How to make surfaces unwalkable?
June 7, 2012 2:57 AM   Subscribe

I remember reading about a material that was designed to make walking across it very difficult if not impossible.

It was not unlike Prikka strips, but for large surfaces instead of fences. The idea was that your feet won't find solid footing and hence you would be slowed down considerably. It might have been developed for crowd control or as a proof of concept, I don't remember.

I would like to install something like this on my roof to deter intruders. Can anyone help me find it?
posted by NekulturnY to Home & Garden (25 answers total) 2 users marked this as a favorite
 
There's an entire class of stuff, usually foams and gels, referred to as "mobility denial" or "anti-traction" systems, but as far as I'm aware they're intended to be used as-needed, ie. crowd control as you mention, not just left around for someone to wander onto. They'd presumably dry out and become ineffective after not very long. Also, everything I've ever seen about them has been in the context of law enforcement or similar; I'd question if they were even generally available for you to buy.
posted by Su at 3:30 AM on June 7, 2012


Can you describe your roof? Is there something that makes it particularly easy to get to/walk on? Perhaps we can then think of other solutions as well, such as planting thorny bushes at access points.
posted by rockindata at 4:35 AM on June 7, 2012


Anti climb paint is difficult to *climb* (it never dries).
posted by devnull at 5:48 AM on June 7, 2012 [1 favorite]


Those prikka strips remind me of a prank I used to use on friends, turning the carpet-protector / chairmat you put underneath desk chairs upside down and then placing it in a well-traveled location; if someone was following me I could hop over it, but if they weren't looking carefully the spikes were unnoticeable and they'd instantly fall upon stepping on it. I believe you can order large swathes of carpet protectors with various adhesive solutions, and surely there's one with the same spikes used on the smaller chair mats. Bonus: not terribly unaesthetic due to transparency. If your intruders are wearing shoes this does nothing though :(
posted by MangyCarface at 5:48 AM on June 7, 2012 [1 favorite]


I would be careful about installing a hazard on your roof. IANAL, but I believe you may be responsible if a criminal or trespasser falls off the roof because you put down something that makes it hard to climb on it. Anecdatally, I heard about a school that was successfully sued because a trespasser fell through a rooftop window.
posted by musofire at 6:04 AM on June 7, 2012


Response by poster: Re the situation on the roof. The roof is easy to climb, because it's relatively low compared to a neighbouring terrace. Defending it against climbing would involve installing a sort of fence (which is easily cut open). It's also difficult to monitor, because it's at the back of our house. So, fencing it off is not optimal. There's roofing on the roof, so plants are not an option.

I am also not looking to hurt anyone (although dudes standing on my roof in the middle of the night do piss me off). I'm trying to find something that has the same effect as closely planted bamboo plants: something difficult and cumbersome to get through. I want an intruder to look at the roof and decide: this will be too hard to get out of in case of trouble. Anyone patient enough will find a way to get over or through the obstacle, but any intruder will be smart enough to see that the obstacle will prevent a quick exit, thereby discouraging the effort of breaking in in the first place.

A passive defense, as it were.
posted by NekulturnY at 6:18 AM on June 7, 2012


If it's for deterrence, what about a dummy video camera instead?
posted by TrinsicWS at 6:23 AM on June 7, 2012


Motion-sensing floodlights are probably something to consider as well. Fairly inexpensive and generally easy to install (assuming there's power nearby).
posted by jquinby at 6:27 AM on June 7, 2012


Response by poster: Dummy camera: are you kidding? Intruders laugh at cameras. They would probably steal it. Floodlights: yes. But not enough (last attempt was in broad daylight). I'm kind of amazed that no one thought of developing some kind of mats with man high, somewhat dense rods of variable height... Maybe I'll make a call to China to see what it would cost to develop this myself ;)
posted by NekulturnY at 6:32 AM on June 7, 2012


This is... problematic. What you're trying to do is deter trespassers. Doing anything which poses a physical danger to them may subject you to civil liability. This would probably include slippery surfaces--you have no idea how many slip-and-fall lawsuits are filed every day. And while the ancient common law doctrine was that landowners owed no duty to trespassers, the courts are more and more willing to impose liability upon landowners even where the injured party was a trespasser.

I think a real, study iron fence might be your best bet. This isn't going to be attractive, but something like this. The kind you can't casually cut through. You could even cover it with anti-climb paint. That and a no trespassing sign seem to be your best bet.

