# Forum Home Renovation Concreting  Footings help for besser brick wall

## wonderland

Hi everyone,
I am in the process of trying to design my retaining wall. My wall will be 0.9m-1m high x 8m wide. The plan was to use besser bricks to build it, and then stick stack stone veneers onto it. My question is about the footing, how wide and deep should I make it? I was thinking 200mm deep x 300mm wide, is this enough or do I need it to be deeper and wider? WIll I need to put reo in the footing so that it doesnt crack? I was also going to put N12 bars every 300mm, is this sufficient? Would I need horizontal bars as well, or will that be overkill? I also plan to concrete core fill the blocks. 
I also just found out that there are a few different sizes of besser bricks, can anyone recommend which size is best for a retaining wall?  
Sorry for the the questions, this is my first time attempting anything like this and I hope to do it right the first time round! :Biggrin:  
Thank you for all your help!

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## cherub65

Every wall design is dependent on many factors, soil, load are the main points
I think your in for a bit of a shock when you relaise the size of footing and steel that go into retaining walls
Have engineer detail here for a wall 1000 mm high and the footing size is 900 mm wide with the toe 450 mm deep x 250 mm wide then the rest 250 mm deep
This has steel mesh as well as Y16 bars
The wall is 200 mm wide with Y16 bars @ 400 mm these are vertical, then Y12 bars @ 400 mm horizontal, core filled with concrete. 
As you can see rather large and this ground is good.
Retaining wall done well are expensive!!

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## wonderland

@cherub Thanks for your reply and advice. I have attached a rough (sorry) plan of where the retaining wall is etc. The distance between the retaining wall and the footpath will be around 1.5m, and the distance from the retaining wall to the house is around 4m. Once the retaining wall is built, i will back fill it and make the retained area flush to the ground of the house.  
The reason why the land slops is because I live in an estate, and the delevopers have used fill to bak the land to be able 1 meter higher than the road. The dirt I have is builders fill, so mostly clay.  _Have engineer detail here for a wall 1000 mm high and the footing size is 900 mm wide with the toe 450 mm deep x 250 mm wide then the rest 250 mm deep_
I dont quite understand this part :No: . I understand that the footing is 900mm wide. But is it also 450mm deep? What is the 250mm wide part, i dont quite get that part. Thanks.

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## Blocklayer

I'd get an engineer to draw it up. 
Like cherub65 said, you're probably in for a shock with the amount of concrete and steel in the footing and the wall itself to do it properly.
There's also water drainage to consider.
Is the ground level along the wall? 
And there are lots of different types as well as sizes of blocks. 
Take a look here Concrete Block Types, Dimensions Core Fill Grout, Rebar - 200 Series for some block types and steel placement for normal walls. 
Imagine the drama and expense trying to fix it if it's not up to the task and moves or cracks. 
:

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## wonderland

Thanks blocklayer. The drawing of your site is attached to my post. Yes the ground level will be along the ground. I will be putting drainage (hose and screening rock) behind the wall. Will also put geofabric behind the wall to make it waterproof. 
As the wall is less than 1m high, I dont have to get an engineer to draw it up. I dont think I can afford to get it engineer certified. With regards to the blocks, i was either going to get the 200 series or the 300 series. I think that is adequate enough. Thanks for the link, i had a look. Seems that I would only need one horizontal bar across the wall. The max it would go is 1m, which means only 5 courses. 
Thanks.

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## jago

Just on the water drainage side of things the Engineer you  choose should specify for the Geotextile fabric, back fill type, Ag pipe positions and possibly a vertical drain etc as well as the footing which council will want to see in drawings and then inspections. 
I'm not an engineer but what mine did was make my footing the same size as the wall ...its a 1200mm high wall so the footing was 1200mm by 450mm with about 300kgs of steel in it!. 
The toe is the area in front of the wall that counter balances it against the pressure from the earth side. 
Have a look at the pdf it shows the construction and calcs for a wall....

