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Posted: Wed Aug 31, 2016 6:27 am
by Donk
Firstly, long time reader and owner of Tony's book which is a real gem and would recommenced to anyone doing groundworks.
We have a new build to start shortly which backs onto a shallow stream which sits around 2-3m below DPC and is a wide V shape banked. The site is tight at the rear and I'm thinking of squaring up the bank by using some gabion cages. This would double the size of the garden near enough by making the bank of the stream vertical rather than a long V so would gain best part of 3m width along the whole length of the bungalow. Not insignifivant.
Building control isnt on site yet so looking for a heads up, will the struct eng have to design the gabion or can we crack on and build it ?
The bungalow footings will be 3m+ away so using the 45 degreee rule there wont be any movement from the building transferred tot he gabions ?
And finally, if we bring the gabions upto ground level will need to fence it to stops people falling in! How to affix posts to the cages or build them in as we fill with stone ?
thanks
Posted: Wed Aug 31, 2016 7:38 am
by seanandruby
Seen people put a pipe in first and build around it but very difficlt as you need you build the face of gabion nice and uniform like a normal dry stone wall, stones need to interlock for strength
Posted: Thu Sep 01, 2016 8:20 am
by Donk
thanks for the reply, I wasn't very clear. We are not building over the watercourse just the banking to one side of it to square it up.
Seems no regs are requires as it isnt really building! The gabion supplier has suggested a 'mattress' sitting just below the invert level of the watercourse to guard against erosion and then stack on top. All common sense and straight forward.
Posted: Thu Sep 01, 2016 5:48 pm
by lutonlagerlout
Gb groundworks will be along soon,he has built a few gabions ,not quite as easy as you may think
think they did a job where the previous one failed and the lot went into the water!
LLL 
Posted: Fri Sep 02, 2016 7:15 pm
by GB_Groundworks
you need environment agency permission to be doing anything with 8m of a watercourse etc first of all speak to them if its only tiny stream/brook they might not be bothered but if it handles run off and flood water then they might not let you as you'll be affecting the flow dynamics and its a big fine for not notifying if they go after you.
if theres no push you should be ok without engineer but we always use an engineer
i use 4-5mm welded cages not the woven ones, you want wall stone to face them in large units like 150mm and flat as possible like you'd use for walling
as sean said, you either set 6 inch twin wall in then concrete the post in or build the post in but its fiddly to build them in
Posted: Sat Sep 03, 2016 6:08 am
by Donk
cheers Giles, thats what we are planning. Been in touch with EA but they arent interested as its such a tiddly flow.
Posted: Sat Sep 03, 2016 9:47 am
by Pablo
Hi Donk, it's essential to get structural advice on a wall as high as that. You may also need to dig a test pit at the lowest point to establish where your starting height from good ground is, however they can be built to a slight slope if the garden has a crossfall. If the wall isn't facing the house then I personally wouldn't blow any cash on facing it with expensive building stone since you'll not see it, also the wall isn't entirely vertical since each cage should be set back from the one below it. My biggest stress though would be the backfill, it's coming into the wrong time of year weather wise for soil compaction and it's also likely that the water levels will be higher from now on too. If the fill isn't done right then your garden will sink and your fence will start leaning inwards.
Good luck with the project, I love doing gabions but haven't had a decent job in a couple of years now.
Posted: Sat Sep 03, 2016 8:25 pm
by GB_Groundworks
Posted: Sun Sep 04, 2016 7:16 am
by Donk
nice job. Any reason your using walling stone instead of (cheaper) washed 150mm+ rocks ?
Posted: Sun Sep 04, 2016 7:30 pm
by GB_Groundworks
only aesthetics and ease of stacking the term escapes me but there is a term for the flat ish stone best suited for walling etc
washed 150mm is a bugger to stack neatly but if its unseen we've down machine filled ones, can even get geotextile lined ones and fill rubble
Posted: Sun Sep 04, 2016 7:42 pm
by seanandruby
GB_Groundworks wrote:only aesthetics and ease of stacking the term escapes me but there is a term for the flat ish stone best suited for walling etc
washed 150mm is a bugger to stack neatly but if its unseen we've down machine filled ones, can even get geotextile lined ones and fill rubble
...try dry stone walling Giles :;):
Posted: Mon Sep 05, 2016 7:03 am
by Donk
GB_Groundworks wrote:only aesthetics and ease of stacking the term escapes me but there is a term for the flat ish stone best suited for walling etc
washed 150mm is a bugger to stack neatly but if its unseen we've down machine filled ones, can even get geotextile lined ones and fill rubble
funny you should say that, I was thinking the same. All that pretty stone is expensive. Railway ballast isnt!
Posted: Mon Sep 05, 2016 8:15 pm
by GB_Groundworks
yeah but there is a specific name for it like dtp type 1 (aka mot) etc stratapheric rock etc has pretty flat tops and and bottom almost coursed
