Scenarios: Unrest: Home invasion Pt5: Physical protection: Fences: Protection levels and standards

Protection levels

Height

  • There are security experts running around saying six feet is a bare minimum. But in reality you should try to make fences up to nine feet high with toppings, and they must be eight feet high before toppings to get even class A or B height under the domestic low risk standard LPS 2081. Still, even nine feet including topping is not enough for high risks, for example American prison fences have to be twelve feet high.
  • It is acceptable in the front garden to harden the front approach with other barriers and electronics, and in return accept only a six feet fence with matching gates. You may have to let people vault a front fence, but you can try to ensure this would trigger an alarm, lights and be filmed, and you can stop vehicles blasting through by hiding concrete blocks.
Fences rarely stop climbing

Siting

  • Keep fences at least 3 metres from buildings and lampposts at least 2 metres from other fences.
  • If you want deterrence approaching embassy level protection, you could push the neutralisation back to the adversary’s staging base outside the perimeter.

Materials

Chain link

  • Chain link only buys typically 30s, or if topped with barbed wire 1 minute, and needs to be 12’ tall to stop easy climbing, and ought to be buried in a concrete foundation. Ideally, rather than chain link you will use 358 mesh.
  • According to Barrier Penetration Tests, US Department of Commerce, National Bureau of Standards NBS Technical Note 837, June 1974 a 7′ unelectrified barbed wire topped chain link fence only kept an intruder out for 8 seconds.
  • Chain links are rendered useless by climbing with a portable ladder or vaulting over protected by a tarp or gloves, lifting (eg with a length of 2×4) or cutting with boltcutters (wirecutters won’t go through 9 gauge wire). Techniques tested include making steps with linemen pliers – which took 1m8s to get over with.
  • Lifting times: 9 gauge 2″ mesh with a 3/8″ messenger cable at the bottom was lifted with 2×4 and crawled under in 6s, 9s if 11 gauge, 7s if 1.8mm / 2mm thick 40mm (or 6s to crawl over), 5s if 2.6mm thick 50mm wire, 12s if 2.26mm wire with three coils of barbed wire).
  • Jumping times: a tarp was thrown over and a man vaulted over in 9s.
  • Ladder times: a wire ladder was thrown over, secured with carabiners and climbed in 28s.
  • Cutting times:
    • Boltcutters got a man through in 19s (combination fencing tool took 46s), 16s on 11 gauge wire and 2mm wire, 20s on 1.8mm wire, 12s on 2.26mm wire, 24s on 2.6mm wire, 12s on 2.65mm galvanised wire in 60mm mesh).
    • Vice grip cutters take 47s on 11 gauge wire, 23s on 1.8mm wire, 28s on 2.6mm wire, 15s on 2mm wire, 13s on 2.26mm wire, 12s on 2.65mm galvanised wire 60mm mesh).
    • Linesmen pliers take 23s , 20s on 1.8mm wire, 17s on 2.6mm wire, 11s on 2mm wire, 10s on 2.26mm wire, 12s on 2.65mm galvanised wire in 60mm mesh.
    • 4″ diagonal cutting pliers take 17s on 2mm wire, and a 6″ version takes 13s on 2.26mm wire and 9s on 2.65mm galvanised wire in 60mm mesh.
    • Disc grinders take 16-29s.
  • Climb times:
    • Gloved hands took 4s over a barbed wire gate or 2.6mm wire.
    • The fastest defeat is bare handed climb over 1.8mm wire. It takes 3s to vault over the 2mm wire, likewise for 2.26mm wire with three barbed wire coils.
  • Cutting outriggers and climbing took 1m7s.
  • Pulling times: the 1.8mm plastic coated wires can be pulled out by straightening by tugging with pliers in 35s, 1m5s for 2mm wire (needing five cuts).
  • Ripping times: 2.6mm wire can be ripped off in 7s.
  • Snapping times:
    • After cutting attachment wires weak posts can be snapped off by a mob in about 34s.
    • A petrol disc grinder can chomp through a post in 9s or the mesh in 7s.
  • Roughly speaking climbing tools and cutting takes too long so lifting (if you have at least two operators) or climbing or jumping is better, although lifting needs a long tool perhaps best found nearby.
  • Barbed wire concertinas can be defeated by hooking them to each other but it takes about four minutes; a faster technique is throwing a tarp over the concertinas and jumping from the top of the fence.
Chain link breach test

Barbed wire

  • Barbed wire fences should have posts at maximum six feet spaces, with a vertical wire in the middle of each run and horizontal wires maximum 6” apart.

