Garden Wall Project - help required

[spiidey]

I am about to start a garden wall project and would appreciate some advice and guidance on how to go about this.

I attach below, in terms of what we are intending to do:-

1. A birds eye view plan;
2. Cross-section of the proposed new garden;

Along with:-

3. A cross-section of the existing garden.

Broadly:-

(a) the first wall will be 0.56m in height, holding back 0.41m tall of clay soil behind it (with paying slabs on top of the soil);
(b) the second wall will be 0.71m in height, holding back 0.71m tall of clay soil behind it (with no paving slabs on top of that soil)

For both of the proposed retaining walls:-

1. What width of brick do we need? Can we use single skin brick or do we need double skin? We like this brick here (90mm wide):- http://simplypaving.com/bradstone-p...9_1403979551_fdfa94f3ea894d6fe50ae6c4e38c6135
2. Do either of our retaining walls need reinforced given the height we're proposing? i.e. do we need any type of concrete blocks at the bottom/back of either of the walls?
3. Should we pitch the wall backwards at e.g. 6 degrees or 12 degrees to the vertical, or can the wall be at right angles to the ground?
3. How do we deal with drainage? i.e. do we need weepholes for a wall of this size?
4. What depth of foundations do we need for each wall?

Image 1 - Birds Eye View of Proposed Solution

Image 2 - Cross Section of Proposed Solution

Image 1 - Cross Section of Existing Solution

 

[wrathkeg]

can't help with the specifics, but loads of discussion of this type of thing here:

http://www.pavingexpert.com/featur03.htm

 

[r896neo]

A 9'' wall will do for the small one but for the larger one will need to be wider.

For ease speed and cost saving you will probably be best off building the walls in blockwork and then facing them will bricks tied in using wall ties built in as you build up the blocks. The low wall could be 4'' blockwork and then your brick skin tied in to give a 9inch wall. the taller one should be 9'' blockwork and brick skin tied in

By doing this you can leave a small 25mm cavity between which will solve many of the staining and spalling issues with brick retaining walls.

Build the walls vertical.

Of course you must have well planned and executed drainage unless you want a dangerous damn. Good info on wrath kegs link.

As for the footings they need to be wider than a normal foundation, so make them something like 600mm wide for the big wall and 450 for the smaller one. Aim to build closer to the front of the footing too.

Depth is hard to tell without being there but dig to at least 450mm or more if the ground is bad. make the footing 150-190mm thick

 

[Andyc84]

Another thing to do will be to check that the volume of soil you have doesnt change, so that you don't have to get rid or import too much, this will save you money in the long run.

 

[spiidey]

A 9'' wall will do for the small one but for the larger one will need to be wider.

For ease speed and cost saving you will probably be best off building the walls in blockwork and then facing them will bricks tied in using wall ties built in as you build up the blocks. The low wall could be 4'' blockwork and then your brick skin tied in to give a 9inch wall. the taller one should be 9'' blockwork and brick skin tied in

By doing this you can leave a small 25mm cavity between which will solve many of the staining and spalling issues with brick retaining walls.

Build the walls vertical.

Of course you must have well planned and executed drainage unless you want a dangerous damn. Good info on wrath kegs link.

As for the footings they need to be wider than a normal foundation, so make them something like 600mm wide for the big wall and 450 for the smaller one. Aim to build closer to the front of the footing too.

Depth is hard to tell without being there but dig to at least 450mm or more if the ground is bad. make the footing 150-190mm thick

Thanks for this r896neo.

With regard to the footings, I agree that need to go to depth of 450mm (or more if ground is bad).

Assuming 450mm depth for the time being though, with the concrete say 150mm thick that would leave 300mm depth below the ground line.

Can part of this 300mm depth be built up using blockwork across both skins (say 250mm deep blockwork then the remaining 50mm would be brickwork on the facing skin and blockwork on the "inside" skin), or can blockwork not be put below the ground due to frost shattering etc?

 

[r896neo]

Blockwork is fine below ground. ideally for both above and below 7N dense blocks would be better as they are more water resistant in long term saturation and a fraction heavier which helps the stability of a retaining wall

 

[spiidey]

Blockwork is fine below ground. ideally for both above and below 7N dense blocks would be better as they are more water resistant in long term saturation and a fraction heavier which helps the stability of a retaining wall

So just the poured/set concrete for the foundations that must be at least 300mm below ground (to prevent frost shatter)?

i.e. anything else can be between 300mm below ground and ground level, or above ground level.

