Onerous Grating Spec

[dozer]

We have a client who is requiring that the cross bar (you know the twisted bar on 4" centers) on bar grating not stick up above the bearing bar at all. My understanding is most vendors make this flush with + or - 1/16" tolerance. The client has been very specific that he won't accept grating that has cross bars that exceed plus zero on the height above the bearing bar. We got a sample from a vendor and sure enough the cross bar was about 1/16" (or so) above the bearing bar which didn't surprise me at all. Has anyone ever heard of such an onerous spec? How in the world are we going to find a vendor who takes this serious? Should it be taken seriously? IMO, we should have never accepted this condition but it's too late now.

 

[steellion]

There are products that achieve the flat surface. Look at McNichols press-locked grating for example, which appears to use dovetail slots in the bar grating to achieve a flat top surface. I'm not sure what is the relative cost compared to the standard bar grating, but it is available. Price it out, and if it's more expensive, you can go back to the client and say, "yes, we can give you a flat surface, but it is X additional cost."

 

[ztengguy]

Any reason given for the ridiculous spec?

 

[JStephen]

Can you just turn the grating upside down?

 

[JStephen]

Can you just turn the grating upside down?

 

[paddingtongreen]

A good guess would say they have had an insurance problem, or else they think they could get one.

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin

 

[fegenbush]

JStephen,

You can turn the grating upside down, but the compression flange (side?) of the bars would be unbraced. This would need to be accounted for and you would not be able to use the load tables provided by the manufacturer.

 

[dozer]

Actually, we can't turn the grating upside down because it is serrated. The press-locked grating is a good idea but the spec. actually calls for welded. Besides the cost is prohibitive, $10 to $40 more per square foot. I seriously doubt if we could get a change order for this. They would just say its our decision to go with that so they won't pay extra.

Let's see what else was asked? Oh, not I don't know why they wrote the spec. this way. I suppose they feel it would be less likely to slip. I'm not saying I agree. I think serrated grating is too agressive as it is. I'm just postulating.

I spoke to one grating manufacturer and asked if they would be able to conform to this requirement. They said "no". Evidently its a highly automated process where they crank this stuff out like nobody's business and they aren't willing to guarantee the cross bar will never stick up above the bearing bar. I can't say that I blame them.

 

[Ussuri]

Can you use GRP grating? As this is manufactured differently the tie bars are always below the top (I think anyway). A couple of suppliers would be Strongwell or Fibergrate.

 

[IFRs]

See if Bustin-USA.com has what you need. They make their own grating.

 

[moltenmetal]

If they're worried about tripping hazards, in my opinion they should stop worrying about the tiebars not being flush and they should avoid the serrated grating! Take a look at subway grating in any high traffic area outdoors (i.e public sidewalks), even in regions with heavy rain or snow- it's NEVER serrated and I'm sure that slips/fall related liability of that application has been well tested on that material. If you have ever fallen on serrated grating, as I have, you'll regret it- the stuff is a freaking meat tenderizer. In my opinion it should ONLY ever be used in locations such as stair treads, or where there's a high risk of heavy accumulations of oil and grease, such as over top of a drainage for such materials.

If they won't relent, fire-retardant FRP is an option. Anti-slip in this case is provided by means of glass granules embedded in a gel coat on the top surface- another dandy thing if you ever have to kneel on it or godforbid fall on it...

 

[Lion06]

steellion-

I don't think they can go back to the owner at this point and say what you have in the spec will cost extra. They own what they bought. If they didn't pay attention to the spec it's unfortunate, but they own it. It sounds like the contract was already awarded.

 

[JStephen]

There does need to be some back and forth here, though. Quite simply, they have specified a product that doesn't exist. Grating like this is not something people build in their garage, it is a commercial product made a certain way, and if you write a spec calling for it to be made some other way, you have problems. They need to adjust their standard to fit what is actually produced, or change the style specified.

One approach would be to ask them if they know of any commercially-produced grating or of any grating company that meets their spec. IE, ask them if this product really exists, as you can't find it. If the answer is "no", then you start working on alternate materials.

Fegenbush- agree with your comment on the load design, it would depend on the details as to whether that would work, and might be difficult to show that it would work. On the plus side, grating is small enough, it wouldn't be too hard to load-test a piece and see.

 

[Lion06]

Does it really not exist or is it just a more expensive product with fewer manufacturers? steelion's post seems to state the latter.

 

[dozer]

Lion06, your right. We should have paid more attention to the spec. It was buried amid thousands of pages of specs and we missed it. Or maybe somebody saw it but didn't think anything of it.

But now for the good news. I have found a vendor who claims they can do it. It will cost a little extra, probably about 10%, because of the extra time and care they have to take. The proof will be in the pudding.

Moltenmetal, I agree with you about serrations. That's a nasty surface to kneel down on. I've taken my clipboard and put it on the grating then kneeled down on it in the past to avoid the pain.

 

[IFRs]

I hate non-serrated grating. When wet or icy it is deadly.

 

[dhengr]

Dozer:
Could you buy the less expensive grating, and have a machine shop mill the high spots off the top? Half of them may not need it, and some part of those that do need some machining won’t need the full 1/16th removed over the full surface.

 

[steellion]

I don't think they can go back to the owner at this point and say what you have in the spec will cost extra. They own what they bought. If they didn't pay attention to the spec it's unfortunate, but they own it. It sounds like the contract was already awarded.

Lion06, I wasn't sure if the OP was an engineer and it was early on in the project and they were going off an RFP spec, or a vendor provided an agreed-upon spec. In the latter instance, you're correct, they're stuck with providing what was specified.

 

[dik]

If it's serrated, why does 1/16" matter? Explain to the owner that he can get what he wants, but the cost will increase accordingly.

Dik

 

[moltenmetal]

IFRs: just try to find serrated grating used anywhere at street level, where large numbers of people walk over it daily. Just saying...I'm confident that's not as a result of people being cheap or not caring about slip and fall hazards.