# backpriming ceder siding?



## Steve Unkie (Jan 21, 2006)

Hi guy's,
I'm building an addition and will be siding soon. I had planned on backpriming the 8'' bevel siding. Everyone that I talk to says that no one does that. I don't think that it's necassary,but would you do it?
The home is in WA. state and on the water so, lots of wind and rain.


Steve Unkie.


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## JMGP (Mar 29, 2005)

Back priming is the best way to go...

It blocks potential moisture from penatrating the back of the clapboards and working its way to the front...

Not many do this because the siding is always up and/or they dont want to pay the extra... its really the proper way to do it...

Its well worth it to back prime... especially were you live... 

also, when you install your siding... prime each end before installing... 

I would use a Premium Oil Primer... such as Ben Moore's 09400


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## Leo G (May 12, 2005)

Hate to say this but primer is not a water blocker, never has been and never will be. Its function is to bind the paint to the wood surface and give the ability to sand so you can get a smoother first coat of paint. I have heard many people say the same thing about back priming but I will not believe it. If you used a latex at least it would have some water resistant properties, but again primer is not designed to be water resistant or water proof.


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## rws (Nov 26, 2004)

Back priming,back painting,and or back coating was a common practise until the housing boom after world war 2.All the paint companys advise back coating as do the paint quality institute ,cedar foundations and many others.The idea is to keep the wood dry but allow some moisture vapor to pass thru.The BM 094 or 100 primer will do this.These and lots of other primers are water resistant,they have perm ratings.The higher the perm rating the more moisture will pass thru.


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## DeanV (Feb 20, 2006)

*back prime*

If possible and you can get paid to do it, always back prime. It seems to help control tannin bleed better and avoid those freaky rare paint failures.

Extreme example: White siding primed with BM 094 or 100 on exterior and solid oil stain would peel off in large bubbles, sometimes within a day of painting it up. Mainly in areas that received direct sunlight. Found out that the back side was not primed and water condensed on the foil lining of the styrofoam insulation under the siding. This moisture traveled through the cedar and pushed out all the primed and stain.


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## Joewho (Sep 20, 2006)

Took years to find out why the old victorians and queen ann's need paint so often. No moisture barrier. Backpriming was used before moisture barriers. I think more attention has been paid to venting in recent years too.

There is a moisture barrier paint, you could check it out for back priming. Two coats of oil paint also create a vapor barrier that will pass most local code. But beware of mold, especially in your location.

http://www.benjaminmoore.com/tds/1033/TDS260.pdf

Check the moisture level of your wood before you hang it.


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## DeanV (Feb 20, 2006)

I use that vapor barrier primer for almost all my new construction drywall, but it is NOT intended for exterior use. The idea is that it prevents moisture in the air from moving through the walls and reducing the efficiency of insulation and may also reduce some exterior peeling since less vapor will be moving through the walls to outside.


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## AAPaint (Apr 18, 2005)

Back priming is the best way to treat any exterior wood. Prime all sides and end grains or cuts before installation. Regardless of vapor barriers, they don't help the siding itself. Backpriming prevents rotting by sealing the rear side of the wood that is exposed to all the moisture coming out of vapor barriers. Wood still drinks water like it did when it was a tree through the end grains, so priming these prevents that also. 

The idea is to keep as much moisture as possible from pushing the exterior coating off, and to prevent rot. This practice is one I recommend on every job we do, especially where wood replacement is involved. 

Most builders today are too lazy, don't know, or just don't want the added expense of back priming. If you leave wood exposed it will decay and absorb moisture. No two ways about it. Siding may last twenty years without peeling or decaying from the elements, but it may last 30-40 if back primed. 

It's like getting a cut on your finger. You'll most likely live without much more than a band-aid, but using a dab of neosporin ensures you won't have to worry about the possible infections.


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## Steve Unkie (Jan 21, 2006)

Thanks everyone,
Backprime it is.

Steve Unkie.


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## Miniroller (Sep 19, 2006)

Best solution- Cement clapboard


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## Richard (May 21, 2006)

Miniroller said:


> Best solution- Cement clapboard


I love hardy board...


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## Steve Unkie (Jan 21, 2006)

'Hardy' would be my choice if we did'nt have to match our addition to the existing house. The existing is ceder, no backprime, great shape. But I don't like call backs so I'll backprime.

Steve Unkie.


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## metomeya (Apr 20, 2006)

Most type of primers are also sealers, its not water proof but it will help keep water out, but it also lets the material breath, so any water kept in will be able to slowly come out.


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## footfootfoot (Oct 25, 2006)

Hi everyone. New to this site and I'll make my intro here since I'd also like to ask for a clarification on the "back prime" question.

I am about to re-side a house in upstate NY with cedar and then finish with a semi transparent oil based stain. I had planned on back priming since most everyone I know agrees that is the thing to do. (That and use 15# or 30# felt intead of tyvek.

I'd always heard that the main reason to back prime was the prevent vapor pressure from inside the house pushing the paint off the siding. Reading the above posts seems that may not be what is actually going on.

My local Ben Moore paint shop tells me that back priming is not needed since I'm going to stain.

I've got about 6600 LF to back prime and it is getting late in the year for painting, we're into cold and rainy most days. As it is, I'll probably have to wait until spring to stain.

If there is a compelling reason for back priming when using an oil based semi transparent satin, I'd appreciate hearing about it. I'll set up an indoor priming shop if I have to. It's the hassle now, once. Versus the hassle later, a callback, a second time.

Thanks.


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## Brushslingers (Jul 28, 2006)

Well 3foot, it comes down to sweat from the house breathing and the oil exterior coating holding it all in, rotting from the inside out. Hope you understand what I mean.


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## footfootfoot (Oct 25, 2006)

Brushslingers said:


> Well 3foot, it comes down to sweat from the house breathing and the oil exterior coating holding it all in, rotting from the inside out. Hope you understand what I mean.


Yeah, I do. On my way to the paint shop now. I'm gonna prime and stain the siding at the same time.


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## Joewho (Sep 20, 2006)

Properly vented and insulated homes aren't in any danger from sweat. In the old days, "sweat", which is cooking, moisture and other vapors from inside, would push to the outside. At this point, back priming cedar is a long, long term precautionary measure. With todays building standards, my opinion is that backpriming cedar is overkill.


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## AAPaint (Apr 18, 2005)

Well, umm.....isn't a vapor barrier doing the same thing behind the siding? It allows moisture to escape but not enter. That's it's purpose. Therefore moisture can still linger behind the siding rotting the wood. I've seen siding taken off and the tyvek being completely wet. Back priming, IMHO, is not beyond it's day. 

Isn't a long term precautionary method a good idea anyways? Aren't we trying to help our customers protect their investment? If wood is back primed it will take a LOT longer for it to rot. If the back is exposed, it will decompose. 

Priming the back side, or even staining the back side with penatrating stains is a way to offer added value to your customers and give them the best assurance possible. Maybe it's just me, but I try to do things in the best manner possible so the customer doesn't have someone else fixing my work....EVER....and finally, the added expense and added value means added revenue and repeat business.


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