Exmesh

  • Fences and gates can be strengthened with exmesh on the inside.
  • To save money, decide if you can make your own fence or buy a low rated fence and reinforce it with 358 mesh on the inside. As chain link is too insecure and looks dreadful, a compromise might be an ornamental metal fence to demarcate the boundary and provide slightly more strength, if you want to see in and out, as long as it is not made ridiculously climbable. Ornamental fences are ideally 9’ high, buried 3’, with ‘U’ fasteners.
Ornamental fence

Wood

  • Normal shiplap is useless. Shiplap is never a security fence, although once torn off might make a handy battering ram if thick enough. There should be a level capping rail with nothing sticking up like posts. The fact that it takes 68mm of wood to buy 5 minutes against basic tools tells you all you need to know about even the 15-25mm panels that police recommend for domestic high security.

Threat levels

  • Decide if the fence needs protection against vehicles and burrowing.
  • Decide if you need a wall against blast and a barrier against observation or whether it needs to be see-through.
  • Randomly check the integrity of the perimeter when tensions rise.

Ratings

Secure by Design

  • SBD recommends steel wires 1.5mm thick, or wooden fence slats 15mm thick but ideally 25mm.

LPS1175

Who sets the standard?

  • The main UK standard for security fencing is the LPCB’s barrier certification LPS1175. More will be said of it in terms of doors as it is more relevant to homes under that heading.

What does the standard cover?

  • LPS1175 rating for fences only covers penetration, so to discourage climbing you still need toppings and to avoid handholds and footholds. There is no standard for topping like electric or spikes, although some firms get independent testing to verify whatever their claims are.
LPCB fence testing

What does the standard require?

  • LPS1175 minimum fence heights for time ratings are 1 min = 1.8m, 3 mins = 2m, 5 mins = 2.4m, 10mins = 2.8m, 15mins = 4m, 20 mins = 5m, with toppings required if over 2.4m.
  • The fence can be a weaker structure to A1 for the height above 2.25m for times over 5 minutes.
  • So the benchmark height for high risk residential is eight feet with A1 panels allowed to make up the last six inches beyond 7’6” and C5 below that.
  • Under LPS1175, A1 means toolset A delayed by 1 minute and C5 means toolset C delayed for 5 minutes.

Which rating do I need?

