Geometry for the Cobb-Hepburn House, Part 1

When does geometry enter into the design and construction of a building?
Not at first.
Only when the basics are answered can layout and design begin, can geometry be considered.

The design of any building begins with need, ‘What?’ and ‘Why?’.

Next comes, ’How big?’, ‘Where?’

Then, ‘What material?’, ‘What will it look like?’  

Of course people often start with the vision, what they want the space to look like, materials they hope to feature. They may focus on a specific use for the space.

Sometimes they just begin with ‘Bigger than this!’ The planning then must cycle around to answer the other questions.

 

The Cobb-Hepburn House began with most of those questions already answered.

About 1780 the Charles Miles family needed a house on their land in Tinmouth, Vermont.

The house would look like houses they knew: a 2 story box with a gable roof and a center chimney, with a layout that was also familiar: a hall, a parlor on the front and a kitchen with service spaces behind. 

Here is their house after the modern siding was removed. The original house was probably not painted. It would have had small paned windows and a larger chimney.

The house would be framed of wood of which they had plenty. The foundation and chimney of stone – which also ‘grew’ right there. The frame would be 4 bents long and 2 bays wide.  

14 feet square +/- seemed good sizes for the Parlor and Hall. The space for the chimneys needed not be as large.

Here began the geometry.

Please read left to right. I have shown in the first 5 diagrams 2 points for each straight line. After that I have assumed the geometry is reasonably clear. I have also added a description even though I often find it easier just to read the drawings. 

1 -- The width of the house was laid out: 28’-6”: the length of the first bent.
 Just a line:  A -B

2 and 3 -- A square was drawn, using the line as an arc:  A -B - C - D
All the sides are equal.

E marks the intersection of the arcs.

4 -- Diagonals were added: F is the center.

5 -- The square divided in half both ways: the second bent. 

6 -- At E a vertical line was drawn: the third bent.

7 -- E is the center of the second square. The length of the sides of the square could have been stepped off to match the first square or laid out with geometry.

The fourth bent is the right side of the 2nd square.   

8 -- is the plan for the house, showing the locations of the posts - almost.

The as-built plan for the Cobb-Hepburn House, shown here, is not quite symmetrical. 

Here is the plan showing the posts and  beams for the 2nd floor with the 2 crossed squares in red.

I have seen the use of 'Crossed Squares' in many New England floor plans.Before I explored the geometry of this house I had not seen layouts use the intersections of the arcs as determining dimensions.

The framer used his intersections as the outside of the post location for the center bents. He seemed to set the center posts and beams back about 8" so that the chimney could more easily exit at the ridge of the roof. 

Here is an elevation of the bents from front to back for the house.
It fits within a square.

If the square is divided into its 4 smaller squares and the arcs of the length of the smaller square are drawn the intersection is the location of the top of the plate - see the green square on the upper left side and intersection.

Once the height of the house frame was set, the rafters could be laid out.
The second floor location was determined very simply: the top of the beam was located at mid point of the distance from the first floor to the plate  -  shown with a dotted green square on the lower right side.  

In both cases the framer used his intersections as the outside, not center line, of his beams.

The elevations of the house used the same geometry. That's next.

  

The Cobb-Hepburn House frame , Tinmouth, VT

Here is the Cobb-Hepburn House coming down.

Glenn Tarbell recorded its dimensions as he and his crew dismantled the frame this past winter. I drew the framing diagrams. My measured drawings of the house before de-construction served as a reference.

The drawings tell a lot about how the house evolved.

Local records show that Charles Miles came to Tinmouth from western Massachusetts. He built this house about 1780. When he moved to Ohio about 1810, he sold the farm to Amos Brown. In 1821 Brown sold it to his son-in-law, Edward Cole. His daughter, Jane Cobb, inherited the farm and house when Cole died in 1852.
Hod Hepburn was the last owner who lived in the house. After he died the new owner asked Green Mountain Timber Frames to take down the house.
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The house is 28'-6" wide by 39'-0" long, 2 bays (3 bents) wide and 3 bays (4 bents) long.
Its layout is derived from some of the earliest houses built in colonial New England

Center chimney floor plans were rarely built in seacoast New Hampshire and Massachusetts after 1760.  However, the first floor plan often appears in 2 story houses in New Hampshire and western Massachusetts up to 1770 and is a common plan for 2 story houses in Vermont through the 1840's.

The drawing is by William Lawrence Bottomley from his introduction  The Architectural Heritage of the Piscataqua, John Mead Howells, Architectural Book Publishing Company, Inc. 1937. His 10 page essay is one of the best introductions I know on early construction on the New England Seacoast from Salem, MA, to Portland, ME, .

