Drying out wet area

Discussion in 'Landscaping' started by geoffw, 29th Nov, 2020.

Join Australia's most dynamic and respected property investment community
  1. geoffw

    geoffw Moderator Staff Member

    Joined:
    15th Jun, 2015
    Posts:
    11,654
    Location:
    Newcastle
    We have a granny flat which is at the bottom end of a sloping block. We are having trouble trying to keep it dry.
    IMG20201128185529.jpg
    The area between the path and the retaining wall is a more. There is constantly water across the path.

    It has only shown itself in the past months due to all the rain - but it doesn't dry out even following a week of no rain. The retaining wall is wet, it seems that water has gone into the soil behind the wall. There is not a lot of water flowing over the top of the wall - we've diverted the water flowing under the fence.

    The plumber has quoted $3.5K for digging sumps and draining, which seems excessive considering the size of the problem. I'm seeking suggestions before a landscaping person has a look.

    We know that the muddy area isn't drained - the day the builder poured the path, we pointed out that the drains which were supposed to have been installed hadn't been. But it hasn't manifested itself this badly before.

    Has anybody overcome similar issues?
     
  2. Mark F

    Mark F Well-Known Member

    Joined:
    29th Jan, 2020
    Posts:
    1,029
    Location:
    Canberra
    I would install an ag drain about 300mm deep directly behind the wall and drill a series of 20-25mm holes through the mortar in wall at the base to allow the soil to drain. Another ag drain may be needed at the base of the wall but can be left till later. Send the bill to the builder.
     
    geoffw likes this.
  3. geoffw

    geoffw Moderator Staff Member

    Joined:
    15th Jun, 2015
    Posts:
    11,654
    Location:
    Newcastle
    Thanks for the ideas.

    It was built about seven years ago, so it's passed the warranty period.
     
  4. Scott No Mates

    Scott No Mates Well-Known Member

    Joined:
    18th Jun, 2015
    Posts:
    27,095
    Location:
    Sydney or NSW or Australia
    A French drain (or spoon drain) at the foot of the retaining wall and hooking into any stormwater drainage if you don't feel like digging too much.
     
    geoffw likes this.
  5. dmb1978

    dmb1978 Well-Known Member

    Joined:
    5th Nov, 2015
    Posts:
    353
    Location:
    ACT
    Not sure it would solve the drainage issue but could you put a slightly raised deck covering that area allowing the water to drain underneath but keep the area dry to walk on.
     
    geoffw likes this.
  6. geoffw

    geoffw Moderator Staff Member

    Joined:
    15th Jun, 2015
    Posts:
    11,654
    Location:
    Newcastle
    The advantage of a raised area, like a deck, is that it would add some value to the place, unlike money spent on drainage. However, I don't think that I could leave the area wet underneath that.

    What about concreting the earth area, raising it slightly? What sort of cost would that be? (I'm guessing I'd have to dig out wet earth, and perhaps replace with clean dry fill).
     
  7. dmb1978

    dmb1978 Well-Known Member

    Joined:
    5th Nov, 2015
    Posts:
    353
    Location:
    ACT
    What about turning that dirt area into a sunken but raised sides water feature. Leave it half full to fill naturally from the retaining wall and put some water lillies or fish in there.
     
    geoffw likes this.
  8. The Y-man

    The Y-man Moderator Staff Member

    Joined:
    18th Jun, 2015
    Posts:
    13,436
    Location:
    Melbourne
    I was thinking better to make it a paddy field :D

    [​IMG]

    The Y-man
     
  9. Scott No Mates

    Scott No Mates Well-Known Member

    Joined:
    18th Jun, 2015
    Posts:
    27,095
    Location:
    Sydney or NSW or Australia

    That looks more like a holiday in Cambodia.
     
  10. Paul@PAS

    Paul@PAS Tax, Accounting + SMSF + All things Property Tax Business Plus Member

    Joined:
    18th Jun, 2015
    Posts:
    23,319
    Location:
    Sydney
    I would look at channel drainage at the base of the wall and run that away somewhere. And dig some ag drain in a narrow trench with gravel in the mid tier of the wall and run that way to the sides too. That wall wont stay put if its got a dam of water behind it. I would argue the plumbers idea is probably spot on and not badly priced for the labour assuming its deep enough. The water problem needs to be addressed and hiding it wont help.

    Reminds me of a house I had in Melbourne. 6 months of the year it was a bog. I dug channels of drainage and it cost a lot of time but not much in materials and never posed a problem again. Itsa basic plumbing issue. Move water from A to B. Its in the soil. Best time to dig is when its wet.
     
    geoffw likes this.
  11. Islay

    Islay Well-Known Member

    Joined:
    28th Jul, 2018
    Posts:
    845
    Location:
    somewhere
    I do not have pictures because it was a long time ago in a previous house but this is what we did. In front of the fence at the back we put a dish drain. Then as @Mark F suggested we used ag drain at the top and bottom of the wall. The area at the bottom we made a "dry creek' feature. We covered the ag drain with large river rocks and planted to look like a dry creek bed. Tall reedy grasses etc towards the back to cover some of the wall etc I think we might have even had Kangaroo Paws on one end from memory. Anyway we made a feature out of what had been a mess. It worked really well.
     
    geoffw likes this.
  12. Mark F

    Mark F Well-Known Member

    Joined:
    29th Jan, 2020
    Posts:
    1,029
    Location:
    Canberra
    If you want paddies in the field then you should plant potatoes. :rolleyes:
     
    craigc likes this.
  13. 14022

    14022 Member

    Joined:
    20th Feb, 2018
    Posts:
    24
    Location:
    The best place
    As some others have said previous ag lines are needed, etc.
    The water needs to go into the property's stormwater system. If this can't be achieved, perhaps an absorption pit away from the property.
    Then, you can do whatever you want - gardens, deck, ponds. Hmmm, rice fields - maybe! :rolleyes:
     
  14. Handyandy

    Handyandy Well-Known Member

    Joined:
    18th Jun, 2015
    Posts:
    651
    Location:
    Sutherland
    Basically the further up the hill you can go to divert the water the better.

    On that basis I would go for an agg drain behind the wall with the pipe in the aggregate sloping to the storm water drain that must be there to drain the down pipe at the end of the house.

    I would not make any drainage holes in the wall as you want to take the water to the storm water drain. You might even consider waterproofing the dirt side of the wall to assist in the diversion of the water.

    It looks like there is a low spot at the end of the path as it seems covered in water. Depending on how deep the storm-water pipe is I would dig a pit adjacent to the low spot and connect the pit up to the storm water. Make sure the bottom of the pit is lower than the outlet so that you can clear out any silt. You can also install a gutter drain along the wall side of the concrete path ensuring that it drains towards the pit.

    Fill the area behind the bins with some extra soil so that the water runs towards the drains.

    Everhard EasyDRAIN Polymer Grate & 3m Prejoined Channel
     
    geoffw likes this.
  15. Paul@PAS

    Paul@PAS Tax, Accounting + SMSF + All things Property Tax Business Plus Member

    Joined:
    18th Jun, 2015
    Posts:
    23,319
    Location:
    Sydney
    When digging the drain trench the use of a geotex membrane can assist to act like waterproofing the wall together with an ag drain that is socked. Usually best to line the wall prior to backfill and hard to retrofit either waterproofing or a geotex liner without a lot of digging.

    Question : Does rear neighbour have a pool leak ? In which case the water may be deep and a shallow drain is ineffective.
     

Do you need help with investment strategies, don’t want to buy the wrong stocks, or you just need a regular income stream? We provide the research to ensure your investment selections achieve the goals. This is the value of advice.