If it is horizontal or vertical wood planking, there aren't any values for this. If it is diagonal wood planking, there are some values in the codes of that time. There were studies utilizing nail spacing and capacities for multiple couples - but these were not in any code. In your case the interior sheetrock or plaster or exterior stucco may provide some shear values - but these have been downrated since the 60's. On the other hand, plywood panels were alive and well and these values are available in the Uniform Building Code's of that time. Are there diagonal let-ins in the wallS? I can't remember what people assign a shear value for these configurations - want to say 1000 lbs but you should check. By the way, you cannot add the capacity of sheet rock or stucco to any wood shear element. Either then or today.
As noted by oldrunner, the size and direction of the siding matter significantly.
How the wood panels or strips or sheating is attached matter.
Thickness of siding and its material type (what species of wood) to a lesser degree.
1x6 and smaller, horizontal lumber sheathing, fastened with 8d nails (2 at end, 3 at field) provide 140plf of nominal wind shear capacity as provided by Table 4.3D in the 2008 Wind and Seismic manual from AWC.
This assumes certain grade and support framing and what not. I think allowable is 1/2 or nominal...
I have a residential seismic retrofit where the board sheathing is covered with asbestos paper and then topped with galv. metal sheeting.
Does anyone know if new plywood can be installed over the board sheathing and if so, what kinds of values we get??
