Joist width for mounting tv?

18 Jul 2007
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United Kingdom
I have just bought a 32" led tv which i would like to mount on my bedroom wall.

The tv weight is 8.3kg
The tv bracket is 1.9kg and can hold upto 20kg (Cantilever but will be mostly closed upto the wall)

When i took some plasterboard off the rear of the wall that i will be fixing to (couldn't find the joist with detector) i noticed that the joist width was only 30mm. Is this still enough to fasten this tv to or do i need to do something to change this?

The bracket has 2 holes at the top and 1 at the bottom for fastening and is about 130mm high by 60mm wide.
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30mm joists are all that's needed for a stud wall. Mounting on to those joists will be fine as long as you hit the centre line rather than an edge. The trick is finding the centres and making sure they line up with the holes in the bracket.

If you don't have an accurate electronic joist finder then finding the centres is done by probing the wall with something thin and sharp. A panel pin, a brawdel or a thin screwdriver will do. What you are looking for is to find the left and right edges of the joist. Once you have done that then the halfway point is the midline.

Once you have the joist locations and centres marked then you may find that the bracket holes aren't in the correct places. If this is the case then you have two options. Either drill out new mounting holes in the metal plate, or fit a wooden board to span the joists and so provide a suitable fixing surface for the bracket. Use real timber rather than MDF.
Firstly thanks for the reply Chris.

fit a wooden board to span the joists and so provide a suitable fixing surface for the bracket.
What thickness would this need to be? Am i right in thinking you mean behind the plasterboard or on top of it?

This is the bracket with the fixing holes showing. 2 at the top and 1 at the bottom.
Thanks for the picture. That's helpful.

Forget about the board. The fixing holes are in a roughly vertical line. Fixing in to a joist will be stronger than short screws in to a bit of half inch thick timber. Just concentrate on getting a really good fixing in to a single upright stud.

I fixed a CRT 15" portable on a short cantilever bracket the same way for my boy a few years ago. They weigh about 12kg. It also had to withstand the rigours of a 6 year old boy. It has been fine. I made sure to drill reasonable sized pilot holes in the joist so that the screws would grip well without splitting the wood.
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Thanks again for the reply Chris.

The only issue i have with just fixing them to the 30mm joist is that the 2 top holes average edge to edge about 20mm meaning that there would be only 5mm each side of the screws fixed to the joist. Would this not be a weak point? Could i do the following..

Do what's easiest. If you are a plasterer and happy to redecorate too then add the noggin. Use glue as well as screws. For my money though I would either find a different bracket or drill out suitable holes in the existing one.
I am not a plasterer. But i have removed the plasterboard on the reverse side of the wall i will be putting the bracket to get at the studs. This wall needed redecorating anyway, i am reasonably good at diy and can manage to board and skim the cleared section.

You mention using glue aswell, what is the reason for this?

If i were to get a different bracket i may still have the same problems with the stud size.
You mention using glue aswell, what is the reason for this?
It's wood glue. Put it on the mating face between the joist and the noggin. The reason is additional strength without adding further screws which could get in the way of the bracket screws.

When you think about the forces involved, the bracket is pulling at 90 degrees to the line of the noggin screws. If you were trying to rip the noggin off the stud then this is exactly the same direction in which you would pull it because it offers the best leverage to break the fixing. Use Gorilla Glue or similar for a really strong bond. (Available from Screwfix). Remember as well, once the wall is sealed up you can't go back and repair a poor fixing, so Do it once. Do it right is a good mantra.

If i were to get a different bracket i may still have the same problems with the stud size.
Only if it had these offset fixing points. But it looks like you have a different solution so there's not much point going further down that road.
If you have rear access fit noggins that are full depth of the stud perhaps 50 x 75 or 50 x 100. It matter not if the noggin are horizontal or vertical so long as they pass over where you want to get a fixing. If you use short horizontal ones ideally use a pair even if they sit side by side.

Put a couple of nails in each end to pin the noggins inplace. e.g. straight through the member you attach to so the nail hits the noggin on the way out. For 30mm stud use 75mm nails. Make sure your noggins are a nice tight fit - If cut accurately they will stay in place on their own as you nail them. When you fit the rear plasterboard back make sure you put some screws into the noggins

You are correct that you will definately need to fix into the studding/noggins. Although for the actual loads an expanding anchor may just do it (not recommended) - If interested see: See page numbered 53 onward (page 40 of the pdf)
Hello and Happy New Year to all. I have exactly the same issue but I have no idea where the studs are and the 2 top holes in my bracket are side by side 30mm apart. My TV is <5kg. Can I hang it directly from the plaster board using these?
If your TV wasn't on a cantilever bracket i.e. it was on a flat wall bracket instead - then the answer would be yes. But as soon as you have a bracket that moves the weight of the TV away from the wall such as a cantilever bracket, which is what you've got, then you start to introduce a lot of leverage. This multiplies up the effect of the weight so it's the equivalent of hanging a much heavier TV. If you've ever tried to open a tin of paint then you'll know that it's virtually impossible to prise off the lid with your finger nails, but much easier if you use a screwdriver with a long shaft. That's the effect of leverage. In situations like this you really want to get a solid fixing on to a stud.

