XLM Stringer Spacing

robert c1

I was reading up on the Timbertech site for an upcoming Earthwood deck when I saw they require a maximum of 6" stair stringer spacing for XLM. WOW.

I didn't see it in there written instructions but if you follow the link below and
click on the video for stair installation it's written clear as day 25 seconds into the video.

http://www.timbertech.com/installati...s/default.aspx

I'm pretty far from an expert on PVC decking but that's hard to believe.

Greg Di

Must be a mistake. It doesn't sound right at all. With 6" spacing, you might as well carve out a tree trunk and use that for a solid stringer.

XLM is not celophane!!!

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PA woodbutcher

Writing says 6" voice over says 12"...Never worked the TT, but the correct deck is rock solid at 12" centers

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BuiltByMAC

It is possible for mistakes to get made...even on install vids.
12" o.c. for stair stringers when installing XLM.
Use strongbacks to beef up your stringers, make 'em rock solid.

Mac

MartyCD

The installation guide I have, dated Oct 2008, shows flatwise 2X under the stair treads, similar to Azek.

Attached Files

Scan7972.pdf (65.6 KB, 100 views)

deckman22

If you do those flat blocks make sure the edges line up with the edges of the decking so crap can fall thru/water can drain. Dog hair can be a pita in those places too if there's no space.

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robert c1

So I e-mailed Timbertech and here was their reply:

"Special conditions will require an engineering inspection and/or reduced spans. Always consult local building codes. Maximum stair joists (stringer) spacing for decking planks is 12" on-center. Make sure there is at least on stringer for support in the middle of the stair opening.
Thank you for contacting TimberTech. Please let us know if we can be of any further assistance."

I replied with:
"Thank you for the quick response, however, I'm not sure if you answered my question.
Timbertech's stair installation video does not reference special conditions in regards to stair joist spacing.
The video clearly claims that all the decking planks except XLM will support 12" OC. Big white letters pop up stating XLM will span a maximum of 6" joist spacing on stairs.

So which is it: Is this a mistake? If it's not a mistake then I must assume it would void the warranty to install otherwise.

I'm not trying to nitpick or play Gotcha and Timbertech has a good reputation in this area. I've just had enough experience with fine print to want a clarification."

Their Reply:
"6" centers are recommended for stair stringers when using the XLM. We have recently done new testing that shows that a 10" center spacing can also be used (max). You could go with either one.

Please let us know if we can be of any further assistance."


They still didn't directly answer the warranty question but FWIW my take is this is just one of those poison pill things lawyers love that allows companies to honor the warranty at THEIR discretion. IE a get out of jail free card from class actions and the like.

One more reason to assume all (big company) warranties are bull**** until proven otherwise. I mean how many products have absolutely ridiculous installation requirements for the express purpose of voiding their warranty.

RobertCDF

Boy I am glad I dont use TT very often... I am all for strong stairs but at that point you might as well pour concrete and steel stairs.

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MartyCD

I'm not here to defend Timbertech, but the ICC testing protocol for stairs is pretty tough. I think they're just being extra careful to make sure they meet it. If I recall correctly, in the testing they apply a point load of 975 lbs at the center of the span and measure deflection, which must be under 1/2" or so (I'll see if I can look this up and confirm my numbers, it's been awhile). This is a much tougher requirement than for the decking, and is meant to simulate a big person climbing the stairs (in every case the code tests at 2.5x design load, I don't have my calculator here but the design load would be 975/2.5). The test is not unreasonable in that it simulates a big man carrying two chop saws placing the toe of his boot mid-span and stepping up and having it not feel springy. But due to the 2.5 factor, it could be a bit of overkill. So I really doubt T'tech would void a warranty over this, it would just be a situation where you might worry about it, or a very thorough inspector might know the difference between the different types of T'tech and ask for the extra stringers.