Anchor bolt size for bolting rack to wall

funkey_monkey

Hi,

I'm in the process of mounting a squat rack to our garage wall. The house is a new build of sound construction made using 440 x 215 x 100 blocks with strength rating of 7N.

I was planning to use M10 x 82mm anchor bolts - like these:

https://www.screwfix.com/p/easyfix-shield-anchor-bolt-type-m10-x-83mm-5-pack/19510

The rack is similar to this:

https://hillfitnessuk.co.uk/collections/squat-racks/products/squat-racks-rigs-1

Each brace will have two anchor bolts holding to the wall - so eight in total. I don't want to use resin studs as if I move the rack it would be more difficult to remove trace of them from the wall.

The rack would not have a static load on it greater than 120kg.

Easyfix has an app to determine the correct item to use, but I'm struggling to use it.

Thanks.

funkey_monkey

Anyone?

GreeBo

I wouldn't overthink it tbh, the weight is going through the floor, the bolts are just to stop it pulling away from the wall.

The Continental Op

I wouldn't even try and work it out, but there are a few points to bare in mind.

Firstly the bolts for the bottom are only locating the legs on the floor they don't have much in the way of any force applied to them. Secondly I'm not sure I'd use 4 bolts in each top support bracket. Two in vertical alignment would probably be not much stronger than just one due to the way the forces get applied in the wall (the holes seem a bit close vertically?). Two bolts one at each end of a diagonal would probably be fine.

Secondly at one time I installed a lot of 40 inch plasma TV's mainly on ceiling mounts often into concrete ceilings any a single M8 anchor bolt would happily take my weight if installed properly and I'd swing off the fittings once installed with four M8 anchor bolts or M8 coach bolts in plastic plugs. So I think you M10's are overkill and might possibly be weaker than M8's if you install 4 in each wall mounting bracket. If you must use all 4 use M8's.

Getting the exact hole size is important (teaching grandma to suck eggs I know) as I've seen anchor bolts fail in over sized badly drilled holes particularly where the load isn't static (like gate hinges) and near the edge of a block. I don't really like them in blocks because sometimes the blocks don't drill cleanly and anchor bolts sometimes don't take. In blocks I prefer plastic plugs like these which I'd be happy using in this case. Whatever you use don't over tighten! I've managed to crack blocks over tightening anchor bolts (particularly near the edge of a block) and I've sheared off heavy duty frame fixer screws and M8 anchor bolts. No excuse really but surprisingly easy if you are using a socket ratchet bar :-(

Edit> Now you have one reply hopefully you'll get a better one or at least one that says not to do it my way ;-)

funkey_monkey

Thanks for the replies guys. I'm thinking M10 is sufficient. I contacted some suppliers under the guise of considering to purchase and some of them said M12 x 100 and others said speak to an expert.

@The Continental Op - Each bracket will have 2 bolts - two brackets at top and two at bottom. None of them will have four bolts. My thought is like @GreeBo - there is no shear load on these bolts - only pull-out.

The only risk is if I drop a weight onto the spotter bars out at the point which would only happen doing squats - which my limit is and probably always will be around 100 - 120kg. It's this dynamic force that is the concern. Dropping in close to the upright should have little effect as the upright should absorb most of the force.

@The Continental Op - what are the plastic plugs you are talking about? Are they better for block walls that the rawlbolts?

The Continental Op

I thought I'd put a link to plastic plugs but it seems not to have worked. I used to use a lot similar to these https://www.amazon.co.uk/Inbrackets-Masonry-Washers-Satellite-Mounting/dp/B088KVRRZ6/ I just prefer them in block walls if the walls don't drill well and don't have clean holes. Either will be fine if set properly. I've rarely used them but a lot of people like self tapping concrete bolts like these https://www.amazon.co.uk/SEQUAL-M10x100mm-Concrete-Tapping-Masonry/ the advantage is a smaller hole and if they do work out you can then drill out for a plugged bolt or anchor.

I doubt any single "drop" will pull the plugs out, provided you eyeball and check the plugs after any sudden shock I don't think you will have any issues. Any failure would most likely occur due to either a massive overload or a lot of smaller shocks loosening the fixtures. You can't do anything about the former but can keep an eye on the latter.

btw I'm sure you now this but you'll need an SDS drill with a decent quality SDS bit.

One further obvious point is don't drill to deeply as if you bust through the back of the block you may bust out a big chunk of the block and because the hole will be blind make sure you check the depth and clean out any dust before putting a plug or anchor in.

Lumen

I'd use the smallest fixings you can get away with, e.g. short concrete screws. Steel is insanely strong, they're not going to snap.

If I understand your picture correctly the holes are fairly close together, so your weakest link is the integrity of the block work. Minimum anchor spacing rule of thumb is 10 diameters.

https://www.screwfix.ie/c/screws-nails-fixings/masonry-screws/cat840054

10-10-20

Steel is insanely strong, they're not going to snap.

Pedantic I know, but let's just be cautious here as in this day and age as I see people buying fixings off Wish/Alibaba and other sites with little consideration to quality.

"Steel from a reputable supplier is insanely strong, they're not going to snap."

