I bought one of these canopies from HarborFreight: https://www.harborfreight.com/10-ft-x-20-ft-portable-car-canopy-63054.html. I'd like to anchor it down so wind doesn't move it. It has a circular plastic base plate with 4 holes per leg. Not super heavy duty.

Four of the 6 legs are on an old concrete slab in front of my detached garage (the other two are on dirt). I purchased some 1/4"diameter 2-3/4" long Tapcons (with the hex head of course). I drilled the hole longer than the Tapcon, cleaned it out well but the Tapcons keep breaking when installing them (I use a 1/4" impact driver). The head is fine but the actual bolts seem to break in half. I also have some 1-3/4" (also 1/4" diameter hex-head) Tapcons and these seem to go in without breaking.


Are the 1-3/4" long tapcons sufficient here or do I need the longer length? I bought the longer ones since it seemed like the long legs of the canopy would have a lot of torque on the shorter Tapcons. But it seems the concrete may be too hard for the longer bolts.

Are there different kinds of removable anchors that I should be considering? Someone suggested Red-Heads but all of the ones I've seen aren't removable. I need to be able to move this thing in the future.

NOTE: I realize this is a flimsy structure that won't hold up to strong winds no matter how it's anchored. The point is to not have it move with the kinds of light winds that are a regular occurrence where I live. I may replace the plastic bases with metal ones and I will use self-drilling screws to attach the legs to the bases more securely (they just slip into them right now).

  • 1
    It is my understanding that if you're snapping a Tapcon when driving it in, it's either because your hole isn't clean (enough), or you've hit some very hard aggregate that the threads can't cut through. Since you believe you've cleaned the hole, it's probably that there's a hard piece of stone beyond 1-3/4" down and the longer screw is hitting it.
    – FreeMan
    Oct 21, 2021 at 17:33

2 Answers 2


If its something you want to remove and replace from time to time, there are threaded inserts you can put into the concrete. You would drill something like a 3/8" hole, tap the insert into the concrete and then thread a bolt into it to hold down your canopy. The bottom of the anchor spreads out and wedges against the sides of the hole.

drop in anchors

Example listing, they come in different styles, and sizes. I haven't used this brand so not a recommendation, just an example.

For the tapcon question - If the concrete is in good condition and you use at least two fasteners per post, the 1-3/4" should be sufficient. If you want fewer holes, I'd use a longer fastener. I agree with your point that the legs and joints will fail before the true strength of the concrete anchors is tested.

  • Cool, something like this would work: redheadanchoring.com/products/drop-in-anchor ?
    – Dan
    Oct 20, 2021 at 22:17
  • Yep, exactly. That’s just “name brand” rather than the cheap Amazon one.
    – JPhi1618
    Oct 20, 2021 at 22:20
  • Do they usually come with bolts or do I have to find ones that will fit myself? Looking at the RedHeads, it's looking to me like the latter.
    – Dan
    Oct 20, 2021 at 22:30
  • The last ones I bought did not have bolts so… It depends. Can’t say for sure.
    – JPhi1618
    Oct 20, 2021 at 22:38

Technical Specifications from "concretefasteners.com"

There are numerous technical specifications that must be considered when using Tapcon® screws. Determinations must be made on the diameter of the screw - standard or large diameter, length of the screw - ranging from 1-1/4" to 6", head style - hex slotted or flat Phillips, material or coating - Blue Climaseal®, Zinc Plated Large Diameter, Envirex Coated Large Diameter or Stainless Steel, embedment depth - 1” minimum to 1-3/4” maximum, and type of base material - concrete, brick or block. Once all of these factors have been determined, you can find the expected holding values in the technical information below.

Anchor Length:

To determine the minimum length required, add the thickness of the material to be fastened and the minimum embedment (1”). To determine the maximum length required, add the thickness of the material to be fastened and the maximum embedment (1-3/4”).

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Read the full spec here to find other concerns - edge distance, spacing, and strength in materials other than concrete.

  • Well the base plate is maybe 1/4" thick at most. So 1-3/4" should be fine by that standard. I don't understand the maximum embedment though. So anything longer than 2" (1-3/4" + 1/4") would be too long here? Why?
    – Dan
    Oct 20, 2021 at 22:09
  • A longer bolt will take additional abuses it wasn't intended/designed for, such as bending and tension occurring simultaneously, it will break the bolt because it is too brittle to resist bending - the longer the embedment, the more moment it is to endure. So, when using post-installed anchors, you shall alway follow the manufacture's instructions without deviation, no matter how small it is. You shall double-check the edge distance and the spacing requirements to see whether the strength reduction factors apply or not on your application. Good luck.
    – r13
    Oct 20, 2021 at 22:25
  • Ah OK, makes sense why my 2-3/4" Tapcons broke then. They're far too long.
    – Dan
    Oct 20, 2021 at 22:32
  • Sounds like it. Follow the recommended hole size, and hammer the bolt in. Do not use excessive force or tilt the bolt, remember it does not take the bending moment.
    – r13
    Oct 20, 2021 at 22:46

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