Expert: Bruce E. Johnson - 5/7/2009

Question
We're currently getting bids on putting in a paver patio along the back of our house and replacing a 3 foot high retaining wall that will run parallel to the house.  the wall will be cinderblocks on a footing, faced with cultured stone.  THe patio will have the non-permeable filling and be sloped away from the house towards the wall.  We have major drainage from the back of our property towards the house, and existing french drains below the current wall.  Two contractors want to do weep holes between the patio and the wall (all will have a drainage pipe behind wall) and one wants to do a drainage field/french drain between wall and patio.  Is one better than the other?  We do have pine trees over the patio.
Thanks.  

Answer
Hi Amy, weep holes will relieve the hydrostatic pressure behind the retaining wall (one of the largest reasons why walls fail).  A proper footing drain that is piped away from the property will do the job also.  If you opt for the weep holes you will still need a layer of gravel and filter cloth behind the wall to filter the water as it comes through the weep holes and then you will need to drain that water somehow since you will be having two sources of water (the sloping patio and the weep holes) going to the same place.  A french drain in this collection area or a "deco drain" installed to collect the water and move it away.  Deco drains are slotte plastic drains most often used in pool decks for similar reasons.  I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com