Bents for 12-Sided Plank Frame Barn.
From J. D., Ubly, Mich.—I send herewith a rough sketch, [Fig. 1], showing one of the bents of a 12-sided plank frame barn, and would like to have the architectural readers of the paper state whether or not it will be strong enough for the purpose, and, if not, wherein changes can be made to advantage.
Note.—With a view to obtaining the opinion of an expert who has had long experience in the construction of plank frame barns, we submitted the inquiry of our correspondent above to John L. Shawver, who furnishes the following in reply:
In the first place, the purlin posts in the sketch of the correspondent are so sloping that while they brace well they are not in position to sustain the most weight, and these with the roof supports are so long that they have to be spliced. While this is easily done in the case of posts, it is not so readily performed with supports, and, when so done, it will not present as attractive an appearance as would otherwise be the case.
Fig. 1.—Elevation of Bent Submitted by “J. D.”
Fig. 2.—One Form of Plank Frame Suggested by Mr. Shawver.
In the second place, one of the weakest points about the barn is the shape. It is true it would be a novelty in most communities, but, like the round barns, is wasteful of material. It is out of the question to place joists, rafters, flooring, sheathing, roofing, &c., on barns of this shape without much waste of both materials and labor. Then, too, it is next to impossible to provide for satisfactory lighting or ventilation, both of which are essential features in every up to date barn.
Fig. 3.—The Preferable Style of Framing.
The frame construction indicated in [Fig. 2] is stronger, and at the same time gives more open space in the interior, this being secured by running the purlin posts up to the first purlin plate, instead of to the second, and supporting the second plate on the truss brace. This saves in the lengths of the purlin posts, but requires the same length of supports and longer sub-supports.
The form of construction indicated in [Fig. 3] is, in my opinion, preferable to either of the others, if it is found that the vertical posts set in 10 feet will not in any way interfere with the purpose of the structure. In this case all the timbers are either shortened or placed in such shape that they may be spliced without in any way weakening the structure. Whichever form may be used by the correspondent, it is important in bents or arches of this size that the purlin posts should be placed on the inner edge with 2 × 6, which will add materially to the strength of the frame, and at the same time prevent any tendency to spring sideways either in the raising or from the pressure of the hay or grain within after the building is completed.
Transcriber’s Notes:
The illustrations have been moved so that they do not break up paragraphs and so that they are next to the text they illustrate.
Typographical and punctuation errors have been silently corrected.