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Posted: Wed Apr 20, 2011 2:46 pm
by leemcd
Hi all,
Im a newly self employed Landscape Garden Designer/Builder. I have a wooden fence boundary and want to build a small (300mm high) retaining wall around some of it to accomodate a flower bed. It seems obvious to me i need to build another wall around the fence line to hold the bed, but i have been told that a waterproofed wooden frame around the fence would be satisfactory. Is this right? I know its a small amount of weight in the bed but something doesn't sit right with me about it. Any advice would be much appreciated
Thanks alot
Posted: Wed Apr 20, 2011 7:19 pm
by lutonlagerlout
could you not use 1800 by 300 by 40 mm concrete gravel boards?
never a good idea put lateral loading onto a fence
LLL
Posted: Wed Apr 20, 2011 7:38 pm
by Pablo
If you built the fence using 100x100mm posts and ensured the timber ran from post to post then it will be fine. I wouldn't go much higher than 300mm and would line all timber with heavy gauge plastic to stop it rotting.
Posted: Wed Apr 20, 2011 8:38 pm
by seanandruby
i would off set it so it's completly independant of the perimeter fence. If you had to say: change a post etc; you'd have to dig up both. Also don't agree with lateral loads like lll.
Posted: Wed Apr 20, 2011 8:44 pm
by Pablo
It's only a foot of compost guys which will equate to the lateral loading of a kitten a fence could easily take it.
Posted: Wed Apr 20, 2011 9:37 pm
by lutonlagerlout
a foot of compost?
what about when its filled with water?
TBH using fences as a retaining structure is a typical landscapers trick
I would use slotted concrete posts and 300mm gravel boards
it will be in for good
LLL 
Posted: Wed Apr 20, 2011 9:45 pm
by leemcd
I should have mentioned the fence is already in with timber posts. The site is an old, grade 1 listed, mental hospital come apartment block so there is no scope to start replacing posts. It seems to me theres no easy way out of this!:0
Posted: Wed Apr 20, 2011 10:25 pm
by Pablo
Compost is full of Fibre LLL so once compacted it binds to itself and doesn't slump. Also if the wall's 300 then the fill will only be 250 so it can be watered and mulched etc. The weight will be negligable. As for landscapers trick yes it is and a good one to if done right. Unnecessary over engineering is a typical builders trick when landscaping. How'd you like them apples. 
Posted: Wed Apr 20, 2011 10:34 pm
by lutonlagerlout
i suppose pablo's idea would work
not my cuppa tea though 
LLL