By: John Miller, PE, SE, LEED AP

One of the challenges that face structural engineers on a historical preservation job such as Simmons’ Stables is balancing the interests of the stakeholders in the project.  In this case the stakeholders are the owners, preservation authorities and the building officials.  The owners and preservation authorities would like to see the building returned to its original condition and the building official wants to make sure that it meets the intent of the building code.  One of the great things about this project was the fact that each of the parties came to the table with open minds and a focus on solutions and moving the project forward, rather than being stubborn on preconceived notions.  

This structure is not only unique in the history of its function, but also in the materials that were used to construct the barn.  The materials were dimensional lumber; similar in size to what is used today that can be bought at any Lowe’s or Home Depot.  Typically, lumber in buildings of this age were built with rough sawn material that varied in size as each mill had their own standards. 

In 1877 there were no building codes, each craftsman was a master of their trade and an owner would hire the contractor who would then erect the structure.  Simmons’ Stable was no exception to this and it has stood the test of time for the past 100 years, with the maintenance that was done, meant to band-aide the problems to pro-long the function.  It is a utilitarian structure and was treated as such. 

One of the first challenges was the fact that there was no permanent foundation for the structure.  When we first visited, some of the frames had settled as much as 18 inches, partially due to lack of foundations and partially due to decay of the bottom of the posts.  One of the committee members that worked at the barn told us that some of the stones that supported the posts were removed because the horses would hit their hooves on them.  Another issue was in the framing itself, the roof rafters were 2x4 members that spanned approximately twelve feet, without collar ties or a center ridge beam,  They would cantilever off the frame at the face of the stalls and bear against the opposing rafters.  As the building shifted, the connections of the rafters failed and the roof dropped and pushed out on either side.  The final issue was the lack of lateral bracing in the building to transfer the lateral loads from the roof diaphragm to the foundations.

The engineering challenge came in the manner in that the building was framed.  It was originally a combination of post and timber frame methods with stick built infill.  The roof was stick built utilizing 2x4 rafters that bore at the outside wall and hayloft beam and then supported against the opposing rafter at the ridge.  There was no apparent bracing in the short direction of the building and as the building settled and deteriorated the ridge and roof framing relaxed causing drops in the ridge line as much as several feet.

After a brief analysis of the structure we realized that we could not simply replace the framing that was there, but would have to provide a structure that met two goals, be true to the intent of the original construction and satisfy the life safety requirements of the current building code.    

We decided that the refurbished structure would meet both criteria, be true to the original intent and meet current building codes.  One of the first things we did was to modify the roof framing both at the main roof and dormers.  We replaced the 2x4 rafters with 2x8’s.   We also installed a ridge beam and collar ties to improve the stability of the rafters and ridge line.  We reinstalled skip sheathing, but added a plywood diaphragm over the top to provide a diaphragm.  At the dormers we installed some engineered wood beams with steel flitch plates, but cladded them with dimensional lumber in an attempt to be true to the original appearance.  

To brace the building we used a series of tie rod braces and custom manufactured steel brackets at each stall line where they would not be visible we used light gauge steel strapping.  

 Simmons’ Stable was definitely a team effort with the owner, contractor, architect and engineering. The final product accomplished the two goals we set out with, be true to the original structure, let it tell the story and be a structure that is safe.