I'm trying to close a gap in the wall with drywall.

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Since the wall is so thick (25cm) it's too expensive to fill it all up with insulation. In addition, there are no 25cm metal studs I can easily buy.

One idea is to go with a single 7.5cm stud and double drywall (2x1.25cm) on each side. This will cover the hole with drywall half way.

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Drywall wise that's a good enough option, but then I'm left with having to smooth the edge on the side that will remain open, and that looks more complicated than dry-walling.

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Update 1

There was a suggestion to do this as two separate walls. This was considered, but it's not clear how to install the inner drywall once the first wall is in place, as shown on the picture below.

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Update 2

The suggestion below was mentioned.

I originally considered a variation of this option to fill everything in between the drywall with insulation. Gave up on that once I couldn't find proof that the so much insulation is worth the money.

I'm considering the suggestion on the picture, to just fill the insulation in between the studs without adding extra drywall inside. I thought the insulation won't stand on it's own without the drywall but and reconsidering this thought.

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How would you solve this problem if the focus is to have it done with drywall as much as possible and the focus is acoustic insulation (so not carrying capacity or thermal)?

  • Can you clarify the term “smote”? It’s not in our local vernacular. And this is a great application for two ‘normal’ (~100mm thick) walls because of the desire for sound isolation. Nov 28, 2023 at 13:01
  • Good update — thanks. 4 layers of drywall would give more sound insulation than 3 (easy to do, btw, if you build one wall first) than 2, but you might be looking at diminishing returns. I regret that I’m not an expert in this; hopefully someone will come along with solid STC numbers. Nov 28, 2023 at 14:22
  • stcratings.com/assemblies.html ... see especially #6, "Drywall between double studs can dramatically reduce the STC rating of an assembly." So easier is better! And I'm an expert now ;) Nov 28, 2023 at 14:35
  • Your bottom option: two rows of parallel 7.5 cm deep metal studs but only use two layers of drywall on the outsides. No inner dywall needed. Fill the inside space with insulating batts. Nov 28, 2023 at 16:13
  • Are you really thinking to do four separate (i.e. not doubled up) layers of drywall? If so, it looks like you have 25 cm to deal with. If you have 1.25 cm drywall and 7.5 cm studs, it seems like you have 5 cm of space. Are you telling me you can't find a stud (or other lumber material) that's 5 cm?
    – Huesmann
    Nov 28, 2023 at 16:14

1 Answer 1


It's not clear to me what your actual preferences are with respect to insulation and drywall. You mention several scenarios. However, the simple fact is that you can build one wall to your liking, then build the other wall on the floor. Apply as much drywall as you like to the inner (upper, when under construction) face, then tip it up and fasten it in place with the appropriate backset for the remaining drywall.

Be aware that you must square the wall carefully since you're sheathing it. Take diagonal measurements of both the opening and your framed wall and be sure they match. Leave a bit of a gap for safety (6mm should do).

One other suggestion is to remove any corner bead around the opening before beginning. It adds unnecessary thickness and curvature to the wall which makes finishing the drywall more difficult.

  • Thanks, I'm comparing options with the focus on best bang for buck acoustic insulation and ease of installation. Eventually I'll likely clean up the question to give a comparison of the approaches so it doesn't grow into a mess. Nov 28, 2023 at 18:02

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