Retaining wall

dandowding

I am looking to extend a patio area out in the back garden. The garden is much lower than the back of the house and slopes away. I am hoping to get an area of something like 7.5m x 3m and to level off the back of the house will need to be about 1m in depth.
Does anybody have good knowledge/experience of the best way to go about doing this.

I have done some research and see that there are particular blocks to build a retaining wall. They interlock and have cavities in which to infill with the gravel/hardcore. Are these best to use? and to fill in the large area before levelling am I right in thinking that general hardcore is good to use with the finer gravel to use in tamping down?

Any help or advise would be much appreciated.

DD

ormus

the easiest way for a diy,er to do this is to use old railway sleepers.

or build a double brick wall.

27col

If you don't use sleepers you will need to use hollow concrete blocks with rebar in them and filled with concrete.A double brick wall is not likely to be able to resist the weight of a large quantity of back-fill. A steel reinforced wall would be much stronger.

WobblyDog

I did look into having a retaining wall of this height built a while ago. Most of the builders I talked to favoured some variation on high-density concrete blocks, layed on their sides and mortared together. Some recommended piers and steel reinforcement. Drainage holes were provided, and the wall would be backfilled with gravel. One problem with this kind of construction is that the concrete foundations need to be quite deep and wide, which poses problems if there are trees, boundaries, etc. nearby.

This site might be useful: http://www.pavingexpert.com/featur03.htm

One unconventional design I have seen involved sledge-hammering thick-walled scaffolding tubes as far as possible into the ground at about 2 metre invervals, and then stacking a couple of layers of "railway sleepers" against them. It was partially backfilled with a low-quality concrete, but I don't think that contributed much strength. It wasn't pretty, but it was cheap, and after 10 years it showed no signs of movement.

A 1-metre hight retaining wall is getting into Structural Engineer territory, so you might want to consult one - the bad news is they tend to charge in the region of £80/hour.

At the risk of offending some readers, have you considered timber decking:eek: instead? It will probably be cheaper than many retaining-wall options, and is probably more DIY-able.

Kiran

It is possible to build retaining walls either out of engineering bricks with a concrete filled cavity or as posted earlier using concrete block on flat. Another more expensive, but asthetically more appealing, method is a system that uses interlocking timber which creates a retaining structure. We have just finished one on a site which is able to be shaped within reason to allow curves etc opening up more options. This is the system used but Im sure there are others available http://www.woodscape.co.uk/retainingwalls.shtml

iamcornholio

A 215mm (ie one brick) thick brick wall will do. Cheapest option would be to build the back skin in 100mm concrete blocks as you wont see these, and then face the front with the brick of your choice

The foundations are more important (suitably deep and wide), and there is not much load from the retained ground, on a wall of this height

You don't need any special blocks or reinforcement

Kiran

If you batter the ground down to the toe of the wall and the back fill the remaining triangle with a free draining material also put in some weep holes the load will be probably as low as you could get it.

tony6403

iamcornholio wrote: »

A 215mm (ie one brick) thick brick wall will do. Cheapest option would be to build the back skin in 100mm concrete blocks as you wont see these, and then face the front with the brick of your choice

The foundations are more important (suitably deep and wide), and there is not much load from the retained ground, on a wall of this height

You don't need any special blocks or reinforcement

I agree with this advice except that I would include butterfly ties between the walls.

Mojisola

dandowding wrote: »

I am looking to extend a patio area out in the back garden. The garden is much lower than the back of the house and slopes away. I am hoping to get an area of something like 7.5m x 3m and to level off the back of the house will need to be about 1m in depth.

Before you get too far along deciding the method, have you got permission to do this?

dick_turpin

Have you thought of this?

http://www.armortec.co.uk/porcupine.htm