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I have a wide window a touch less than 6' across and I want to install a blind with 2" deep horizontals. The blind that was within my price range comes with five support brackets, which can either attach to a vertical, or a horizontal surface. The kit comes with two screws per bracket, (although the end "cap" brackets appear to be more load bearing, with the center 3 for stability).

I don't know the exact weight, but likely between 30 and 50 lb. [Edit: actually 20 lb.] That's before I've stripped out the unneeded horizontals from the bottom of the blind.

I cannot drill into the vertical surface, because that's the plastic window frame, and doesn't really have enough "meat" on it for supporting something this heavy.

The horizontal surface above is a thin (1/4") cake of old plasterwork, over a steel joist; possibly an I-beam.

The walls are adobe brick.

I've considered building a minimal plywood support frame, with a piece of steel angle to match the window frame. That's not outside my skill, but it's still a lot of work.

I found some magnets about 2" long, pack of 10, which say the breakaway force is 60 lb each. They have two screwholes each. I'm looking at using two magnets per bracket, with a piece of 3/8" plywood in between the magnet and bracket for their respective screws to attach. I'd check how strong they are before hanging, and possibly clean away the old plasterwork to achieve a direct contact between the magnet and the steel beam.

Does this sound reasonable? Other suggestions?

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  • * I ordered the pack of 10 magnets regardless, because I'm curious if I can do this without altering the window surround. Using 2 magnets for each of the 5 brackets, each magnet will be supporting 30x its own breakaway force on average. Resting the blind upside down, it extends upwards with < 1 lb starting force. I have some thoughts on how to prevent angled pulling, i.e. away from the window. Thing is, I can't find anyone saying "no that's a bad idea" anywhere else. Whatever I do, I'll write it up and illustrate.
    – Rich
    Commented Mar 27, 2019 at 0:08
  • Here's a seller saying how great they are. (I didn't buy from these guys.) kjmagnetics.com/blog.asp?p=mounting-magnets
    – Rich
    Commented Mar 27, 2019 at 0:10
  • And here's another of their informational pages showing a tiny graph of the dropoff of force, as distance increases. kjmagnetics.com/blog.asp?p=how-much-will-a-magnet-hold This essentially informs me that (per my original writeup, I will need to pare back all the old plasterwork, right back to the steel beam. I would then paint with primer and overcoat (much thinner than 10 sheets of paper), and likely hit a minimum of 75% specified pull-away force.
    – Rich
    Commented Mar 27, 2019 at 0:16
  • Apparently it wasn't an RSJ / I beam, and for whatever reason, did not extend the full length of the window frame, so magnets wouldn't work exclusively. Once I'd tried a tiny pilot hole to test the thickness of the steel (~2mm, thin enough), I took the plunge and drilled out for self-tappers. Took a lot of patience getting through, and I'm out three drill bits, but this will hold. That's all I was looking for.
    – Rich
    Commented Apr 1, 2019 at 19:09

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You need to worry about not just the weight of the blinds, but also a weight slightly greater than the blinds focused at the string when the blinds are pulled up. I'm going to make up some numbers, but if you had a blind that was 10lbs, you would see maybe 7lbs on the left bracket and probably upwards of 20lbs on the right bracket (assuming string on the right) when they are lifted. The weight of the blinds plus friction is going to add up.

I have some 6' blinds and haven't measured it, but it takes a lot of force to raise them. I normally lift them with my free hand as I pull the string, but my wife isn't that "nice". There's also some lateral force if you're not pulling straight down and when you have to pull sideways to unlatch the mechanism.

Any pull force listed on the magnet is in a purely perpendicular force performed in a lab. They are very, very strong, but I wouldn't trust a "working load" with that listed weight. You're going to get a stronger hold from a mechanical fastener like a screw or bolt.

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  • That's a very good consideration! All the other blinds in the home are magical "stringless" ones, and even though I looked for pull-string blinds for price comparison, couldn't find them. You pull the base vertically down from the center, and push it up at the same point. The force necessary for this is best characterised "easy at arm's length", it's really very little force at all. (I don't know how they work.)
    – Rich
    Commented Mar 26, 2019 at 3:54
  • To your point about using mechanical fasteners, do you have any suggestions for how to do that, other than my fantasy box frame thing?
    – Rich
    Commented Mar 26, 2019 at 3:55
  • The wooden internal frame for the window sounds like a good option. I would use 1" boards rather than plywood because the exposed edge of the plywood would be ugly. You may be able to drill a hole into the metal above the window, but without knowing how thick it is, etc, that might be very hard. And the "cordless" blinds you mention are much easier to operate and don't take as much force because of the counterbalancing/spring mechanism they use. They are nice, but can be expensive!
    – JPhi1618
    Commented Mar 26, 2019 at 14:54
  • you might consider greasing up the blind mechanism. On a house i moved into, the blinds took a ton of force to pull up; to the point where the cord dug into your hand slightly. I used 3in1 oil on anything up top that looked like it moved, and after, they could all be opened with a pinky...
    – dandavis
    Commented Mar 26, 2019 at 16:42
  • @dandavis, he said 2" deep, so I assumed he was talking about the larger faux wood type blinds. Those are just plain heavy even when they work well but that's a good tip for particularly hard blinds.
    – JPhi1618
    Commented Mar 26, 2019 at 17:20

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