Have you ever wanted to attach something really heavy to a wall, floor or ceiling? And I mean stupidly heavy… like giant TVs on cantilever arms, network cabinets or huge, ridiculously heavy radiators? Welcome to the world of the Wall Bolt! Today we’re taking a look at how to use wall bolts / expanding anchors.
Watch the full video here:
Tools & products used
- Makita SDS Drill (UK / US)
- Makita Combi / Impact Drill Set (UK / US)
- Screwfix M8 x 60mm Shield Anchors (UK)
Wallbolts are pretty much the strongest mechanical fixing I would ever use. They can handle MASSIVE loads and are my go-to fixing for giant TVs, big cabinets, heavy radiators or anything else where normal plastic plugs just aren’t up to the job. These go by a number of different names:
- Wall bolts
- Rawlplug refer to them as Rawlbolts
- Screwfix call them Shield Anchors
- Fischer call the Wallbolts
I’ve always known them as wall bolts – they’re also quite similar to ‘sleeve anchors’ and I’ve seen some suppliers refer to them under that name too (although sleeve anchors are slightly differently designed).
They’re ONLY for use in solid surfaces such as concrete, brick or blockwork. They’re no good for drywall or wooden walls. I have used them successfully on dot & dab walls but you need to make a spacer to fill the cavity between the drywall and the blockwork otherwise you’ll end up crushing the plasterboard when you tighten the bolt.
How to use wall bolts
The ones I’m showing you on the above video are M8 x 60mm and require a 14mm hole. I would almost always use an SDS drill for this as it makes light work of drilling such a big hole in concrete – you’ll be on it forever with a normal combi-drill. I like to set the depth stop to the overall length of the bolt – you don’t want it ‘bottoming out’ in the hole. Vacuum out the hole after drilling it – if you get dust or debris in the thread of the wall bolt you’re in trouble!
Where possible I like to fit the wall bolt to the fitting and then offer the whole assembly up to the wall. The advantage of doing it this way is that you’re less likely to run in to problems with the thread getting debris in it. This isn’t always possible with things like giant heavy radiators. Trust me, if you get the thread jammed up it can be VERY difficult to remove the bolt. Worst case you’ll have to cut it off and start again – not a fun job with carbon steel.
Once the bolt is in the hole it’s simply a case of tightening it. As the bolt is tightened the chamfered end piece is pulled in to the fitting causing it to expand. The more you tighten it the more it expands – simple as that! I generally make them ‘comfortably tight’ using a socket set. After you’ve done a few you’ll get used to how tight they need to be. If you’re using them in industrial applications you should use a torque wrench and follow the manufacturer’s recommendations.
Use of expanding anchors in brick or block walls
Firstly, as per usual, always follow the manufacturer’s specifications. In non-domestic / industrial situations always follow the recommendations of your structural engineer.
With that aside I’ve used expanding anchors such as these in brick, block and stone walls for many years very successfully. There are two main factors to consider in this scenario:
- How close are you to the edge of the brick / block and could the anchor cause cracking when it’s tightened?
- Is the brick / block hollow?
Cracking of bricks caused by expanding anchors
In short, don’t use these close to the edge of bricks or blocks on the outside corner of a wall! To be fair this applies to solid concrete too. In reality this is rarely a significant problem on internal walls since the brick you’re drilling in to is likely to be supported by surrounding bricks. This normally prevents cracking, as there’s nowhere for the brick to go. Worst case if it does crack it’s unlikely to be structural, it will be covered by the plasterwork and you should still be able to tighten up the bolt to get a strong fixing. If you’re using these on exposed brick and don’t want to take the gamble on an unsightly crack you’re probably best going for a different type of fixing. For standard construction internal brick walls in older Victorian properties where solid bricks are normally used, you should be absolutely fine.
Use of expanding anchors in hollow block / brick walls
Expanding anchors are only for use in solid walls – i.e. they’re no good in hollow blockwork or modern perforated bricks since there’s nothing for the anchor to grip on to. You really take your chances on whether you hit a solid section or a hollow section, for example in the frog of a brick. For that reason you might need to come up with an alternative fixing solution for outside walls. Another hack is to go for the mortar line – not ideal but it can work (see above).
