# Caulking Hardie plank siding



## A+HomeWork

My prospect is having me bid this lake house to paint this summer. I even get to stay there while I work!
My question is this: Is is ok to caulk all the horizontal boards across this porch side of the house? He says they have had bad storms blowing 40 mph rain up and under the siding and wants me to caulk every one of the lap boards all the the way across the house.
I was thinking the siding needs to breath. Would it hurt to only caulk one side since that's where the problem occurs?


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## Bender

$6800.00


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## straight_lines

I would not caulk it. Explain that it traps moisture, and if he insists make him sign a waiver.

Nice house btw.


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## WisePainter

I've done it before at the request of the H.O. and my fingers are still healing. He was a proven C.M. and this was his custom dream home, so I did it.
He even rented me a lift...nice.


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## jacob33

I have seen it both ways. It could crack out on you though as the house expands and contracts and that looks terrible. If you do I would use a caulking that stretches like big stretch but that stuff is expensive.


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## NEPS.US

Never caulk horizontals.


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## CliffK

My instincts tell me it's a mistake. Maybe touch base with a Hardie Plank rep and get their take on it. We don't see that much Hardie Plank siding in this area. We've only worked on a few and never caulked the lap. How much does that stuff expand and contract? I imagine their is a breathable house wrap under that siding? To seal it up that tight sort of defeats the purpose and could cause some issues I would think?


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## LA Painter

I just used 20 cases of SherMax on a Hardie Siding job - per the HO's insistence. Caulked EVERYTHING! Primed, and finished with two coats of Super Paint. Looks awesome. Hardie isn't going to expand/contract like wood. The studs it's nailed to may move, but I doubt enough to cause any cracking. We'll see...


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## Schmidt & Co.

CliffK said:


> Maybe touch base with a Hardie Plank rep and get their take on it.
> 
> 
> 
> You can never go wrong by following the manufactures spec's. :thumbsup:
Click to expand...


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## A+HomeWork

CliffK said:


> My instincts tell me it's a mistake. Maybe touch base with a Hardie Plank rep and get their take on it. We don't see that much Hardie Plank siding in this area. We've only worked on a few and never caulked the lap. How much does that stuff expand and contract? I imagine their is a breathable house wrap under that siding? To seal it up that tight sort of defeats the purpose and could cause some issues I would think?


I will contact the owner. He had it built. I think he is mainly concerned about the siding around the upper fixed windows. He is not wanting the entire house caulked.


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## Bill Thomas

LA Painter said:


> I just used 20 cases of SherMax on a Hardie Siding job - per the HO's insistence. Caulked EVERYTHING! Primed, and finished with two coats of Super Paint. Looks awesome. Hardie isn't going to expand/contract like wood. The studs it's nailed to may move, but I doubt enough to cause any cracking. We'll see...


 
On the contrary fiber-cement siding expands and contracts much more than wood or wood-fiber hardboards. 

www.ScottsPainting.com


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## Gough

Bill Thomas said:


> On the contrary fiber-cement siding expands and contracts much more than wood or wood-fiber hardboards.
> 
> www.ScottsPainting.com


Not only that, but, unlike wood, it does so in both width and length.


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## Gough

If the HO was problems with water intrusion, I'm guessing that the drainage plane under the siding wasn't properly detailed. Caulking the bottom edges would be a mistake, and would probably cause even more problems.


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## NEPS.US

Bill Thomas said:


> On the contrary fiber-cement siding expands and contracts much more than wood or wood-fiber hardboards.





Gough said:


> Not only that, but, unlike wood, it does so in both width and length.


If Hardie's are not finished to spec they will crumble in no time.


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## Wolfgang

They use Hardi for probably 75% of the tract home siding here. Pure junk. Have never caulked the underside seam due to moisture trapping issues. One of the biggest hassles is sealing the lower edge. One nick or ding and darn near the whole edge will swell and rot.

