Monday, June 24, 2013

Post and Beam Introduction

 If you are interested in post and beam construction, and wish to know about the historic background of post and beam in New England, then this book is for you.  I have never seen a better resource.  It shows the different plans, and joint work that were used in the first centuries of English occupation in Massachusetts.  There are clear drawings and lots of photos of old houses that have been demolished as well as those still standing. 
I bought several copies of these over the years from SPNEA, which was the Society for the Preservation of New England Antiquities.
It has since merged into another organization, amid lots of controversy, and is called Historic New England. 
Copies of this book are available on line at both new at over $120.00 and used for as little as $20.00.   There may be copies available in local libraries or in used bookshops.  I know that this was out of print years ago, but they always had a few copies in each of their museum houses for purchase.  I guess that it has been reissued since then.
The name is:  "The Framed Houses of Massachusetts Bay 1625-1725".    By Abbot Lowell Cummings   
This is a remarkable book and is the definitive resource as far as I am concerned.   It is well worth the search and the expense.

Post and beam work is not really difficult.  It is time consuming, requires careful planning and moderate wood working skills.  The big issue is planning well, and being exact in measurements.  It is sometimes difficult to get your head around the drawings of joints, so the greatest gift you can give to yourself is a trip to old house museums and looking at the joints first hand.
A simple building will not have that many types of joints to do.  There are just a handful that will be repeated throughout the building.
The sills are simple half lap joints at the corners, with a vertical mortise through each corner and where each post occurs, to stand the tenoned post in. 
If you are building a stone house and only need to add an upper floor and a roof, then the joints will be rather simple, and there will only be a handful to learn.  Many can be roughed out with power tools and finished with chisels and mallets.
I do have the skill to draw these joints, but it is an enormous undertaking to make clear drawings.  I just do not have time.  Pick up this book, or one of the many "on line" resources or books, and you will have an enormous jump start.
The only really complicated joint that you will encounter in a simple house will be the tops of the corner posts, which are often gun stock in shape.  At that, it is only the top of that post that is at all complicated.  Everything else is rather simple.
Many joints were simple enough, with something approximating a dovetail to hold them together, but in practice, house-wrights often simplified even those, except at corner braces.
I know you can do it!
A positive aspect of post and beam is that they are not difficult to put together.  They were often assembled in Bents(floor to roof slices of a building) that would be stood up by a few people and joined to their neighbors.  Smaller houses might be just piece by piece and never too big a piece for a few people to handle, except for top plates, and sills that they tried to make continuous if possible.  A cape house could probably be put together by one strong person, with the occasional help of a second person for lifting and juggling heavy members into place.
When mixing old techniques like this with newer materials, you run into a few problems.  In the old days, a building would often be roughed together, then allowed to dry and shrink before continuing with plaster etc.  Today, we so often work with plywood, OSB, drywall etc., that are absolutely stable. Their application does not allow for shrinkage of the frame.  If you are using boards as they did, then you have more leeway, as they will shrink along with the frame.
Basically, you could build the entire house in wood, including all the moldings on the doors and windows, and later you would fill in the walls with plaster, around and butting up to the woodwork.  Also, many of the interior walls were done in wood like the Space Saving Partition Walls I have described elsewhere, and these too would shrink into place.
The problem with all this shrinking, was that you would then have an incredibly drafty house.  This was OK except in windy conditions, because they had so much wood in the early years that they could burn cord after cord of wood to keep warm...which was not expected to be that warm anyway.
We demand a tighter house these days and allowing the house to shrink and using dried wood for the frame are the only way to add on our more stable modern materials without running into problems with variable shrinkage.  Once you apply plywood or drywall, there should be no more shrinkage allowed in the frame.  
Large beams and posts take a while to dry out, and are difficult to purchase pre-dried.  The one saving grace, is that most shrinkage is radial, or across the width of the wood, perpendicular to the direction of the grain.  Lengthwise shrinkage does occur, but is less obvious.
Another option is to buy old wood.
There are thousands of old barns demolished every year.  It is possible to purchase these old pieces, re-use them to build the same building that was torn down, or to re-cut them to new dimensions.  Be prepared to buy new blades for your power tools on a regular basis.  The wood can be riddled with nails.  If you have a bigger budget, the frames of entire antique houses can be purchased, ready to be reassembled on your site, often with minor damage already repaired or new pieces cut where necessary. 
The beauty of the old beams, other than being big and dry, is that they have lovely finished surfaces, with the original marks on the faces.  When you cut into them, you must plan carefully to preserve the surfaces that will be seen in the finished rooms.  The fresh cut joints will glare out at you with their fresh cut color against old patina.  You will have to be adept at staining the new cuts to match the old surfaces.
You could also, re-mill the old wood completely.  This would remove the old planed or broad ax cut surface.  If this does not bother you...then all is well.  The beams for barns can be enormous, so there is usually plenty of wood to work with.   Generally, the only posts or beams that would be fully visible in an old house, might be the corner posts.(except in VERY early houses which were often completely framed with carefully planed and molded wood)  With these, you can cut two adjacent sides of a large beam, and leave two sides in the original surface.  You might be able to cut huge barn beams in quarters to get four corner pieces with two sides in original surface on each piece. 
Usually though, a nice house was always completely finished.  The beams were cased in nice boards and painted.  Only boats were varnished, and there would have been damned few of those.  modern varnishes were unknown.  Clear finishes at that time were oils or shellac.  Both were difficult to maintain.   All the wood was painted, unless they used some exotic and expensive variety of wood.  Modern remodelers often go to great expense to expose the original wood in 18th century houses and furniture, only to find mis-matched colors, qualities and varieties of wood, even in a small area.  They were almost always painted and sometimes false grained to look like expensive wood.  These faux finishes might be quite fanciful or even wild.  Sometimes they were very convincing renderings of expensive wood.

