Browse Forums Landscape & Garden Design 1 Oct 22, 2012 8:28 am ok retainings a pretty common topic so id thought i would start (another) thread detailing what we have to do for our retaining and the decisions we have to make. we have a two tiered system otherwise the wall would be two meters high and we'd need council approval we are lucky enough to have plenty of room so can set the walls back as far as we feel like from each other and as someone else said in another thread when i asked, two meters is a minimum you would want to have the second higher wall if the walls are each a meter high so thats that bit sorted the walls are a meter high and tiered. ok, so what product do we use? to me the best would be concrete sleepers we got a decent price including delivery on some flash looking concrete sleepers (not the smooth industrial ones) and i can get the steel uprights from a local steel supplier who do the H or I channel and end caps (although they do not do the right angle pieces or 45 degree angled pieces, but im guessing i can a few C channel ends welded up to make the appropriate angled pieces i need) now the installation of the concrete sleepers is where im having trouble...physically the sleepers weigh 86 kilo each (so we were told) and when you have around 150 to 180 to install, a friend and myself would be completely stuffed lifting all those sleepers a meter high and sliding them down the channel into place, it would also take quite a while as lifting that much weight constantly would need to be broken down over a few weeks...to save our backs!! so we could get a bobcat or a friend with an excavator to help us lift them, but at $80 an hr for the bobbie or $95 an hour for the excavator its prob going to be quite hefty in price just to help us lift them in so therefore the price increases over all. so we looked at treated pine timber. if we use timber i would like to use the 2.4 meter long by 100mm thick by 200mm high ones, nice and bulky and strong and less likely to bow bunnings have the timbers at a reasonable price, $23.90 each. roughly $10 cheaper each than we can get the concrete sleepers for. so ok timber is cheaper (obviously), but we need bolts to fix the timber sleepers to the timber uprights, and when you have around 180 sleepers (more if you use timber uprights now) the bolts are going to add up in price pretty quickly. so do we use timber sleepers with steel uprights??? while to me it doesnt look as nice and putting a top cap on would prob be a bit trickier it seems like a good idea but when we slide the timbers down the steel H channel they are obviously not fixed into anything and just sit there. are they likely to bow causing unsightly gaps? could i fix all the timber sleepers together like a big panel and slide it down the H channel? but then if im drilling a fastener into the timbers do i now need to treat where im drilling and fastening (seeing as this will be covered with backfill)?? have plenty more questions to ask and i will post up photos of the areas we are retaining later today but for now we are off out again to go to numerous places and ask plenty of questions about our options the decision that needs to be made on what type of material to use is doing our heads in! Re: Retaining Thread 2Oct 22, 2012 11:47 am Sounds like quite a pickle, First up I wouldn't be getting treated pine quotes from the big green shed for sleepers. Hit up a timber yard, for the number your looking you should be able to get a volume discount and site delivery is also something to consider the cost of. With the concrete sleepers, have you considered hiring a small excavator, dingo/vermeer or similar. Hiring for 24 hours should work out quite a bit cheaper than the per hour rates, even with the cost of some rigging gear. Another option you haven't mentioned that i'll throw into this mix is concrete masonry retaining blocks. eg http://forum.homeone.com.au/viewtopic.php?p=686794#p686794 If i can do it, anyone can. The austral heron blocks we used are easily suitable for building 1m walls see page 7 http://www.australmasonry.com/Site_Assets/download.aspx?guid=60519751-f844-4362-9424-9faaf3cbe3fd Benefits over timber and steel is that once its in it shouldn't ever need maintenance, nor do you have to worry about bowing/cupping, however it is more expensive than steel post/treated pine sleepers. Food for thought, good luck with the decision. Our Build - Places Fairhaven 23+ - https://forum.homeone.com.au/viewtopic.php?f=31&t=28045 Our Landscaping - Belial's Backyard - https://forum.homeone.com.au/viewtopic.php?f=19&t=45375 Re: Retaining Thread 3Oct 22, 2012 3:49 pm cheers for the advice hit up a timber yard today got some decent prices, better than the green shed by a couple of bucks a sleeper too we've decided that steel uprights and 75 mm sleepers is the go we can get the 100mm thick ones but the diff in price when you add it all up (plus the costs of the diff steel sizes that you need) is a saving of $1600 by using 75mm im being told that 75mm would