CONSTRUCTION DETAILS— WALLS 45 



RETAINING WALLS 



Oftentimes walls are difficult to design as it is sometimes hard to 

 estimate the strength required. WaUs need not be as large in land- 

 scape work as in engineering work. If a wall is to be used about a 

 garden or near the house it should have a coping, made a little wider 

 than the wall to keep out rain, etc. If balustrades are to be used, a 

 stringer course (Fig. 43) is first placed on the wall, then by means of 

 SLX-inch dowels the balustrade is held in place. 



A wall should, if possible, be one soHd whole and not be made up 

 of parts. Retaining walls must have a good foundation, never less 

 than three feet, and for strong walls four feet, deep. Never build a 

 wall on filled ground unless it has had at least a year to settle and 

 pack. It is best to go down to the original surface if possible. A foun- 

 dation for a wall on a hillside should be built in steps (Fig. 49) ; and 

 see that it is well drained. The width of walls should be one-third 

 to one-half of the total height (Fig. 49). If made of cut stone masonry 

 the width of the base is one- third of the height retained; one-fourth 

 should be satisfactory for brick and ordinary masonry. The thickness 

 should be greater in a surcharged wall (Fig. 44), say five- tenths to six- 

 tenths of the height retained for stone masonry, and six-tenths to 

 seven-tenths for concrete. A long, heavy retaining wall may have 

 buttresses placed about fifteen feet apart to prevent its breaking. The 

 work should be well bonded by the use of mixture of one part of cement 

 to one and one-half of sand. Provide weak holes or openings through 

 the bottom part of the wall for drainage. If plenty of stones are handy 

 they may be used at the bottom of the fill to take care of the drainage. 

 Weak holes are placed about twelve to fifteen feet apart (Fig. 47). 



STEPS IN DESIGNING A RETAINING WALL (Fig. 49) 



1. Decide on height to be retained. 2. Decide on batter to be 

 used (not over one and a half inches to one foot). 3. Decide on 



Fig. 48. — A dry wall can sometimes be used as a retaining wall where the cut is not too deep 

 and the amount of soil to be held not too great. This sectional diagram suggests such a use 



