A Cabin on Magnolia Plantation, Louisiana

May 14, 2019. I have rewritten this post. The new one is based on being there.
I will leave this one for a while  since so many people have read it. The comparison between  analysis by HABS drawing and an actual site visit is worth noting.  The italicized notes were added as I saw what I had mistaken.

I will be in Natchitoches, Louisiana, April 23- 25, teaching Practical Geometry, in a full day workshop on Thursday, and 2 hr. workshops on Friday and Saturday. 

This image - the cross section of a cabin, built c, 1830, on the Magnolia Plantation, its geometry and a compass - is my on-line poster for the Thursday workshop. It and a description of the workshop is now posted on the Preservation Trades Network website: www.ptn.org 





uiul 
I have the HABS drawings for this cabin, but no picture, as I have not seen yet it.
I hope to visit when I am at the conference. It's too easy to miss something essential when I work on the geometry of a building I have not be in and around. On the other hand, including local buildings in my workshops and power point talks is important, and researching their geometry will help me see them more clearly when I am there. 

Corn cribs and cabins were utilitarian, built using ordinary construction. Studying these simple structures helps me understand what geometries the local carpenters used.

This cabin has brick walls. It has 2 rooms with back to back fireplaces in the center. The floor plan begins with a square space and its diagonal used as a radius to draw an arc. Then another square space was added on the other side. The space created by the arc is for these fireplaces - possibly including their foundations.  
Follow the  black  line and arc with arrows and the red line and arc with arrows.
This layout is possible. The layout inside the brick wall (see the new post) is simpler and would have easier to to build. 

 


The section of the cabin shows a floor set above the ground.  The height of the cabin is half the width, here shown by 2 squares, beginning at  grade, not at the floor.  
The diagonals of the squares becomes the radius for arcs; the point where they meet is the cabin's ridge.  Follow the  black  line and arc with arrows and the red line and arc with arrows.

The squares could be moved up; base on floor, top on the rafters. But then the arc would be above the roof line. 







The end elevation matches the section and locates  the window - see arrows.









The side elevation continues the pattern: 2 squares on either side of the center partition, the windows centered on the double square. The red square shows both the partition location, left, and the window location, right. This geometry is not consistent with the construction that I saw. I redrew the elevations.

There are 2 issues I can't resolve without more knowledge of the building and its construction.

1) The window locations on the floor plan do not match those on the end elevation. Which should I use for my analysis?  Most were added later. I can ignore them when I look at the geometry.
Most of the brick houses I have studied use geometry to mark where an opening begins rather than a center line. This is why I think my geometry here is wrong and that in the new post is right.

2) I do not know enough about brick construction in Louisiana to make educated assumptions about framing.
How do the floor and the walls join? Is there a sill?  There seems to be a plate. How is the roof framed? What is the reason the end walls are higher than the sides? Some of this I could not see. People could tell me about details that they had worked on.
The site appears level in the drawing,  with brick footings maybe 18" deep, slightly wider than the walls. Is that the whole foundation? Yes The footings are about 12" deep.Is there a foundation for the chimney? I did not find out about the chimneys.
All the buildings whose geometry I've analyzed have been no farther south than Virginia. Their geometry begins at the place where a flat base, a foundation, can be set true and level. Where is that here? Has this to do with climate or topography? Topography.

I look forward my visit.

The website for Magnolia Plantation is:  https://www.nps.gov/cari/learn/historyculture/magnolia-plantation-history.htm 


Note: 

The NPS has several articles about slavery in Louisiana including this: https://www.nps.gov/cari/learn/historyculture/african-american-history.htm

The HABS drawings call this a "slave cabin".  I refer to it as a cabin.
The first people who lived here probably were enslaved. They were people first, with skills and families. Maybe their names have been recorded, possibly connected to this cabin. Later free blacks and Creoles lived in these houses at the plantation.
Maybe a mason or a brick maker lived here and I am studying his skill and knowledge.
I have learned that on some plantations tutors and overseers who were not enslaved often  had similar housing. 
This is a "cabin".

The Tuckahoe Cabin Geometry

 This is the double slave cabin at Tuckahoe Plantation, Thomas Jefferson's childhood home in Virginia.
I have written about it before:  http://www.jgrarchitect.com/2014/06/cabin-tuckahoe-plantation-goochland.html


The simplicity of the cabin and its HABS drawing make it an easy building to use when I teach hands-on Practical Geometry.




The beautiful hand drawn lines and details of HABS drawings fascinate students. And they get a little history.
Here the elaborate paneled front door for the plantation house, its ceiling pattern, and columns are shown with the little, uncomplicated cabin.
Craft, wealth, slavery c, 1750,  are visible side by side.


Remember that you can click the drawings to enlarge them.

The cabin illustrates the Rule of Thirds.
Students unused to geometry can grasp the basics quickly as they discover the design simplicity of the floor plan.They explore the geometry of the elevations with curiosity, not in trepidation.

For a tutorial on the Rule of Thirds:
http://www.jgrarchitect.com/2016/10/practical-geometry-drawing-diagrams.html




BUT -  This is academic.
How did a carpenter actually use this knowledge?

I wasn't there. So, I am guessing? No.

I've read the written documents, 'read' the drawings that have no words - from that period and the more recent era of HABS. I've measured and documented these buildings, participated in repairing and framing them as well as their deconstruction.
I make connections to the old ways of laying out a frame from the way we lay out today using the same tools our ancestors had - a line, a square, a plumb bob, a pencil - and  a compass.


Here is a construction scenario for this cabin.

