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Azek and Finish Nails

jn_freedman's picture

I'll be doing some exterior trim work and am looking at a product such as Azek.

I went to their website and they insist on not using wire based finish nails (I'm assuming either a 16 or 18 gauge finish gun nail).

Since these are the only two finish nailers I have, I want to see if this is really the case and if I need to step it up to something like a 15 gauge nailer?

Any input would be appreciated.


(post #77765, reply #1 of 14)

Although I am guilty of using wire finish nails from a gun with Azak, I don't think it should be done, or at least it shouldn't be the only fastener used. Azak is too heavy, and the PVC doesn't grip too well on the shank so the little head of the nail can slip right on through. Now, I like to tack up the stuff with 15g nailer, and then go back and either hand nail in ring shank ss siding nails, or trim head ss screws.

It's ok if the azak is a smaller trim piece I suppose. The heavy pieces I like to use a full size bugle head deck screw that has been counter bored. They now make a filler for the stuff. Quite pricey and you can only use the nozzle of the stuff in one shot since it is an epoxy.

I use the pvc glue on Azak trim joints

(post #77765, reply #2 of 14)

Azek and similar PVC trim moves too much (expansion and contraction with the weather) to use what is an essentially headless wire nail.  We use SS or galvy siding nails and nailers with good results.  With the exception of smaller or delicate moldings, I generally don't like the idea of using pnuematic finish nails on exterior work.  For small stuff I'll use the 15ga nailer or the narrow crown stapler but only if I think I risk blowing up the piece with a siding nail.

One more thing.... don't use ring-shanked nails on the Azek either.

(post #77765, reply #3 of 14)

Diesel-why no ringshank on the Azek?  I have little experience with the product.  Whenever I've used it, I fastened with stainless trim screws.


(post #77765, reply #7 of 14)

Blow-out has been my experience with R/S nails in PVC.  Especially if you need too nail close to the edge.  But even in the field they will frequently blow a big chunk out the back that you often don't even notice at first but can then telegraph through.  I've had much better results with smooth shank nails. 

(post #77765, reply #8 of 14)

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(post #77765, reply #11 of 14)

Oh yeah?


says U!


    Buck Construction

 Artistry In Carpentry

     Pittsburgh Pa

    Buck Construction

 Artistry In Carpentry

     Pittsburgh Pa

(post #77765, reply #4 of 14)

I'd also like to know why not? Of course for me it's much too late.

(post #77765, reply #5 of 14)

I never use finish nails for any exterior trim work.

Trimhead screws and trimhead SS nails or even eight penny galvanized box nails set and puttied in.

but headless finish nails have never been able to hold trim on the outside in the weather. They are for interior finish work



Welcome to the
Taunton University of
Knowledge FHB Campus at Breaktime.
 where ...
Excellence is its own reward!



Oh Well,

We did the best we could...

(post #77765, reply #6 of 14)

I've installed a lot of Azek, and tried every fastener out there.  What I've found to be the best is GRK stainless steel #8 composite decking trim head screws.  They have the reverse threads at the top of the shank that help with fine adjustments. 

They also have Torx heads which are much better at resisting cam-out than square heads, at least in that application.  If you're going to use an impact driver, spring for the GRK Torx bits--they hold up much better than regular gray ones.

(post #77765, reply #9 of 14)

I had several hundred lf of Azek installed using my Senco 15 GA nailer (2" SS nails (Very expensive).


(post #77765, reply #10 of 14)




  • For best results, use fasteners designed for wood trim and wood siding (thinner shank, blunt point, full round head).
  • To take advantage of the performance of AZEK, use a highly durable fastener such as stainless steel or hot dipped galvanized.
  • Staples, small brads, and wire nails must not be used.
  • The fasteners should be long enough to penetrate the solid wood substrate a minimum of 11/2".
  • Standard nail guns work well with AZEK trim products.
  • Like wood, use 2 fasteners per every framing member for trimboard applications. Trimboards 12" or wider, as well as sheets, will require additional fasteners. See Figure 1 below.
  • Fasteners must be installed no more than 2" from the end of each board. See Figure 2 below.
  • AZEK should be fastened into a flat, solid substrate. Fastening AZEK into hollow or uneven areas must be avoided.
  • Pre-drilling is typically not required unless a large fastener is used or product is installed in low temperatures.
  • 3/8" and 1/2" sheet product is not intended to be ripped into trim pieces. These profiles must be glued to a substrate and mechanically fastened.


(post #77765, reply #14 of 14)

That makes sense on the ring shanks blowing out.  The stuff can get somewhat brittle under cold conditions especially.  Thanks for the heads up. 

Mike G, how did you come across the plastic nails?  Are any of your local yards carrying those?  I'll have to check those out.


(post #77765, reply #12 of 14)

That is too bad.
Now do the permanent nailing.



Welcome to the
Taunton University of
Knowledge FHB Campus at Breaktime.
 where ...
Excellence is its own reward!



Oh Well,

We did the best we could...

(post #77765, reply #13 of 14)

I've had success using plastic nails with Azek.

One advantages is you can leave the nail heads a touch proud and sand them off flush. No need for filler.

I use the siding nails - they run through most plastic collated coil siding/sheathing nailers.