Heel-Less Basement Retaining Wall
Heel-Less Basement Retaining Wall
(OP)
An old residential structure with failed basement wall (structural cracks all around). Any ideas on how to reinforce the retaining structure such as an L-shaped wall with Toe lying on top of basement slab? Sliding becomes an issue...any ideas...Much appreciated.
Thanks,
FEM4Structures






RE: Heel-Less Basement Retaining Wall
RE: Heel-Less Basement Retaining Wall
BA
RE: Heel-Less Basement Retaining Wall
Thanks,
FEM4Structures
RE: Heel-Less Basement Retaining Wall
Thanks,
FEM4Structures
RE: Heel-Less Basement Retaining Wall
RE: Heel-Less Basement Retaining Wall
RE: Heel-Less Basement Retaining Wall
The calculations are pretty straightforward if the design pressure is known. I have always assumed that the existing wall is incapable of resisting any lateral pressure but is capable of carrying gravity load, subject to site confirmation.
PWF material is recommended for the bottom plate which will be fastened to the existing grade slab. Studs may be untreated unless there is a lot of water coming through the old walls in which case they should be PWF material too. The top of studs must be adequately anchored to the floor system to resist the horizontal reaction due to earth pressure and the floor system should be checked to ensure its adequacy. Sometimes, extra bridging is required between joists where walls are parallel to joists.
After building the stud walls and fully anchoring them top and bottom, wedges or shims are installed in the variable gap between the studs and the existing wall to transfer earth pressure directly to the studs.
In your case, with an eight foot height of retained earth, you should obtain a soil report to provide recommended design values of lateral pressure which vary according to soil type.
If there is no weeping tile around the exterior of the footing, exterior grading must ensure that rainwater and snow melt will flow away from the foundation. Alternatively, a drainage tile system inside the existing basement wall may be required.
BA
RE: Heel-Less Basement Retaining Wall
I am assuming you are a recent University graduate, and don't have any experience with wood, which is very common.
I could help if you don't have the time at work to research all this, and you are not able to seek advice from co-workers.
This is merely wood studs in flexure, with no axial load, and Load Duration factor = 0.9 because of soil pressure, correct?
Give me height of stud wall, pressure distribution of soil, and wood species and I could run a quick check on my "software".
RE: Heel-Less Basement Retaining Wall
Thanks for responses...Much appreciated
Thanks,
FEM4Structures
RE: Heel-Less Basement Retaining Wall
Active Moment will be 3,400 #.ft per ft. To be on conservative side, I can use DFL 4x4 16" O/C with sheathing on both sides. What should be the sheathing selection given that wall is exposed to insitu soil and moisture. Also, don't have numbers on existing roof beam. How would one conservatively deal for connecting studs to the roof beam? Recommendation highly appreciated.
Most of my experience is in concrete and steel structures but don't want to use concrete retaining wall solution. Just want to have confidence in the wood solution.
Thanks,
FEM4Structures
RE: Heel-Less Basement Retaining Wall
I don't think 4x4@16 o/c is a good choice. How did you arrive at 3400#' per ft? Doesn't sound right. Sheathing can't be installed on the outside and is not required on either side. Wall is not exposed to soil and moisture if it is inside the existing wall.
Roof beam? Don't you mean main floor joists? Provide a cross section.
BA
RE: Heel-Less Basement Retaining Wall
For 7.5 ft, I have following numbers
Active force = 0.5 x 120 #/ft3 x 0.333 x 7.5ft ^ 2 = 1124 # per ft @ 2.5' above base
Active Moment = 2810 3.ft per ft
It is floor joist. Please ignore the typing brevity as I was typing on smartphone.
Thanks,
FEM4Structures
RE: Heel-Less Basement Retaining Wall
Thanks,
FEM4Structures
RE: Heel-Less Basement Retaining Wall
W = 300*7.5/2 = 1125# @ 2.5' from bottom (5.5' from top).
Rtop = 1125*2.5/8 = 352#
Mmax is at 0.5 + x where 40x2/2 = 352
so x = 4.19'
Mmax = 352*(0.5 + 4.19*2/3) = 1160#'/' which is less than half the value you reported.
Please confirm my numbers.
BA
RE: Heel-Less Basement Retaining Wall
You must provide an adequate drainage system if it isn't there now. Exterior grading could be done to guide water away from the foundation or you could provide a weeping tile system connected to a positive drain.
Sheathing can't be installed between the new studs and the existing wall. Even if it could, it wouldn't prevent water from entering the basement.
BA
RE: Heel-Less Basement Retaining Wall
Please confirm if you don't agree with the number.
Thanks,
FEM4Structures
RE: Heel-Less Basement Retaining Wall
Thanks,
FEM4Structures
RE: Heel-Less Basement Retaining Wall
RE: Heel-Less Basement Retaining Wall
Also, PT lumber (and all modern lumber in general) seems to creep alot more than the NDS would lead you to believe.
RE: Heel-Less Basement Retaining Wall
BA