One of the biggest problems we have here, is the foliage and plants the HO decides to put right against the foundation. Add to that, in-ground sprinkler systems and you have the perfect recipe for siding failure. I can't even begin to to tell how many jobs I've done where I either replace the bottom siding course or trimmed it up 3 1/2 inches and added a 1x4 pine "ledger board", or one of the composite products if the HO was willing to pay the price. Oil prime the board, caulk with a polyurethane caulk, and it was good to go. I've had some on their 15th year and still looking good.


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## straight_lines

The thing about hardi is that it is a great surface to paint, but caullking joints tend to fail faster. This is usually caused by improper installation, and there should be a 1/8 gap the the ends where it meets windows or corners. 

The installers almost never caulk the butt joints properly either. They are supposed to be done behind the joint and caulk squeeze out when the butt is put together.

I do alot of my exteriors in hardi, and we are on the coast many right on the beach. No other place inland will ever have that much water intrusion through the siding.


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## Gough

straight_lines said:


> The thing about hardi is that it is a great surface to paint, but caullking joints tend to fail faster. This is usually caused by improper installation, and there should be a 1/8 gap the the ends where it meets windows or corners.
> 
> The installers almost never caulk the butt joints properly either. They are supposed to be done behind the joint and caulk squeeze out when the butt is put together.
> 
> I do alot of my exteriors in hardi, and we are on the coast many right on the beach. No other place inland will ever have that much water intrusion through the siding.


I don't know about the other fiber cement siding manufacturers, but Hardie is very speciifc about NOT caulking butt joints. The detail that we see omitted most often is joint flashing. This is a spline of felt or some other material to ensure that water that makes its way through the butt joint is directed back out and over the top of the next course down.


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## A+HomeWork

Wolfgang said:


> They use Hardi for probably 75% of the tract home siding here. Pure junk. Have never caulked the underside seam due to moisture trapping issues. One of the biggest hassles is sealing the lower edge. One nick or ding and darn near the whole edge will swell and rot.
> 
> I can't even begin to to tell how many jobs I've done where I either replace the bottom siding course or trimmed it up 3 1/2 inches and added a 1x4 pine "ledger board", or one of the composite products if the HO was willing to pay the price. Oil prime the board, caulk with a polyurethane caulk, and it was good to go. I've had some on their 15th year and still looking good.


 Are you referring to concrete board? I know pressed board does that, but I have not seen Hardi-board swell because of nicks or dings. I don't want to argue about whether it's junk or not. I personally think its the best choice over masonite or OSB type siding. Builders are going to use it anyway. I'd prefer they used Hardi. I have dealt with rotted siding too.

I will get a ladder up there and see if the window sills are sheding water correctly. There is evidence of water on the inside wall.


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## A+HomeWork

Gough said:


> If the HO was problems with water intrusion, I'm guessing that the drainage plane under the siding wasn't properly detailed. Caulking the bottom edges would be a mistake, and would probably cause even more problems.


So, since this siding has been in place for a few years, is it ok to caulk the vertical seams with painter's caulk? Wouldn't that allow the siding to expand and contract? Looking at the picture provided, I might caulk the pieces between the tall verical fixed windows. Those shorter pieces won't expand and contract that much, would they?
I really don't want to caulk 5 miles of siding, so this will help me better explain what the procedure should be.

Also, I spray and back-brush the bottoms of every board when painting siding. It looks better and protects against moisture and mildew.

Thanks for everyone's input.


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## straight_lines

Gough said:


> I don't know about the other fiber cement siding manufacturers, but Hardie is very speciifc about NOT caulking butt joints. The detail that we see omitted most often is joint flashing. This is a spline of felt or some other material to ensure that water that makes its way through the butt joint is directed back out and over the top of the next course down.


 After I read your reply I went to the James Hardie site and didn't see anything about not caulking the butts. It did mention corners, and windows but nothing at all about butts. I have seen the joint flashing once or maybe twice.


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## Gough

straight_lines said:


> After I read your reply I went to the James Hardie site and didn't see anything about not caulking the butts. It did mention corners, and windows but nothing at all about butts. I have seen the joint flashing once or maybe twice.


Here's the link to the Hardie pages on installation:

http://www.jameshardie.com/pdf/install/hardieplank-hz5.pdf

The instructions for hz10 and Canada are identical in that regard.


