Wall plugs need brick, block or concrete to hold well.
Plaster just will not do, because it has minimal holding power.
It’s usually way too soft you see. Sure, if the wall is plastered with hard cement render and thin skimming coats, you might get away with some light to medium loads, but generally the plastic plug needs to be pushed into the wall itself so it’s entire length is into a brick, a block or concrete etc.
Why? Because the way a wall plug works and holds in place is by expanding in a radially outwards fashion. Simply put, when you put a screw into a plastic wall plug (or an old fashioned wooden plug for that matter) it acts as a wedge, pushing the two halves of the plug apart and filling the hole very tightly. Friction then takes care of holding everything in place for all eternity; handy stuff friction… and it’s free!
Most wall plugs are only 1 1/4″ to 1 1/2″ (32 to 38mm) long and most plaster on walls is between 1/2 (12.5mm) to 3/4 (19mm) or so thick. So, doing the maths and taking the thickness of the plaster away from the length of the plug you’ll figure out that not much of the plug is actually going into the brick/block/concrete if you leave them flush with the plaster. Also, the front part of the brick is not able to take much load either without risking a ‘fisheye’ breakout under load.
Wall plugs work best when their WHOLE LENGTH is fully inside the walls main building material, thus relieving the plaster and the front face of the walling material from stress.
Quick ‘n’ dirty sketch of ‘textbook’ installation of Rawlplugs….
How to put screws into plastic wall plugs (rawlplugs) on a plastered wall.
How to install plastic wall plugs
- Mark out all your holes using a spirit level and/or tape measure.
- Carefully drill your holes, starting off slowly (possibly with the hammer action off) until the drill bit forms a shallow hole (see pic above for depth), speed up and hammer back on to finish the hole.
- Vacuum out the hole if you want to be really proper, mostly not necessary or done however….
- Push or tap your rawlplugs into your holes, flush with the plaster.
- Position the item to be fixed over the hole and put the screw through it and into the plug, twisting the screw a tiny bit by hand till it bites.
- Sometimes the above step is easier if you push the screw all the way through the item and then you’ll easily get the pointy end of the screw into the plug, sliding the item down the screw until it meets the wall.
- Using a small hammer tap the screw to push the plug through the plaster and into the wall itself and stop when the length of screw sticking out equals the length of the wall plug.
- Tighten up the screw, being careful not to push for the first few turns or you might push the plug in deeper (not good).
- Working this way ensures the plug is exactly the right depth into the wall and the screw will go all the way to the end of the wall plug when pulled up tight.
- Perfect. Rinse and repeat with the other screws.
- Put the kettle on or head to the fridge depending on the time of day….
If you want to learn more about screws and plugs check out this post: Screws Explained…
Hope that helps you figure out how to use plastic wall plugs and screws on plastered walls….
Let me know if you still have any questions.
Stay well
Ian
Comments 18
“Put the kettle on or head to the fridge depending on the time of day….”
My favourite part – made me laugh 🙂
Great article otherwise, Ian!
Author
Thanks Julian!
Got to keep it light eh?
Have a great weekend, hope the sun is shinin’ where you are.
Cheers
Ian
I’ll be putting this to the test this weekend! I was fixing a rope-banister to a wall covered in old victorian plaster – about 18mm thick before brick. It seemed to take a rawl plug well, but as you point out most of the plug was in the plaster not the wall. Then when too much load was put on the support, the plaster gave way in a big lump!
Now to try sinking the rawl plugs fully into the brick, filling the hole I made in the plaster, and re-fixing….this time the plaster (filler) is merely acting as a spacer between the wall and the bracket, so fingers crossed!
Author
Exactly Ben, plaster is a spacer, nothing more 🙂
You can mostly tell if the hole is ‘good’ when you drill it. If it drills clean and hard all the way it’s good, if the bit finishes wobbling about then it means the bit hit a crumbly bit, or broke out of the edge of a brick etc. If this happens you can improvis a ‘chemical or resin’ fixing by pumping some ‘no nails’ type adhesive into the hole, followed by the plug and then push the plug into the correct depth and leave to set for 24 hours.
Good luck with your project and I hope the plugs hold well.
