Retaining wall in garden

[danped]

Hi,

I'm after some comments on my plan. I have had a retaining wall built in the garden, it is double skinned. Length is about 15m x 4m return with a depth of about 1m. It is there to level off a sloping garden.

The spoil from the foundations has been levelled off and I've had a builder (he didn't build the wall) explain it needs 40ton of MOT compacted and then concrete inbetween the two skins to reinforce the wall as currently the weight goes all onto one skin. Once this is done then we can add a foot or so of topsoil.

I don't think the wall needs reinforcing based on previous conversations and research so I've asked to not do this and proceed anyway. Builder has explained thats fine but if the wall cracks don't blame him, this is fair enough he didn't build it. However I'm looking for some reassurance that the wall without filling in will be sufficient and also if the MOT is a good idea as I know it will compact things down but thought it might limit growth a bit. My plan is to turf it but I will add a tree and possibly some bushes in future.

Finally I figured if the wall did required any reinfocement that It would be easier and cheaper to fill the cavity with expanding foam rather than concrete which would distribute any force just as well.

Thanks,
Dan

 

[Notch7]

what provision is there for drainage?

is there nothing bonding the 2 skins together?

what is the reason for the cavity -is the wall to be rendered?

 

[danped]

The cavity is there as yes I may render the outside. There are metal wall ties, picture attached. For drainage I have backfilled 12 inches of aggregate and in there is a 110mm drainage pipe which outlets through the bottom of the wall. I also put in 1m3 of soakaway for good measure.

 

[Notch7]

The cavity is there as yes I may render the outside. There are metal wall ties, picture attached. For drainage I have backfilled 12 inches of aggregate and in there is a 110mm drainage pipe which outlets through the bottom of the wall. I also put in 1m3 of soakaway for good measure.

Water pressure is a major facture in regards to damage to retaining walls -if youve sorted that fine, I would think the wall ties should be ok

If you fill it you have removed the benefit of the cavity to keep the render dry

once the soil settles over a year or so it will tend to combine into a solid mass. Turf will help bind it together

 

[Agile]

It all depends on what you plan to do on the reclaimed land.

If it is to be just turfed and plant a few bushes then I do not see any need to do anything more that fill with topsoil.

If the wall has plenty of wall ties then they will help to enable the outer skin to resist the force on the inner leaf. Leaving the cavity unfilled will enable the outer skin to remain dryer. Interesting question of has a DPC been used.

I suppose that I could just understand a builder/landscaper wanting to make it into public lawns at Windsor Castle gardens might want to lay tons of aggregate and compact then and cover that with a thin topsoil where cost is not important. ( Or rather the higher cost the better for the builder. )

But for a domestic garden for family use that all sounds totally over the top to me.