Shiplap support strength

Questions and answers relating to houses built in the 1800s and before.

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Acehigh1
Posts: 1
Joined: Sat Jul 13, 2019 3:09 pm

Shiplap support strength

Post by Acehigh1 »

I have an early 1700s (built between 1703-1725) NH house with an outer wall that we need to attach a rather heavy OTR microwave with built-in fan to vent (Jenn Air w/ convection and it is 92 lbs). The outer and inner walls are 5/4-in thick shiplap with 15-in facing boards run horizontally with 2 1/2 inch of what looks more like grey dirt in between the outer and inner walls. It is very hard but hitting it with a chisel breaks it easily. Unlike horsehair plaster on interior room walls and not doesn't appear to be mortar. The distance from floor (2 boards thick over support beam) to beam in ceiling is 84-in and wall is all shiplap, so would rather utilize the existing structure than tear out and create stud supports between beams. If I ran 5" screws through the microwave bracket so it would screw in both inner and outer shiplap, would that be adequate, as Jenn Air states that wall should be 150-lb weight support. I will also be using iron L-brackets to screw into the top beam against the wall and some more spots in the wall shiplap and attach it to the plank that will run over the microwave (in place of no cabinet)and will have the bolts in front of microwave attach to. I plan to finish off the sides with old reclaimed wood from the barn to blend in with the exposed beams. Is there any reason I could not do this, knowing the 150-lb weight requirement, and is this grey matter in the exterior walls a different type of plaster that could hold up better to the elements than typical horsehair plaster? It was still very intact (solid), even with new clapboards being put on the outside over the years, including just last year. Only the chisel could break it and then it crumbled rather easy when started. Thanks for any insight :D

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