 

[r896neo]

Yes thats right its just the actual poured concrete footing that needs to be down 450mm. And that's the bottom of it.

Its related to frost heave which realistically is not really a major problem in the uk as we don't get very severe cold temperatures regularly. A very hard frost can freeze and expand the ground under a footing and lift it fractionally and this tiny movement is called frost heave.

Engineering bricks and dense blocks and some facing bricks are almost totally resistant to frost affecting them.

 

[spiidey]

Thanks again, r896neo.

Foundations:-

Keen to keep cost of foundations down as far as possible, and happy to mix the concrete on site - what would you recommend for a good quality at reasonable cost?

Also, reckon I'll need to lay c. 3.2 cubic metres of concrete foundations - roughly how much of each product do I need to achieve this?

Mortar
Trying to work out how much mortar I am actually going to need, so I can price it to get a total cost for the job. The total area of the new brick wall is c. 24.1m2, with each individual brick 215mm x 90mm x 63mm.[/u]

 

[r896neo]

You shouldn't try to mix that on site. you will have to buy readymix.

Not only will the cost of materials needed to mix it be probably 85% of the cost of readymix but the concrete will be much better and set as one unit rather than endless variation of curing times caused by mixing over a day.

Even with a large 2 bag diesel mixer you would still struggle to make more than 2 cube in a day

 

[spiidey]

You shouldn't try to mix that on site. you will have to buy readymix.

Not only will the cost of materials needed to mix it be probably 85% of the cost of readymix but the concrete will be much better and set as one unit rather than endless variation of curing times caused by mixing over a day.

Even with a large 2 bag diesel mixer you would still struggle to make more than 2 cube in a day

Which readymix product would you recommend for a retaining wall foundation job, and how many would I need for 3.2 cubic metres?

 

[r896neo]

you buy readymix by the cubic metre. Just phone around local companies and tell them what its for and they'll send you the right stuff.

123 foundation mix would be a common choice.

 

[spiidey]

you buy readymix by the cubic metre. Just phone around local companies and tell them what its for and they'll send you the right stuff.

123 foundation mix would be a common choice.

Thanks.

If I'm using the 7N breezeblocks initially (then using brick for the outer skin), which way should the breezeblocks be laid?

http://www.online-building-supplies.co.uk/100mm-7n-solid-dense-concrete-breeze-block-42-p.asp

They're 440x215x100mm

So should they be laid such that they're 215mm high, or 100mm high?

Either way, should the breezeblocks be laid directly vertical, or slightly staggered back (similar to figure B in the link below)? Is this even possible if they're laid such that they're 215mm high (therefore only 100mm width each).

http://www.familyhandyman.com/lands...ow-to-build-retaining-walls-stronger/view-all

 

[r896neo]

for the low wall lay them on the flat 9'' til your out of the ground and then start your brick face on the front and the 4'' blockwork behind it and tie them together with wall ties.

for the bigger wall either lay them lengthways so the wall is 18'' deep or if you prefer its less blocks to lay them to form a 13'' wall

To do this lay two blocks flat and one on edge behind them butter all joints to bond them together well.

 

[spiidey]

for the low wall lay them on the flat 9'' til your out of the ground and then start your brick face on the front and the 4'' blockwork behind it and tie them together with wall ties.

for the bigger wall either lay them lengthways so the wall is 18'' deep or if you prefer its less blocks to lay them to form a 13'' wall

To do this lay two blocks flat and one on edge behind them butter all joints to bond them together well.

Thanks again r896neo.

I can follow what to do for the small wall, but am struggling for the large wall.

We don't have an unlimited budget and whilst the breezeblocks are relatively cheap we need to be economical where we can whilst still ensuring that the wall is strong enough.

Where you suggest (for the large wall), "if you prefer its less blocks to lay them to form a 13" wall" how is this achieved?

In an earlier post you recommended 9" would be sufficient for the larger wall - I presume this is 9" deep blockwork plus the 4" brick facing? What actually gives the strength in this method - is it simply the blockwork, or is it the combination of both the blockwork and the bricks, assuming they're tied?

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The missus is asking about curving the retaining wall (nothing major, just a slight curve) - would these products allow that, or do we need specially designed bricks to do this?

http://simplypaving.com/bradstone-pitched-walling-buff-block-215-l-x-90-w-x-63-h-202-per-pack.html