Browse Forums Landscape & Garden Design 1 Oct 10, 2014 8:46 am Hi everyone, Long time reader, first time contributor. I am planning on building a retaining wall made of tasman blocks. The maximum height will probably be 800mm to 1000mm max. I see a lot of DIY guides on the internet which say that no concrete footings are required. I was thinking of following one of the guides and laying the appropriate thickness blue metal and then going over it with a plate compactor. However, speaking to a couple of landscapers they have advised me to do a proper concrete footing. I'm now in two minds. On one hand I'm thinking 'why would they say a road base foundation is good enough in the DIY guides' and on the other hand I'm thinking that a concrete foundation does sound more solid. So I guess my question is, what does everything think? Is there anyone who has built a block wall around this height with a compacted road base footing? Has it lasted the test of time? Thanks in advance Re: Foundation for tasman block retaining wall 2Oct 10, 2014 10:06 am Get in touch with KnockItDown on here. He's done both types and is a great source of info. I was planning on doing a block wall (600mm high) and would have done a concrete footing although compacted roadbase would have been fine. My reasons for doing concrete were that it would have been done quicker (I would have paid somebody to do the footing and then laid the wall myself) and I wouldn't have had to muck around with the levels. However, I've since stumbled upon concrete sleepers that look like Tasman blocks (www.concretesleeperscanberra.com.au) which will give me the same look, will be quicker again and will be significantly cheaper because they don't need a footing. Check them out. Re: Foundation for tasman block retaining wall 3Oct 10, 2014 10:31 am Hi Matt Thanks for your response. I have seen photos of "Knock it Down's" work. He's done an amazing job with his wall including the stairs. I will send him a PM. As for the concrete sleepers, its funny you mention that because that was the first solution I was thinking about a few months back. The materials do work out to be a bit more than the blocks. Those steel posts aren't cheap. And I think from an installation point of view the blocks would be easier. Granted you've got to do more work on the levels than what you would have to do with the concrete sleepers. Ahh the joys of building!! Re: Foundation for tasman block retaining wall 4Oct 14, 2014 9:39 pm Hi guys, Both my walls are as the day they were completed. Both have not moved at all. Budget is the biggest factor to consider when thinking about concrete and don't forget about access. A concrete truck doesn't hang around too long once it's onsite so if the access is crap then you may need to pump it which adds cost. When I used the road base for the wall in my back yard I prepped the trench and got the bottom pretty level then loaded the road base a bit at a time and I also mixed in some concrete powder and a spray of water and compacted it in layers until I reached the required level. Hope this helps you in making your decision. PM me if you have any other questions. Rgds Leonard Re: Foundation for tasman block retaining wall 5Mar 16, 2015 4:07 pm Greetings, In the process of (re)building our last retaining wall. The first two walls had steel RSJ posts and timber sleepers, however, the last wall had both timber posts and sleepers, and wasn't to the same standard as the others. Site access is woeful; it would be dangerous trying to get 80-120KG sleepers to the site, plus our soil is crappy shaley limestone, so digging new post holes would not be fun. Given this wall has a maximum height just under 1000mm, I've decided to use boral gardenwall blocks instead, but like jackofalltrades, I'm not sure about what foundations to use. One landscaper said that road base, and maybe with a layer of quartz sand on top to help with levelling is fine, another suggested what KnockItDown said, and add some concrete powder to the mix, but to leave it dry...I guess rain or air moisture would eventually harden it? KnockItDown When I used the road base for the wall in my back yard I prepped the trench and got the bottom pretty level then loaded the road base a bit at a time and I also mixed in some concrete powder and a spray of water and compacted it in layers until I reached the required level. Could I ask what ratio of road base to concrete powder you used? Approximate amounts is fine. Also, what height was the foundation when finished? I've dug my trenches around 250mm deep so far, and was thinking 100mm for foundation height with the extra 150mm so the first layer of blocks sits halfway in the ground. Cheers! Re: Foundation for tasman block retaining wall 6Mar 16, 2015 4:24 pm si618 Also, what height was the foundation when finished? I've dug my trenches around 250mm deep so far, and was thinking 100mm for foundation height with the extra 150mm so the first layer of blocks sits halfway in the ground. Did some more searching and found this site (by KnockItDown?), which recommends 200mm depth for foundations, so some more digging to do! Re: Foundation for tasman block retaining wall 7Apr 06, 2015 5:40 pm si618 Could I ask what ratio of road base to concrete powder you used? Approximate amounts is fine. Answering my own question again was recommended ~1 to 4 or 5 mix by the landscape suppliers, and from ~1 tonne of road base/quarry rubble I mixed in around 240kg of cement powder, so just over 1 to 4. Used a watering can to lightly dampen each layer, then mixed the rubble and cement using the back of a fire rake before tamping down. Quartz sand is definitely easier to level, but the rubble/cement mix looks very solid. On this 12m wall, 80kg of quickset concrete was used to help embed the first layer of blocks, as I had left a ~50-75mm offset between the front of the block and the ground. First layer of blocks were a minimum ½ their height under ground level, although due to the sloping land, some ended up being completely covered. One mistake I made was not allowing for the 30mm batter the boral gardenwall blocks have as the ground height changed, as each level overlaps the previous, so you lose 30mm for each step up. End result was in a few spots I had to scrape away extra soil to leave adequate room for drainage (blue metal). there is a standard besser block wall pdf somewhere online with footing sizes, also have a look at dincel. 1 2904 Thank you again Simeon.. I will call my certifier for that. Have a good day 4 5188 Thanks for the insights, that makes perfect sense, and yeah, I will be leaning on the experience of the excavator operator entirely. 6 16147 |