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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?
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  • You say "two 18mm/0.75" OSB outer panels", are both pieces on the outside face, and drywall only on the inside face?
    – Jack
    Commented Oct 17, 2020 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
    Commented Oct 17, 2020 at 21:05

3 Answers 3

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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
    Commented Oct 17, 2020 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
    Commented Oct 18, 2020 at 23:39
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    We did go with the board. Used a 3' x 4' 3/4" plywood board, cut out the drywall to fit (which was 3/4", so the new board sits flush with the surrounding drywall). Sank 12 lag screws in 3 rows of 4 across (staggered slightly), then mounted the articulated bracket to the plywood. Worked great and the TV is easily positioned for direct viewing from a small dining area and then swung for direct viewing from recliners on the other side of the room.
    – Kim Crosser
    Commented Mar 31, 2021 at 21:11
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Just wanted to share my experience, in case someone lands on this page while searching how to mount their TV on their SIP wall — like I did... while doing lots or research...

My wall is basically 1 cm of OSB, then 1 cm of plasterboard:

enter image description here

My TV is less than 20 kg, but the bracket is full motion (the TV can go as far as 43 cm from the wall), so it can make the tension applied on the wall much higher.

I used four spring toggles, as well as the four wood screws that were included with the brackets. Here are the spring toggles:

enter image description here

I made four 14 mm holes, then, to allow the spring toggles to expand behind the board, I scratched bits of insulation foam with a bent metal rod placed at the end of a drill:

enter image description here

After that, I inserted the spring toggles, pulled on their screws to expand them, then removed the screws. The spring toggles stayed in place, thanks to the insulation foam:

enter image description here

enter image description here

Then I attached the bracket. Basically, the four wood screws prevent the bracket from moving vertically; and the four spring toggles prevent the top of the bracket from being teared off the wall:

enter image description here

It has been like this for three weeks, and it hasn’t moved :-) Note that I keep the TV close to the wall; I only move it when I need to plug some wires.

Hope that will help someone.

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  • Sounds good. After 9 months, our TV on the articulated bracket is still very secure and easily swung around. We probably overkilled the situation, but I like that we can have the 70 lb. TV fully extended from the wall and still have no appreciable wobble. We didn't have any access to the back (unless we punched holes through an exterior wall), so all the mounting had to be from the front surface. We tried opening some foam space behind the OSB, but couldn't really get the toggles to reliably open and feel safe.
    – Kim Crosser
    Commented Jan 18, 2022 at 20:03
  • Mind editing the photos into this answer so it still fully works even if your link breaks for whatever reason?
    – ThreePhaseEel
    Commented Jan 19, 2022 at 4:12
  • Well done @Kim-Crosser! No worries @ThreePhaseEel, it's done.
    – Zwyx
    Commented Jan 20, 2022 at 0:46
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I mounted an articulated (Down & Out) bracket on the SIP wall over my fireplace. The TV is an 80” Vizio with a big sound bar so over 120 pounds — more than the bracket provider recommended. I was lucky because there is a chimney box outside the SIP wall with a couple of feet of enclosed space but I was concerned that simple bolts might pull out of the SIP. I ended up using using a piece of 3/4” plywood mounted on the outside of the wall into which I drilled the bolt pattern, inserted T-nuts into those holes and ran long bolts through the bracket, through the drywall, through the SIP and into the T-nuts. There is no way the weight of an TV will pull that piece of plywood through that SIP wall. The bracket is extremely solid. I may do the same thing in reverse to hang an 80 pound AC unit on an outside bathroom wall.

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