Cement Fiber Board - Water Resistant Barrier

[Mickey Roach]

We are building a detached garage that will be siding (cement fiber board) on 3 sides. I noticed that there was no water barrier or anything used (Tyvek was used on the house, which was 95% brick and rock).

I was concerned about moisture harming the plywood underneath. Is it OK that there is no barrier?

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[Steven Turetsky]

I would have sealed the plywood with a liquid applied moisture barrier. Good time to install flashing (if any), seal the moisture barrier overlapping the flashing.

[Mickey Roach]

I would have sealed the plywood with a liquid applied moisture barrier. Good time to install flashing (if any), seal the moisture barrier overlapping the flashing.

Unfortunately, the siding is already on. Trying to determine if I need to demand it be taken off and have a barrier installed or not.

[Steven Turetsky]

I would... flashing too.

[Ray Norton]

Not required. This is a copy of the code section:

R703.2 Water-resistive barrier.

One layer of No. 15 asphalt
felt, free from holes and breaks, complying with ASTM D 226
for Type 1 felt or other approved water-resistive barrier shall be
applied over studs or sheathing of all exterior walls.

Exception:

Omission of the water-resistive barrier is
permitted in the following situations:

1. In detached accessory buildings.

[Steven Turetsky]

Not required. This is a copy of the code section:

R703.2 Water-resistive barrier.

One layer of No. 15 asphalt

felt, free from holes and breaks, complying with ASTM D 226

for Type 1 felt or other approved water-resistive barrier shall be
applied over studs or sheathing of all exterior walls.

Exception:

Omission of the water-resistive barrier is

permitted in the following situations:
1. In detached accessory buildings.

Are you saying it is "better" without a moisture barrier? I recommend using some type of internal moisture barrier when applying anything directly on wood sheathing or any sheathing where moisture intrusion is a concern.

[Rick Cantrell]

Even though building codes may not require a WRB, check with the manufacturer instructions on if there is a requirement for use of WRB.

[Jerry Peck]

I was concerned about moisture harming the plywood underneath. Is it OK that there is no barrier?

Not required.

"not required" and "I was concerned" along with "Is it OK" are completely different things.

The moisture barrier is required to help keep moisture and the weather out, whether or not it is code required or not (keep in mind that the code is a *minimum* standard, *not* good practice).

You are correct that you should be concerned about not having a moisture barrier behind the HardiePlank. "Is it OK" is another question, and that answer is mostly likely "nope, it will not be OK in the long run".

Then there are the manufacturer's installation instructions which need to be considered and followed as an additional *minimum standard* along with the code's *minimum standard*.

James Hardie HardiePlank installation instructions states:
- A water-resistive barrier is required in accordance with local building code requirements. The water-resistive barrier must be appropriately installed with penetration and junction flashing in accordance with local building code requirements. James Hardie will assume no responsibility for water infiltration. James Hardie does manufacture HardieWrap™ Weather Barrier, a non-woven non-perforated housewrap1, which complies with building code requirements.

[Jeff Zehnder]

JP got to it…the code is only a portion of the necessary requirements needed to build properly. Manufacturer’s specification must also be followed or technically there is an out for any warranty claims. It was penny wise and dollar foolish to finish the building this way!

[Wayne Carlisle]

James Hardie HardiePlank installation instructions states:
- A water-resistive barrier is required in accordance with local building code requirements. The water-resistive barrier must be appropriately installed with penetration and junction flashing in accordance with local building code requirements. James Hardie will assume no responsibility for water infiltration. James Hardie does manufacture HardieWrap™ Weather Barrier, a non-woven non-perforated housewrap1, which complies with building code requirements.

That could be interpreted differently.... - A water-resistive barrier is required in accordance with local building code requirements.

"Required in accordance with local building code requirements."

If the code that is adopted locally doesn't require a WRB then I don't see how you could enforce it.

Is it a good idea? Yes! Required? I don't believe it is.

[Fred Weck]

I think the bigger question (since the other posters have shown that code does not require it) is... Did you pay for it? Is it listed in your contract?
If it is in the contract then it should be on the building, or you should be getting a reduction in the price of the contracted work.

[Jerry Peck]

Before I continue ... ... how many say the IRC does, or does not, require the house wrap behind the HardiePlank?

[Wayne Carlisle]

If the surface to which the hardi plank is installed on requires it then yes. If the surface is water resistant then no.

OSB would require an overlayment that is water resistant. Some of the other exterior sheathings that are water resistant do not need an underlayment.

That is why the manufactuer istallation procedure says...
- A water-resistive barrier is required in accordance with local building code requirements.

[Ray Norton]

The IRC does not require WRB on detached accessory buildings. However the IRC also states:

R102.4 Referenced codes and standards.

The codes and standards referenced in this code shall be considered part of the requirements of this code to the prescribed extent of each such reference. Where differences occur between provisions of this code and referenced codes and standards, the provisions of this code shall apply.

Exception:

Where enforcement of a code provision would violate the conditions of the listing of the equipment or appliance, the conditions of the listing and manufacturer’s

instructions shall apply.

The manufacturer's instructions apply, which in this case do not seem to be stricter than the code. I am not saying it is better or if I agree with it. As a municipal building inspector I am only authorized to enforce the code not my opinion. I am glad that home inspectors draw attention to potential problems and if you can get them to house wrap it thats great. But you can't enforce things beyond the code, can you?

[Jerry Peck]

Not required.

Ray,

You've quoted that section twice, have you read the section above it?

R703.1 General.
Exterior walls shall provide the building with a weather-resistant exterior wall envelope. The exterior wall envelope shall include flashing as described in Section R703.8.

If the siding does not provide such, and HardiePlank does not, then a WRB (or some other means of creating a weather-resistant exterior wall) *is* required behind it. Even if the next section on WRB says differently.

Remember:
- R102.1 General. Where, in any specific case, different sections of this code specify different materials, methods of construction or other requirements, the most restrictive shall govern. Where there is a conflict between a general requirement and a specific requirement, the specific requirement shall be applicable.

[Fred Weck]

IRC Table 703.4, under fiber cement lap and panel siding, the column for whether a water resistive barrier is required has a footnote x in the 2006 version (in the 2012 IRC, it is footnote u), both direct you back to the exceptions in section 703.2. As you'll recall the exception allows the ommission of the barrier in detached accessory buildings.

The products legacy evaluation report NER 405 states:
The exterior plank and panel products installed on exterior walls shall be installed over a weather resistive barrier in accordance with applicable codes.

The applicable code (703.2) allows the barrier to be ommitted.

[Wayne Carlisle]

I agree if it is an accessory building as the original post indicated.