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## briancreary

It is possible to make a home TOO air tight and trap moisture comming from inside the home. I would tread lightly, and definitly would not caulk all horizontals. The last thing this guy wants in his dream home is to see his drywall screws leaking rust through the interior paint and black mold.


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## LOSTinDETAILS

NEPS.US said:


> Never caulk horizontals.


Winner winner chicken dinner!


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## Charisb

*Caulking butt joints*

I'm late to the discussion here, but let me give you the perspective of a sealant manufacturer: don't caulk butt joints! Fact is - there is not enough space there for proper joint design (2 point adhesion). This is all besides the fact there there is also not enough room there for a sufficient bead. The most that fits is a 1/8" bead. With such a small bead, there is simply not enough bulk there to both adhere to the joint and stretch properly. Even the stretchiest caulk in the world would readily fail.

All of that to say - don't do it! Hardi and Certainteed both recommend metal joint flashing at butt joints. Sashco always recommends against caulking them.

Of course, if you really want to help us stay in business, feel free to caulk (and re-caulk and re-caulk and re-caulk) all of those butt joints. We're happy to sell you our product! :thumbup:


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## michaelsaam

The answer is no. Big MISTAKE. That siding still has to breath and if moisture gets in it needs a way to get out. GOod way to make the paint blister. Might look good but the end result is gonna put your name to shame or gonna have you back on the job fixing it. I would highly recommend not doing it. Ask your paint rep or even a general contractor. I ve been on some jobs where yes i agree it would even make the job look better but dont put yourself on the hook for a disaster. www.mikespaintingonline.com


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## A+HomeWork

*Update*



michaelsaam said:


> The answer is no. Big MISTAKE. That siding still has to breath and if moisture gets in it needs a way to get out. GOod way to make the paint blister. Might look good but the end result is gonna put your name to shame or gonna have you back on the job fixing it. I would highly recommend not doing it. Ask your paint rep or even a general contractor. I ve been on some jobs where yes i agree it would even make the job look better but dont put yourself on the hook for a disaster. www.mikespaintingonline.com


I plan to help the owner determine the cause of the leaking. He had the house built and may have to contact his builder, who is adding another room to the back. I will not be caulking other than a few spots where there is a need. I am pretty sure there is another reason water is getting in around those upper windows.

Thanks to all who chimed in on this thread!


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## SemiproJohn

I know I'm posting on an ancient thread, but just wanted some recent confirmation concerning whether to caulk the butt joints on newly installed pre-primed Hardie siding (the yellow kind).

I've been on the James Hardie site, and it says there to only caulk the butt joints if a gap recommended by caulking manufacturers was properly maintained. They recommend a type of flashing that is installed behind the butt joints.

I'm thinking I only should caulk verticals, specifically where the siding meets trim at the corners only. I want the stuff to breath and I can't see how caulking the butt joints is going to be good for this or for the actual appearance of the siding over time. I was going to use Tower Tech II caulking, as I know that stuff is rated for this kind of use.

What say you? Leave all horizontals and butt joints alone, and only caulk verticals at corner trim?


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## Gough

SemiproJohn said:


> I know I'm posting on an ancient thread, but just wanted some recent confirmation concerning whether to caulk the butt joints on newly installed pre-primed Hardie siding (the yellow kind).
> 
> I've been on the James Hardie site, and it says there to only caulk the butt joints if a gap recommended by caulking manufacturers was properly maintained. They recommend a type of flashing that is installed behind the butt joints.
> 
> I'm thinking I only should caulk verticals, specifically where the siding meets trim at the corners only. I want the stuff to breath and I can't see how caulking the butt joints is going to be good for this or for the actual appearance of the siding over time. I was going to use Tower Tech II caulking, as I know that stuff is rated for this kind of use.
> 
> What say you? Leave all horizontals and butt joints alone, and only caulk verticals at corner trim?


The yellow kind of pre-primed?? I've only seen grey pre-primed Hardie.

If the butt joints are properly flashed, caulking them would be only for aesthetic reasons. If they aren't flashed, I would first try to install flashing. If that doesn't work, I would caulk them to reduce water infiltration behind the Hardie.


