Cement Fiber Butt Joints

[R Clark]

Our house was built in 2004, with the shop building built in 2005.  Both structures are stick framed, and both are sided with cement fiber lap siding.  I don't know if this is HardiePlank or another brand.  We bought the house in 2014.

The butt joints on the longer pieces have plastic trim between adjoining pieces of lap siding.  Since we moved in ten years ago, some of the plastic trim siding has slipped out of place and I've pushed them back into position.  For the first time, one of the pieces has fallen off the house.  Here are the pics:

Up near the top of this picture you can see where the trim cap has fallen out of the joint.

   

This is what fell out:

   

First:  I need to get this plastic cap back in.  However, if I just slide it back in, it will slide back out.  I think I'm going to put a little dab of acrylic caulk on one side to act as an adhesive to hold it in place.  I don't know what else to do; if anybody has any thoughts, I'm willing to listen.

In researching these plastic trim pieces in the butt joints, I think I'm coming to the conclusion that they were NOT intended to be used on cement fiber siding.  James Hardie's install instructions say to butt the adjoining pieces together with NO gap over a small piece of metal flashing directly that is installed behind each joint.  Those instructions say nothing about using plastic joint trim in the manner I see on my house.

Further, as far as I can tell from my searches, cement fiber planks do not expand and contract significantly like vinyl or wood.  The installation gap as seen in the picture above appears to point to an incorrect installation.  I don't think the situation is "fixable", short of residing the house.  All of the lap siding has these gaps at the butt joints.  Caulking all of these joints would result in the siding looking like (excrement).  

I have not had issues with water intrusion and the house is wrapped with Tyvek under the siding.

Any inputs on the way ahead are also welcome.  Am I as "stuck" in this situation as I think I am?

[Snipe Hunter]

I've never seen those but that is basically the flashing between the planks. You need flashing between the planks. I'd try to figure out the manufacturer and get more of those. I don't like them, rather see nailed on aluminum flashing like Hardie specifies. Used to be we caulked the gaps. Then got away from it because the caulk fails. Most manufacturers recommend each plank be "in contact" with the next plank with aluminum flashing behind the joint but not caulked. So you have something with it's own unique flashing. I would assume if you called a builder supplier and described it, they might lead you to a manufacture. I assume your siding expands and contracts more than Hardie and the like and they came up with some sort of clip-on floating flashing. Might think about gluing on one side so they don't fall out. Leave the other side un-glued so it can still float.

[R Clark]

I've never seen those but that is basically the flashing between the planks. You need flashing between the planks. I'd try to figure out the manufacturer and get more of those. I don't like them, rather see nailed on aluminum flashing like Hardie specifies. Used to be we caulked the gaps. Then got away from it because the caulk fails. Most manufacturers recommend each plank be "in contact" with the next plank with aluminum flashing behind the joint but not caulked. So you have something with it's own unique flashing. I would assume if you called a builder supplier and described it, they might lead you to a manufacture. I assume your siding expands and contracts more than Hardie and the like and they came up with some sort of clip-on floating flashing. Might think about gluing on one side so they don't fall out. Leave the other side un-glued so it can still float.

I'm certain the laps are cement fiber.  I have some leftover from the construction up in the loft.  I had to make a repair a couple of years ago on the back of the house.  The stuff cut like cement fiber, and it acts like cement fiber.  In fact, four years ago, it failed in a spot like fiber cement (see thread from 2020).

I've now looked at two different manufacturer's installation instructions.  One was James Hardie, and the other is a brand called "Allura" and it's sold at Menards.

Consistent with what you said above, both brands instruct installers to butt the ends together with no spacer.  They also call for aluminum flashing behind the butt joint with no caulk.  Here's a screen capture of the Allura instructions.  James Hardie is essentially the same.

   

So, here's what I did for my problem.  Since I can't correct the gap between the ends of the lap planks, the plastic butt joint trim is going to have to go back into place.  But first, I cut a piece of aluminum flashing and slid it into place behind the butt joint.  It's nailed into place using an electro-galvanized roofing nail.  Then as you suggested, I put some acrylic caulk on the upper portion butt end of one side of the open joint and slid the butt joint trim into place.  The caulk will act as adhesive.

That plastic piece is called "butt joint trim" on Home Depot's web site.  HD's product description says it's for use with composite lap siding.

[jteneyck]

You might consider getting some aluminum coil stock the same color, if possible, and bending pieces into J strips, or having someone make them for you.  I'd make them wider than those plastic pieces.  Put some silicone caulk on one plank, then slide the J strip up under the course above the joint with the J going under the bottom of the two planks.  I suppose you could drill a hole through the plank above the J strip and install a small brad to hold it in place, as an alternative fastening approach.  