Ian
Hi I am trying to mount a wall mounted wall to my brick wall in my living room. This is the table: https://www.ikea.com/gb/en/p/norberg-wall-mounted-drop-leaf-table-white-30180504/. A size 5mm screw fits in the whole a 6mm would but is very snug, would you go for a long 5mm screw or a short one and what drill bit and wall plug would you use,
Thanks
Author
Stuff like this needs a ‘fatter’ screw as there will be some weight on it. Generally, you’d use the biggest screw you can get into the hole.
If the wall is plastered you need something long enough to go into the brick/block itself and not just in the plaster (read this… Quick Tip: Using Wall Plugs (Rawlplugs) in a Plastered Wall.
I’d use a 7mm hole and a brown plug and about a 2 1/2″ or 3″ x 10gauge screw (65mm to 75mm x 5 or 6mm).
Hope that helps. Let me know if you get stuck!
Ian
Hi Ian. Got a question. I’m building a faux fireplace to attach to brickwork in my lounge. I was going to use timber that is 45mm X 120mm x 2400mm. Height will be trimmed to my needed size. But I was looking at using it with the 45mm edge flat to the wall, then the 120mm width as the depth of my frame. So looked at a 150mm screw into a brown plug in the brickwork. Would this work? The screw would be 32mm into the brick and the other 120mm in the timber. Is that enough depth into the brick to give sufficient hold? It won’t have any weight on the frame as my TV and fire will bracket directly to the brickwork too. Any advice appreciated. Thanks
Author
Hey Adam.
To be honest, you’ll struggle a little, trying to go through that much thickness and then only into the wall a small amount. There are two other ways to consider, but it depends if you’re covering up the frame? The most obvious way is to reduce the thickness by drilling a bigger hole half way through the timber with a flat or spade bit. Using a 20mm (or thereabouts)bit, drill a 70mm deep hole in the front of the timber to create a ‘pocket’ and then a 5mm hole the rest of the way. Then you can use a normal 100mm screw half in the wood and half in the wall; perfect (but only if the 20mm hole doesn’t cause issues). If you’re covering up the wood with say plasterboard you could also consider using little brackets up to 50mm x 50mm for example on the side of the wood and then into the wall with 2″ screws.
Aaaand finally. If the above is pants, then stick with the 150mm screws, but get the smallest gauge you can 10 or 12g if possible and drill into the brick 50 to 60mm and knock the plug almost all the way in. Usually you’ll want the top of the plug to be 8 to 15mm deep (to prevent the front face of the brick overloading and breaking out). Then drill a clearance hole all the way thought the 120mm timber (same diameter as the screw shank).
Then you’ll be able to drive the screw deeper into the 120mm wood, you might even get the head a good inch into it. This will give you enough screw in the wall and still a good hold on the wood.
Hope that all makes sense! Give me a shout if I’ve misunderstood you 🙂
Cheers and thanks for reaching out
Ian
Author
Incidentally; if there is plaster on the brickwork you’ll need to allow for that as well. The whole of the plug needs to be inside the brick, not in the plaster at all…
Ian
Another quick hint.
Cleaning the holes out can sometimes be important but you may not have electricity available or wish to drag a vacuum cleaner around.
Another problem is that plaster & concrete dust is also some of the worst material for a normal dry vacuum cleaner – I have been a repair tech for vacuum cleaners.
The dust is extremely fine & abrasive, so fine it goes through many filters & quickly coats the inside of bags so the bag may be nearly new & almost empty but needs to be replaced because no airflow is going through it.
Dry vacuum cleaners (not wet & dry) require the airflow through the bag to cool the motor so a clogged bag can quickly burn a motor out.
If you are using a wet & dry vacuum then putting a bit of water in the bottom of the drum will make most of the really fine dust become mud & get caught.
An alternative to using a vacuum cleaner is to use a decent hand pump & the inflating needle used for sports & exercise balls.
Just insert the needle into the hole & give a couple of blows & you have a clean hole.
The pump & needles are inexpensive & don’t take much space in your tool box.
One major fastener supplier actually used to supply a rebranded pump like that with some of their drill sets.
Regards,
Brian.
Author
Great advice right there Brian, thanks! So true about builders dust killing vacs, it’s terrible stuff.