Internal load-bearing walls are likely to be made from solid blockwork in newer UK properties or solid bricks in older Victorian houses, either way you should be fine. Low density aerated blocks, such as Thermalite, are another matter, see below.
Hidden advantage of expanding anchors and mortar lines
When you attach things to walls in domestic properties you rarely know what that wall is made of until you start drilling. Even then, there’s a reasonable chance you’re going to hit a mortar line sooner or later. That mortar can sometimes be quite solid. Sometimes, especially in older properties, it can resemble dry sand fresh from a sunny beach. Ideally you need to re-drill and find new fixing points in to solid brick / block but this isn’t always possible. Chemical fixings are useless in this scenario. It’s also a big problem for self-threading concrete screws.
However, in comes the expanding anchor as a potential problem solver. It doesn’t take much drilling to take a 10mm mortar joint up to a 14mm hole. Insert your fixing and proceed as normal. The anchor can grip on to the upper / lower bricks or the sides of bricks in a vertical joint. This has the added advantage of not cracking the bricks / blocks. However this is a completely out-of-spec hack so you take your chances!
Expanding anchors in low density blocks (Thermalite)
Low density blocks offer many advantages over other building materials. They have very high thermal insulation properties so are great for external applications where low U-values are required. They’re also easy to handle and cut.
The main disadvantage from a joinery perspective is that they’re a pain to attach things to. They’re so soft you can push a screwdriver straight in to them with your bare hands. Traditional plugs and screws just don’t work very well at all. In dot & dab construction you’ll probably get a better fixing from the plasterboard than the blockwork below.
As such, for really heavy things in aerated concrete you’re probably best looking at a chemical fixing such as the Fischer Undercut PBB Cone Drill used with an injection mortar such as Fischer FIS V. In Fischers own tests this gave safe loadings of around 100kg per fitting. Alternatively have a look at Fischer’s Aircrete Anchor FPX-I system. The disadvantage of these are:
- They’re expensive
- They’re hard to get hold of in the domestic market
- Complicated to use
- Drying time for resin fixings
I have used traditional shield anchors and wall bolts in low density blocks but it’s really not a recommended solution. Try it at your own risk and watch this space for a full test!
Other considerations e.g. vibration
One of the final considerations with expanding metal anchors is vibration. Are they likely to work themselves loose over time? I’ve never seen this happen with static objects. I’ve also never seen it happen with vibrating machinery but it certainly could happen. It’s something you’d have to test yourself as it would all be down to how heavy the vibration / movement is.
Chemical Resin vs Mechanical Fixings
Again, in industrial applications this is something the structural engineer would specify. Both mechanical and chemical fixings are available in a wide range of sizes to cover most conceivable load ratings. As mentioned in the above video, your bigger risk is the wall failing before the fitting fails. So take extra care in single leaf construction! (e.g. garage walls)
The biggest single disadvantage of going down the chemical route is that improper use can lead to very weak, near useless fixing. I’ve seen several bodged attempts at resin fixing. I’ve never seen a mechanical wall bolt come loose, ever. You need to weigh up the pros and cons:
Chemical Fixings – Pros
- Very strong if used correctly
- Less risk of cracking
- Automatically waterproof (generally)
- Less problematic with vibration
- VERY permanent
Chemical Fixings – Cons
- Substantially longer installation time
- Potentially long curing time for resin
- Need to account for temperature
- Harder to install correctly
- No good if you hit a mortar line
- VERY permanent
Mechanical Fixings – Pros
- Easy to use
- Can be loaded immediately
- Problem solver for mortar lines
- Relatively inexpensive
- Fine for most domestic scenarios
Mechanical Fixings – Cons
- Can cause cracking
- If the thread clogs you’ve got problems
- Vibration may be an issue
One other point I’ve not covered above is fire rating as these can vary from fitting to fitting. If fire rating is a consideration then this is something you’d need to investigate for both chemical and mechanical fixings.
Wrapping this up
In short, wall bolts are still a fantastic product and problem solver for attaching heavy things to walls, ceilings and floors. As with everything, there’s a million different ways of accomplishing the same result. Do your own research and always follow the manufacturer’s instructions. For me, wall bolts remain a staple part of my fixings stock.
- Fischer Fixings Thermalite Blocks Report (2002)
- Excellent article by Mark Salmon in the Fastern + Fixings Magazine