# DougFir Deck - Stain Before or After build?



## mntnvew (Mar 14, 2008)

I am working on a deck it is almost all doug fir, w/ exception of faceboards being cedar.

Should I spray it before building to cover all sides with stain? or Just build and then spray?

Spraying does cover rather well... but I was thinking since it is only select doug fir I should spray before building and again after just to cover ALL sides of the materials.

Thoughts???


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## Scuba_Dave (Jan 16, 2009)

I'd cover all sides - before building
I do this for trim on my house
My deck is unstained - natural


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## Termite (Apr 13, 2008)

Doug fir is not a deck material. It lacks the weather resistance of cedar, redwood, or pressure threated southern pine. Fir is/was commonly used as porch flooring, but must be primed and painted (and constantly maintained) in order to last. 

You need to strongly reconsider the use of fir in a weather-exposed condition. There's no stain or coating you can put on it to make it a good product for this application.


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## Scuba_Dave (Jan 16, 2009)

Is the douglas fir old growth wood or new growth?
You won't get the time out of new growth
And the support joists should be PT

Have you already started?


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## mntnvew (Mar 14, 2008)

Scuba_Dave said:


> Is the douglas fir old growth wood or new growth?
> You won't get the time out of new growth
> And the support joists should be PT
> 
> Have you already started?


I have purchased materials and dug post holes.

I was told by lumber yard that DF is the only way to go for strength of joists.

It is my understanding it is old growth.

The cost of materials was just under 900 for DF and **** load of screws. For same materials in Redwood, it would have been 2k.

I spent 100 on stain last night, so half price for DF, over Redwood.

Also note this is a deck/landing for a pole barn to get to my work shop in the raised center, so it isnt on a house or going to be used in fashion that looks are important.

I was thinking I would spray stain entire boards and again after built, and again in 3 months before fall.

Then next year stain again at the beginning and end of summer.

I know DF is dense so it doesnt absorb stain well.

Lastly, since I am in MT and we have BRUTAL winds where I live, I was thinking of eventually enclosing the landing with the same tin that is on the pole barn, so that was taken into account as well. Albeit it would be 2-3 years before I get to it.


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## curapa (Nov 13, 2007)

Is this treated Doug Fir?


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## mntnvew (Mar 14, 2008)

curapa said:


> Is this treated Doug Fir?


No it is not Pressure Treated Doug Fir.


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## curapa (Nov 13, 2007)

mntnvew said:


> No it is not Pressure Treated Doug Fir.


In another post I was reminded that different areas have different materials available. Here, pressure treated Southern Yellow Pine is the only material that is used for exterior joist/framing. In many areas treated Doug Fir is used but the wood is so dense that it is not "pressure" treated but treated with a different method which I am not completely familiar with.

That being said, you need to use a wood that is treated chemically to handle the elements or a material that is naturally resistant to rot and decay. Doug Fir is none of these therefore it would be in your best interest to return the material for one of the better options being treated Doug Fir or PT Southern Yellow Pine.


Curt


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## mntnvew (Mar 14, 2008)

curapa said:


> In another post I was reminded that different areas have different materials available. Here, pressure treated Southern Yellow Pine is the only material that is used for exterior joist/framing. In many areas treated Doug Fir is used but the wood is so dense that it is not "pressure" treated but treated with a different method which I am not completely familiar with.
> 
> That being said, you need to use a wood that is treated chemically to handle the elements or a material that is naturally resistant to rot and decay. Doug Fir is none of these therefore it would be in your best interest to return the material for one of the better options being treated Doug Fir or PT Southern Yellow Pine.
> 
> ...


My understanding is that the stain (w/sealer) is all that is needed to protect Doug Fir from elements, it is just a matter of doing it more often then not (twice a year is my understanding for first 5 years, then once a year after that).

Has anyone else heard this?


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## mntnvew (Mar 14, 2008)

curapa said:


> In another post I was reminded that different areas have different materials available. Here, pressure treated Southern Yellow Pine is the only material that is used for exterior joist/framing. In many areas treated Doug Fir is used but the wood is so dense that it is not "pressure" treated but treated with a different method which I am not completely familiar with.
> 
> That being said, you need to use a wood that is treated chemically to handle the elements or a material that is naturally resistant to rot and decay. Doug Fir is none of these therefore it would be in your best interest to return the material for one of the better options being treated Doug Fir or PT Southern Yellow Pine.
> 
> ...


