Specializing in post frame design, construction and restoration
Barns
Barn, garage and workshop design and build
How are barns constructed? There are 3 main types of barn frames-
Timber Frame (sometimes called Post and Beam)
Post Frame (also know as Pole Barns)
Stud Wall (the most common type of residential building)
Here is a brief explanation of the styles:
Timber Frame:
As the name suggests, the frame of the structure is made from large and small wooden timbers connected by mortised and tenon ends, fastened together with wooden pegs. Large posts and horizontal beams are joined and braced in such a way that heavy roof and floor loads are transferred to the foundation. The walls are not load bearing and can be left open or covered with siding. The bottom of the frame sits on a concrete or stone foundation.
Post Frame:
Know for years as “pole” barns, this type of building is centuries old. Vertical posts are set in the ground below the frostline and extend to the top of the wall. Horizontal boards tie the posts together and provide the framework for siding. The tops of the posts are joined by heavier horizontals to carry the roof loads. Probably the main difference between timber frame and post frame is in the foundation. While a timber frame sets on top of stone or masonry, post frame buildings use the posts in the foundation, eliminating the effort and expense of excavation and concrete (or stone) work.
Stud Frame:
For most people, this is probably the most familiar type of building frame. Many of our houses are built this way and many contractors feel comfortable with this method. It is not, however, the best way to build a barn. Barns have larger open spaces and often have to allow for heavy storage on second floors. This openness means that the frame has to be resistant to “shear” loads, which are the forces that would tilt or twist a building. Stud framing resists these forces by applying plywood sheathing on the walls and using interior partitions to tie outside walls together-neither of these are desirable in a barn.
In most situations, a Post Frame barn is the most economical and the strongest structure you can put up. Rural builders have known this for hundreds of years. There was a time when large barns were built as timber frames, back when long timbers were plentiful and skilled builders were abundant. With the introduction of pressure treated wood, most modern agricultural buildings are now post frames. Given the fact that the exterior can have any look, post frame buildings can also be used for a variety of commercial and residential applications.
Which is best for you?
The type of barn frame you select depends on your budget and your personal preference. The table below gives the pros and cons of each:
|
Post Frame |
Timber Frame |
Stud Frame |
Minimal site prep No excavation No concrete or stone work Structurally superior Allows for any type of interior or exterior finishes-even open walls Easy to expand Variable wall heights easily accommodated Lowest cost per square foot Disadvantages: No cellar allowed Ledge and large rocks are problematic Lack of familiarity by building officials and contractors |
Structurally sound Aesthetically pleasing framework Allows for any type of interior or exterior finishes- even open walls
Disadvantages: Highest cost to build Requires significant site prep-excavation and frost wall construction Specialized equipment required to fabricate and set large frame members |
Uses commonly found materials Well understood building methodes-even open walls
Disadvantages: Not suitable for high walls or large perimeter buildings Requires significant site prep: excavation and frost wall construction Requires significant “over-building” to handle heavy stresses inherent to barns Visually un-appealing framework |
Some frequently asked questions about Post Frame building:
What are the posts made of?
Most posts are pressure treated with CCA or ACQ treatments to resist rot and decay. They are usually 6x6, 6x8, or 8x8 inches wide and can be 20’ or longer.. They can be rough cut or planed lumber. Southern yellow pine and hemlock are common wood types.
How is a post put in the ground?
Typically a machine is used to augur a hole in the ground, about 16”-20” in diameter and at least 4’ deep. The soil condition is evaluated and sometimes a concrete pad is set in the bottom of the hole. The post is set on this and crushed gravel fills in around the post. It is imperative that the posts be set plumb, straight and square to the building’s perimeter.
Will they rot at all?
There are some situations where a wood post, even pressure treated, would not be feasible. Poorly drained sites and sites that have problems with animal waste removal benefit by using other types of posts. Set properly, the posts will last decades and buildings put up 40-50 years ago still stand.
What if I want a concrete floor?
Most horse barns don’t have concrete floors but many other post frame buildings do. The issue with pouring a slab has nothing to do with whether there is a concrete frost wall around the perimeter. It has everything to do with ground preparation, concrete thickness and strength and whether the interior is heated. A structure that is heated will not let the floor heave if the sub-surface is prepared properly. An unheated structure can be built to minimize the cracking of a concrete floor.