John

[MKepke]

Ray - the I-butt joint cover *is* (or was) an approved method. See explanation here.

https://www.howtolookatahouse.com/Blog/E...iding.html

-Mark

[R Clark]

Ray - the I-butt joint cover *is* (or was) an approved method.  See explanation here.

https://www.howtolookatahouse.com/Blog/E...iding.html

-Mark

Thanks for that...I must admit my willingness to believe the original installers "did it wrong" has probably been influenced by my experience with the HVAC guys in that link I posted above.  James Hardie installation instructions that I downloaded said nothing about those joint covers, so I guess it's no longer considered a recommended method.

Anyway, since it was done with the large gap and the "H" or "I" joint cover, it's going to have to remain that way for both the house and the shop building.  I did buy a roll of aluminum flashing for the spot repair of other joints.  The aluminum flashing is to provide a backup behind that cover piece.

[MstrCarpenter]

I know your siding doesn't require painting often, but I think John's idea of covering the open joint with thin flashing (possibly even wood grained) would be an effective and more visually appealing way of dealing with those gaps once and for all. I also wouldn't count on Typar to keep water out. On all my jobs with cedar clapboards, every butt joint gets a 3" wide piece of felt paper so any water intrusion gets diverted back onto the exposed surface. Of course every butt joint also got primed, painted, and left with a nickel gap to be caulked before the finish coat.

In the meantime, on a quick search for " 1/2" plastic H channel" I found several results that would work for any missing pieces.

[R Clark]

I know your siding doesn't require painting often, but I think John's idea of covering the open joint with thin flashing (possibly even wood grained) would be an effective and more visually appealing way of dealing with those gaps once and for all. I also wouldn't count on Typar to keep water out. On all my jobs with cedar clapboards, every butt joint gets a 3" wide piece of felt paper so any water intrusion gets diverted back onto the exposed surface. Of course every butt joint also got primed, painted, and left with a nickel gap to be caulked before the finish coat.

In the meantime, on a quick search for " 1/2" plastic H channel" I found several results that would work for any missing pieces.

Thanks.

I haven't lost any of those H channel covers to this point.  Some have gotten loose and slid down a little bit, but until this past week, I've only pushed them back into place.

I'm kind of "stuck" with the original configuration.  If the house and shop were one story structures, I might approach it differently.  But, there's plenty of tall outer walls, some up to 30+ feet tall.  I'll spot fix what needs to be fixed.  My plan is that "fix" will be to slide the flashing behind the joint, fasten it in place, and then replace the H channel.  I'll fix what needs to be fixed when it needs to be fixed.

[vernonator]

Our house was built in 2004, with the shop building built in 2005.  Both structures are stick framed, and both are sided with cement fiber lap siding.  I don't know if this is HardiePlank or another brand.  We bought the house in 2014.

The butt joints on the longer pieces have plastic trim between adjoining pieces of lap siding.  Since we moved in ten years ago, some of the plastic trim siding has slipped out of place and I've pushed them back into position.  For the first time, one of the pieces has fallen off the house.  Here are the pics:

Up near the top of this picture you can see where the trim cap has fallen out of the joint.



This is what fell out:



First:  I need to get this plastic cap back in.  However, if I just slide it back in, it will slide back out.  I think I'm going to put a little dab of acrylic caulk on one side to act as an adhesive to hold it in place.  I don't know what else to do; if anybody has any thoughts, I'm willing to listen.

In researching these plastic trim pieces in the butt joints, I think I'm coming to the conclusion that they were NOT intended to be used on cement fiber siding.  James Hardie's install instructions say to butt the adjoining pieces together with NO gap over a small piece of metal flashing directly that is installed behind each joint.  Those instructions say nothing about using plastic joint trim in the manner I see on my house.

Further, as far as I can tell from my searches, cement fiber planks do not expand and contract significantly like vinyl or wood.  The installation gap as seen in the picture above appears to point to an incorrect installation.  I don't think the situation is "fixable", short of residing the house.  All of the lap siding has these gaps at the butt joints.  Caulking all of these joints would result in the siding looking like (excrement).  

I have not had issues with water intrusion and the house is wrapped with Tyvek under the siding.

Any inputs on the way ahead are also welcome.  Am I as "stuck" in this situation as I think I am?

Our house built in '04 had the same thing, thats how they did it back then. We had the same issue, of them dropping out. Dab of caulk did the trick. Only fix is to re-side the house.

[rudedan60]

Our house built in '04 had the same thing, thats how they did it back then. We had the same issue, of them dropping out. Dab of caulk did the trick. Only fix is to re-side the house.

I installed Fiber Cement on my house in 2002 after my vinal siding was holed during a hail storm. At that time they said to chauk the joint with some flashing behind it.  The issue I have is I painted mine. Overtime the joints expand and the paint cracks. So far I still have the original paint job I did so I have not touched it. If I did it again, I would flash behind the joint, paint it, then use a clear chaulk that would not be painted.