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Community and Q&A

Which long screws are really necessary?

Dave B | Posted in Green Building Techniques on


So I know an engineer should confirm everything, and are useful in most cases ,but lets see if I can get cheaper advise and experience form others. (I have paid for numerous other required Eng. stamps).

Also this is a storage/work shop so I am not as concerned.

I’m looking for best bang for the dollar(LIKE EVERYONE) in a 6″ screw for holding my horizontal furring strips on the walls. I’m in Ontario Canada, so less choice of stores willing to ship.

Wall inside -out
2 x 6 stud wall @ 16″ OC.
7/16 OSB sheathing
3″ Polyiso
1 x 4 furring strips ( horizontal ) @ 12″
Vinyl Board Batten siding.

I have looked at FastenMaster TiimberLOK screws vs. HeadLok, as recommended here

Is a screw with a large washer style head, really necessary?
The tensile/ shear strength of the two are similar, but the TimberLok are cheaper.

Thanks for any advise.

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  1. Tim Brown | | #1

    I'm in the same situation and rebelled against the brutal pricing in Canukistan...So I chose to buy via I needed Fastenmaster 7" (i'm using 4" of exterior EPS) and vertical 1x4 furring.

    I bought 2 pails (of 250 each) for about $400 Cdn (total for 500 screws) and had them SHIPPED FOR FREE to a US postal service about an hour away in Pembina ND. I drove down in my Yaris (55 mpg) and picked em up and crossed the border...I paid no duty, taxes or other fees...maybe I got lucky I don't know but since they are a USA product and building materials it was all good.

    I will need more than 500 screws but thought that was a good place to start...

    Just a thought!

  2. Dave B | | #2

    I have been looking at Amazon .ca and they seem to be the cheapest , even for my 3M tape.
    Did you buy HeadLok ?
    It would be a bit of a drive to the border for me. So it would have to be a big savings.

  3. Tim R | | #3

    Simpson offers similar screws and design tables. I got them from Hub. Lots cheaper full retail.But I am not in Canada.

  4. Malcolm Taylor | | #4

    Did you look at GRK? They are based in Ontario.

  5. Tim Brown | | #5

    Yes I bought Headlok.

    Where in Ontario are you located? Just asking...I'm in Kenora.

    7" Fastenmaster Headlok are not even available in Canada but easy to find on Amazon. If you need several items it might be worth the trip....unless you are N of Timmins...then ????

  6. Dave B | | #6

    I'm an hour East of Toronto
    I looked on Amazon , both .ca and .com so
    TimberLok are $218 CDN and $131 USD for 250count difference of $87 plus exchange
    HeadLok are $353 CDN and $145 USD for 250 count difference of $208 plus exchange

    All are sold from Fastenmaster , so I'm not sure why the difference in the timberlok and headlok price is so great in Canada. They are similar priced in the US.

    That's why I'm leaning towards buying the timberlok screws, I just don't know if the washer style head is really necessary? Anybody use non-washer style heads for attaching their furring strips?


  7. Malcolm Taylor | | #7

    If you were using 2x material for the furring something like the GRK R-4 structural screw would work, but with 1"x4"s you need the washer style head.

    Have you checked with your local lumberyard? Mine sells 6" GRK RSS screws for around a buck a piece retail, but I get them for close to 60 cents contractor pricing.

  8. Dave B | | #8

    I will be using a 1x4 and the screw will need to be counter sunk flush.
    I will look into GRK , would use 5/15 or 3/8 screws the 5/16 seem to have higher bending yield strength.


  9. Rob Hunter | | #9

    What are the recommended/required furring strip screws (Climate Zone 3) if only 1" of exterior insulation on top of 1/2" plywood? 4" screw - can I use something like the GripRite 4" Exterior screw?

    And, to complicate the question - I'm going to use vertical board siding, so will have 2 layers of furring strips: 1x2 vertical for rain screen over 1" insulation, then 1x4 horizontal for siding nailers. Can I use the 4 1/2" HeadLok for the horizontal furring strips (assuming, of course, that they're screwed into the studs)?

  10. Rob Hunter | | #10

    This article ( covers/answers the length question, but the 'what type of screw will provide enough hold-down' is still open. At 50 cents a screw for HeadLoks, this is a significant incremental expense: @ 24" spacing, it's 250 screws per 100 LF of 8' exterior wall - 500 if it's vertical board siding.

  11. User avatar GBA Editor
    Martin Holladay | | #11

    I'm not an expert in this topic; our usual advice is, "When in doubt, consult an engineer."

    Some information on screws from "REMOTE: A Manual" is shown in the image below.


  12. Quinn Sievewright | | #12

    For what it is worth I used a combination of Headlok and standard 5" ACQ wood screws on my 1x4 furring strips over my 2" exterior insulation (roxul comfortboard). Every 3rd screw or so I used a Headlok but I needed to quickly countersink the furring strips with a forstner bit or the Headlok pan head would protrude too much, perhaps with rigid foam insulation rather than mineral wool the head will dig into the would sufficiently without over compressing the insulation in your case.

    My exterior cladding attached to the furring strips was a mix of Cedar T&G and corrugated metal siding. No specific engineering behind my mix of screws though, just what the builder and I thought was sufficient.

  13. Jonathan Lawrence CZ 4A New Jersey | | #13

    For what it is worth, my engineer spec'd 7 1/2" Headlok screws with vertical 16" spacing for the following assembly:

    2 x 6 studs 16" OC
    1/2" Zip sheathing
    3" Roxul ComfortBoard
    2 x 4 furring
    5/8" Boral cladding

  14. User avatar
    Dana Dorsett | | #14

    7.5" seems longer than necessary for 3" foam (@ Jonathan). With 2x furring (1.5"), and half-inch ZIP your stackup from the studs to the exterior side of the furring with 3" foam is only 5", which means the screws are penetrating fully 2.5" into the studs. The minimum penetration for most siding types would be 1.5" , but anything longer than 7" (for a 2" penetration into the stud) seems like overkill.

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