CONSTRUCTION DETAILS— WALLS 



47 



TTdte-d 



depth of foundation. 4. Decide 

 on proportion of width to 

 height (three-tenths to five- 

 tenths). 5. Establish a verti- 

 cal line for the back of wall. 

 6. Decide on width of top of 

 wall. 7. Draw a diagonal line 

 from this point through half- 

 way point in rear line. 8. Erect 

 a perpendicular from lower end 

 of diagonal line. 9. Extend top 

 of wall horizontally to meet 

 this perpendicular. 10. Divide 

 this horizontal line into some 

 even number of spaces (nine 

 to twelve inches each). 

 11. Divide the perpendicular 

 into the same number of parts 

 plus one. 12. Adopt a regular 

 step form for the rear of the 

 wall using the vertical line pass- 

 ing through the one half-way 

 point previously estabUshed. 

 13. The upper step goes in 

 diagonally. 14. Extend the foundation six inches to nine inches 

 beyond the wall at front and rear. 15. Design parapet. 



Pry \Vall 



Fig. 50.— Sectional view of a dry wall showing 



location of perforated pipe to provide irriga- 



gation 



DRY WALLS 



For retaining purposes the dry wall is not very practical. In the 

 first place it is not substantial enough to hold any appreciable amount 

 of fill. It is, however, sometimes used as a facer wall where the mate- 

 rial back of it is cut away and not filled in, in which case this type of 

 waU in the garden is very desirable and can be made very interesting. 

 For the location and construction of such a wall see Fig. 48. 



It is often necessary to provide a subirrigation system for the rock 

 wall when Alpine plants are used in the prepared pockets. This may 

 be accomplished by running a two-inch agriculture tile along the top 

 of the slope about a foot below the surface; for best results it should 

 be embedded in crushed stone or cinders. Let the tile come up to the 

 surface some place where it can conveniently be filled with water — 