Here is the probable floor plan for the Tinmouth House. I have labeled the rooms to match Bottomley's drawing.

The kitchen and the  pantry/dairy had been divided into smaller spaces by the time I measured the house in 2015. The other rooms still existed.
The first floor joists and sills were too rotted to be saved. The actual location of the original fireplaces is educated conjecture. A bake oven may have been beside the kitchen fireplace - we uncovered a mantle and cabinet door set in that wall.



The frame is massive, 10"x 10" posts rising to 10"x 14" and 10"x 16" gun stocks. The beams are 6"x 9", the plates 12" x 9". This is the 2nd floor SE corner seen from the 1st floor.
The roof rafters are of similar heft. The basic house frame was erected all at one time. Completing the interior frame took about 50 years.

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The way the framer set back the longitudinal center bent -  about 12" from the center - allows the chimney (drawn in red) to rise through the roof at the ridge.



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The frame for the north wall has missing and added studs as well as blocked windows, showing  how the house was changed through the years. The original 1st floor windows were directly below those on the second floor.








The west wall framing also shows window openings where we found no sash.
A door was added at some point and then closed off. A stud pocket remains in the beam above.









Empty joist pockets at the stair opening in the front hall indicate that the frame was reconfigured to allow space for the narrow, steep stair to the 2nd floor.




The second floor joists were made at the same time as the original frame.

The  Parlor, Hall, Bedroom and Kitchen joists are regularly spaced. The pantry/dairy joists aren't.
Quite a few of the joists have bark and wane; those above the parlor and the pantry/dairy are more logs than hewn.
The larger space between joists beside BII may indicate a stair.



Here is a possible explanation:


Charles Miles framed the house. He finished the Hall, Parlor and Kitchen; the Bedroom (which was usually reserved for the infirm or new mothers). Then he ran out of money, time, or energy. He finished the last joists with rougher wood. His family lived on the first floor.
Living in a partially finished house was not uncommon. Sections of a house were often used for storage and then added into the living space, just as we today add dormers to attics and insulation to  porches.



The attic framing was a different pattern: joists 2'-0" oc with intermediate 12" x 9" plates.
The joists all match: 3"x 6", cut by a sash saw at a mill.
The stair was relocated to where we found it.

As the frame was exposed we saw that bedrooms #1 and #2 were once one room, that bedroom #4 had neither lath nor plaster while the other rooms were finished.



Which owner installed the attic floor? The answer might depend on when sawn joists were readily available from a local mill.


The photograph shows the attic floor joist pattern. The window to the right had been blocked, but its outline was visible in the plaster wall. The window to the left was not original:the cut stud above and the lack of a stud on the left side were the signs of later construction.




Probably the Coles eliminated the fireplaces. Cast iron stoves were being manufactured in the 1820's.They were widely used by 1840.

 After stoves came central heat.We dismantled a modern cement block chimney serving a furnace and a modern wood stove.
Soot and char on beams implied that the framing around the chimney coincided with the installation of wood stoves.


For views of the house as dismantling began please see the previous post: http://www.jgrarchitect.com/2015/02/baring-bones-of-house.html

Baring the bones of a house: The Cobb- Hepburn House

The Cobb- Hepburn House is coming down.

Luckily it will be saved and reused.

I was there to measure and record.






The house suited its site. It was "built to the weather".

Set on a foothill ridge with fields sloping off on all sides, it had good drainage all around.

It faced east and looked south to the road, the view, and the sun. The parlor was in that sunny front corner. Deciduous trees just beyond let in winter sunshine, shaded the house in summer.

The wind here comes from the west and the south, The house was backed up against the mountain to the west, sheltered by it, below the wind coming over the ridge. The kitchen and its door were on the north end. An orchard to the southwest scattered the wind's force.

The family had died out; the land sold to the farmer who lives next door.
His daughter didn't want to live in the house.


It wasn't built for our modern era and it had not been cared for.


The entry hall is 4 feet deep, almost too small for 2 people to pass; certainly too small to welcome visitors.
The stair is 30 inches wide, and steep.
The only bathroom is on the first floor off the kitchen.

The bedrooms are only accessible through each other.

One door was mounted upside down, including the latch. Was it a quick fix - 100 years ago? - so the door would swing the right way?

Except for electric wires stapled to the walls and some interior storm windows the house hasn't been updated since the 1950's.

I was there to record its layout and proportions, to record how the builder used the materials he had: wood, plaster, nails, some iron, marble, stone, and glass.
It was cold - 5*F when I began measuring in the morning, about 15*F when I left mid-afternoon: not ideal for exposed fingers.The crew needed me to measure so they could continue dismantling, so I kept my hand warm with a propane heater. I photographed the rooms as an auxiliary record.

