20kg wall-mounted shelf mounted in drywall

[mattek]

After some searching in the forum, I haven't found an answer to this specific question (although there is a lot concerning screws+plugs in plaster). So, I dare to make a first post.

The conditions:
- Wall-mounted shelf of the String type (no legs down to the floor)
- It has a total of 6 attachment points and weighs 20kg, I want the mount to hold at least 40kg
- It will be mounted in a plaster wall (approximately 1.5-2cm)
- The plasterboard has a larger space behind it, probably 5cm
- No studs behind the plasterboard as far as I know

Molly plug/expander? Universal plug? Set up your own framework and attach to it?

 

[Jan-Å]

Read the post from Thomas59 in the thread below, he writes about Molly who might be able to solve your problem.

http://www.byggahus.se/forum/byggmaterial-byggteknik/135950-faesta-tv-i-ett-hoern.html

 

[mattek]

Good tips! However, I don't have a concrete wall behind the drywall, just air and then another piece of drywall against another room. Drywall-air-drywall

I think I need to rethink this...

 

[Jan-Å]

"4 Molly can easily support your TV's weight even on single drywall, with a good margin. Expect about 15-30 kg in vertical load capacity for each Molly with a safety factor of 3."

6 attachment points x 15 kg = 90 kg just that. As I interpret Thomas's post, it works well on single drywall.

 

[Huvudbrytaren]

Thomas 59 said:

Count on about 15-30 kg in vertical load capacity for each Molly with a safety factor of 3.

If you have 6 attachment points in single drywall, then it's only 10 kg per Molly plug. You seem to have studs behind the drywall, probably with a center distance of 60 cm. The question is just whether they are made of wood or metal, requiring slightly different screws...
The String shelf you are going to put up consists of two rows of shelf boards and three side pieces? Ideally, you would fasten the middle side piece centered on a stud and use Molly for the four outer points.

 

[andreascarlsson]

I myself have a 40 kg TV mounted on 2+2 (i.e., two pairs with about 60 cm spacing) Mollys in a single drywall. Works without any issues.
Drywall is stronger than one might think. If you also find a stud, you can surely increase the weight fivefold without problems.

 

[mattek]

Thank you! Then it doesn't seem completely hopeless after all. I will try to find a rule behind the wall with a few small holes.

Asgarvad: Exactly! 3 ends, 6 shelves, and a total width of 140 cm.

Thanks everyone for the help!

 

[jarlen84]

There is something called a regelsökare...

 

[mattek]

Now I have a bit more understanding of how the wall looks after a test drilling:

- In two out of three holes, I hit a metal stud behind the drywall.
- The holes I have made have luckily/unluckily hit holes in the metal stud itself.
- In one of these, I drilled up with 9mm and hit an approximately 3.5-4mm hole in the stud, behind it seems there is only insulation.

What type of plug should I use when I have drywall-metal stud to work with?

Grateful for any tips!

 

[Enk Projektet]

http://www.norwesco.se/page/350/362

 

[mattek]

Enk Projektet: I believe the depth of the plaster is about 20mm, would a mini plug work? In one of the holes, it is already drilled with a 9mm drill, so the mini plug would probably only sit in the metal there?

 

[mattek]

Could a solution be to get a metal drill and drill through the metal beam, then use a molly bolt through it?

 

[Enk Projektet]

In metal it doesn't work well, but in old holes in gypsum, leca, lightweight concrete, siporex and similar materials they are excellent.

If you've hit right in the metal stud, it might work with drywall anchors (molly) but it's not certain.
If you can move it in any direction, I think it's easier/better.