be quite sufficient hopefully the three or 4 people that have said this are right as i was going to use 100mm thick Re: Retaining Thread 4Oct 22, 2012 5:14 pm 2400mm is to far to span with treated pine sleepers, would need a post between Landscape Design & Construction http://cherub.squarespace.com/ Re: Retaining Thread 5Oct 22, 2012 6:03 pm can i get some opinions on this guys and gals im being told that 2.4 is fine with steel i originally wanted 100mm thick and timbers at every 1.2 meters but was told this is overboard even for 1 meter high walls Re: Retaining Thread 6Oct 23, 2012 6:36 am no more on this? so 2.4 is too far apart even for 100mm sleepers?? not getting much help on this and im hearing its fine from tradies when we are out and about getting quotes etc? Re: Retaining Thread 7Oct 23, 2012 9:17 am Well it depends, firstly I'll say from what I've seen Cherub knows his stuff. Additionally I fall into the category of people who over-engineer so personally I'd look at shorter spans and/or additional posts. The thing to consider is the deflection, as the center of the beam deflects under the pressure from behind it will warp the sleeper and tend to draw it away from the U of the channel its sitting in. Get enough deflection and its possible for it to let go, it also depends on the steel section itself as to how much gap is allowed to either side of the sleeper when its fitted in the channel. When I looked at it, I found there was differences in steel suppliers with some of the cheaper ones either using thinner wall thickness or a wider cross section that allowed for significant movement. I suppose the other thing to do would be to look at some larger retaining walls built in that fashion, we have several around our estate and I'd estimate the span would be 1.5->1.8m in the ones over 1m high. So making some assumptions, including a post length of 2m. So whilst steel isn't cheap, based of your figure of 180 sleepers you're looking at 2 walls 1m high with 18 sleepers each. So effectively you're looking at 19 steel posts per wall (minimum) * 2m per post for 76 l/m of steel total. Moving to 1.2m spans would mean 37 posts per wall *2m posts for 148 l/m of steel. Which is at least another arm and a kidney by my reckoning over the arm and a leg you're already looking at. If you went to a 1.8m sleepers, your sleeper count increases by 6 per wall , but the post count only goes to 25 per wall. So you'd be looking at 100 l/m of steel. Additionally if you wanted to go to say a 1.5m span, you could look at docking 3m sleepers , so you reduce the number of sleepers but at higher cost per sleeper and 120 l/m of steel. So its swings and roundabouts to an extent, I'd expect the timber to be cheaper than steel so I'd look at maybe a 1.5 or 1.8m span as a compromise. You don't need that kidney right? Our Build - Places Fairhaven 23+ - https://forum.homeone.com.au/viewtopic.php?f=31&t=28045 Our Landscaping - Belial's Backyard - https://forum.homeone.com.au/viewtopic.php?f=19&t=45375 Re: Retaining Thread 8Oct 25, 2012 5:55 am thanks guys and gals after all the working out for over a week and sleepless nights we had our local excavator out (who originally did the walls) for another look and to pick his brain. we 're going to cut into the tiers, take them back a bit and slope them. we have that much room in front of the house its not funny so sloping and completely covering the slopes with plantings and ground cover seems like a much cheaper option. we'll still do the drainage system all the way around the front so anything that comes down the slopes will still drain away and go down past both sides of the house, plus we now dont have to do walls (so all the lifting and cutting and digging post holes and filling them with concrete doesnt have to be done. we did some math and we reckon we can do it for easily half the price of the originally retaining we were going to do. (this includes the cutting and sloping and the plants we were always going to do the drains anyway so that cost stays it has been doing our heads in, but now we have made the decision once we are in the house (tiling grouted today, caulked tomorrow and carpet in monday) we can start getting stuff into the house and disconnect the old house (power, water and old septic system) and then get the excavator back out to slope and start some kind of driveway. we briefly spoke about driveway and the word asphelt was thrown up. around $16 or $20 a square meter was mentioned thru another contact so we'll look into that as a possibility. Hi, Apologies - I know there is plenty out there on this but struggling to put together the puzzle. We're planning our garage/external laundry to master bedroom and… 0 11117 Thanks for the insights, that makes perfect sense, and yeah, I will be leaning on the experience of the excavator operator entirely. 6 16142 Hi All, I engaged a tradie to install concrete retaining wall 600-800mm high over 32 meters in Victoria. Sleepers are 200*75*2000 mm installed over 17 steel posts. I… 0 6903 |