Mixing Thick and Thin Lagging Boards 1

[cap4000]

Is mixing 2 x random widths and 3 x random widths wise to do in the same 8 foot wide H-Pile bay?? Typically down to 4 feet deep can be 2 inch thick material and from there down to 10 feet deep can be 3 inch thick. I could easily spec one thickness but I am trying to save money for a Church. The soil on site is a dense clay with rock below. Thanks for any information in advance.

 

[TDAA]

If the spec is clear, the boards ar good enough to do the job, and the contractor can get them in the right place, there should be no problem.

Does the length really make it worth the cost to change them though?

 

[cap4000]

The problem I have with using 2 inch thick boards is that it CAN NOT span unbraced for an 8 foot H-Pile bay spacing. Max. Span for 2 inch thick boards is around 5 feet.

 

[PEinc]

I agree with cap4000 on this one. Use 3 inch nominal thickness boards.

 

[MSEMan]

Go ahead then but its a real shoe string decision. make sure that any fill directly behind the lagging is completely free draining (i.e. #57 stone or similar) so that you don't get any hyrdostatic pressure building up against the lagging.

 

[PEinc]

If you place free-draining, granular material or stone behind the lagging boards, it will probably run out when a subsequent level of excavation is made below the previously installed boards. This is bad practice.

If the wall is temporary, nothing is needed behind the lagging, except tight contact between the boards and the dirt. If the wall is permanent and less than about 5 feet high, you could place material behind the lagging. If the wall is permanent and high, it probably should not be wood lagging, especially random width or variable thickness.