Re blowing out holes, to be honest I agree that in most cases a bit of dust doesn’t really affect the hold, it’s a friction hold after all. IMHO it’s only for resin/ adhesive type fasteners which need to be spotless. I often just turn the drill once I’ve drilled the hole and let the powerful fan inside the drill blow out the hole for me. But it’s a bit messy and I need to watch my eyes. I also do the same when routing, to blow away the sawdust. Free air!
Many thanks for taking the time to leave a useful comment Brian,
Best of luck with all your DIY endeavours 🙂
Ian
Hello Ian! This has been very useful. Just to double check, I believe the wall I’m trying to install a shelf on is a mix of drywall over concrete. I tried drilling a hole after the self drilling metal anchor I had been using in other walls in my home failed to go in, and the dust that came out looks like cement. Would you suggest I drill a deeper hole (applying the math on your diagram) with the hammer/drill function on in order to go as deep as I apparently need to? Also, after I tried with the self drilling anchor, I made a seizable hole on the drywall and I’d still like to hang my shelf at the same height… Do I need to plaster the hole before I do anything else or is it just a bad idea altogether to keep drilling and working the same hole? Thanks a bunch and I’m sorry for the lengthy consultation!
Author
Hi Cindy,
No problem! If you have time, I’d definitely fill/plaster up the hole up and smooth it over. Then you’ll need to leave it for a day or two to dry. Then mark out again and drill the hole using a straight masonry bit if you’re sure the wall is brick/block/concrete etc. Start slow until the the tip of the bit is through the drywall and into the wall behind, then you can increase the speed and pressure. Wrap some tape around the drill bit to give you an idea when you’re deep enough. Put the tape about 5mm deeper than you need to go and stop drilling when the tape is 5mm from the wall face (if you run the tape right up to the wall it’s easy to drill too deep as the tape moves up the bit).
As you’ve found out self drilling anchors are difficult to place accurately.
I wonder though, is there any way to confirm the wall is masonry behind the drywall? Just that hitting a stud/timber will also thwart a self drilling anchor.
Let me know how you get on Cindy,
Cheers
Ian
Isn’t a plaster wall different from a wall made of drywall? But there is no mention of drywall, so I wonder if you’re refering to both kinds.
Author
Hi Clare,
No this applies just to plastered, solid walls. To fasten to drywall you need special fixings specially made to hold in drywall. Drywall fixings need to go through the drywall sheet and open out a little behind the sheet.
Here, like this…
Hope that clarifies, let me know if not 🙂
Ian
Star Plugs give the following hints:
Always drill the hole so deep that the outer end of the plug enters until slightly behind the surface of the wall.
In a plaster wall, the outer end of the plug must be farther in that the plaster layer, otherwise there is a risk that the fragments of plaster will come off around the hole when the screw is tightened, because the plug expands in the soft material first. And frayed holes are always unsightly.
In general, do not ever place plugs in plaster or in joints. You will only be kidding yourself, as plaster and mortar have no bearing capacity whatsoever. The plug belongs in the solid wall.
I have seen that many people have drilled the mortar between bricks so the last hint is very helpful.
I am trying to hang a long book shelf in a wall that has 75mm insulation between plaster and block.
I am using 120mm screw with plug in order to anchor into the block.
I drilled a good hole of the right depth, tested with screw.
however I can’t push or hammer the plug in even though plug and drill bit are both 8mm wide.
the plug gets stuck about two thirds the way in, even with a hammer.
What’s causing this?
thanks,
John
Author
Wow, never seen a plasterboard with 75mm of insulation before, pretty hi tech. Did you vacuum out the hole first? Horizontal holes are terrible for leaving a lot of debris behind, especially in insulation which tends to ‘ball up’ on drilling rather than cut out cleanly. Also, did you put some insulation tape (or sellotape in a pinch) around the drill bit at 125mm or so depth? Just to absolutely make sure you’re all the way in?
If that’s not the case well, then it’s odd! Logic dictates if there is a hole and it’s the right diameter and depth, it’s got to go in!
Another alternative is that the plug is not following the sometimes rough hole in the insulation and is veering off to the side, then it will stop when it hits the block and that’d be about 2/3’s of the way in….
Lastly, you could switch fasteners and try a frame fixing, then the plug and screw are the same length and inserted as one fixing. might help.
Hope that’s given you food for thought!
Good luck and let me know how you get on.
Cheers
Ian