Thread: Retaining Wall Advice

A retaining wall needs to be a third as wide as it is high, if I recall correctly. So a 1 metre high wall needs to be 33.3 cms wide. Some would also tell you half as high, which is obviously better and stronger.

The easiest way to gain this depth is by using blocks behind the wall, like steps, but you can also use coffee rocks or similar, tied into the wall with reo-rods and cement. This is cheaper, but much, much more intensive.

You definately need some drainage behind the wall too, probably some ag-pipe, with blue-metal surrounding it. I am not an expert at drainage, I live on the coast, so drainage is not really an issue.

If it were me, I would not do the retaining wall on the cement in place, I would do a separate footing for the wall.

Remember, the retaining wall needs to be strong enough to hold the dirt back, but when it gets wet, it weight increases substantially, so think of the wall being like a dam holding back water and dirt, it needs a nice heavy base.

Don't forget the stairs too!

Originally Posted by daftandhungry

The land slopes into the house and down hill along the length of the house, but there is a slight elevation in the lowest area which I believe doesn't drain properly, so when it rains heavily I have water building up on the concrete path along the side of my house, although it does drain eventually.

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To me this is the worrying thing. Water is the enemy to walls and brick and bessa ones in particular IMO.

If asthetics is the only reason for going bessa and you are open to change then I would look at a sleeper wall with ag pipe and lots of blue metal behind it. I would have it so that the bottom sleepers are about 1cm highter than the path to ensure that no water gets trapped behind it and the thing will last forever.

If you go bessa blocks remember drainage drainage and drainage or you will be sorry sometime.

I wonder if the green algae growing on the bricks is water trapped already.

It definately isn't for aesthetic reasons, we have had termites in the house before and are trying to avoid using any type of wood anywhere near the house.

I plan on adding as much drainage as possible, once I have researched it, I haven't done anything like this before, 1st house I have bought and first time renovating anything.

Treated pine will be fine provided you dont cut the sleepers or if you do you must treat the exposed timber.

We have termites around here and all the new decks going up are treated posts into rapid set.

Pine will definately be easier to do...I may go that route yet...the other side of the house has sleepers but they are falling over, whoever built it put the posts on the inside so there is no support to keep it from toppling, well that's the way I see it anyway, so if I go with sleepers, aesthetically it will match the other side of the house.

My house is a mess soooo much work to be done

Remember that termites love dampness as much as timber, and they postively love damp timber! So drainage is definately your friend with this retaining wall.

I'd even be tempted into looking at ag-pipe with two soak-wells at either end.

Ideally, ground should slope away from the house at about 5 percent for a distance of about 10 feet (about 3m). It looks like you have sufficient space in your parcel to place a retaining wall at that distance, provided you have someplace to dispose of the excavated soil. I had a similar situation owing to substandard original construction. I placed a retaining wall at my property line with filter cloth and gravel backfill, with a perforated drain at the bottom of the backfill; the drain leads to a rock pit (French drain). In my case, I was able to batter the block wall to balance the overturning forces and eliminate a footing. (The blocks are laid without mortar, to allow the wall to deform slightly.) BTW, I'm a civil engineer, but I'm not licensed in Oz so I can't provide a specific design. An Oz engineer can help you with the arithmetic.

Joe