But really, it would sort of help to know why people seem to want to get up on your roof. Without knowing why they're up there, it's hard to give advice about changing their minds.
posted by valkyryn at 6:43 AM on June 7, 2012


You could cover the whole roof with barbed or razor wire, not particularly aesthetic, but effective.
posted by borkencode at 6:44 AM on June 7, 2012


Response by poster: I specifically said that I don't want to hurt anyone, just make it hard to wade through... something, without hurting themselves. I just want them to go: "this is kinda hard, let's turn back". Why they want to get access to my roof is this: because they can. This seems to suffice for the intruders.
posted by NekulturnY at 6:48 AM on June 7, 2012


Without seeing the structure it's hard to say with certainty, but I think the fence suggestion is as good as it gets. I'd make sure it was a fence that was hard to climb (like this one from valkyryn's link, with pickets extending above the top rail) and fairly solid. Sure, any fence can be cut, but you'll hopefully notice someone back there sawing away or using a cutting torch.
posted by Forktine at 6:48 AM on June 7, 2012


Does the roof give easy access to windows and such? They're not the greatest thing to look at, but window bars may something to move your house into the 'more trouble than it's worth' category.
posted by jquinby at 7:22 AM on June 7, 2012


Hm, a neighboring terrace? So these people are coming from inside another building? In that case, calling the cops, yelling, and signs sound much easier than trying to find something here that will both work and not mes sup your roof.
posted by zvs at 7:24 AM on June 7, 2012 [1 favorite]


Are all the intruders coming from the same place? Are they your neighbors? If they are all coming from the same building, have you tried talking to the owners/residents there? Or are the owners the problem?

If the same people are consistently trespassing/allowing their guests to do so, don't you have any legal options?

Unless your roof is open to the public at large for some reason, you should have some kind of recourse.
posted by emjaybee at 7:25 AM on June 7, 2012


Response by poster: It's too long to explain but I've looked at it from just about any angle. Believe me when I say that the best solution is to work with the surface of the roof rather than the edges (mainly because of a big glass skylight that would suffer considerably from the view of a big, sturdy iron fence). And yes, all the intruders come through the neighbouring terrace (but they are not the neighbours).
posted by NekulturnY at 7:36 AM on June 7, 2012


Instead of slippery, what if it's sticky? Ooey-gooey, like tar or glue, esp. on the part where one would use hands to climb up. Also, motion-activated water sprinklers.
posted by theora55 at 7:56 AM on June 7, 2012 [2 favorites]


How about anti-climb paint on the wall between the terrace and the roof?

Also, the fact that the roof has some kind of roofing material doesn't preclude putting plants on it as some kind of rooftop garden. There are different ways of handling it that allow you to put plants on some or all of the roof. Just a row of planters with any old kind of plants in them, along the edge where people gain access, might be enough to make it difficult/awkward to get through and so discourage people. (And at the same time improve the look of the roof and the building in general, by adding some greenery to it.)

But if generic plants aren't enough to deter climbers, certainly including something with thorns or the like would do the trick.
posted by flug at 9:01 AM on June 7, 2012


Another possibility is rolls of barbed wire laid across the entry points, or perhaps a few rolls stretched across the roof at different places to make moving around the the roof a lot of trouble. I'm thinking of something like this concertina wire that comes pre-manufactured and set up for this kind of use.

Of course this might introduce a prison/industrial vibe to your house that you don't want, but the flip side is that it would have the same type of deterrent effect of a much taller fence while being far lower profile, light, and easy to install. You might even be able to install it in such a way that it isn't visible anywhere except from that neighboring terrace. Also, it is very effective which is why it is used in places like prisons or industrial yards where they don't want people crossing a certain point.
posted by flug at 9:18 AM on June 7, 2012


I don't know what your weather is like but there are several thorny plants that make it distinctly difficult and get caught in clothing.
See here and here. It won't require a very deep trough if you can water regularly in the dry season.
posted by Wilder at 9:58 AM on June 7, 2012 [2 favorites]


If you want them not to bother your roof in the first place, then the deterrent has to be visible, and recognizable as such. A problem I see with paint on the roof is will the intruders recognize it as something difficult to walk on BEFORE they actually walk on it. If not, you may just end up with intruders with sticky feet.
posted by SuperSquirrel at 11:13 AM on June 7, 2012 [2 favorites]


Why not convert that roof area to a "green" roof and plant sharp looking succulents that mimic cactus but won't hurt anyone who actually climbs up. Some times just the appearance of harm may deter someone.
posted by jaimystery at 1:53 PM on June 7, 2012


What about a motion detecting alarm of some sort? Set it a foot high so it doesn't go off for squirrels or birds.
posted by elizeh at 7:42 PM on June 7, 2012


I specifically said that I don't want to hurt anyone, just make it hard to wade through...

This exposes people to physical danger, which raises all of the problems I mentioned. You can't do what you're suggesting without thinking about the legal implications, which seem to be more serious than you anticipate.
posted by valkyryn at 6:33 AM on June 8, 2012


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