I see lots of references to installing a perforated pipe French drain system behind retaining walls. Usuallying laying the pipe behind the first course of block.

Usually the block is level so as to make the wall level obviously. Shouldn't the perforated pipe have a downward slope to it? If so, how much? My wall will not be very tall but will be about 40 feet long.

I appreciate any help

On Wednesday, May 20, 2015 at 8:54:34 AM UTC-4, wrote:
I see lots of references to installing a perforated pipe French drain system behind retaining walls. Usuallying laying the pipe behind the first course of block.

Usually the block is level so as to make the wall level obviously. Shouldn't the perforated pipe have a downward slope to it? If so, how much? My wall will not be very tall but will be about 40 feet long.

I appreciate any help

yes, buthonestly walls always fail, you far better off reslopping the yard.....

my moms house had a retaing wall, i tore it down and let ivy take over. appearance just so so. cost zero, future maintence zer.

sold the home, the new owner killed the ivy, and built nice wall.

its falling over and will need rebuilt.

if he had left the ivy he wouldnt need to do a thing.

i tore out most of my retaing walls here, and only rebuilt ones i had no choice but to keep.

those are showing their age, and will need rebuilt again. y bad knee means it wouldnt be me......

On Wednesday, May 20, 2015 at 8:54:34 AM UTC-4, wrote:
I see lots of references to installing a perforated pipe French drain system behind retaining walls. Usuallying laying the pipe behind the first course of block.

Usually the block is level so as to make the wall level obviously. Shouldn't the perforated pipe have a downward slope to it? If so, how much? My wall will not be very tall but will be about 40 feet long.

I appreciate any help

I'd say about 1" in 10 ft is good.

wrote:
I see lots of references to installing a perforated pipe French drain system behind retaining walls. Usuallying laying the pipe behind the first course of block.

Usually the block is level so as to make the wall level obviously. Shouldn't the perforated pipe have a downward slope to it? If so, how much? My wall will not be very tall but will be about 40 feet long.

I appreciate any help

if you have cold weather you'll need to put the footing
deeper, it also should have drainage not behind it but also
down deeper so the footing itself is kept drained.

behind the wall put a layer of gravel and keep it apart
from the soil by using some landscape fabric (which lets
water through). this will let it drain behind the wall
and keep the soil from pushing the wall out.

half circles and buttresses are stronger than straight
lines (if you were going taller).

most problems i see are materials are poor, no footing,
not enough drainage and not enough allowance for forces.

in the case of using blocks these can gradually degrade
if kept in contact with the soil behind it and moisture or
plant roots can degrade them too, so keeping the plants
from growing on it and having a gravel layer behind it with
good drainage will make it last much longer.

failures abound as many people just pile stuff up and
expect it to hold without considering the frost heaving
and other forces.

slopes are difficult themselves in that they tend to get
poor over time as organic material and nutrients are washed
away. the thicker the ground cover you can put on the slope
the better, but if you have shading bushes or trees then it
tends to be too thin and prone to erosion losses.


songbird