Fiber Cement Board - HardiePlank - Butt End Joints

[Andrew Kolar]

The current revision of the installation instructions from HardiePlank requires all but end joints to have "joint flashing" installed (i.e. coil stock, WRB, etc.). Are you finding a lot of installs without any butt joints flashing, caulking, etc.? When you guys find no flashing at the butt ends (i.e. you can see the Tyvek or WRB between these junctions and the top edge of the piece of siding below)... What are your recommendations?

If you are just recommending a qualified siding contractor further inspect and repair... has anybody followed up to see what their fix is?

[James Duffin]

I normally state that the siding is not installed per the manufactures installation instructions and state what I see that makes me say that....like the missing flashing or caulking. Just report what you see.

[Jerry Peck]

The current revision of the installation instructions from HardiePlank requires all but end joints to have "joint flashing" installed (i.e. coil stock, WRB, etc.). Are you finding a lot of installs without any butt joints flashing, caulking, etc.? When you guys find no flashing at the butt ends (i.e. you can see the Tyvek or WRB between these junctions and the top edge of the piece of siding below)... What are your recommendations?


My recommendation is to NOT mix up terms ... such as thinking/calling/referring to WRB as a "flashing" - it is not a "flashing" material. Even the HardiePlank installation instructions makes a distinction in Figure 2 with the "water-resistive barrier" being shown in light gray in back of everything else, and with "joint flashing**" being shown in a darker gray over the WRB, over the top of the overlapped HardiePlank piece, and under the overlapping HardiePlank piece.

[Andrew Kolar]

Thanks for the advice... However, just so you know what I was referring to, this is a quote from James Hardie, specifically regarding "Joint Flashing" materials:


"James Hardie recommends 6-in. wide flashing that overlaps the course
below by 1 in. Some local building codes may require different size flashing. Joint-flashing material must be durable, waterproof materials that do not react with cement products. Examples of suitable material include finished coil stock and code compliant water-resistive barriers. Other products may also be suitable."


So James Hardie is saying that water resistive barriers can be used as the "Joint Flashing". For instance, maybe ice and water shield. Any joint flashing would be better than no joint flashing, which is what I was originally asking about


This subject of what type of flashing or confusing terms doesn't really have anything to do with my original questions...

[James Duffin]

I inspected a new house last Thursday that had cement fiber siding with butt joints with no caulking (thank goodness!). When I peaked though the butt joints I saw what I thought was siding all the way up behind the joint. After finding a piece of siding that was a bit loose I was able to see there was a piece of metal flashing behind the butt joint that was the same color as the siding. It made for a nice job. If I see wood or white "house wrap" I write it up as not installed per the manufactures installation instructions.

[Matt Fellman]

There can be strips of house wrap used like flashing.... so, just because you see house wrap doesn't mean it's wrong. The tricky part is it must be lapped over the next course below which can be difficult to see.

I see both metal flashing strips and house wrap strips frequently.

[Jerry Peck]

Did you notice the discrepancy in what James Hardie recommends? See bold highlighting.


Thanks for the advice... However, just so you know what I was referring to, this is a quote from James Hardie, specifically regarding "Joint Flashing" materials:


"James Hardie recommends 6-in. wide flashing that overlaps the course
below by 1 in. Some local building codes may require different size flashing. Joint-flashing material must be durable, waterproof materials that do not react with cement products. Examples of suitable material include finished coil stock and code compliant water-resistive barriers. Other products may also be suitable."


So James Hardie is saying that water resistive barriers can be used as the "Joint Flashing". For instance, maybe ice and water shield. Any joint flashing would be better than no joint flashing, which is what I was originally asking about


WRB is not waterproof nor is it intended to be. It is also supposed to be protected from sunlight, thus it is not - MAY not be - "durable".

If you use WRB for that flashing and it fails years later, do you really think James Hardie is going to be on your side? Especially when they keep changing their installation instructions every year or two to correct for mistakes they have allowed in their installation instructions.

[Andrew Kolar]

I understand and agree with your point. It is just not what I had asked about... However, thank you for your insight.

[Jules Falcone]

The flashing behind the joints should last as long as the siding. This eliminates the use of a wrb or felt paper, etc. Logical choice would be aluminum coil stock painted the same color as the siding.
If it has to be installed on a job that was installed without a proper flashing, the aluminum can be bent into a soft curve and slid up, behind the joint. The slight bend will hold it into place without a nail.

[brian schmitt]

i have always been under the impression that aluminum and cement (siding) don't mix. i think galvanized metal would be a better match perhaps!

[Kristi Silber]

When I've installed fiber cement board we used squares of roofing felt under the joints.