I have been back several times. The temperature has never been above 20*F at 2pm in the sun.






The crew is knowledgeable, experienced and interested. We share what we find and what we know, what we wonder about. We measure together.They need accurate dimensions to repair the frame for reconstruction.

2 kinds of scribe marks and offset marks are clearly visible. The 'B' on the post and beam are one pair of many.

The frame seems to have been built several years before the second floor ceiling joists - cut by a saw mill, laid out in a different pattern - were installed. Other joists were moved to allow space for the stair.
A third fireplace and another exterior door (frame and door!) were found under layers of wallpaper.
The 1st floor sheathing on the front facade had been replaced with plywood. One bedroom had not been finished until cast iron stoves were in use, 40+ years after the house was framed.

The videos are by Dan McKeen of Green Mountain Timber Frames. http://www.greenmountaintimberframes.com

                                      
  

A barn built in the 1830's

Green Mountain Timber Frames http://www.greenmountaintimberframes.com/ measured this barn before they dismantled it to use its frame anew.

Due to the wood used - poplar, beech, hemlock - the layout and the construction we think this barn was built by a farmer without an extensive background in framing. We think it dates to the  1830's.

 The floor was dirt, the head room under the hay loft not quite 6 ft.
What was it used for? Sheep perhaps? Sheds, windows and a silo were added over the last 180 years, making the original purpose hard to read.


I start with the farmer.
He had some wood of a certain size and length he could use for posts and beams for a barn. He knew how the barn would be used and where it would go.

Probably he had a carpenter square - they were readily available. But maybe not, as his dimensions don't quite fit. And he was much more comfortable with the old-fashioned geometry of the 'whirling square'.

He started with the width - 18 feet. He made a square: 18 ft wide, 18 ft. high - first diagram.\
Or so it seems. Today that height is 17'-10", 2". I think originally the width was also 17'-10". His inch seems to have been just a bit smaller than today's inch

He could have started with a string about 18 ft. long. He could have used a compass with a 27" radius, stepped it out twice for 4'-6", twice more for 9' and doubled that for 18'; or a pole 4'-6" long.

In his square he laid out his center lines and then the star that joins the points - the second and third diagrams. This is a medieval framing system which came to New England with the English colonists.

I have added circles to mark how the lines of the star cross at the locations of the girts, I've added a green dashed line to show how the height of the wall is 2/3 the height of the end wall. Almost. It's off by 2"

Using a carpenter square to layout a 3/4/5 triangle does not work as well. The wall height isn't high enough. The lower girt can be determined - see the green circles - but not the upper one.

While the frame appears governed by the traditional English framing geometry, the frame itself has dropped girts - a Dutch traditional way of framing. The girts are mortised into the posts below the upper beam. This combination of framing methods is sometimes referred to as 'American'.


The floor plan is simple: three 3/4/5 triangles. If the width is 18'  the length should be 40'-6" . It was 40'-2" measured on site. The men repairing the frame tell me it is 40'-1"; that the 2 interior bents are at 13'-4 1/2" from each end.

If one arm of the 3/4/5 triangle is 17'-10", the other is 13'-4 1/2".
3/4 of one side of a 17'-10" square = 13'-4 1/2". So either framing system fits the floor plan.

Dan McKeen, GM Timber Frames, also tell me 3 girts are beech, one poplar.The top plates are poplar and in good shape. The posts are sawn hemlock and hewn beech. The ties are sawn hemlock.

I looked at how did this farmer/framer laid out his girts in the side walls.
Here I tried - on the right in red - 3/4/5 triangles. The intersections - red circles - using a triangle that includes the rafter tails, are close, but convoluted. Not simple.
However, a square laid out inside the frame - on the left in green - neatly divides the space in thirds - green circles.

The star of the square used for the gable end laid out along the side also notes the placement of all the  girts.








The numbers on the early carpenter squares were engraved by hand. It is possible that this farmer/framer owned a square that was very slightly off. Or he used his own measure.

The man who built this frame comes alive as I study it; I've met him. Now I want to ask how he learned to frame - who taught him? what tools did he like? where did he start? were we right about his choice of materials?

House to save!

WHOM  do you know  who is just yearning for a c. 1780 western  Vermont farmhouse with a pristine post and beam frame?
The house itself is quite plain inside, fitting to its time and place. There are few parts to salvage beyond the frame. perhaps the clapboard and brick, doors and hinges. The window sash are c. 1900 or later.

