Could anyone tell where I can find out the industrial standards for the size of the retaining wall drainage, please. I heard that it the wall is less than 1m high then the 65mm Ag pipe can be used, but if the wall is more than 1m high then 100mm Ag pipe should be used. However I haven't been able to get confirmation from any official documents (such as Australian Standards or Building Code Australia). Thanks for help.
Retaining wall drainage standards
- Thread starter chris01
- Start date
I can't login to SAI right now so don't put too much faith in my answer, but...
I don't believe this will even be covered by an australian standard. It sounds more like anecdote to me.
In determining whether drainage was necessary at all, and how big the pipe should be/what type of drainage system to use, you would have to take into cosideration the soil profile, wall type, ARI for the area, water table, the rest of the drainage system, and possibly othe factors.
If you're building the wall without consulting a civil engineer or drainage specialist, use a great big ag pipe and lots of weepholes.
I don't believe this will even be covered by an australian standard. It sounds more like anecdote to me.
In determining whether drainage was necessary at all, and how big the pipe should be/what type of drainage system to use, you would have to take into cosideration the soil profile, wall type, ARI for the area, water table, the rest of the drainage system, and possibly othe factors.
If you're building the wall without consulting a civil engineer or drainage specialist, use a great big ag pipe and lots of weepholes.
Just use the bigger one. It will rarely be tested but its the one in 20 or more years rain that will fill the thinner one, back the water up behind the wall and push it sideways creating total carnage and expensive fixing. then you will regret not spending about $2 more for a larger diameter pipe.
Note: costing suggested may be approximate, but its really not that much more.
Note: costing suggested may be approximate, but its really not that much more.
The size of the drainage will be dependent upon several factors: height of wall, length of wall, type of soil which is being retained etc. Been all too long since I learnt the calculations but they aren't that hard, even I was able to do it!
Remember that you will need to put your ag drain in a geotextile sock,cover with plenty of free-draining coarse aggregate and again more geotex over the aggregate. Weep holes, adequate footing design etc don't go astray either.
You might consider something like Atlantis drainage cell which will fit up against the wall or check out the products at Bunnings/plumbing supplies place.
Just to re-emphasize, don't skimp to save some bucks!!!
This is there to stop your wall falling over, and whatever is on the high side destroying whatever is on the low side.
This may be a garden bed into a garden, or your house into a pool. Either way, it's not worth the money you may save skimping now.
This is there to stop your wall falling over, and whatever is on the high side destroying whatever is on the low side.
This may be a garden bed into a garden, or your house into a pool. Either way, it's not worth the money you may save skimping now.
Hi guys, thanks for your input.
I just read "Queensland Construction Specifications" Aus-Spec C231 - "Subsoil and Foundation Drains, in which C231.05 (b) says "the 100mm diameter corrugated slotted lastic piping.....shall be laid on a bed of filter material ...."
I'm not sure this C231 is applied for domestic, commercial or both.
Retaining wall drainage is subsoil drainage.
I just read "Queensland Construction Specifications" Aus-Spec C231 - "Subsoil and Foundation Drains, in which C231.05 (b) says "the 100mm diameter corrugated slotted lastic piping.....shall be laid on a bed of filter material ...."
I'm not sure this C231 is applied for domestic, commercial or both.
Retaining wall drainage is subsoil drainage.
Retaining walls can be complicated, and usually require an engineer. If you're going to have to use an engineer anyway, why bother learning about the codes when they're going to do it for you anyway? (unless it's a simple one that you aren't planning on having certified or something)
"SUbsoil drainage" refers more to a full system of earthworks, sand pads and clay-base shaping. Something an engineer does.
Again, it really depends greatly on the soil report and other factors I mentioned above. For example, I've got a 700mm limestone retaining wall with no drainage because the soil behind it is all rapidly draining A class sand. (Even though there is a soakwell discharging into the soil only a couple of metres away on the high side)
Whatever heresay you've got from your mate-who-knows-about-retaining-walls-and-that, you really need an engineer to assess your individual situation.
Again, it really depends greatly on the soil report and other factors I mentioned above. For example, I've got a 700mm limestone retaining wall with no drainage because the soil behind it is all rapidly draining A class sand. (Even though there is a soakwell discharging into the soil only a couple of metres away on the high side)
Whatever heresay you've got from your mate-who-knows-about-retaining-walls-and-that, you really need an engineer to assess your individual situation.
Try the Plumbing Industry Commission.