As I mentioned before, post and beam houses(unless you want to make a fancy house) can be extremely simple.  there are only two real trouble areas.  One is the tendency for the roof to push down(not a problem) and to push outward at the same time.  Because of the weight of the construction and snow load on the roof, the house has a natural leverage where the roof joists want to push outward on the top plates of the walls.  The ceiling joists are dovetailed into the top plate of the walls to help the walls to stay upright and not be pushed out.  Also, the top plate has the tendency to roll out from the top.  This is helped by proper joints at the bottom of the roof joists, and proper mortising of the wall posts into the top plates to keep the plate upright.  Also, each of the second story floor joists can be dovetailed into the top plate.  That holds them from pushing outward or rolling.

The second big issue is common to all buildings that are squared off.  A round building will support itself diagonally by the curve of the walls.  But any corners will tend to catch the wind and be pushed to the side.  The entire house may twist in the wind, the roof eaves and flat "sails" that are the walls being buffeted in even mild wind.
Our modern sheet goods help a modern building.  They provide diagonal strength because of the sheet goods' stability in all dimensions, and their great area, usually 4 feet by 8 feet.
Post and beam buildings do not have as many structural uprights as a modern building. Modern buildings have all of those studs in each wall.  Lots of points are joined to the sheathing materials along the length of the studs, and over four studs in width.
To make up for this swaying weakness, a post and beam house must have corner braces, dovetailed into the posts and top plates and sometimes into the sills of the house.  The diagonals keep the building from racking or swaying in the wind.  All the corners remain square.  This is a little like the diagonal pieces attached to screen doors to keep them from sagging under their own weight.
See the corner braces in metal in my sister's house in the photos below.
Also note the solution to all the major joinery in their post and beam.  All the joists are joined to the top plates with bolts and steel brackets.  Not as atmospheric, but very practical and easy to assemble.
notice the trusses that help support the snow load.

