September, 1916 
THE G A R D E X M A (J A Z I X E 
49 
The face of a retaining or brest wall may be effectually utilized to accommodate certain rock plants, which are best when planted in a dry wall as it is built 
wall. I might add that the following figures are 
for sand filling, one of the most difficult to hold 
and are therefore safe for all garden conditions. 
THICKNESS OF B-ASE IN TERMS OF HEIGHT A-B 
TOTAL HEIGHT OF THE 
EARTH COMPARED 
WITH THE HEIGHT OF 
THE WALL ABOVE 
GROUND 
WALL OF CUT 
STONE IN 
MORTAR 
GOOD MORTAR 
RUBBLE OR 
BRICK 
WALL OF 
GOOD DRY 
RUBBLE 
I 
0-35 
0.40 
0.50 
1 . 1 
0 .\l 
0.47 
0.57 
I .2 
0.46 
0.51 
0.61 
1-3 
0 49 
0.54 
0.64 
1.4 
0.51 
0.56 
0.66 
1 5 
0.52 
0 57 
0.67 
1 .6 
0-54 
0.59 
0.69 
I -7 
0-55 
0.60 
0.70 
I .8 
0.56 
0.61 
0.71 
2. 
0.58 
0,63 
0 73 
2-5 
0.60 
0.65 
0.75 
3. 
0.62 
0 67 
0.77 
4 
0.63 
0.68 
0.78 
6. 
0.64 
0.69 
0.79 
A wall of considerable height is frequently 
stepped back (figure 3) and if the earth does 
not rise above the top of the wall, the thickness 
at each step .A-A is never less than one third 
the height from the top of the wall to this 
point. It is to be well noted that this 5 rule is 
only applicable when the earth is level with the 
top; when it goes above, the thicknesses are 
found by using the table. Always carry the 
footings below the lowest frost line and for 
stability make them of large stones or of con- 
crete, the thickness of the concrete depend- 
ing on the weight of the wall above but never 
less than 8 inches. Let them extend for 6 
inches on each side of the wall. The minimum 
bearing power in tons per square foot of soils is 
as follows: Clay in thick beds and always dry, 
4 tons; the same moderately dry, 2 tons; clay, 
soft, I ton; sand, 2 tons; loam, firm and dry, 3 
tons; firm stiff gravel, 4 tons. These figures 
vary in localities but are the ones generally 
accepted. Stonework weighs from 125 lbs. 
per cubic foot for dry rubble to 165 lbs. per 
cubic foot for dres.sed granite or limestones. 
Brickwork is figured at 125 lbs. per cubic foot 
for medium quality and 140 lbs. per cubic foot 
for pressed brick with fine joints. Ordinary 
concrete, i to 8, will support at the end of 6 
months 10 tons per square foot and at the end 
of a year will hold i 3 to 20 tons; so for our gar- 
den work it is safe to apply the load ten or 
fifteen days after the setting of the concrete 
footings. From the above figures it is easy to 
find out how far to spread the footings to safely 
distribute the wall load over the soil. For the 
average wall it will not be necessary to do this, 
for the weight is not great; but for high, thick 
walls it would be wise to make the calculation. 
A technical discussion of masonry walls was 
given in last month’s issue and need not be en- 
By breaking the courses an efficient bond is provided. 
This may be done in rough stone walls by using large, long 
stones at irregular intervals 
larged upon now, but I zvoiild say that careful 
workmanship counts for more in a retaining 
wall than in one that is freestanding. 
BREST WALLS 
A brest wall is generality more for protection 
than to sustain earth pressure, unless there is a 
natural slope toward the walls or loose sand is 
found. In these cases some of the elements 
of a retaining wall problem occur. In budding 
a brest wall the important factor is to leave un- 
disturbed as little as possible the earth behind 
the wall, allowing no air or moisture to act 
upon It. Do not leave any space between the 
wall and the earth for the latter to move, for 
earth, if held in its natural position, requires 
but little force to retain it, but if allowed to 
shift has tremendous power. Be careful in 
noting whether the earth slopes in a strata 
against the wall. If it does apply the prin- 
ciples of a retaining wall. If the brest wall is 
but a protection, as it is in most cases, pay 
special attention to the drainage. It is diffi- 
cult to tell exactly hozv this is to be done as no 
two conditions are alike. Openings in the 
base, not too large, will bring the water to the 
lower level. The drain pipe sy'stem as shown 
in figure i may be used if it can be put in with- 
out disturbing the earth too much. .Soils that 
drain quickly are easier to take care of in this 
respect. 1 ry to preserve the natural drainage 
as this is exceedingly important, for earth kept 
in its natural state is not apt to change. 
In some cases reinforced concrete may be 
cheaper than stone or brick or it mayy be used 
to carry out a scheme of design and color al- 
ready established in the garden. It certainly 
reduces material, which is a consideration if 
the space to be occupied by the wall is limited. 
Reinforced concrete is purely an engineering 
problem and should not be attempted by an 
amateur without expert advice. 
What we have gone over above is for the 
average garden wall which is not excessive in 
height and offers no unusual difficulties. 
hL 
