Load bearing wall removal - Acrow prop spacing

[psychedomination]

Hi there, I don't tend to deal with the removal of load-bearing walls much but will be removing a 12' wall in my house to create a bigger opening. I designed an appropriate concrete lintel to replace the wall and I am intending on giving the contractor some guidance for safe practice during demolition to be used as a minimum.

I am leaving about 14" of the wall above the new lintel. I will recommend the traditional approach of load-bearing wall removal using acrow props and needles although if the contractor comes up with a cheaper solution that is just as safe I would be happy to entertain it.

The wall is not holding much load, only the roof above and its own self-weight.

My question pertains to the spacing of the acrow props.

As the load on the wall is quite small the capacity of the acrow props is not really a concern because they can easily sustain the load. I am wondering about the spacing, to ensure that the brick between the props don't catastrophically fall out.

So I guess the question is more what can the free span of the wall be without support (clear span between acrow props). I am not too sure how this is normally done? I was assuming arching action in the wall at 45 degree angles. With the height of 14" above the lintel it leads to a length of 2'4". Should this then be the minimum uniform spacing of props?

 

[r13]

I think the spacing of shoring is the least of concern at this moment, before you are clear on how to build the concrete lintel once the shore is up and in the way, and how the lintel is going to be supported - on new posts or remaining wall segment? How long the wall is to be removed?

 

[psychedomination]

Hi retired13, I did a quick sketch in AutoCAD on how I envisioned the wall to be removed. Your opinion on this would be appreciated, especially if there is a cheaper option. The length of wall to be removed is 12'.

Steps I considered for the wall removal are:

1. Cut small 5"x6" openings above lintel for the acrow prop needles (4"x6" needles)
2. Put props on either side of wall using the needles. Have props offset from the face of the wall to be demolished by ~1' on each side.
3. Knock out wall beneath the needles and create pockets for lintel in adjacent walls.
4. Set up formwork between pockets with intermediate supports if required.
5. Place hole in formwork for pour.
6. Pour lintel and let it cure, then remove the temporary works.

See the attached sketch.

 

[r13]

Your procedure is fine. Are the ends of lintel will be bear on existing structures, or dowel in? Just curious. The linked paper is very helpful for your project, though the author is in UK, the concept should be the same.

https://www.diydoctor.org.uk/projects/using-acro-props.htm

Here is another one. Link