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We want to hang a 65" 70-lb TV on a SIP wall with an articulated mount. The SIP wall is a sandwich of two 18mm/0.75" OSB outer panels filled with 8" of a "solid" insulating foam (and covered with drywall). There are no studs anywhere near the mount area, and we can't use toggle bolts as they won't expand due to the inner foam (a professional already tried). The Sony (SU-WL855) swivel mount can swing out the entire TV about 6" from the wall. I believe the best solution is to mount a hardwood board on the SIP wall and then fasten the mount to the board, but have questions.

  1. Is there a better solution? (Or is this even safe to do?)
  2. If this is best, what panel would be best - I am thinking either 1/4" or 3/8" hardwood, about 2'x3'. Recommended dimensions and thickness/material?
  3. To mount the wood to the SIP wall, I would think screws would be best, but some people say nails are better with OSB. Screws or nails? And what is the recommended size (obviously about 1.25" long thru mount board, drywall, and OSB, but what screw size or nail size)?
  4. What have I missed?
  • You say "two 18mm/0.75" OSB outer panels", are both pieces on the outside face, and drywall only on the inside face? – Jack Oct 17 at 20:58
  • No - the OSB panels form a sandwich around the inner foam insulation - a cross section would be: 1/2" drywall - 3/4" OSB - 8" insulation - 3/4" OSB - stucco exterior. – Kim Crosser Oct 17 at 21:05
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Just mount it to the wall with short lag bolts. 3/4" OSB is a solid mounting surface unless you soak it with water.

Since you did not specify drywall thickness, you basically want a lag bolt roughly 1/8-1/4" longer than 3/4" plus drywall thickness - so if 1/2" drywall, 1-1/2" lag bolts. Predrill for the core of the lag bolt so it's just cutting threads with its screw, not trying to crush a hole in the wall (as per normal for proper use of lag bolts.)

If mounting a supplementary board to the wall, don't fool around with 1/4-3/8" thick - that's not going to hold (nor help) much at all. Cut out the drywall to the size of your board, use at least 3/4" solid wood or plywood, and attach directly to the OSB with construction adhesive and screws equal to the board + the OSB thickness. Let the adhesive cure before mounting the TV, with lag bolts.

...sent from inside my SIP house.

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  • Since it is 3/4" OSB and the makers of these brackets usually requires at least 2 or more screws into the framing and I have seen kits with plastic anchors for hollow walls as well. (maybe not for an articulated bracket). Since there is no issue with stud centers, your idea of lags is great, I would increase the count, maybe 8 or more since it is an articulated mount, concentrating most at the top holes. Not even mess with the extra board, although your idea for that is a good one too. – Jack Oct 17 at 21:17
  • We are going to go with the supplementary board approach for a couple of reasons. Drilling multiple holes for the lag bolts directly thru the drywall and OSB seems like we will possibly introduce a moisture problem to the OSB. The mounting board with construction adhesive will help provide some moisture barrier. Also, using the articulated mount "feels" like it could cause the OSB fibers to loosen around the bolts. As a "belt & suspenders" kind of guy, the board seems much safer over time. Ecnerwal - Thank you. – Kim Crosser Oct 18 at 23:39

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