Finding the stud without using fancy tools

Tools: For this you will need either a thin nail/panel pin or a sewing kit pin with a ball end so it doesn't hurt your fingers. If you're using a nail or panel pin then a pair of pliers might be useful to help you push it in to the wall and pull it out after. You'll also need the mark 1 human knuckle.

Info: Studs run vertically - floor to ceiling - and in a straight line. The timber width is generally 50mm. The stud spacing will (or should) be either 400mm apart or 600mm apart depending on the thickness of the plasterboard.

Safety: Electrics - it's possible your stud wall will have a light switch and it'll definitely have a mains socket somewhere near where you want to mount the TV (otherwise how would you power it, right?). Bear in mind then you'll have electrical cables inside the wall. Generally power cables should run vertically, and for power sockets the feed should come in from below but it's not unheard of for them to be wired from above. Remember too that stud walls are generally built between rooms, so do check about the location of power sockets and light switches on the other side of the wall before you go making holes in the wall with bits of metal. In general then, avoid fixing anything to the wall directly above or below any sockets and switches. Nailing or drilling in to a power cable could end your day pretty quickly.

Method: Start off with the mark 1 human knuckle and knock on the wall.


It'll probably sound hollow unless you happen to knock over where a stud is located. Work your way across the wall in the area where you'd like to mount the bracket. You'll soon get a feel for hollow or solid soundings, so this will give you the rough location of the studs. Tip: If you find that the wall sounds solid even though you've moved well past the width of a vertical stud then you might have found a noggin. This is the name for a horizontal stud fixed in between the verticals to give the wall strength and help support the plasterboard.

Once you have a rough feel for a stud position you can then go on to fine tune the exact location. This is where the pin or nail comes in. Probe the wall with the pin or nail starting from the more hollow-sounding side and working towards where you think the stud is. If there's nothing behind the plasterboard then the pin will go straight in. If it doesn't then you've found the stud. Your goal is to find the left and right edges of the stud, so work across methodically until you have them marked. Tip: The reason you want to know where the edges of the stud are is because when you come to fix your bracket you really want to drill in as close to the centre of the stud as possible.


Fixing your bracket: If possible, align the bracket with the centre-line of the stud. If not then at least try to get two sold fixings - one each for the top and bottom holes. It would be better to use larger screws than come with the standard fixing pack unless those ones are particularly large. There are two reasons for this: First, a screw with a larger surface area provides better grip. Second, many of the screws supplied with brackets are made of a softer metal than those you'll buy from a DIY store. This means when fixing in to something firm the soft metal heads get chewed up by the screwdriver. After that then it's much harder to get then tightened up properly and they may even be impossible to remove to fit something better. It's simpler to use better screws from the outset. Tip: Pilot drill the fixing holes before screwing in the bracket. Pilot drilling is where you drill using a smaller diameter drill bit than the screws. It reduces the risk of the wood splitting; especially where the fixing holes are close to the edge of the timber. It also makes the screws easier to tighten up because you're not having to apply a lot of force to cut through the wood.

bracket alignment.jpg

Good luck with your job, and if you found this useful then please click on the THANKS button to show your appreciation :)
Wow, thanks a lot for the information Lucid. I knew that when the arm is extended it would increase the weight but I don't know how to calculate the increase, as my TV is relatively light (4.5 kg) I was hoping to get away with it. I will use my mkI knuckle to find the stud as you have instructed and let you know the end result.
If your TV bracket cannot be fitted directly to studs due to spacing consider fixing the bracket to a plate such as MDF and fixing the plate to the studs so bolt the bracket to the MDF sheet (use 18mm as you need to recess bolt heads with large washers) then fix the MDF.

Studs come in different sizes with 50mm often in older houses and 38mm in newer ones. It could even be metal stud sections (C section) which I have encoutered on various occassions. However you will tend to find the same system used thoughout a house once you know what is used.

Personally I use a very small drill to find studs and always watch the depth carefully or mark the drill with something as a guide. Once through plaster it is usually air, stud or pipes! So beware. I once drill for a set of cavity anchors using a small drill to test each hole five were clear the sixth I found an obstruction and using a thin rod I have, I tapped the obstruction I decided it was a copper pipe so tried elsewhere!

As for stud centres just be aware that while 600mm is common it may be quite a bit different for each depending on the quality and care it was put up with!

As for cavity anchors you could probably use the metal ones after checking the table for the pull out weights. As Lucid has indicated it is the pull out capacity that is important and the further the TV is away from the wall the greater the force so vertical fixings say 150mm apart and a swing out bracket giving 300mm distance to wall will effectively double the weight of the TV leverage. i.e a 5kg TV would need at leat 10kg anchors

See for some examples of the tension ratings in different walls


To convert kn to kg multiply by 98 (100 usually near enough!)
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The sping toggles are in my opinion the last choice as you fit them and cannot remove and re-fix. The gripit seem to need a very large hole and are in my opinion better suited to dry lined walls where you don't have the space for the anchors. Although I use a frame type fixing in that situation and go through plasterboard and gap to fix into the brick or block behind.

I prefer the metal anchors in hollow stud walls such as rawplug, fischer and others all of the type linked below

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