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Painting Wood Siding- Not All Wood is Paint Grade

"I just need a paint grade wood"

People always say it like that means some less expensive lower grade of wood is fine because they are going to be painting the wood. That is absolutely NOT the case.

You have to be very careful what type of wood you decide to paint. Knots will show through some paints and indications of knots are apparent in most painted applications.

The wrong species can be disastrous under paint. Ponderosa Pine wood for instance will bleed pitch through the knots which causes major problems under paint.

Buffalo Lumber specializes in wood siding applications. Siding has to perform for years to come. You have to take long term performance into consideration as well as upfront costs.

Painting Wood Options

When we prescribe painted wood options to our customers we have 2 main choices -

CLEAR Finger-Jointed CEDAR

The finger joint is a seamless wood connection made by cutting a set of matching rectangular cuts into the end of two pieces of wood, which are then glued. The finger joint is the most common joint used to form long pieces of lumber from solid boards.

Finger-Joint Cedar Clear

As soon as I say "finger joint" everyone has the same reaction "It will come undone- I have heard horror stories - telescoping where the fingers swell and rise above the board surface."

I have heard those same stories however we have NOT experienced them. Look at the picture above. The new milling of finger-joint is more akin to T&G (Tongue and Groove) joinery - where each "finger" fits into a groove between the board edges. You can see that the seams are straight across. They do not show up under primer and they don't telescope because there are no fingers- only a straight seam.

The finger joining process has evolved as have the polymers that go into glue formulas. This wood product is specifically designed to be primed and painted to look beautiful and perform for years. Refer WWPA HRA & Finger-Jointed Lumber.pdf

Here is an example of a respected manufacturer's Finger Joint Cedar performance warranty
"... Finger-Joint Wood Products will be free from manufacturing defects which cause rot, corrosion, delamination or excessive swelling from moisture for a period of fifty (50) years from the date of purchase".

That means they cover the finger-joint cedar substrate for 50 years!

Between our supplying mills and our own sales we have had great results with this product and I feel confident in prescribing it as a long term performance option. It is offered primed and usually falls into the $3.50 per sq ft category delivered.

finger-jointed cedar Bevel home

Finger-jointed Cedar - PrePrimed & Painted Thin Bevel pattern (Clapboard) home

"EEGAD man $3.50 per square foot!?"

Yes - in our opinion that is the cost of doing it right. You can find someone who will prime knotty pine for you and let you use it at your own risk - however we would not quote that option as we know it is a recipe for disaster.

In the wood siding business you can't afford to quote options that will not work out for the customers long term. Our customers need to be as happy 10 years from now as when they purchase the wood. Unless we are talking about a barn siding customer who does not mind seeing knots under their paint most customers get really pissed. They get even more pissed if their wood rots off the wall in 5 years.

Structural Finger-Jointed lumber products are graded using the same rules and design values applied to solid-sawn dimension lumber. Because it is typically fabricated from wood seasoned below 19% moisture content structural glued lumber is exceptionally dimensionally stable. Refer WWPA TG9 Structural Glued Lumber.pdf

Primed SPF

Another affordable option is the Primed SPF option. SPF stands for Spruce, Pine and Fir. They are considered one species (SPF) for the topic of this discussion. They grow in the same cluster of trees and are similar enough that all three are mixed into one product line.

"But SPF is not a wood that is naturally resistant to moisture and insects!"

This is true- in this case the manufacturers are providing artificial protection (special borate primers that resist rot and insects) by imbedding primer deep into the actual fibers of the wood. This process uses the wood's own susceptibility to moisture to protect it - by accepting the primer into its own wood tissues a barrier of protection is created for the end product.

factory finish machine picture

PRE-Finishing Process. "Look at that bad boy- Gnarly!"

"But you said customers get pissed if there are knots in their painted wood?!"

I said they get pissed if they can SEE knots under the paint. In this case the knots are not visible under primer + 1 top coat. A mill (Gorman Brothers) has created a "super tight knot" grade specifically designed to be primed and painted. They allow knots but only knots of a certain size and type are permitted into this grade.

This highly SELECT knotty grade of SPF - often referred to as J-GRADE - runs around $3.50 per Square Foot primed and delivered. In the case of bright white paint we will sometimes move up a grade notch to a Near Clear SPF which falls in the $4.50 per square foot category.

Factory Primed Painted SPF Bevel Siding

This is a painted SPF application

This painted wood product comes with a 15 Year Warranty on the primed SPF wood siding substrate (surface to which a coat of paint is applied). You can add a second factory applied topcoat, apply a final coat in the field and get a 25 year limited warranty on the wood finish.

In our experience the best results are achieved with factory applied primer + 1 paint topcoat and then doing a final paint coat in the field to blend the whole painted wood siding result together. This is how you get a 25 year warranty and this is how you achieve peace of mind.

Again to do it right comes in around $3.50 square foot primed and delivered with a 15 year warranty against rot.

CLEAR Grade - Rot Resistant Woods

Paint Clear Cedar Siding?

"CLEAR Cedar - Now why would you paint this gorgeous, expensive wood?"

Final and most expensive option is CLEAR Cedar, CLEAR Redwood or CLEAR Cypress and few people except for historical districts want to pay the money for beautiful clear grades and then paint over them.

Clears run from $6 per square foot and on up which is why they invented the clear finger joint option.


Finger-Joint Cedar and Primed SPF are the only two affordable options in painted wood siding that we will recommend because we know you can't risk even the slightest chance of failure. These painted wood siding options have performed in the past and continue to prove themselves today.

I know that $3.50 and $4 a square foot is not what you wanted to hear - however the cost of doing things right is measured in perspective. It costs 10 times as much to fix something done incorrectly than to do it right in the first place. 100% of the people who have done it right feel it was worth it in the end.

That is the truth as we know it.

Good luck out there!

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