Garden Wall Cracked & Moving

Section62

Exodi said:

Yes regarding the venturi thing, I don't think this is the case here. The gate blew open a couple of times during storm Eunice. For this to happen, the wind would have been blowing from the back of the house to front, into the gate and would have needed to push the wall outwards maybe an inch so the gate latch no longer caught. The wall is mostly shielded from wind running perpendicular by houses, and in my (uninformed) view, wind running parallel to the wall shouldn't be an issue if it's able to run through.

Wind effects on structures is a specialism in its own right as it is so complex.  But it is not just (over) pressure which is a problem, the effect of suction (negative pressure) is as much of an issue, as is vortex shedding.

In other words, wind forces could pull the wall outwards, it doesn't have to be a case of pushing.

Because of the complexity of wind effects, most domestic structural detailing is based on rules of thumb - rules based on things which went wrong in the past.  E.g. using plenty of restraint straps to tie roof structures to walls.  Likewise, the 'rules' on slenderness ratios of walls are based on empirical evidence.... and people just 'know' that a masonry wall that thin and high is asking for trouble.

theoretica

I wonder if that is even a block wall - a few of the cracks look like that, but others have me wondering about some concrete construction.

stuart45

A concrete wall is a bit more time consuming to build, as it needs formwork both sides. Next to the brick pier the cracks looks like blocks moved out of line. It also looks like a crack in the bed joint between the bottom course and the second one. Some of the other cracks could be just in the render.

Section62

stuart45 said:

A concrete wall is a bit more time consuming to build, as it needs formwork both sides. Next to the brick pier the cracks looks like blocks moved out of line. It also looks like a crack in the bed joint between the bottom course and the second one. Some of the other cracks could be just in the render.

I agree.  A wall that thin and high wouldn't be easy to build with poured concrete - keeping the reinforcing in place to ensure sufficient cover isn't easy with such a narrow width, and ensuring good compaction is also difficult.  In a domestic-type setting it would almost certainly mean constructing it in multiple (3 or 4?) lifts, with the formwork and time issues as you say.

Although if it was properly built with RC then it wouldn't be causing the problems it is.

stuart45

RC walls are popular in the USA in hurricane zones.

FreeBear

Section62 said:

stuart45 said:

A concrete wall is a bit more time consuming to build, as it needs formwork both sides. Next to the brick pier the cracks looks like blocks moved out of line. It also looks like a crack in the bed joint between the bottom course and the second one. Some of the other cracks could be just in the render.

I agree.  A wall that thin and high wouldn't be easy to build with poured concrete - keeping the reinforcing in place to ensure sufficient cover isn't easy with such a narrow width, and ensuring good compaction is also difficult.  In a domestic-type setting it would almost certainly mean constructing it in multiple (3 or 4?) lifts, with the formwork and time issues as you say.

Although if it was properly built with RC then it wouldn't be causing the problems it is.

Hollow blocks back filled with rebar & concrete as the wall is built ?

Would depend on the state & size of the foundation.

stuart45

Reinforced block walls are strong as well, but the rebar needs to be in the foundation and come up a few ft into the wall. At that height more would need to be tied to the bars, and horizontal bars put in as well.