Garden retaining wall

[iceman2013]

Hi all i really need some good advice please , Im building a wall in my garden after digging out some of my garden that slopes up and away from my house to extend the size of my patio.

Im going to use 100mm solid concrete 7n block and then have it rendered the wall is going to be 4ft high by 23ft wide there will be stairs in the middle and smaller walls either side about 2ft high going back towards the house,

Do i need to build piers into the wall as additional strength?, will the 100mm blocks im using be ok single skinned, ive dug footings to 300mm deep (150mm hardcore and will have 150mm concrete) by 300mm wide is this ok,?
The soil under the footing is clay type soil

What sort of drainage do i need what ratio for the concrete footings would you recommend

Any advice tips is my appreciated. will try to add pics.

Untitled

• iceman2013
• 29 Jun 2013
• 2

Untitled

• iceman2013
• 29 Jun 2013
• 2

Untitled

• iceman2013
• 29 Jun 2013
• 2

Untitled

• iceman2013
• 29 Jun 2013
• 2

 

[i_am_fubar]

I did a 4ft one with 215mm hollow blocks filled with re-bar and concrete. Probably massive over kill, but its not going anywhere.

I would say that at 4ft, 100mm blocks aren't enough. 215 (without concrete) would probably be more suitable, especially on a wall that long. Piers would help with 100mm, but again, gut feeling would be to go thicker.

Drainage wise, be sure to install a water IMpermiable membrane behind the wall with weep holes though. Then drainage pipe with gravel over it. 100mm of gravel behind the wall top to bottom will massivly aid in drainage.

Providing your hardcore is properly compacted, footings should be ok.

I've been down the same path, and there is so much more to retaining walls than I first thought.


//www.diynot.com/forums/viewtopic.php?t=215729&start=0

Fubar.

 

[iceman2013]

I was told when i was ordering the blocks at build base that solid concrete would be stronger than hollow i will also be using wall ties for added strength.

The wall is going to be built into the steps in the middle aswell.

The hardcore has been broken up and is no bigger than 100mm particle size and tamped down, the trench is now 600mm in width and 150mm of hardcore and 150mm of concrete foundation ontop.

what do you think, once again thanks for the help so far.

 

[i_am_fubar]

'stronger' in engineering is such a meaningless word...

Stronger in tension?
Stronger in sheere?
Stronger in extension?
Stronger in hardness?

A solid block of the same material and size WILL be stronger in compression than a hollow one. However, a retaining wall doesn't just have vertical loading. Most of it is lateral and your concern is the wall being pushed over, rather than crushed.

As such, the same amount of material (by volume) as a deeper structure will provide more strength.

Fubar.

 

[iceman2013]

to verify the wall is only just 4ft.

ok how about if i turn them on there sides so it will give me 215mm of width.

 

[r896neo]

Firstly never put hardcore in the base of a footing. Your concrete should go straight on to firm dug out earth.

100mm is far to flimsy for a 4 ft wall. Fubars method is not that much overkill for your needs.

Even a 9'' wall of block on the flat is getting dodgy at 4ft high

Footings for a retaining wall should be wider than a normal wall so your 600mm sounds plenty.

I would build the first 6 courses in 13'' block work and then 9inch from there up.

Also if you want to render it make sure you properly waterproof the back of the wall with membrane or liquid DPM

 

[iceman2013]

Right so get rid of the hardcore then, and lay my concrete foundation on the soil. shall i still go with 150mm depth and 600mm width of concrete then

once again thanks for all the help so far.

 

[r896neo]

Yes that sounds fine.

 

[WabbitPoo]

I was told when i was ordering the blocks at build base that solid concrete would be stronger than hollow i will also be using wall ties for added strength.

If the wall is single skin, where were you going to put the wall ties.......?