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## stelzerpaintinginc.

*Caulking butt joints in hardie-plank siding.*



SemiproJohn said:


> I know I'm posting on an ancient thread, but just wanted some recent confirmation concerning whether to caulk the butt joints on newly installed pre-primed Hardie siding (the yellow kind).
> 
> I've been on the James Hardie site, and it says there to only caulk the butt joints if a gap recommended by caulking manufacturers was properly maintained. They recommend a type of flashing that is installed behind the butt joints.
> 
> I'm thinking I only should caulk verticals, specifically where the siding meets trim at the corners only. I want the stuff to breath and I can't see how caulking the butt joints is going to be good for this or for the actual appearance of the siding over time. I was going to use Tower Tech II caulking, as I know that stuff is rated for this kind of use.
> 
> What say you? Leave all horizontals and butt joints alone, and only caulk verticals at corner trim?



It may be an ancient thread, but it's still a topic in debate, and a valid question. Also goes to show how much searching you did before you even asked. Best suggestion I could offer would be to contact the siders, should be easy since it was just sided. Ask them if they flashed behind the butt joints, and ask their recommendation. More often than not, the siders have already caulked everything that needs to be caulked. If no flashing was used behind the butts and they don't advise against, it, you can caulk it if you or your customer wants it caulked. However, if flashing was installed in lieu of caulking butts, and/or the siders specifically recommend against caulking butts, do not do it. This process takes the guesswork and culpability out of the hands of the painter as much as possible.


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## lilpaintchic

NO. If the siding is properly installed there should be no issues you will create a mountain of issues by caulking them. Properly installed, the siding expands, contracts and drains. Caulking any of that will potentially cause boards to crack as they won't be able to move like they're supposed to. It will also increase the likelihood of water becoming trapped vs. Draining properly.

Oops, old thread.


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## RH

Years ago when I resided my house with HP, they weren't telling you not to caulk butt joints - so I did. Have never had a bit of issue as a result of it. 

When the new addition got sided two years ago, I didn't caulk the butt joints as per instructions and IMO, it looks like crap. Tempted to just say screw it and go back and caulk them anyway.


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## SemiproJohn

stelzerpaintinginc. said:


> It may be an ancient thread, but it's still a topic in debate, and a valid question. Also goes to show how much searching you did before you even asked. Best suggestion I could offer would be to contact the siders, should be easy since it was just sided. Ask them if they flashed behind the butt joints, and ask their recommendation. More often than not, the siders have already caulked everything that needs to be caulked. If no flashing was used behind the butts and they don't advise against, it, you can caulk it if you or your customer wants it caulked. However, if flashing was installed in lieu of caulking butts, and/or the siders specifically recommend against caulking butts, do not do it. This process takes the guesswork and culpability out of the hands of the painter as much as possible.


I was out to this job on Friday afternoon. They had only just started installing the furring strips. I was called by the owner/customer this morning and he said all the siding was up and ready for me. I am hoping the owner knows whether flashing was installed behind the butt joints. He's operating a large farm and is so busy I rather doubt it. I'm sure the siding guys are gone, but perhaps he can give them a ring.

I have a tight deadline to complete the exterior and interior painting, and am just wanting no issues now, but especially in the future. I also read on the Hardie site that if caulking is used on the butt joints, expect it to be a maintenance issue over time. They are very ambivalent about whether to caulk or not to caulk the butt joints on the pre primed siding. The only firm "no" they give about this pertains to the pre-finished Hardie siding with color fast technology. Perhaps they are concerned about liability/warranty issues, I don't know. This is the only question mark, but I will explain what you, Gough, and Lilpaintchic advised and let him make the decision. I hate when I am not 100 percent certain about proper procedures. yet I always strive to do the right thing. When I'm not sure it's the right thing....I ask those more experienced than I. Thus, I'm here! I appreciate everyone's input.