I'd advise if going to a DIY store then go with branded fixings or the general masonry fittings from a proper builders-providers.

funkey_monkey

https://www.boards.ie/discussion/2058265567/calculating-a-force-applied-at-a-point

Stuck up a thread in the maths forum to see if anyone could work out what I'd need. Can any of you solve it???

@The Continental Op - Yes, I've got a SDS drill and a few masonry bits, so should be okay.

@Lumen - snapping is not a concern - it is the fixings pulling out.

@10-10-20 - I'd only be looking at Easyfix, Rawlbolt or Fischer fixings.

The Continental Op

Stuck up a thread in the maths forum to see if anyone could work out what I'd need. Can any of you solve it???

I don't think it can be solved because the material you are fixing to isn't homogeneous enough (mixed up in a way that makes it all the same). Concrete blocks have mortar around them and there is no calculation I know of for bolting into a corner of a block, or the edge of a block. I guess the calculations will be OK if you are drilling into the middle area of the block but how often does that happen? The forces anchor bolts can be made to exert can easily split a block in half or make cracks that run into the mortar course.

Lumen

This is a fun read. Specifically, the failure mode.

As I understand it, properly installed fixings don't pull out from the concrete, they pull out the concrete.

691d-calculating-pull-out-strength.pdf

funkey_monkey

That's worse!

I'm beginning to worry I've taken the wrong route here, but a lot of other folk have some got this type of setup. Would just be nice to know where the limit is.

The Continental Op

I wouldn't worry so much. Just try pulling out any well fitted M8 wall anchor. You are over thinking this. Worst case scenario is that you drop the weights on the spotter arms from a good height. In which case I strongly suspect they will bend and the plugs will be fine. Do that on a regular bases and the anchors may start to loosen but you'll notice that when you next use it and can take corrective action.

GreeBo

As long as the rack is sitting firmly on the floor you dont need to worry at all. Even dropping a bar on the extreme end is going to send most of the force through the floor, it would be more likely for the arm to shear off than the rack to come out of the wall.

I would certainly echo not using all 4 holes for anchor bolts as the block could end up in ribbons.

You might even get more success by fixing boards to the wall and then using all 4 holes for screws into the board.

But again, I think it would be critical that the rack is firmly supported by the floor and not in any way hanging from these brackets. This will avoid any shear load and use the screws as they are designed, to resist being pulled out.

funkey_monkey

There will only be two per bracket. See below image for example.

The Continental Op

There really is very little load on any of those wall bolts.

funkey_monkey

The load only come on when you drop the weight onto the spotter arms which can be placed up and down the upright.

The Continental Op

If you have your squat rack already then assemble it and hold it upright by the top brackets while someone stands on the spotter arms. Then assuming its easy to hold upright get them to jump up and down and see how easy it is to hold upright. I can't explain why but to my eye the spotter arms aren't well placed to put a whole lot of leverage on the top wall brackets.

chooseusername

https://www.boards.ie/discussion/comment/119688935#Comment_119688935

Use whatever bolts were supplied with it, or the 83mm X M10s you suggested yourself above if the holes can take them.

There will be some pull force on the top wall bolts, but most will be directed downwards onto the floor. ( I don't know what %)

Add rubber feet to the legs if they're not supplied, to stop them scraping on the floor.

If don't plan on folding it back when not in use you could bolt the legs to the floor for stability.

If the horizontal arms are adjustable, you could make the top ones shorter than the bottom ones so it tilts back slightly, that will transfer the weight directly over the feet.

The Continental Op

Another option for those that worry about these things is to make a couple of supports for the spotter arms. Nice bit of 4x4 fence post cut just a bit to long and then notched to fit. Slip them under the end of the spotter bars when you are using the rack and move them afterwards. Don't think you need them but belt and braces to be sure to be sure.

GreeBo

https://www.boards.ie/discussion/comment/119688935#Comment_119688935

8 bolts or screws with plugs arent going to have any issue holding the tiny amount of tension force they would face in normal use. Even dropping a full bar isn't going to do much.

You could probably hang the bar from 2 of the bolts into a concrete ceiling (way more force than they would get in the correct orientation)

standardg60

Completely agree with Continental here OP.

M8 80mm bolts with plastic plugs is the way to go here. I'd never use anchor bolts in blockwork, they're designed more for poured concrete floors (and ceilings). Also the larger diameter the hole you drill the weaker the block will become, and the bracket holes are too close together for the size you're drilling, there'll be a weak point between the two holes which could crack as you're tightening the anchors. The plastic plugs will exert much less pressure on the block.

Drill straight snug correct depth holes (wrap masking tape around the drill bit at the right depth), and i doubt you'll have any issues.

Edit to add that if you're dealing with bare blockwork here then place the rack so you're drilling into the centre of the blocks.

funkey_monkey

Is plastered block work so I can't see where the joints are. No outline either.

I've settled 12mm holes so M10 bolts will have to be used.

standardg60

https://www.boards.ie/discussion/comment/119693412#Comment_119693412

By settled do you mean drilled? You could always move the rack.