I have read about treated doug fir, it has perforations/dents put into it to allow the chemical to seep in due to its intense density. But again, was told it is not required as long as you stain/seal deck as I previously stated.


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## Tom Struble (Dec 29, 2008)

i would do 1 coat before 1 coat after ,its important that you treat the ends after you cut but before you install ,i would space the cedar fascia off the joist alittle for drainage and air circulation


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## mntnvew (Mar 14, 2008)

tomstruble said:


> i would do 1 coat before 1 coat after ,its important that you treat the ends after you cut but before you install ,i would space the cedar fascia off the joist alittle for drainage and air circulation


Good to know, thanks for sharing!


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## Termite (Apr 13, 2008)

mntnvew said:


> I have read about treated doug fir, it has perforations/dents put into it to allow the chemical to seep in due to its intense density. But again, was told it is not required as long as you stain/seal deck as I previously stated.


Doug fir is typically not pressure treated because it is a refractory species, which means that it does not take treatment to the appropriate levels of retention of treatment like southern yellow pine does. As you correctly understand, doug fir must be incised in order to take any waterborne treatment at all. It isn't any more dense than pine (the stuff they use for treated lumber), actually less. It isn't quite as strong as southern yellow pine and the span tables reflect that. 

Whoever told you that stain/sealer will adequately protect this wood in an exposed exterior application told you incorrectly...Period. Stain/sealer will help, but the wood lacks the properties necessary to adequately resist repeated moisture exposure. Sealing the end grain would be incredibly important provided that the rest of the wood is 100% sealed, and stain WILL NOT do that. If wood's end grain is sealed, the wood can't naturally take in and expel moisture from its tubular fibers. If it can't expel the moisture, you have a problem.

Price comparisons between doug fir and redwood don't have any relevance. You don't use cedar or redwood for the structural framing of a deck in most applications besides posts. There just really aren't any options for the floor structure of a deck besides pressure treated.

I would strongly encourage you to return the material in exchange for pressure treated material. I'd also have a firm chat with whoever the person at that lumberyard was that told you this was a good idea. I spent a number or years in lumber buying/sales, and can assure you that you're being led astray and are paying your hard-earned money on a product that is going to perform poorly.


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## mntnvew (Mar 14, 2008)

thekctermite said:


> Doug fir is typically not pressure treated because it is a refractory species, which means that it does not take treatment to the appropriate levels of retention of treatment like southern yellow pine does. As you correctly understand, doug fir must be incised in order to take any waterborne treatment at all. It isn't any more dense than pine (the stuff they use for treated lumber), actually less. It isn't quite as strong as southern yellow pine and the span tables reflect that.
> 
> Whoever told you that stain/sealer will adequately protect this wood in an exposed exterior application told you incorrectly...Period. Stain/sealer will help, but the wood lacks the properties necessary to adequately resist repeated moisture exposure. Sealing the end grain would be incredibly important provided that the rest of the wood is 100% sealed, and stain WILL NOT do that. If wood's end grain is sealed, the wood can't naturally take in and expel moisture from its tubular fibers. If it can't expel the moisture, you have a problem.
> 
> ...


Thanks, I appreciate your candor.

I have decided in stead of spending the money on PT/redwood/cedar for the deck, I am going to instead put it towards the tin walls, roof trusses, girts, etc... and just finish the exterior to protect the wood. This has always been my end goal but at least now I know that next time I want to build a deck, PT is the only way to go for structural lumber and then redwood/cedar for the other.

PS - I am still going to stain it so the summer rain wont get to it directly as it will take me that long to get the other stuff done!
Thanks All!


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## Tom Struble (Dec 29, 2008)

always prime your cuts


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## wpaustin (Jun 9, 2015)

*Doug Fir decking*

hi - just came across this post about putting Doug fir down as a deck. I'm about to do the same, and wondered how your deck fared over time, and if you'd do it again.

Thanks!


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