Are splayed screw fixings a thing? And fixing grab bars

[foxhole]

i'm not worried about a guarantee, i'm worried about people getting hurt.
Its silly to chase a comment like that so doggedly, one death would be too much, one injury would be too much. I want to make my house safe, and i know screws can pull out of bricks at the right angle

No they can’t .

 

[GhostIntMachine]

RE: Multiple screws in the same brick, that is a valid concern, which makes me wonder why commercial bars i'm seeing have the screws all close together. Wouldn't it be better, in that case, to have some kind of mounting plate, like is used for TVs, to spread the load over a larger area of wall?

The grab rails themselves are never more than 4 to 6in off the wall, so a lot of the force exerted will be near vertical. I also hope that you are aware that a single good quality 5 x 100 screw into good quality masonry with a good quality plug will support something in the order of 350 to 400kg static load (and that is per screw - the Fisher site used to have actual load figures on it somewhere)

TBH a lot of these grab rails are installed in environments where the walls are stud walls. In that case it is normal for the architect to specify something like 18mm hardwood ply or OSB pattresses incorporated into the wall structure (i.e. between the studs, fixed to them) before the plasterboard is fixed - if that isn't done, the installer needs to cut away a section of the plasterboard , install a pattress then make good the PB as stated by an earlier poster. Screws should always be of good quality and of adequate length - often something like 100 to 120mm long x 5 or 6mm diameter (although I have seen 8 and 10mm coach screws on some specific installs, e.g. for "trombones" and in bariatric environments) and fastenings are always driven perpendicular to the surface of the wall, never skewed at an angle. Even with closely spaced screws this gives adequate capacity for a 150 to 200kg adult to partially pull themselves up using the bars, again as stated above.

I've been told that angled drilling is more likely to cause cracking or spalling of the masonry - unsure about that, but an angled screw head is unsightly, can be a cut risk (in the case of a countersunk head) and it can result in undue strain on one side of the screw head, so maybe best avoided. In ropey masonry it is sometimes necessary to use "tricks of the trade" such as using multiple plugs in the holes to ensure a decent fix, putting resin down the drill holes to "glue" the screws (in which case NO plugs) or in extremis to chisel out a section of plasterwork to a depth of 18mm or so in order to install a large plywood or hardwood pattress which will spread the load over a greater area using more fixings than the ironmongery allows for, and to which the fitting can then be secured - this might even end up being hidden beneath a skim of plaster. To add to the confusion brittle hollow bricks, such as Poroton, may require specialist plugs, as can hollow block work.

It is ALWAYS down to the installer to ensure that adequate fixing methods are used which are appropriate for the wall sttructure beneath - and if you don't know how to install stuff properly, safely, rather than winging it and going "off the reservation" by utilising bodges like skewing the screws, you really need to install someone who knows what they are doing because you patently don't.

Some ironmongery which is designed for very heavy loads, such as drop rails (aka "trombones"), are not only designed with larger mounting plates which allow larger diameter and greater numbers of fixings, but may incorporate gravity deployed legs such that when the rail is dropped into its' usage position, a further support leg drops into place which will directly transmit half the load into the floor. Of all the bars installed, it is the "trombones" which carry the heaviest loads - and they always come with a large base plate to affix them to a wall, often with 4 or 6 heavy screws (e.g. M8 or M10)

This is written from the point of view of someone who regularly installs the Doc M Pack stuff you are talking about on public buildings (disabled toilets, changing places suites, etc) as part of the general works

 

[GhostIntMachine]

its all well and good saying that until it comes away in the hand, and someone slips and cracks their head open. People have died from this. Many, many people.

OK I'll say it - BALDERDASH and POPPYCOCK! Show me in any HSE or RoSPA report where it says that and I'll apologise. Just because you have read that on a crackpot discussion on FB doesn't make it true

So, in a commercial setting (which includes schools, hospitals, town halls, etc) you may, VERY OCCASIONALLY, get a situation where a rail gets rived off a wall. Often it is down to vandalism. The vertical bars are set in specified positions to help people steady themselves, and the horizontal bars designed to carry someone's full weight are often of the drop down "trombone" style of bar have massive connection plates (see above).

My own feeling is that the fixings are over engineered by a factor of at least 50% to ensure that failure almost never happens - you would more than likely get away with four or even two screws on a standard handrail without ever seeing a failure. Oh, and on the point of stainless vs. plated screws - where fixings are supplied they are invariably hardened steel, either galvanised or more chromrium plated because staimless has a lower load capacity for a given screw size

For correct positioning I refer you to Doc M of the Building Regs