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## SemiproJohn

Gough said:


> The yellow kind of pre-primed?? I've only seen grey pre-primed Hardie.
> 
> If the butt joints are properly flashed, caulking them would be only for aesthetic reasons. If they aren't flashed, I would first try to install flashing. If that doesn't work, I would caulk them to reduce water infiltration behind the Hardie.



It seems the yellow variety is common down here. It's a terrible picture, but here's a stack of the stuff (I wasn't trying to get the stack in the picture. It just appeared in spite of things, as it were).

This place is about 35 miles away from my home, and about 5 miles from any signs of civilization.


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## lilpaintchic

If those butt joints are to be caulk ed it gets done by the siding company at time of installation, not over the seams after install but between the joints as they go along.
See, the biggest problem goes wayyyyyy back to LP and vulkem. Remember the striped communities? Crappy product and they kept going over the butts when harding was first introduced. Know what happened? It makes a smooth spot, the vulkem wasn't compatible with the hardi primer so eventually one side would split because of expansion and contraction. Then quad became the "go to". They still went over the seams instead of between. Expansion and contraction was causing siding to break (especially if a nail was driven into a corner first). And the caulk would still crack as it wasn't between the surfaces, it was over the gap. Finally some contractors figured it out that the best way (that I've experienced anyway) was to quad at time of installation as they go along which allows the caulk to do its job. The problem comes when the seasons change. It only looks "good" when it's the same season as the install. Otherwise there are white (insert caulk color here) stripes where paint isn't present due to(drumroll....) expansion. It appears cracked. It's the paint that's usually cracked, not the caulk in that scenario. That's just my 2 cents worth of experience. Worth just about as much. I just know I've made a lot of money pulling caulk out of butt joints over the last let's say "few"--(as in more than I'd like to admit so I don't feel so old, haha) years. To each their own I guess...maybe it's somewhat dependent on region also.?


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## Gough

lilpaintchic said:


> NO. If the siding is properly installed there should be no issues you will create a mountain of issues by caulking them. Properly installed, the siding expands, contracts and drains. Caulking any of that will potentially cause boards to crack as they won't be able to move like they're supposed to. It will also increase the likelihood of water becoming trapped vs. Draining properly.
> 
> Oops, old thread.


That's an awfully big "if" in my experience. 

I scarcely pass by a HardiPlank job without taking a good look at the installation. The big three improper details: insufficient clearance over window or door heads; insufficient clearance above roofs, grade, sideways, decks, etc; and failure to install spline flashing at butt joints. I can't recall EVER seeing another job where these three were done according to the James Hardie specifications.

If there are no flashings at the butt joints, water intrusion behind the siding is virtually guaranteed. At least the missing spline flashing can often be dealt with reasonably. Adding the flashing is not especially difficult on blind-nailed installations. If it's face-nailed or pinned back, caulking is about the only solution.

While it might be possible to cause wood siding to crack by caulking it so tightly that it can't expand and contract, I've yet to see that happen with fiber-cement...and I've seen a lot of crappy fiber-cement jobs. Caulk, especially low-quality caulk, will fail long before the siding.


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## Gough

SemiproJohn said:


> It seems the yellow variety is common down here. It's a terrible picture, but here's a stack of the stuff (I wasn't trying to get the stack in the picture. It just appeared in spite of things, as it were).
> 
> This place is about 35 miles away from my home, and about 5 miles from any signs of civilization.


Thanks! I just remembered about the "HardiZone System". You're in HZ10, and the primer there is yellow.


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## SemiproJohn

Gough said:


> Thanks! I just remembered about the "HardiZone System". You're in HZ10, and the primer there is yellow.


Yes! I saw the two zones depicted on the James Hardie site. By the way, I tried clicking on the link you provided all those years ago and it wasn't active, but it did provide a link to their current site, which I scoured for anything and everything caulking related, so thanks for that!


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## RH

When they did my addition a few years back, the HP was also yellow. Well, kind of a sickly greenish yellow (think Oregon Ducks ).


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## Gough

RH said:


> When they did my addition a few years back, the HP was also yellow. Well, kind of a sickly greenish yellow (think Oregon Ducks ).


Well, you are in HZ10, the same as FL, TX, and those other dry, sunny states.


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