Roof -hoards and Shingles 165 



matched — tongued and grooved — and covered 

 with 23aper to prevent cold and draughts of air 

 from passing into the attic. Since slates, on 

 account of their somewhat rough surfaces, do 

 not lie closely together, the wind is likely to 

 pass through the cracks in the roof, if thei'e are 

 any, and carry snow and rain into the upper 

 part of the house ; therefore the roof covering 

 immediately under the slates should be virtually 

 air-tight. The roof boards for a shingle roof 

 should be narrow and laid with openings of 

 from IX to 2 inches between the boards. Rain 

 and snow seldom drive up and through the 

 shingle roof, and since wooden roofs are more 

 likely to rot out than to wear out, the more per- 

 fectly the shingles are dried out after a storm 

 the better. The narrow roof boards and the 

 spaces between them allow the shingles to dry 

 quickly, and therefore are better than matched 

 boards. 



The short, or common, shingle of commerce 

 is 16 inches long, %- to %-inch thick at one 

 end, and % of an inch at the other, and is 

 computed at 4 inches wide. A bunch of shin- 

 gles contains one fourth of a thousand. It 

 should have 25 double courses and the band 

 should be 20 inches long. Not infrequently 

 there is a course or two wanting, or the bands 

 are an inch or so short. Having this data, one 



