I I IS not the intention 
of the words that fol- 
low to treat thor- 
oughly the subject of 
retaining walls nor to ap- 
proach it in a scientific 
fashion as would an en- 
gineer in his treatise. Rather it is to state a 
few precautions viewing the matter with the 
eye of the garden builder who wishes to super- 
vise or execute the work himself. 
Of all the walls in the garden the retaining 
wall exacts the greatest care as to construction. 
It is not a great or expensive matter, compara- 
tively speaking, to repair a freestanding wall 
but when trouble arises in the retaining wall 
affairs become serious. Not only is reparation 
difficult but the damage done is often so great 
that the most careful planting can be irre- 
parably ruined. Do not go ahead blithely to 
put up your retaining wall without first giving 
a careful study to the conditions. I recall 
the sad experience of a Staten Island amateur 
who, with the comprehensible ignorance of an 
incompetent, had built for him, sans expert 
advice, a beautiful wall retaining an irregular 
plot of ground upon which the garden was to 
flourish. Some months after it was finished 
small cracks appeared; they increased, the 
earth sank in great batches and the last time I 
saw it, the workmen were frantically trying to 
hold it back with tie-rods and the poor garden 
plot was just a plain wreck. It was indeed a 
sad sight. 
l echnically, all walls holding back earth are 
not retaining walls. A simon pure retaining 
wall is one that sustains the pressure of some 
filling material after the wall is built, while one 
that stops the fall of earth from its natural 
Retaining Walls — w. h. butterfield 
FACTORS THAT GOVERN THEIR THICKNESS, ETC— PRINCIPLES OF 
CONSTRUCTION AND MATERIALS USED 
special one. The cohesion of the earth, its 
degree of moisture and how it was packed 
against the wall are the important considera- 
tions. I he factor of safety is always high. 
Experience counts for a great deal and the 
rules and precautions that follow are based 
Trouble coming! The wall is breaking away because the 
thrust behind is too great for this style of constuction 
IlLTAINiNC 
WALL 
position IS a brest or face 
wall. In the latter case it 
is assumed that earth has 
been cut away on the clear 
side of the wall. Figs. 
I A and iB show what I 
mean. Greater care must 
be taken in the construc- 
tion of retainingwalls than 
in the constructionof brest 
walls. Let us leave the lat- 
ter for a moment and 
discuss the more im- 
portant as in most 
garden work there 
will be some filling in. 
Ihere are many 
theories and much 
literature on the subject 
FIG. lA. 
Fig. 2. Diagram show- 
ing the filled earth 
height as compared with 
the wall height 
upon experience and are established by actual 
construction. 
Of prime importance is the drainage, for dry 
earth slips less than wet earth; and it is the 
slipping of the earth that puts the pressure on 
the wall. A good drainage is shown in fig. lA. 
The surface water is 
caught in the concrete 
gutter. A, con- 
veyed by the 
pipe to the open 
tile drain, B, and by open- 
ings in the wall carried off 
to the lower level while the sub- 
surface water collects in the tile 
drain and is quickly disposed of. 
The drainage question is so im- 
portant that under no conditions 
should it be overlooked. 1 he thing 
to do is to take away all surplus wa- 
ter as soon as possible. The natural 
earth that rests in place should be 
cut in steps inclined away from the 
for this will make the layers of 
wa 
earth. 
of the thrust of 
earth against a wall, hut in practise no formula 
can be given to accurately determine what this 
thrust amounts to; the aim being to have the 
minimum amount of material to do the work. 
Fhe conditions vary so that each 
case IS a 
if well rammed, slip the op- 
posite way from the wall and thereby 
reduce the pressure. If by any 
chance the layers should slope toward 
the wall, the pressure will be greatly 
increased. 
When the face of a wall slopes back 
from the perpendicular it is termed a 
"batter,” and retaining 
walls are usually thus 
built. This makes them 
thicker where the heaviest 
pressure comes and means 
a saving of material. A 
batter may not always be 
desirable in a garden for often a vertical sur- 
face is wanted as a matter of design. 
Where stones or bricks are used, incline the 
courses toward the earth. This is an assis- 
tance to resist pressure for if the latter is great 
It tends to push the stones or bricks one over 
the other and, while the mortar has some hold- 
ing power, the added friction is needed es- 
pecially if the mortar is a long time in setting 
and one does like to leave the filling in until 
this action occurs. The rougher the back of 
the wall below the frost line the better. This 
also increases friction and tends to direct the 
force of the pressure in a vertical sense and 
make it fall within the base. To accomplish 
this let bricks or stones project one beyond the 
other. 
A well bonded wall makes a more solid wall 
and if stone is the material have long ones at 
the back extending up through several courses; 
in other words avoid courses of equal depth. 
If there is apt to be deep freezing of the ground, 
splay the top as shown in figure 3, as it allows 
of less displacement. Surfaces coming in con- 
tact with frost are best if smooth for they give, 
thereby, little hold to it. 
gineers,” a standard 
authority. Reading 
the table and refer- 
ring to figure 
2, it will be 
seen that the ,*■' 
EARTH 
ULMDVLD 
^TARJH IN 
NATURAL 
STATL 
FIG. IB. 
BLL/T WALL 
A aL 
Kifi. 3 . “A wall of 
siderable height is 
quently steppied back” 
numbers in the first column refer to C D of the 
diagram which is the filled earth height as 
compared with the wall height from A to B. 
The dotted area shows the filling and the 
hatched area denotes the 
earth in its natural position. 
The other columns give the 
thickness of the wall at the 
base in terms of the height A 
B. Say the wall height was ten 
feet and the filling was deep 
enough to be one and one half 
times ten feet or fifteen feet 
and being of brick we would 
search in the third column for 
the number opposite one and 
one half or 1.5 in the first 
column; finding this to be 0.57 
which is 0.57 of the height ten 
feet we multiply and have 5.7 
feet for the thickness of the 
base. A batter of one and one 
half inches to the foot may be 
safely put on the wall after the 
base dimension is found, but 
there are few cases where less 
than one and one half feet is 
safe for the top of a retaining 
V 
THE REPUIRED THICKNESS 
The following table, which is for calculating 
the thickness of the base, is from Trautwine’s 
“ Pocket Book for En- 
.a: 
aL 
con- 
fre- 
48 
