I currently have a block wall that is approx. 19' tall. It has a retaining wall that is 15' out and 3' high that slopes up to approx' hieght of 6' against the main wall leaving 13' of exsposed wall above the retainer. There are houses that share the other side of the block wall however the lots are elevatedto the point that the block wall from there perspective is 6' tall. My question is this: do we need more of a retaining wall ?(hieght & depth) to support such a wall and are flying butresses required where side yard walls connect to main wall to help support it ? My city ordinance calls for block walls no higher than 10' without supporting retianers of some kind. Any information would be greatly appreciated. Thanks, j.

roundmonkeylover

Hey, I'm from the UK and we have a slightly different legal system over here. But under both Common Law and the Party Wall Act you have a legal obligation to ensure that you do not adversely affect the neighbouring construction or place others at danger.

That said you should really engage a competent engineer to undertake a review of your proposals and prepare a construction design. To get geeky - beacuse of the weak tensile strenth of mortar, masonry construction is not great in bending and thus it is typical with retaining walls to strengthen the formation with:-

1. Deep piers to the front; or
2. A stepped back face; or
3. To bind the blockwork using steel reinforcement down onto a base.

If you go ahead two things may happen. The wall above the point of retained earth my not be strong enough to resist load from the wind and will crack and fall. Or it may be strong enough up top - but furtherdown, where it's doing more work, it may upset the equilibrium and the whole system may become unstable.

An engineer will be able to assess the actions on the wall and what you can and can't build. In the UK the engineer will then communicate with the local-building officier to gain the nesecary approval.