Thomas Jefferson Papers

To Thomas Jefferson from Chapman Johnson, 19 June 1819

Staunton 19. June 1819.

Dear Sir

Mr Brooks, who tells me that he is going to the University, to cover some of the buildings with tin, has asked my opinion as to different modes of putting it on, and desired me, to communicate that opinion to you—

I do so, not from any confidence at all in my judgment upon the subject, but because I have been able to learn the opinions of others in this place, who have used this covering for their houses, and who have experienced the effect of the different modes of putting it on—

Four roofs were covered with tin, in this town, last year—On three of them, the courses of tin were put on diagonally, on the fourth they were put on horizontally—All of them are found to answer very well, in keeping out the wet, in ordinary seasons of rain and snow.—But in very hard driving rains, the three that are covered with diagonal courses, leak—This effect was very sensibly experienced during the storms we had here, about ten days ago—But the horizontal courses I understand resisted that storm, and have never leaked at all—This has induced me to form a decided preference in my mind, for the horizontal courses, over the diagonal—

The objection to the horizontal courses, as I understand it, is, that the wet is more likely to settle in the joints, and create rust—This seems to be the opinion of all, but than the greater security against leaking, in the opinion of the most judicious here, counter balances this objection, and indeed outweighs it very much, especially on roofs in which the angle they make with the horizon is not very great—roofs inclined to be flat—It is thought, too, that this danger of rust might be in a great measure guarded against, by very careful painting, which would give a good covering to the perpendicular joints—

It seems to be the general opinion here, that an error has been committed, in the covering of the roofs in this town, by giving too little lap to the squares of tin, upon their roofs at least when the courses are diagonal—and all concur in the opinion that the sheeting should be put on with great care and with an even exterior surface—It is thought too that the plank should be seasoned so as prevent shrinkage—

Excuse me for troubling you on this subject—and believe me

with very great respect your very obt Set

C Johnson

CSmH: Jefferson File.

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