2304.12.1.2 Wood supported by exterior foundation?

[hans@dha-architects.]

I had inquired about this a while ago but can't find the thread - what do you think, I have a building with slab on grade floor and top of foundation wall is flush with the slab, which is less than 8" above grade, that section states that any wood framing members or wood sheathing in contact with foundation walls shall be of naturally durable or pressure treated wood - so, obviously the sill is pressure treated, the sheathing will be flush with the outside of the foundations so my CI can run straight down the entire wall, so, two pronged question - if the sheathing were to set, lets say 1/4" above the slab, would it need to be PT? there will be sill seal, so technically it wouldn't be touching even without a gap, or is that grasping? second, we're using zip panels - would they be considered naturally durable? they're not pressure treated.....really just trying to avoid having to have a 12" strip of pressure treated plywood at the bottom of the wall if I can, frankly the wall will be covered with continuous foam insulation from footing to eaves, so there won't be any exposure to earth regardless, so I'm not terribly concerned about moisture or termites being an issue.

 

[hans@dha-architects.]

I had inquired about this a while ago but can't find the thread - what do you think, I have a building with slab on grade floor and top of foundation wall is flush with the slab, which is less than 8" above grade, that section states that any wood framing members or wood sheathing in contact with foundation walls shall be of naturally durable or pressure treated wood - so, obviously the sill is pressure treated, the sheathing will be flush with the outside of the foundations so my CI can run straight down the entire wall, so, two pronged question - if the sheathing were to set, lets say 1/4" above the slab, would it need to be PT? there will be sill seal, so technically it wouldn't be touching even without a gap, or is that grasping? second, we're using zip panels - would they be considered naturally durable? they're not pressure treated.....really just trying to avoid having to have a 12" strip of pressure treated plywood at the bottom of the wall if I can, frankly the wall will be covered with continuous foam insulation from footing to eaves, so there won't be any exposure to earth regardless, so I'm not terribly concerned about moisture or termites being an issue.

I guess Zip wouldn't be naturally durable as by definition IBC says can only be the heartwood of a few species of wood, so there goes that option

 

[RLGA]

Just to clarify, are the studs flush with the face of the stem wall, or are they set back so the sheathing will be flush with the stem wall?

 

[hans@dha-architects.]

Just to clarify, are the studs flush with the face of the stem wall, or are they set back so the sheathing will be flush with the stem wall?

there is no stem wall, which is why I have this situation, so top of foundation is at floor level. the studs are set back from the foundation edge by 1/2" so that the sheathing will sit on (or maybe not) the foundation wall, so sheathing and foundation are flush

 

[RLGA]

there is no stem wall, which is why I have this situation, so top of foundation is at floor level. the studs are set back from the foundation edge by 1/2" so that the sheathing will sit on (or maybe not) the foundation wall, so sheathing and foundation are flush

Technically, a stem wall is the foundation wall that extends from the footing to the surface of the slab or above. But either way, you provided the clarification I was seeking.

I would interpret the code literally. If the sheathing is not in "contact" with the concrete, then PTW or naturally durable wood would not be required.

 

[hans@dha-architects.]

Technically, a stem wall is the foundation wall that extends from the footing to the surface of the slab or above. But either way, you provided the clarification I was seeking.

I would interpret the code literally. If the sheathing is not in "contact" with the concrete, then PTW or naturally durable wood would not be required.

that's how I would read it, and that quarter inch gap I would caulk as well - I just don't know how the building official will interpret it, he's a very "by the book" type.

 

[RLGA]

that's how I would read it, and that quarter inch gap I would caulk as well - I just don't know how the building official will interpret it, he's a very "by the book" type.

If he is "by the book" as you say, then "in contact with exterior foundation walls" should be interpreted exactly as it is written. If he questions it, ask him this: "Is the sheathing in contact with the exterior foundation wall or with the framing only?"

There is only one correct answer.

 

[TheCommish]

does number 5 of 317.1 come into play?

PROTECTION OF WOOD AND WOOD-BASED
PRODUCTS AGAINST DECAY
R317.1 Location required. Protection of wood and woodbased
products from decay shall be provided in the following
locations by the use of naturally durable wood or wood that is
preservative-treated in accordance with AWPA U1 for the
species, product, preservative and end use. Preservatives shall
be listed in Section 4 of AWPA U1.

5. Wood siding, sheathing and wall framing on the exterior
of a building having a clearance of less than 6
inches (152 mm) from the ground or less than 2 inches
(51 mm) measured vertically from concrete steps,
porch slabs, patio slabs and similar horizontal surfaces
exposed to the weather.

 

[RLGA]

does number 5 of 317.1 come into play?

PROTECTION OF WOOD AND WOOD-BASED
PRODUCTS AGAINST DECAY
R317.1 Location required. Protection of wood and woodbased
products from decay shall be provided in the following
locations by the use of naturally durable wood or wood that is
preservative-treated in accordance with AWPA U1 for the
species, product, preservative and end use. Preservatives shall
be listed in Section 4 of AWPA U1.

5. Wood siding, sheathing and wall framing on the exterior
of a building having a clearance of less than 6
inches (152 mm) from the ground or less than 2 inches
(51 mm) measured vertically from concrete steps,
porch slabs, patio slabs and similar horizontal surfaces
exposed to the weather.

