Another brick wall question.

[Bleedin Thumb]

Sorry I have bricks on the mind today!

When building a brick retaining wall say under 800mm high you have to build it double brick right?

1.So is there any reason to have a cavity between. Assuming drainage behind and a waterproof membrane?

2.Say if you didn't have a membrane behind would a cavity fulfill this function?

[ozwinner]

Sorry I have bricks on the mind today!

When building a brick retaining wall say under 800mm high you have to build it double brick right?

1.So is there any reason to have a cavity between. Assuming drainage behind and a waterproof membrane?

2.Say if you didn't have a membrane behind would a cavity fulfill this function?

If you have a cavity and dont intend filling it up with concrete you end up with only one skin of brickwork doing the retaining, so it sort of defeats the purpose of the second skin.

Al

[Bleedin Thumb]

Yes that was the reasoning behind the question.
As most walls fail heel over toe- a brick wall will only be as strong as the lower mortar joints if layed in a streacher bond. I would assume that by laying the wall using English or Garden Bond you create a stronger retaining structure so these should be utilised when using clay brick construction?

[ozwinner]

Id be more inclined to have starter bars and do the wall with a cavity and fill it with concrete, that way the wall extends down to the very base of the concrete and will be less inclined to fall over.
Back fill on top of an agi drain with gravel, you could even paint some bituminous paint on the back of the wall if you are worried about moisture.

Al

[Bleedin Thumb]

Id be more inclined to have starter bars and do the wall with a cavity and fill it with concrete, that way the wall extends down to the very base of the concrete and will be less inclined to fall over.
Back fill on top of an agi drain with gravel, you could even paint some bituminous paint on the back of the wall if you are worried about moisture.

Al

If I was going to go to the trouble of using starter bars I would probably build the wall out of block and use a brick skin if that was the effect that was required.
I think bituminous paint or similar is essential otherwise the joints always show up wet.

[silentC]

I had a lower portion of a wall spec'd as a retaining wall. It had a thickened footing with starter bars up through the bricks and cavity filled. We ended up not doing it because it was going to cost more than it was worth and we decided not to back fill against the wall and put a TP retaining wall in a couple of metres away instead.