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## mijati

Hi,
Cherub65's detail is pretty standard and sums it up pretty good. Also worth noting that an engineers costs are miniscule compared to knocking down and rebuilding a failed wall...!! 
Consider using 10mm aggregate in the concrete to help in getting the concrete into the block's cavities (and through the horizontal rods).
And knock/drill a small hole in each of the lowest blocks (on the blind side) to help let the air out as the blocks fill....
Good luck with it

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## ozizu

I am in the process of boxing my foundation for concreting for a retaining wall out of besser blocks. Mind you though my wall is 1.6 mt high and 2.4 mt long. However it will be linked to low walls of besser blocks for garden borders to seperate the grass and garden area, so it is not an isolated structure.  
My foundation for the retaining wall is 2.6m by .85m. Inside is 50mm crushed rock, 350mm concrete (mpa25) with two layers of 12mm trench mesh and also 16mm starter bars going upwards that stick up about 600mm.  
The difference with my structure is that 
- the retaining wall is actually not holding back soil, and is going to be used a feature wall with cladding etc. so there is no soil pressure as such therefore my engineering of the foundation is not extreme. 
- I have linked the wall with other smaller walls of 60cm high that have a concrete depth of 200mm.
- A professjional engineer has given me guidance on the footings and has said because there is no soil pressure, and because I have a smaller wall in front of the retaining wall, a 2.6 by 0.85m rectangular slab will be sufficient for my needs.
- Also was advised to use the 200 series blocks and not the smaller ones, however am contemplating using the 100 series blocks for the wall but put a pier of 100 series blocks behind the wall at the ends to stiffen the wall 
 So in answering some of your questions
= Yes you should use the 200 series blocks core filled, or use smaller series but use pier system like I am planning on doing
= Horizontal bars are added protection, so why not use them.
= Use link in the other posts for more accurate besser block installation guidelines
= Dont skimp out on quality steel reinforcements. Use 12mm trench mesh like I am going to do and 16mm starter bars
= Drainage is recommended which I myself havent done yet

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## DAZ

In response to the first post in this thread.. 
I would consider contracting someone to lay a row of gabion cages in this situation as an economic alternative to constructing a masonary retaining wall. Coupled of course with your drainage stratagies (geofab, aggpipe etc). You will most likely have to install a drain box a low-point on the ground level (at the footpath). 
You should specify the distance the wall is from your house footings. If the house footing lies withing 2.0-2.5m of the wall, gabion cages will generally not be suitable.  
Assumed:
Fill bulk density (saturated) = 31.38 kN/m3 (3138 kg/m3)
Cage dimensions = (1.0 m x 1.0 m x 1.0m)
Gabion cage fill density = 2000kg/m3

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## wonderland

Thank you to everyone who has given me such great advice!!!
I just have a few more questions: 
@Mijati, do you mean put 10mm rocks into the concrete before pouring? I am getting the concrete from mentone premix, it might be abit hard to add the rocks. What do you suggest? With regards to drilling holes, do you mean drill holes at the back of the wall where the drainage and dirt will go? I am going to paint the wall with gripset 51, so it might seal the holes. 
@Ozizu, with regards to the 12mm trench mesh, which direction did you lay them? As your trench was 0.85m deep, did you lay a few of those mesh flat, or did you lay them upright? What is the best method to lay the mesh? Also, do you need crush rocks as well as the trench mesh in the trench before you pour the concrete? How much crush rocks should be put into the trench before concrete is poured? 
@Daz I dont really like the look of the gabion cages, I think I will stick to the blocks 
I went to Austral and the 200 series cost $3.23 per block. Does anyone know where I can get these blocks cheaper around South East Melbourne? 
Thanks.

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## jago

10mm agg - you need to specify this to the concrete company it should also have at least 280kg of cement per m3 of concrete with no flyash. 
Mijat is refering to the knock out blocks for the bottom row which you will need to shutter before you pour and then remove once set. Have a look at the pictures in the pdf  I attached in my last post. 
TM lays flat on bar chairs with a least 50 mm cover top and bottom. 
The price from Austral is about right. 
I would suggest as others have before, this is a huge wall in terms of forces and I would urge you to seek an engineers advice on this,  you won't be insured if god forbid something was to happen.

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## wonderland

Thanks Jago for your advice. How much would it cost to get an engineer's advice. I think I might make my wall 800mm high so that I dont scare people. The wall isnt exactly 1m high, its around 800mm-900mm high. I've spoken to council and they say I dont need an engineer unless its over 1m  high. That's why I havent gone to an engineer. Also, I will be doing my research before I construct the wall, so I wont be going in blind, hoping for the best. I will ensure that its a structurally sound wall.

