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What type of retaining wall?
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Author:  davidj [ Dec 19, 2010 8:27 pm ]
Post subject:  What type of retaining wall?

Hi all,

Looking at building a retaining wall. Basically have 3 options which I need some advice! Basically total length is around 30 meters with high varing from 400mm to 1000mm.

1. Timber sleepers with steel posts - seems like the strongest wall and clean look. Also steel posts create an additional expense, posted at 2.4m intervals.
2. Timber sleepers with timber posts - strong but need more posts at 1.2/1.5m intervals, however come out cheaper then steel. More labour also installing posts and sleepers.
3. Brick product/gravity wall - boral and austral. These look great and not much of a $$$ premium compared to timber. However these just 'sit' on each other. I'm questioning the strength of this wall, expically at 1m high, these blocks will be 5 units high. What reinforcing is available, and what cost?

Comments would be great.

Author:  Mozzie [ Dec 19, 2010 8:47 pm ]
Post subject:  Re: What type of retaining wall?

I've built all three and the gravity walls are alot more expensive - about 3 times the price. They sound easier due to the fact they don't require post holes but the ground needs to be dead level and a gravel base with compaction is required. Also depending on the product, type of wall and if you use caps you may need to cut some of them which requires a brick saw. So the reality is that these are the hardest wall to install. At 1M height the wall will be perfectly fine - check the specification as some smaller blocks have a max height of 800mm.
Galv posts are easy but can looks a bit average especially after the timber deforms.
Timber posts are a bit more work however I don't think you need to space them any differently to galv posts - if they are half in half out then 2.4m intervals will be solid enough. The main drawback with timber is that it will deform as it dries out and nothing you do can stop it. There is an alternative to treated pine as I've seen it used but not sure what it is exactly.

Author:  davidj [ Dec 19, 2010 8:55 pm ]
Post subject:  Re: What type of retaining wall?

Thanks for the quick reply. With bricks do I need to fill if they are hollow, or just leave hollow? Have seen some pics where they are filled with small rocks/gravel. Would filling with concrete be okay?

If I leave hollow and just use liquid nails (or nothing) are they really strong? I get lots of run off that would be going towards the wall, but I plan to install good drainage. This would place lots of presure on the wall, and I don't really want the bricks to start moving or falling over after a few years!

What do you think?

Author:  bashworth [ Dec 19, 2010 9:17 pm ]
Post subject:  Re: What type of retaining wall?

Basically the type of wall depend s on what is on the top of the wall. If you want to build something close to the top use a vertical wall.

It the top of the wall is just more garden you can use the retaining wall blocks. They don't usually need any reinforcement or adhesive unless the manufacturer recommends it for a particular application. they rely on gravity. the interlock, and the fact each row lays back from the one below. Ive used them for lower walls than you and found them very easy to use.

Which ever wall you build on of the key things is to avoid water building up behind the wall. With the block walls the fact that water can drain through the wall means that water won't build u. Whatever you do don't make the wall watertight!

Author:  JohnMar [ Dec 19, 2010 9:51 pm ]
Post subject:  Re: What type of retaining wall?

Hi davidj,

We have just gone through having a 900mm to 1000mm high retaining wall installed. We considered using Treated Pine sleepers with Hardwood posts at 1200mm centers, this is the least expensive option and will last for around 10 to 15 years depending on ground and moisture conditions. There will be warping to the sleepers so it would have started to deteriate after a year or so.

We nearly went this way but decided we didn't want to have to think about replacing it if we still own the house then, especially after having landscaping installed as well, so we went with the "Besser Block" walls with reinforced foundations. The blocks are filled with concrete after laying and we also installed galvanized 50mm x 50mm posts into the blocks for the side fence to be attached to later. The walls can be rendered, painted, tiled or have decorative wooden panels attached to help with landscaping.

You can see the progress on our thread, link below.

viewtopic.php?f=31&t=39708&start=0

Author:  Planned LScape [ Dec 19, 2010 11:51 pm ]
Post subject:  Re: What type of retaining wall?