  • Fencing is available up to SR5 rating against toolset E (eg battery powered rescue tools) for 10 minutes. As it seems most unlikely an intruder will be that bothered about carrying stuff if they can bust out your front door much easier, or that they would be so incapable of bringing ladders if you are such a high value target, or that they would be so scared of being silhouetted as they vault over if you do not have 24h armed guards, SR5 is almost certainly overkill for a home. Products exist, such as the Jacksons Trident 5 which is basically a Supermax prison fence.
Jacksons Trident 5 LPS1175 SR5 fence
  • By comparison, GCHQ has a hideous mesh fence topped with a barbed wire coil (with handy gaps on the turns), without the bars of the Trident but with beefy crossbars, and they benefit from standoff the depth of the car park. However, MI5 have no such luck, they do not have a fence, instead they walk out straight onto the pavement on a main road adjoining a river with vantage points on the other side, the worst security imaginable especially for a trophy target. So do not beat yourself up about not having a massive fence and massive garden.
  • SR5 and the next level down, SR4 (against toolset D eg 20 inch boltcutter), uses ‘358 mesh’ of wire spaced too close to get common tools or goods between, attached to bars, topped with barbed tape. They are popular with prisons but would look out of place in a domestic setting, so would need hiding with shiplap, but then it would still look strange if tall enough. It would be justified if you had reinforced concrete house walls and considered terrorism-level attacks a prospect, but it is most likely intruders will climb over or come in the front. So, unless you have exceptional vulnerability round back you are rather unlikely to put in the perimeter electronics to back up an SR4 fence and would largely be wasting cash on what could have bought lights, cameras, alarms, booby traps, reinforced facade or a saferoom, especially if you have a defenceless front garden allowing an attacker to sprint straight to your front door and start laying into it. Zaun do an SR4 Corrusec D10 triple layer mesh of HiSec Super 10 faces with HiSec 3/5/10 in the middle.
Jacksons Trident 4 LPS1175 SR4 fence using 358 mesh
Zaun Corrusec SR4
  • SR3 fencing against toolset C (eg 16 inch boltcutter) for 5 minutes is available using double layer 50 x 30mm ‘UHS mesh’ 8 or 10 feet high; privacy versions are available up to around 8 to 11 feet high using a double layer of tongue and groove wood panels totalling 68mm thickness, and can be upgraded to hold off toolsets F or G for 1 minute. Heras do fencing up to SR3 in their Zenith (SR1-3), Pallas Xtra (SR1) and Tangorail ranges with 4mm wire in the SR1 Zenith and the SR3 bolting together their SR1 and SR2; they also do HVM gates and the CPNI B960 swing pedestrian gate. Zaun do Corrusec twin skin mesh to SR3.
UHS 50x30mm mesh
  • Although they do not do fences, a big name for HVM, and gates up to SR3, is Frontier Pitts who for example sorted out the GCHQ black hat centre at Cheltenham. They do pedestrian gates to SR3 and sliding, double & bifold gates up to SR3 or HVM standards.
Frontier Pitts SR3 pedestrian gate
  • Once you have posts that can take thick wood panels to take impact then you could insert metal sheets or mesh to slow down cutting, which is what Jacksons have done with their CPNI Jacoustic 3 counter terror beast, sandwiching 7’8” high mesh between two 13’ high layers of horizontal slats in steel posts. Its sister product, Jacoustic Class 3 is shorter and thus not CPNI but is instead rated SR3 and comes 8’4-10’10” high.
Jacksons Jacoustic Class 3 LPS 1175 SR3 fence
  • Like SR4 to SR5, SR3 mesh will look like you have something worth burgling. SR3 is effectively but unofficially the rating for exceptional domestic risk. You could easily decide that the fact of SHTF and you having a stash is ‘exceptional risk’ even though you are not a Russian oligarch.
  • The other way of getting up to SR3 is exmesh from reseller Procter or direct from Expanded Metal Company.
  • SR2 fencing using 76mm x 13mm Securimesh is available 8 and 17 feet high to see off toolset B (eg 14 inch boltcutter) for 3 minutes, but that is not wooden. As long as the intruder is not expecting trouble with the fence, SR2 is probably proportionate, but still could do with disguising and will let an amateur through quickly, although buying a very short amount of time is all fences are about anyway. An alternative is Barkers Secureguard SL2 which also has C1 rating and Betafence Securifor to SBD and SR1 or SR2 (and unrated gates to match), also available to CPNI or ASTM. CLD sell mesh SR1 & SR2 fences Dulock, Fencesafe & Ultimate, plus Securus up to SR3. Fastline do Imperium mesh to SR1 or SR2. Zaun do mesh to SR1 and SR2.
  • The only LPS rated wooden fences that roughly fall between SR1 and SR3 is the CPNI version of  Jacksons’ SR1 rated Euroguard Combi, and the SBD terror rated 8’ high Trident Combi 2 – which hides mesh (presumably 358 like their Trident) behind 40x17mm vertical slats held by 5mm cables and topped with barbed wire bolted to slats (but is still partly see-through).
Jacksons Euroguard Combi LPS1175 SR2 fence
  • Their 10’ high Jacoustic 2 – which is the SBD terror rated & CPNI version of an SR3 – hides 5’8” high mesh behind solid horizontal slats, and is labelled ‘2’ but is probably more like SR4.
  • SR1 fencing is typically pale through rale, with barbs at the top (sometimes more than there are pales). It comes 6 to 10 feet high but with 4 inch gaps, or in a budget version using mesh 6 to 8 feet high or 5 inch spaced bars 6 to 10 feet high, or you can get a privacy version (eg Jacksons Euroguard Combi SBD) 7 to 10 feet high using 200mm x 50mm mesh covered with wood slats, or 6mm x 13mm mesh as a visual deterrent from 6 to 20 feet high using mesh rated A1 that can stop a pocket cable cutter for a minute.
  • SR1 is also available in 358 mesh such as Barkers Secureguard SL1, Lochrin Bain 358 and NK Fencing Ibex Hi Security.
  • These factory fences look horrible and would need disguising and are only rated for low domestic risk. They may look fearsome, but anyone with tools will be through in no time between the pales. Think of them as ‘keep out’ signs. A possible exception to that rule is the Lochrin Bain SR1 Combi SL1, which is SBD terror rated thanks to up to 4 rails and 28 x 4mm pales per bay bolted through the rails; if disguised it could deliver a nasty surprise to an intruder once they get past whatever wood dressing you give it, assuming you do not need the surveillance of a see-through fence.
SR1 fence breach demo