HOWEVER:The frame is chestnut with gunstock posts. It could be exposed to the roof if an owner wanted.

http://blog.greenmountaintimberframes.com/2014/12/27/demolition-is-just-days-away-save-this-tinmouth-vt-barn-home/

I will be measuring and analyzing this house on Monday - if the roads from here to there aren't too icy.

More later after I have dimensions.
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Geometry of a Hartford, NY barn, c.1790

A Hartford, New York, barn was carefully dismantled for reuse this fall by Green Mountain Timber Framers.

I was there and later analysed the timber frame. Dan McKeen, owner of Green Mountain TF asked me to write a guest blog on the geometry of  the barn for his website.
I wrote about the basic layout, how it was developed from just one dimension, the width of the barn.

To read that post use this link:

 http://blog.greenmountaintimberframes.com/2014/12/04/geometry-in-historical-frames-a-guest-blog/ 

Here are two more diagrams that continue the exploration of the geometry.

The section is the measured drawing of the end of the barn seen above.

I found that the mortises in all the posts (the mortises hold the tendons of the rails) were all cut in the same pattern. 

The arc the framer used to locate the intermediate lefthand post also located the upper horizontal rail.

The diagonal intersecting the arc of the length of the square can be easily rotated so that it marks a horizontal line instead of a vertical one.

The framer then turned his compass and swung an arc from lower right to upper left. The intersection of the diagonal and arc became the location for the lower rail. (See the green circles!)

All the rails for the barn are located at the same heights on the posts. This means the framer could set up one jig to cut all the mortises - simplifying his job, getting the work done faster. And  a bit of mass production, ie: a precursor to square rule framing. 

There is also the roof layout.  I have not yet drawn the diagrams. 

Be awestruck with me! Full of wonder!  

Old First Church Geometry, the Elevations - Part 3

This is part of a series on the geometry of the Old First Church (OFC). Bennington, Vermont.



I began looking at the geometry of the church in 2012 beginning with the  'rolling circle' muntin pattern in the rounded tops of the windows.









I found that the repetition of the circle I saw in the windows was used in the window and column placement of the side elevations. The length of the sanctuary is also governed by the repeating circles.

The circle divided into its 6 parts - the daisy wheel - defines the church's width and height and its roof.



These drawings I have already discussed in the earlier posts.  

Now for the new ones,





The daisy wheel rotated 30*, or with a horizontal axis instead of a vertical one, the line between the 'petals' defines the column placement - the outer side of the columns.
The diagram below shows how the same proportions - the main nave of the church and it's side aisles can be laid out by locating the circles 90* instead of 60* to each other ( 4 petals on the daisy instead of 6).






The front elevation of the church is governed by the same circle.
Then the first circle's center is the bottom point of the diameter the second circle. The second circle's center is the bottom point of the third circle's diameter. The 3 circles together encompass the church and its tower.
They lay out
1) the height and width of the church meeting space
2) the height of the first 2 levels of the tower
3) the location of the Palladian window in the tower

If the center of the middle circle is used as the outer edge for parallel circles on either side, the 4 petals that result determine 4) the size of the protrusion of the narthex - and the location of the columns inside,
5) the location of the bottom chord of the pediment,
6) the placement of the bell platform
7) the height of the architrave above the columns and their arches that surround the bell.

I have drawn the diagonals of the bottom circle in green which mark the rectangle of the church body. Note how it determines the roof of the main door. I have added dashed red lines at the sides of the extended narthex ('porch')  and extended those lines up to meet with the line marking the top of the belfry.


Here is the diagram of circles extending both horizontally and vertically, creating squares instead of daisy wheels. It's just a reminder. 
I've laid out its construction in earlier posts.
http://www.jgrarchitect.com/2014/09/how-to-construct-square.html














Lastly, here are the circles in the same rhythm as those which determine the pattern in the windows.

(1) The first red circle at the bottom encompasses the church. Its center is at the top of the pediment over the main door.
(2) The second red circle sits on the center of the first. Its center is the Palladian window in the tower.
(3) The green circle's center is on the line laid out by where the first 2 circles cross which is also the peak of the oerdiment over the 2nd floor Palladian window. It extends from the floor of the church to the  rail of the belfry.

The circles can 'roll', just as does the muntin pattern of the windows.
 Here are some of the circles that grow of the 3 laid out above. Each circle's location is determined by those on either side.
The centers are noted with small red circles. Note that they determine important features of the facade.

The circles themselves were numbered in green - visually it was too confusing.


 There are many points I have not called out. It is just clutter at this small scale. Remember that pictures can be enlarged by clicking.