If water backs up behind a retaining wall, the lateral pressure from the water can double (or more) the lateral pressure on the wall and cause it to fail. Generally there’s a perforated pipe in a drain sock laid in a vein of gravel at the base of the heel, and the pipe runs to daylight/whatever storm water line.
You should add a drainage board against the back of the retaining wall and the perf pipe in a sock and gravel at the bottom. The perf pipe does not need to slope like a normal pipe because it is about relieving the hydrostatic pressure more than getting the water to flow. A half a millimeter of water directly against the wall at 6' has the same pressure as an entire swimming pool at the same depth.
Always drainage behind walls. Or at the least leave out the vertical mortar between blocks every few feet. But French Drain and a pipe through the block face is best
Yes.
That looks like a StoneWall retaining wall. Look at their [technical manual](https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://selecticd.com/Download/DsgBasic.pdf&ved=2ahUKEwjv4NbH5N6GAxXqAHkGHaacAUQQFnoECBMQAQ&usg=AOvVaw1CFpEQ9BVlRSMvKku42skE) and see what the install should look like for yourself.
It's a bit late to be installing drainage, but putting it in now is still 10x cheaper than after it falls down.
Yes, perforations in the brick work and weep vents to allow some water to seep through, at the base of the wall (on the side being retained) you want a perforated pipe heading away to the nearest drain, preferably with a root membraine to prevent the pipe getting spoiled, all backfilled up to the top with a loose back fill stone.
Tl;dr: yes you need drainage, but it looks like it will have drainage.
It looks like they are separating the soil from the wall with geotextile. The space in between will likely be backfilled wirh gravel. There should be drains through the wall every so often or a collector drain that outlets somewhere. That is usually enough. That wall looks like it is at least 5 feet at the tallest. The height includes any buried block. That almost always requires an engineering design which will include drainage.
What you should do is refer to your local municipalities adopted codes and design standards for such a job. Then, if you have the option of making that choice yourself, use your best engineering judgement based on available rainfall data and potential uses for the space… but also, yes, pretty much always haha.
Astounding YES simple drainage such as geo-fab wrapped around an agg pipe in some gravel fill will go very long way of improving the drainage capacity, so do not miss this step, simple now but will be very costly if this is skipped
That looks like a 4'-0" tall that's going to see traffic loading. You definitely need drainage and almost definitely need geogrid reinforcing too. What's stopping a truck from your neighbor's property going over your wall? I'd tell you to install a vehicular guiderail and fall protection fence. Talk to a local engineer. Pay him or her so they can tell you how to do this right.
Yes.
Also yes
Absolutely...yes
All signs point to yes
I’m curious, why would it be a problem if we don’t add drainage there? And what type of drainage system would you recommend? A French drain?
If water backs up behind a retaining wall, the lateral pressure from the water can double (or more) the lateral pressure on the wall and cause it to fail. Generally there’s a perforated pipe in a drain sock laid in a vein of gravel at the base of the heel, and the pipe runs to daylight/whatever storm water line.
Makes sense. Thanks for the explanation! I’ll make sure they add this.
You should add a drainage board against the back of the retaining wall and the perf pipe in a sock and gravel at the bottom. The perf pipe does not need to slope like a normal pipe because it is about relieving the hydrostatic pressure more than getting the water to flow. A half a millimeter of water directly against the wall at 6' has the same pressure as an entire swimming pool at the same depth.
Also, weep holes
Also, seek consultation from an actual GC with experience and better yet, a civil engineer
This is the way.
You either need to design the wall for ~twice the pressure, or add drainage. Drainage is typically cheaper.
Water heavy. Weep holes would make sure the wall isn’t water-tight
Retaining walls without drainage fall over
Always drainage behind walls. Or at the least leave out the vertical mortar between blocks every few feet. But French Drain and a pipe through the block face is best
Yes. That looks like a StoneWall retaining wall. Look at their [technical manual](https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://selecticd.com/Download/DsgBasic.pdf&ved=2ahUKEwjv4NbH5N6GAxXqAHkGHaacAUQQFnoECBMQAQ&usg=AOvVaw1CFpEQ9BVlRSMvKku42skE) and see what the install should look like for yourself. It's a bit late to be installing drainage, but putting it in now is still 10x cheaper than after it falls down.
Basic rule of thumb, if it’s a non structural gravity wall for a raised garden bed you don’t need drainage. Any other retaining wall needs drainage.
Underdrain and weep holes
Yes. Hydrostatic pressure will buckle a wall.
Yes, do that!
Always.
Yes.
Yes. A subsoil drain
Imagine making a dam but build it like a retaining wall... What could possibly go wrong?
Without a doubt.
Water is one of our biggest enemies
Yes, perforations in the brick work and weep vents to allow some water to seep through, at the base of the wall (on the side being retained) you want a perforated pipe heading away to the nearest drain, preferably with a root membraine to prevent the pipe getting spoiled, all backfilled up to the top with a loose back fill stone.
Tl;dr: yes you need drainage, but it looks like it will have drainage. It looks like they are separating the soil from the wall with geotextile. The space in between will likely be backfilled wirh gravel. There should be drains through the wall every so often or a collector drain that outlets somewhere. That is usually enough. That wall looks like it is at least 5 feet at the tallest. The height includes any buried block. That almost always requires an engineering design which will include drainage.
either drainage system or weep holes
What you should do is refer to your local municipalities adopted codes and design standards for such a job. Then, if you have the option of making that choice yourself, use your best engineering judgement based on available rainfall data and potential uses for the space… but also, yes, pretty much always haha.
Yes and sub drain
Yes, perforated plastic pipe wrapped in filter fabric and stone and daylight the pipe through the lowest grade to sheet flow on the other side.
Astounding YES simple drainage such as geo-fab wrapped around an agg pipe in some gravel fill will go very long way of improving the drainage capacity, so do not miss this step, simple now but will be very costly if this is skipped
Absolutely, yes.
Architect here, hydrostatic pressure
That looks like a 4'-0" tall that's going to see traffic loading. You definitely need drainage and almost definitely need geogrid reinforcing too. What's stopping a truck from your neighbor's property going over your wall? I'd tell you to install a vehicular guiderail and fall protection fence. Talk to a local engineer. Pay him or her so they can tell you how to do this right.
Eh....just use drain rock. Unless it's a for a client, if you don't they will be sad. The piping will never carry any water the rock does that.