Spec'ing wood screws

[Lion06]

Sorry for the ton of posts here recently. I'm looking at our General Notes for wood and I don't see any mention of standards that the fasteners need to meet. I think this is something that needs to be added to our General Notes so I wanted to see how you guys spec fasteners for wood construction. Do you just have a note requiring Bolts to be ANSI B18.2.1, screws to be ANSI B18.6.1, and nails to be ASTM F1667? Is this necessary? Are there "wood screws", nails, or bolts out there that don't comply with these standards?

 

[TXStructural]

Nails which are spec'd are fairly standard, EXCEPT gun nails (collated nails) are typically smaller diameter than standard nails. Box nails are thinner than common nails. Unless noted, they will use collated nails. Search the ICC reports for nails if you want to know the details.

Screws are more problematic, since most deck screws (which you will get) are not the same as old school wood screws. They are often a tempered steel, which makes them strong but brittle. I'll just leave it at that.

Bolts are not a problem when spec'd to NDS - you almost always get a wood failure rather than a steel bolt failure.

You will probably never find a box nails or common screw which have a ASTM spec on them. Look at the Fastenal website to get a feel for what is generally available.

 

[Lion06]

So what do you do to ensure the fasteners that get used on the job match the properties of the fasteners you assumed in design?

 

[Ron]

When you specify a product, require certification of their compliance with standards. When they submit a cut sheet on the product, the cut sheet must state compliance with your specified standards (or they submit separate certification) or you reject it.

Fasteners bought at home improvement stores might or might not comply with typical standards. Assume that they don't unless otherwise proven.

Next you will need to specify the performance of the fastener in the wood you specify. There is an ASTM standard for this as well.

 

[rscassar]

My notes and specifications don't call up any specific standard which nails and screws must conform with nor do they require any specific compliance criteria (not to say that this is correct, I just couldn't find them anywhere in the documentation).

My guess is that the majority of fasteners which are used in wood-framed construction would be imported from oversees with no testing performed to ensure that the product is up to code (whatever code they must comply with).

 

[Splitrings]

I'll second what Ron stated. Follow NDS chapter 11 when specifying your fastners. You will be amazed what shows up on the jobsite if you don't. I don't think you can overstate this enough on a design. I have had contractors using 0.131" smooth shank nails when 0.207" hardened ring shank nails are called for. They seem to think all 16D nails are the same. As far as bolts I typically specify 307A or SAE Grade 5, just because I want to see a grade mark on the head of that bolt. SAE grade #1 and #2 are acceptable but there is no marking on the head. Then you don't know if it is an ungraded bolt or if it is a SAE graded bolt.

 

[Lion06]

Where do you see SAE Grade 5 or 307A bolts called out in chapter 11 of the NDS? I only see ANSI specs.

 

[Splitrings]

That ANSI standard is simply a dimensional standard, it doesn't contain anything on strengths of the bolts. You need to specify what strength bolts you are using. If you are using the tables in Chapter 11, they are based on a bending yielding strength of 45 ksi. This is a SAE Grade 1 bolt. If you go to the American Wood Council site there are several technical reports on fasteners.

 

[msquared48]

If you are using holddowns by a specific manufacturer that require certain screws, usually the sdrew is either wpec.d in the tables or provided with the holddown when purchased. So I require that the screwa spec'd or required by the manufcturer be problded/

For thru-bolts, I always spec A307 for wood connections.


For nails, I use the descriptions proviced in the IBC.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[Splitrings]

I have used A307 grade A bolts a number of times on my wood projects. They have the same tensile strength as a SAE Grade 1 bolt. The issue is that ASTM A307 does not require a yield strength be published. You need the yield strength to compute the bending yield strength used by NDS. If I understand the material specs they are the same bolt just a different standard for the different industries. I guess it is a question as to whether you are comfortable making that assumption.