Note the bottles in the fill of the wall that let colored light through the walls.
True post and beam construction is much more laborious than the frame pictured here.  This was a wonderful solution from New Brunswick.  It was delivered as a package, and assembled in record time after it got across the border.  There are many, many post and beam kit providers, and untold numbers of local people that will be able to cut out, assemble and finish a post and beam building for you. 
There are a number of companies that will only work in certain woods.  Oak is one of them, and probably among the most atmospheric and beautiful options, but also rather expensive.
Through the centuries, however, many woods have been used.  The wood has to take a certain amount of wind torque.  Twisting, and turning, and pulling at the joints.  It must not be too brittle.
Of course, any wood can be used, but you cannot count on very long term use with palm trees...just a for instance.
I have seen buildings made very successfully from a number of different woods.  My 1766 house in Maine, was made of a mixture of pine and spruce.  The spruce floor joists(beams) were un-peeled and just flattened on the top to provide a nailing surface for the floor boards.  Of course, if you use these weak woods, you must build using enormous dimensions in all parts of the house skeleton.
Oak is tough as hell.  Chestnut is OK but not ideal...all species have drawbacks.  Hemlock is good where there is moisture.. I used it for the replacement sills in my 1766 house.  It needs to have the moisture kept away.
If you are only worried about your own lifetime, and have local species that are commonly used for construction, then use it.   The big issues are:  keeping the maintenance up.  Keeping the moisture away, while providing good air circulation.  Discouraging mold etc..
Use woods that do not have a super straight grain for pegged together joints.
The part of the wood joint, where the pin, or Trunnel(Tree Nail) goes through the joint, is near the end of a member.  The grain that starts at the hole, cut for the pin, and continues to the end of the wood can split and pop out, leaving the joint free to slide apart.  This happens if the grain is very straight, if there is a lot of movement that causes stretching of the joint or the pin was put into the joint much too tightly.
The piece that comes out is called the "relish".
When a pin is put into the joint, the holes drilled for the pin are usually just a little mis-aligned.  In other words, the hole in the outer part of the joint(usually the two side parts) is in the proper place.  The inner hole is just a tiny bit farther toward the end of the member to line up perfectly.  The pin is usually just a bit tapered at the end, so when it is driven into the three holes, the inner part of the joint is pulled into the joint a little tighter than if they were perfectly lined up.  If this is too tight, it can lead to splitting out the Relish, and the joint can come apart.
Generally the pin is not round at all.  Sometimes they are square or hexagonal, or just un-smoothed, so that the facets from trimming(shaving) form an octagon or decagon etc.  The ridges of these pins grab onto the joint, and they will stay in the hole without turning, and without pulling out.
The old timers used to use Black Locust when they could get it.  It was used for Trunnels and fence posts.  They used to say that Black Locust would last two years longer than stone.  Oak will do.  Try not to use soft woods for these very important and stressed parts of the construction.
Do not just measure up an old house and start building it.  People were smaller then.  Headroom was not as important.  Doors could be narrower.  They did not have to get refrigerators in, king sized mattresses up stairs etc..  You can, of course, leave floor boards un-attached to the beams, and lift them out to take large furniture upstairs. 
The big issue, if you want an exact reproduction is that many towns and states will have height and width requirements, fire codes, etc., that the average 18th or 19th century building will have trouble passing.
It is funny that people did not use more stone in New England, or anywhere that it was plentiful.  In France, you even see substantial houses made of small water worn stones, with plenty of mortar.  I remember these well, as I could not remember the names of the stones in my French Vocabulary...It always bugged me!  I want to say:"Rondelles", but I know that is probably wrong.
Anyway, stone was everywhere, and England had plenty of stone buildings.  It turns out, that there was a time when stone construction was thought to be unhealthy.  Perhaps it was the lime smell of the mortar or something.  The smell is remarkably like a cave sometimes. 
I had a dear friend in Maine, who was one of the heirs to the oldest recorded stone house in America.  It was the Spencer-Pierce-Little house in Newburyport, ma.  It was willed to SPNEA by her maiden aunt, leaving her and her kin...out in the cold.   I relish the idea of letting the public see these old houses, but surely disinheriting the family completely is not the way to go. 
As it turns out, this cruciform, Jacobean house had a long end to the "cross" floor-plan.  While the entire house was in stone, some bride in the federal era(I am guessing at the time period) refused to set foot in the stone house, so a timber house was added on to the end for her to live in.  I guess she never did set foot in the rest of the house!
Most early houses were set on large stones under the sills.  They were placed under the points where the posts attached.  This transferred most of the weight of the building to the ground.  The sheer mass of the sills and floor joists kept the frame stiff and level enough to nail the floor boards down without the house seeming like a collection of trampolines under the roof.  The house might be balanced on 8 to ten really big stones that lifted the house a few inches off the ground.  This is rather like the modern practice of pouring Sonotube posts to support a building.  Air would flow under the house to keep moisture down... Unfortunately, wind could also come up through the floor boards.  Old timers often covered the gap between the ground and the floor with bales of hay or whatever they had to cut the wind.  Unfortunately, the materials often held the dampness of the snow or rain against the wood walls and forced them to replace sills and the lower part of the house when they rotted.  (It was easier than it sounds)
Later on, they might put a new foundation under the house, sometimes in field stone or granite.
Granite is a problem in some cases, especially if the house it is supporting is very air tight.  Granite and other volcanic stones and even the soil beneath you, can put out radon gas and minor radiation.  This is not a big issue for us "too old to care" types, but someone spending a lifetime in one of these houses might wish to have the house tested for radon before buying, or take ventilation precautions if building new.
Granite counter tops are not going to kill you... There is radiation from everywhere, and a thousand other environmental issues to worry about.  The radiation is sooooooo minor that it will have no real effect on you....Remember when we used to have Radium painted dials on our watches?   I loved to hold the dial up to my eyes in the night...why, I don't know, but I did.  I also played with droplets of mercury while my dentist worked on my teeth!  God, those drops break up and go EVERYWHERE when you drop them!  This all probably furnishes some explanations as to my life after that time period.            

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