVAC in the basement. Obviously this is not
so good as far as efficiency goes.

Yes, that's my house.

In my section the ridge is 34'-6" above the ground even if the first floor is 4 ft off the grade. Could the average grade add 2 ft to the height calculation?

The truncated hip that you called a French hip would add about 460 s.f. to your gross floor area if the interior truncation occurred at 7 ft above the attic floor. To avoid creating gross floor area, the interior truncation would have to occur at 5 ft above the attic floor.

For a regular hipped roof the floor is calculated exactly the same way as a gabled roof.

When item 3 refers to the "required floor area" I believe it means the area below and between where the 5 ft high plane intersects the bottoms of the rafters. The rest of the floor is exempted by item 1.

Heat loss and gain in an uninhabited space is only through the surfaces of the exterior enclosure so if the rafters are well insulated there is no initial premium except the additional quantity of insulation since the area of the roof will be about 17% greater than the area of the floor. The constant heating and cooling loss from HVAC equipment and/or ducts in an unconditioned attic will be a great deal more costly than the one time expense of additional insulation and you don't have to pay to air-seal the ceiling below. IMO insulating the rafters is always a net cost savings. The leakage from the equipment and ducts will easily remove any moisture.

My brother in law recently told me he wished I had insulated the rafters of the house I had designed for him so he could store things in the attic without worrying about the temperature. I sent hmm a copy of an old email where I told him he would regret taking his contractor's advice to insulate the attic floor instead of the rafters. That house was built 15 years ago. I haven't designed an unconditioned attic in 25 years. The same goes for hydro-air. The energy efficiency will pay for the system eventually and I don't like putting a gas-fueled device in an attic.

You mentioned what developers do as if that might be helpful. Are you a developer?

I double checked my ridge height and it is actually 35' 4 1/4" from the 4 ft below the first
floor subfloor. I’m not sure why we are a
foot apart though. I’ve attached my cross section.

No I’m not a developer but was just wondering what the next best option is
so I can have some frame of reference as I research the hydro-air system.

The steepest allowed roof slope by my calculations is 7 3/8" per foot which creates a ridge 10 1/2" lower than an 8" per foot slope. I found an 8" per foot slope resulted in the width at a height of 7-0 being 60% of the width at a height of 5-0. That puts 34 s.f. of gross area in the attic which would be easy to remove from the house..

that makes sense. My ridge height is based on an 8 in 12 slope which works if the 50% ratio rule goes by areas and not by widths. I haven't heard back from ISD but will follow up on Monday.
Again thanks you so much for all the invaluable help:)

I looked up the original proposal for the 2011 Gross Floor Area (GFA) change to the Zoning Ordinance and found the twisted logic that led to the current arcane rule.

The definition of Gross Floor Area above the highest floor level (ie under a sloping roof) was borrowed from the requirements for Habitable Space under a sloped ceiling in the 2009 IRC (since revised). The code said, "R305.1 Minimum height. Habitable space ... shall have a ceiling height of not less than 7 feet." "Exceptions: 1. For rooms with sloped ceilings, at least 50 percent of the required floor area of the room must have a ceiling height of at least 7 feet and no portion of the required floor area may have a ceiling height of less than 5 feet."

The 2011 revision to the Zoning Ordinance used the above requirements not to define Habitable Space but to define GFA for uninhabitable as well as habitable space under a sloping roof. In a proposal, the requirements for including such a space in the GFA were summarized as : "Included if it meets the dimensional definition in the Building Code of a habitable room (70 sq. ft. or more, with minimum ceiling heights of 7’ on at least 50% of its area and 5’ ceiling heights on the remainder).

So, using this new insight into the wording of the rule, it appears that if the area measured at the 7-0 height is LESS than 50% of the area measured at the 5-0 height, then NONE of the area measured at the 5-0 height will be included in the GFA.

Conversely, if the area measured at the 7-0 height is MORE than 50% of the area measured at the 5-0 height, then ALL of the area measured at the 5-0 height will be included in the GFA.

You should still verify this with Inspectional Services.

The only way I can think of to make the roof taller/steeper is to build a raised floor above the attic floor structure which would add to the cost. City acceptance would depend on the zoning officer but I got away with it in Cambridge where the zoning officer is very strict.

I was afraid that they would want to include all of the 5 ft area. I'll confirm with ISD and let you know what they say.

I like the raised attic floor option. I can just imagine the conversation that went with its justification. I would think a raised or vaulted ceiling strategically placed so that more of its area is under under the 7 ft section rather than the 5 ft would also do the trick. I have a raised tray ceiling in my master but because its in the corner of the house it actually reduces the 5 ft area more than the 7 ft area so the ratio goes in the wrong direction.

It seems that the only thing I could raise that would help is the
ceiling over the L-shaped stair/central hall way. I wonder if that would look too strange even if I can get a Gabled roof out of it.

I just saw a new house being framed so that the ceiling of the 2nd floor center front room slopes up towards the center of the house and therefore takes out more 7 ft area than 5 ft area. I would bet that was done to game the FAR.

The old habitable space rule was measured to a furred ceiling but the GFA rule is measured to where a horizontal plane touches the "underside of the roof rafters" whether the space is finished or unfinished.

I suppose if the members are large enough it is possible to raise the attic floor above the top plate of the walls. The small portion of sloped 2nd floor ceiling could be left exposed or a hung ceiling could hide it and perhaps hide ductwork.

Or a raised floor in the attic could act as rafter ties and enclose ductwork.

These options might be expensive but its the price for maximizing floor area on a relatively small lot. My house is the same size as yours but on a 20,000 s.f. lot.

The raised ceiling didn't quite lower that ratio enough to use a 8 in 12 gable. I am thinking of going with the 8 in 12 hip and two decorative chimneys on each end (or midway up the hip) to give some more mass/presence to the hip. Ive seen lots of historical homes with hip roofs and double chimneys and IMO it really makes a difference. Im just hoping the fake chimneys will look real enough. Its a stucco home so I think a stucco chimney would work.