You have checked the diameter of the holes in the brackets too i assume?

chooseusername

https://www.boards.ie/discussion/comment/119693412#Comment_119693412

I think you need 16mm holes for M10 anchors.

SPECIFICATIONBolt SizeM10BrandEasyfix

Drill Size16 mm

Manufacturer Guarantee1 Year Guarantee

Max Fixture Depth25 mm

Pack Size5Pieces in Pack/Case5Product

Length83 mmProduct TypeShield Anchor Bolt Type

The Continental Op

https://www.boards.ie/discussion/comment/119693432#Comment_119693432

Yep M10 anchor bolts normally 16mm but perhaps the OP is using M10 sleeve bolts which are normally 12mm?

OP M10 anchor bolts are the easiest to remove later, sleeve bolts will leave the sleeve inside. Plastic plugs can be drilled out.

funkey_monkey

I've bored 12mm holes in back of bracket - so that will take a M10 bolt. Could ream it out a bit more for a M12, if necessary. The Easyfix anchors are 16mm for M10. I had looked at the plastic ones, but they don't seem to be as strong as the anchor bolt and require deeper holes.

Was looking to get a plastic plug, but the problem with them seems to be that they require a long hole bored - comparatively speaking in relation to a std anchor bolt. Plus I can't seem to find them easily.

This is classed at 10 x 80, but requires a 10mm hole 112mm deep - which is beyond the width of the hole. 80 relates to the anchor length. Rated for 420kg in concrete.

https://www.amazon.co.uk/Fischer-Duo-Power-Dual-Component-538247-Pack/dp/B01M0PBKL0/ref%3Dpd_bxgy_sccl_1/260-8824160-3466412?pd_rd_w=XPe9f&content-id=amzn1.sym.79b812bf-5c8b-4c0c-851c-784423adaff5&pf_rd_p=79b812bf-5c8b-4c0c-851c-784423adaff5&pf_rd_r=YJ4ATD97KA0TQGANRSMX&pd_rd_wg=fC160&pd_rd_r=94cd0db1-702f-472c-8dd9-8cbd08458925&pd_rd_i=B01M0PBKL0&psc=1

Info is here:

https://www.fischer.co.uk/en-gb/products/standard-fixings/plastic-fixings/duopower/538247-duopower-10-x-80-s

So, it looks like I'll be getting a M10 anchor bolt. Either one of these:

https://www.screwfix.com/p/easyfix-shield-anchor-bolt-type-m10-x-83mm-5-pack/19510

https://www.screwfix.com/p/easyfix-shield-anchor-bolt-type-m10-x-68mm-5-pack/13025

funkey_monkey

https://www.boards.ie/discussion/comment/119693429#Comment_119693429

These are holes in the brackets - I'm making this rack myself. If i had bought it in they would have supplied all this for me and I wouldn't have to worry!

The Continental Op

Could ream it out a bit more for a M12

Don't ream it out thats when anchor bolts fail, if you need to buy a 16mm drill bit. You really do need to drill the exact size hole to get anchor bolts to work correctly. I speak from experience of messing up a few and having to redrill for the next size up.

GreeBo

https://www.boards.ie/discussion/comment/119693805#Comment_119693805

I think the is talking about the bracket rather than the holes in the wall.

OP you can "unream" via washers, which I think you should be using anyway, depending on the thickness and material of the brackets.

standardg60

https://www.boards.ie/discussion/comment/119693964#Comment_119693964

They would need to be reamed if the OP wants to use anchor bolts rather than plugs, which they seem to have decided on despite the advice given, so i'll gracefully bow out here.

funkey_monkey

I've not decided on any thing. I've looked for plugs, but I can't see anything that suits spec wise.

Screwfix don't seem to have any affordable ones.

standardg60

You don't have to resort to online for everything, have a look in your local hardware/diy store, bolts and plugs should be at least the same price as anchors, if not cheaper.

funkey_monkey

I've found these on Amazon, but their rating does not appear to be sufficient.

https://www.amazon.co.uk/Fischer-sx-10x50-sk-SX-10-5-Uds/dp/B00UCAQMWI?ref_=ast_sto_dp

@standardg60 - nearest place is Screwfix and that is a 1hr round trip. Local town would not have anything.

The Continental Op

Screwfix don't seem to have any affordable ones.

?????

M10 Screwfix https://www.screwfix.ie/p/rawlplug-rawlbolts-m10-x-75mm-5-pack/20828

M8 https://www.screwfix.ie/p/rawlplug-rawlbolts-m8-x-65mm-5-pack/62313

Both under €8 for 5?

standardg60

https://www.boards.ie/discussion/comment/119694147#Comment_119694147

He's talking about plastic plugs in fairness

The Continental Op

https://www.boards.ie/discussion/comment/119694141#Comment_119694141

Also https://www.amazon.co.uk/Fischer-555110-DUOPOWER-D%C3%BCbel-Sechskantschraube/dp/B016ABX5NG/ which iirc from looking at the spec sheet earlier have something greater than 1.2kn pull out force in brick so would hold at least 120 kilos each. In the middle of a concrete block the rating is over 2kn or 200kg.