The carpenter plans to build a 2 room cabin with a loft, 2 doors, 2 windows, back to back fireplaces on this site.
The size is standard, each room about 16' x 16'. He either builds right here, or he uses a framing floor. In either case it is a flat, level surface. His geometry will establish his points and keep his frame square.
 He measures off 16' with twine, using his own handmade rule. He then stretches out his twine another 16-20 ft, pulls it taut.
He now has a straight Line.
Maybe he has chalk and snaps it, making a line.  Maybe he pegs it.
Modern carpenters snap and set lines regularly. We still call them 'lines'.


1 - On his Line he marks his first point (A).

2 - He chooses a radius and draws 2 arcs, one with its center at (B), one with its center at (C).  He now has 2 points where his arcs cross and can draw a line perpendicular to his Line.

3 - He chooses his dimension -  here, 16 ft -  puts his compass - perhaps a string with a knot at 16' -  at (A) and draws a semi-circle (D-E).
Now he has a new point (F). His cabin is now 32' long; its width is 16' (A-F)

4 - Using (F) as his center he draws another semi-circle.

5 - Then he draws 2 quarter circles using (D) and (E) as his centers. Where the arcs cross (G) and (H) are the upper corners of his cabin.

6 - He swings the other arcs, and now has 4 internal points in each room of the cabin. He marks those points.

7 - Just to be sure, he trues up the space by checking that his diagonals are equal (G-A, D-F etc.).

8 - The interior points give him the centers for the doors, windows, and fireplaces. The plan of the cabin is done.

The end elevation, or  the 3 bents of the frame:
 9 - He sets up the 16' square with its arcs.

10 - The interior points give him the location for the 2nd floor joists.

11 - The points also give him the center of his elevation. He can draw his Lines and use the Rule of Thirds to find the upper third of his square (J-K). 

12 - (J) and (K) mark the eaves for the roof. He extends the sides of the square, draws his arcs to find the upper corners ( L) and (M), adds his diagonals  (J-M) and (L-K). Ahh - there's the roof!







 The window in the eaves is placed and sized:













A carpenter before the Industrial Revolution would not need my description. He would have learned the geometry as an apprentice. If he needed a reminder he would practice a bit with his compass. He probably didn't have a drawing for such a simple cabin.

However, books with instructions to builders (not architects) did exist. Here are 2 examples.





Batty Langley in The Builder's Director, London, 1751, draws moldings "Proportioned by Minutes and by Equal Parts".  He writes that his little book is to be available to "Workmen" and "any common Laborer."

These window and door 'Weatherings' are all composed of squares and arcs of circles. Langely lays out the parts; the Workman can read the rest.





 Asher Benjamin in The Country Builder's Assistant, Greenfield, MA, 1797, says his book "will be particularly useful to Country Workmen in general".
 He assumes the Workman knows geometry.

Plate XXIX  says only
 "C, is a roof; divide the width of the building into 4 parts, one of which will be the perpendicular height. Divide Fig. D, into 7 parts,give 2 to the perpendicular height.
Fig. E, is intended for a roof to a Meetinghouse; divide the width of the building into 9 parts; give 2 to the perpendicular height; the ends of the Beams, a, a, are to be supported by columns."




My first post on Tuckahoe Plantation is here:    http://www.jgrarchitect.com/2014/05/tuchahoe-planatation-richmond-virginia.htm

Cabin, Tuckahoe Plantation Goochland County, Virginia

I came to Tuckahoe Plantation to look at the cabins. Drawings for them are in the HABS archives. They are the size and layout of the houses whose floor plans Henry Glassie recorded and whose geometry I have written about.
 Dr. Glassie's book,  Folk Housing in Middle Virginia, includes photographs of poorly maintained houses, most beyond repair.

I wanted to see what they might have looked like when they were built and how tall they were. Yes, the HABS elevations show how tall they are. However, for me reading a drawing is a beginning, one  part of
understanding. I need to see the building.


It is very simple. in appearance and geometry, and not only because of its shape and lack of anything beyond the essentials.









It is just squares: 2 across the front, 2/3 of a square for the sides, 2 for the floor plan.




The chimneys are centered on the square.




The doors and windows are centered on the plan and on the center of the square for the front elevation.




The  front and side elevations are two thirds of the square.

 The roof pitch is 12/12 - the diagonal of the square - and begins at the 2/3 line of the lower square.


This way of dividing a square and using the diagonals to determine dimensions is called the Rule of Thirds.
To learn how it is drawn please see my blog post:
http://www.jgrarchitect.com/2016/10/practical-geometry-drawing-diagrams.html

The book, The Chesapeake House, reports that the plastered interior walls of the house are original as is the door between the two rooms. This 'cabin' then perhaps was built for the use of an overseer, or craftsman.

As you can see from my photograph, the little house sits on a green lawn with a dirt path, surrounded by towering leafy green trees. Clean white paint, variegated wood shakes on the roof, a neat brick chimney - all in excellent condition - may give too cheerful an interpretation of conditions in 1750, but I am glad it is being preserved.
Studying the adjoining kitchen, office and storehouses, walking down the path, then around behind the cabin across the lawn to the main house, gave me enough understanding so that as I traveled back roads to Madison's Montpelier I easily spotted similar cabins, now out-buildings on farms or wings to later homes. At Montpelier, where timber framed and log cabins are being rebuilt, I was also able to better read what was there. My visit to Tuckahoe was excellent.

The Chesapeake House, architectural investigation by Colonial Williamsburg, edited by Cary Carson and Carl Lounsbury, The colonial Williamsburg Foundation and the UNC Press, Chapel Hill, 2013.


My previous post about the main house at Tuckahoe Plantation is here: http://www.jgrarchitect.com/2014/05/tuchahoe-planatation-richmond-virginia.html