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## jago

Not sure of the cost for you, call a couple of Engineer and get quote. Ask if they come out and consult on the job without a call out fee some do some don't? 
Indicative only (as different state, job etc)  I've a 1.8 > m high by 19 m long retaining wall on a steep block and my engineer is going to charge $800 for full specification drawings and calculations, I could of worked it out but for me I think a good investement in terms of peace of mind. 
Arm yourself with as much information before you speak to an engineer. 
The pdf I sent is a good start as it comes from Hansons a concrete company.

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## nww1969

Who would have thought this thread was going to be so complicated.

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## wonderland

^ :lol: yes who would have thought that it could get so technical and complicated!
But I'm very grateful for all the useful advise! 
I will look into get engineer specs but not sure I will go this route.
The ways is only 0.8-1m, no where near the 1.8m that you have. If my wall was higher than 1m, I would definitely get an engineer.  
One other question, with regards to the starter bars or N12 bars, can I get them just straight, or do I have to get them with the right angle? 
Thanks!!

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## ozizu

@Ozizu, with regards to the 12mm trench mesh, which direction did you  lay them? As your trench was 0.85m deep, did you lay a few of those mesh  flat, or did you lay them upright? What is the best method to lay the  mesh? Also, do you need crush rocks as well as the trench mesh in the  trench before you pour the concrete? How much crush rocks should be put  into the trench before concrete is poured?
 - My trench was not 0.85m deep, but 0.85m wide and 350mm deep, since I had a small wall infront of it tying it all together. Yes I would recommend compacted crushed rock maybe 50mm after compacted under the trench mesh and concrete. The trench mesh is layed flat with plastic chairs (little brackets that the mesh sit on that is off the surface) holding them above the surface and depending on depth of trench, I would be inclined to use two layers of trench mesh.  
One other question, with regards to the starter bars or N12 bars, can I  get them just straight, or do I have to get them with the right angle?
- The steel supplier can bend them for you if you need them bent bud they generally come in straight. I would use n16 starter bars to be safer. 
I went to Austral and the 200 series cost $3.23 per block. Does anyone  know where I can get these blocks cheaper around South East Melbourne?
- $3.23 is a rippoff, check ebay, you might be able to get them for about $2 a piece. Try some landscaping yards they have them for about $2.50 i think 
I will look into get engineer specs but not sure I will go this route.
The ways is only 0.8-1m, no where near the 1.8m that you have. If my  wall was higher than 1m, I would definitely get an engineer. 
- Spend the extra bucks and get an engineer to deisgn everything. These sort of things you dont want to skimp out on extra steel or footings etc. Do it once, do it right.

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## jago

Any wall over 600mm up here needs planning permission and generally inspectors will want it designed by an engineer, the reason liablity. I know you Mexicans have your own rules  :Wink 1:  
Besser block prices will differ in price depending on quality in IMHO.See if you have a PGH or Boral yard call them. Building retaining walls yourself? DIY retaining wall systems are supplied by Melbourne Brick try these guys they might even offer some help on your wall design F.O.C of you buy  your materials from them. 
Don't skimp on the steel and you need the starter bars to be  L shaped, short side into the footing and with long side inside the the wall. Some metal companies will design the steel workfor walls F.O.C but of course they will ensure there's enough in there :Wink 1:  
I would put horizontal  bars the length of the wall at the 1st course and 1 below top course. 
How are you going on costing the total project? 
Concrete alone will be runing close to a couple of grand.

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## DAZ

> Thank you to everyone who has given me such great advice!!!
> I just have a few more questions:  
> @Daz I dont really like the look of the gabion cages, I think I will stick to the blocks  
> Thanks.

  You mentioned you were going to adhere a stone sheet on to the the block wall. Gabion cages can be finished with a shotcrete lining resembling stone.

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## Pulse

> . Will also put geofabric behind the wall to make it waterproof.

  geofabric isn't waterproofing.. it stops fine material filling your aggregate drainage material.  Here's the info you need from Hanson. 
Cheers
Pulse

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