You can get some gravity/link block walls from companies such as Adbri, Boral, ECS and similar that make walls suitable for 1000mm high. They have an approx 30mm setback each course so the wall slopes back a few degrees. Each company will have their own max height specifications on brochures. Some may suggest to use geotech fabric behind the wall which is added every few courses and buried within the soil behind to stabilise the wall. You can also fill the wall block and behind it with no-fines concrete, which is basically just cement and aggregate without the sand so water freely drains through. There are also vertical walls without a setback each course, but they generally only go to 800mm high before they start to weaken at the top.

Besser block walls have the opportunity to clad the wall with stone, tiles, render, timber, also very strong. But a fair labour exercise as well.

Timber sleeper walls a good cost effective solution. You can make them look better for longer by running a plane along each edge to clean up the sleeper edges, you can also stain them as the pine goes grey after a few months. They also start to warp and bend due to the moisture content, so you can attach some timbers behind the wall linking each sleeper flush together with long batten screws, this eliminates warping of the sleepers. As with any wall also, make sure it has drainage behind it and backfilled with aggregate.

Author:  keen [ Dec 20, 2010 10:57 pm ]
Post subject:  Re: What type of retaining wall?

I personally would never place timber in contact with soil, to me it is too much maintanence down the track. Even if it lasts 15 years it is still going to need redoing, and you will wish you had used something else.
I like the look of natural stone but over here we have abundant cheap limestone which may not be available in other states, so natural stone may be too expensive.
If going the sleepers I would use concrete ones like these http://www.wonderwalls.com.au/, very strong, cheapish and DIY if you want. Not the greatest look but better than looking at timber in the ground IMHO, that to me just looks like a maintanence nightmare. I do like the look of timber but off the ground ie screens, slatted fences, gates etc, pref in the shade.

Author:  KnockItDown [ Dec 21, 2010 9:31 pm ]
Post subject:  Re: What type of retaining wall?

I got quoted just over $12K for construction of a retaining wall in Besser blocks similar to your requirements.

34m long x 1m high
Core filled
Trench mesh in the concrete footing
and
Starter Bars

The $12K did not include backfilling, ag pipe and drainage aggregate etc Which I would have to do myself.

I ended up spending under $6K, inclusive of drainage aggregate and built the entire wall myself out of Tasman Blocks (you fill the core of the Tasman blocks with 20mm blue metal) on a concrete footing.

I did not use the no-fines concrete method behind the wall. I opted for a filter fabric barrier between the backfilled soil and a 250mm wide layer of blue metal up the back of the blocks. (100mm Ag pipe at the base of course) The combined total of blue metal used for core filling the blocks and behind the wall was approx 9 tonne. (sounds a lot but it really isn't)

goto page 31 of my build thread to see some pics of the wall in the early stages.

viewtopic.php?f=31&t=12911&hilit=memphis&start=600

Author:  keen [ Dec 22, 2010 9:41 am ]
Post subject:  Re: What type of retaining wall?

That is a very nice job, KID.
I like the concrete kerb in front of the first course, finishes it off nicely.

Author:  KnockItDown [ Dec 22, 2010 6:14 pm ]
Post subject:  Re: What type of retaining wall?

keen keen
That is a very nice job, KID.
I like the concrete kerb in front of the first course, finishes it off nicely.


I did that for 2 reasons. I wanted to lock the bottom course in (not really necessary but that's just me) and I also wanted a really easy mowing strip.

Author:  Lex [ Dec 23, 2010 8:44 am ]
Post subject:  Re: What type of retaining wall?

KnockItDown KnockItDown
I got quoted just over $12K for construction of a retaining wall in Besser blocks similar to your requirements.

34m long x 1m high
Core filled
Trench mesh in the concrete footing
and
Starter Bars

The $12K did not include backfilling, ag pipe and drainage aggregate etc Which I would have to do myself.

Does everyone get fairly detailed specs like these during quotations for their ret. walls? :shock: If yes, we should re-evaluate our approach to tradies and quotation process ::hyst::

Author:  keen [ Dec 23, 2010 10:33 am ]
Post subject:  Re: What type of retaining wall?

keen keen
That is a very nice job, KID.
I like the concrete kerb in front of the first course, finishes it off nicely.