LPS2081

  • There is a low risk domestic LPCB standard below LPS1175 that covers fences facing only a risk of stealth attack by small tools, LPS2081. This requires height of 1.8m for SRA rating and 2m for SRB rating, which can include permanent topping of equal strength. Its toolset ‘a’ includes tools like 6” wirecutters and 12” crowbar which have to be resisted for 1 minute to achieve SRA, while toolset ‘b’ includes tools like 14” boltcutters, 8” tin snips, hand drill and junior hacksaw which have to be resisted for 3 minutes to achieve SRB. These standards can safely be ignored as they do not exist because insurers do not require them for householders, although Premier SS do an SBD & LPS2081 SRB rated G81 gate.

SBD

  • Police approve fences including non insurance rated ones.

ASTM F2781-15

  • There is also the USA standard ASTM F2781-15 for noisy manual attack on fences from gangs with tools graded low (‘L’, eg boltcroppers), medium (‘M’, eg battery grinder) or aggressive (‘A’, eg pneumatic drill), and options for guns or 2 ton vehicles ramming at 20mph with 6”x42” bumper 24” above ground. Ratings are similar to LPS in that they use a letter for tool group followed by a number for minutes, eg M10. Products in Britain include Barker’s Stronguard MA palisade-mesh combo with 3mm 358 mesh on 80x120mm posts 8′ or 10′ high rated SBD and M10 or M10-A5, and Betafence’s Guardian 7000 double layer mesh system rated SBD and M14-A4.

Military

  • USA DoD standards, such as Marines, assume chain link buried 2” in concrete and include two 7’ high fences 30’ apart for nuclear sites, and 9 gauge (3.7mm) 2” square 6’ high mesh for arms dumps.
  • The US Marines standard is for selveges to be twisted barb top and bottom, the fence 7’ high plus 1’ topper, with reinforcing wires, fastening welded or peened, 45 degree 15” ‘Y’ outriggers with three strands of barbed wire each side and potentially also barbed wire or tape coiled between, although openings to only have 0.5” bars on 9” centres.
  • US DoD arms standard is 6’ high 2” 9 gauge (3.7mm) chain link buried 2” plus topper all to RR-F-191K(aq), with gates locked with 3/8” chains.
  • NATO requires 2.5mm thick 76mm grid 2m high chain link with 3.76m post separation.

Ballistic fences

  • Ballistic fences are available also with claimed blast resistance, to UL752 and NIJ 0108.01, such as Betafence Armorguard.
Betafence Armorguard

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