I did that for 2 reasons. I wanted to lock the bottom course in (not really necessary but that's just me) and I also wanted a really easy mowing strip.[/quote]

Those are exactly the reasons I like it. A feature that is practical, ads strength and looks good - that's good design right there I reckon!

Have you got pics of the finished job now with vegetation re-instated etc ?
As for your comment about taking so long on one job, - there is no such thing as a short cut in building, and what else could you be doing, sitting on the couch?
Cant beat the satisfaction from a job done right that has saved a lot of money. Only the best contractor would have done as good a job and it would not have been the lowest quote!

To get back on topic (sorry Davidj), I think the Tasman blocks are a great alternative if done well like KID, and I have seen a wall built to about 3m out of them (in good drainage sand though). Check the manufacturers specs and overbuid, overbuild, overbuild & and overdrain, overdrain, overdrain !! (Well I would).
Good design is the key, plan, plan, plan, what I do is draw everything (CAD), - if I can draw it I know I can build it and how to go about it.
It's good fun too!
In relation to the timber & steel walls, steel in the ground will rot away eventually as well, unless it is 316 stainless. (Big $$)

Author:  KnockItDown [ Dec 23, 2010 5:54 pm ]
Post subject:  Re: What type of retaining wall?

Quote:
Those are exactly the reasons I like it. A feature that is practical, ads strength and looks good - that's good design right there I reckon!


2 "must follow" golden rules, correct drainage and with any dry stack wall like Tasman, the bottom course needs to be dead on level. Any issues with the bottom course will be reflected in every subsequent course(s).

What and how you choose to construct your wall comes down to a number of factors such budget or the finished look you want or your materials and method may be governed by engineering requirements to satisfy Council Regs.

Do your research - continue to ask questions as you have until you are happy with the approach you choose to take.

Quote:
Have you got pics of the finished job now with vegetation re-instated etc ?


Sort of - I have not finished the council verge area yet as that's where I land all of my materials and will be done last. (I have the back yard to do yet)

Sorry, I'll stop hijacking this now

Before -
http://i459.photobucket.com/albums/qq311/EB_Photos_2009/IMG_1703a.jpg

After -
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Author:  davidj [ Feb 06, 2011 4:55 pm ]
Post subject:  Re: What type of retaining wall?

very nice wall there. Am starting to consider brick 'blocks' and then rendered for the front yard. Any comments on these re-price, and maybe even some picies?

Author:  KnockItDown [ Feb 10, 2011 9:16 am ]
Post subject:  Re: What type of retaining wall?

davidj davidj
very nice wall there. Am starting to consider brick 'blocks' and then rendered for the front yard. Any comments on these re-price, and maybe even some picies?


Prices per block vary so I would ring around to get the best price. Depending on the amount of blocks you need will determine how much per block and delivery charges etc.

Her is a pic taken this morning of my completed wall.

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Author:  Lex [ Feb 10, 2011 12:12 pm ]
Post subject:  Re: What type of retaining wall?

Oh wow, that's very nice! I love the fence too ... nothing beats a good strong fence :D

Author:  SydneyWebsites [ Feb 10, 2011 1:52 pm ]
Post subject:  Re: What type of retaining wall?

If I leave hollow and just use liquid nails (or nothing) are they really strong? I get lots of run off that would be going towards the wall, but I plan to install good drainage. This would place lots of presure on the wall, and I don't really want the bricks to start moving or falling over after a few years!

::

Author:  KnockItDown [ Feb 10, 2011 4:43 pm ]
Post subject:  Re: What type of retaining wall?

SydneyWebsites SydneyWebsites
If I leave hollow and just use liquid nails (or nothing) are they really strong? I get lots of run off that would be going towards the wall, but I plan to install good drainage. This would place lots of presure on the wall, and I don't really want the bricks to start moving or falling over after a few years!

::

A standard 390mm Tasman block like the ones I have used weigh in excess of 15kg each and are designed to be core filled with aggregate which makes them even heavier.

My wall has not moved 1 mm from the time it has been constructed and its got just under 1 metre of drainage grave and fill behind it. My wall caps are just sitting on top and are not fixed in place with any type of glue or liquid nails.

Effective drainage is the key to any retaining wall. Most walls fail due to the backfill swelling when it gets wet because the drainage is not done correctly.

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