Probably not, if the project is not subject to the IRC. Even it if was, #5 addresses vertical distance from the ground or horizontal surface. If the foundation wall in OP's post is more than 6 inches above the ground, then I would say it complies. The 2-inch vertical distance only applies to horizontal surfaces exposed to the weather. The foundation wall will eventually be covered with an exterior wall covering and not be exposed to the weather.

 

[hans@dha-architects.]

does number 5 of 317.1 come into play?

PROTECTION OF WOOD AND WOOD-BASED
PRODUCTS AGAINST DECAY
R317.1 Location required. Protection of wood and woodbased
products from decay shall be provided in the following
locations by the use of naturally durable wood or wood that is
preservative-treated in accordance with AWPA U1 for the
species, product, preservative and end use. Preservatives shall
be listed in Section 4 of AWPA U1.

5. Wood siding, sheathing and wall framing on the exterior
of a building having a clearance of less than 6
inches (152 mm) from the ground or less than 2 inches
(51 mm) measured vertically from concrete steps,
porch slabs, patio slabs and similar horizontal surfaces
exposed to the weather.

This building is under IBC, so if there is a similar section in it, which I don’t believe there is, then it might…..I hope there’s not!

 

[hans@dha-architects.]

Probably not, if the project is not subject to the IRC. Even it if was, #5 addresses vertical distance from the ground or horizontal surface. If the foundation wall in OP's post is more than 6 inches above the ground, then I would say it complies. The 2-inch vertical distance only applies to horizontal surfaces exposed to the weather. The foundation wall will eventually be covered with an exterior wall covering and not be exposed to the weather.

Yes, project is IBC (apartment building) my issue is half the building I probably only have a couple inches between grade and finish floor (slab), but I will have continuous foam insulation protecting the sheathing as well.

 

[TheCommish]

2015 IBC section 2304.12

2304.12 Protection against decay and termites. Wood shall
be protected from decay and termites in accordance with the
applicable provisions of Sections 2304.12.1 through
2304.12.7.

2304.12.1.5 Wood siding. Clearance between wood
siding and earth on the exterior of a building shall not
be less than 6 inches (152 mm) or less than 2 inches (51
mm) vertical from concrete steps, porch slabs, patio
slabs and similar horizontal surfaces exposed to the
weather except where siding, sheathing and wall framing
are of naturally durable or preservative-treated
wood.

Also consider termites, bugs, ants or the landscaping material that my be used around the base of the building being a pathway fo bad things happening to the building.

 

[hans@dha-architects.]

2015 IBC section 2304.12

2304.12 Protection against decay and termites. Wood shall
be protected from decay and termites in accordance with the
applicable provisions of Sections 2304.12.1 through
2304.12.7.

2304.12.1.5 Wood siding. Clearance between wood
siding and earth on the exterior of a building shall not
be less than 6 inches (152 mm) or less than 2 inches (51
mm) vertical from concrete steps, porch slabs, patio
slabs and similar horizontal surfaces exposed to the
weather except where siding, sheathing and wall framing
are of naturally durable or preservative-treated
wood.

Also consider termites, bugs, ants or the landscaping material that my be used around the base of the building being a pathway fo bad things happening to the building.

Siding I’m good with, using hardie plank, I guess I’m wondering if the foam insulation will provide protection for the sheathing, I have one inch continuous down to top of footing, and an additional inch of plaster faced foam from top of footing to 8” above slab/top of wall, then hardie above, so the sheathing will never be exposed in any way. All wall panels are pre-fab and typically use full height zip panels so there’s no seam blocking. Heck, I have 8” exposed foundation on my house and while stripping the siding last year found the rim board full of termites, if they want to get in, they’ll find a way

 

[Robert]

Siding I’m good with, using hardie plank, I guess I’m wondering if the foam insulation will provide protection for the sheathing, I have one inch continuous down to top of footing, and an additional inch of plaster faced foam from top of footing to 8” above slab/top of wall, then hardie above, so the sheathing will never be exposed in any way. All wall panels are pre-fab and typically use full height zip panels so there’s no seam blocking. Heck, I have 8” exposed foundation on my house and while stripping the siding last year found the rim board full of termites, if they want to get in, they’ll find a way

correct. That's part of the reason the code has those clearances....not just for decay but to see the vertical termite tubes. I'm in an older stucco home where the stucco was allowed to run below the soil....no weeps. It's a wonderful clean look but I've had termites and I'll never be able to see where they get in.

 

[hans@dha-architects.]

correct. That's part of the reason the code has those clearances....not just for decay but to see the vertical termite tubes. I'm in an older stucco home where the stucco was allowed to run below the soil....no weeps. It's a wonderful clean look but I've had termites and I'll never be able to see where they get in.

Good point, i’ve just been reading about that lately, hadn’t really given that much thought before….I’m thinking of applying a termite barrier by Polyguard - I’d overlap top of foundation and up sheathing 12”, then overlap the top of that with an L shaped piece that’d cover the top of the rigid - so I’d have a break in the rigid, so if they do tunnel up, they’ll hit the barrier at that break and either go back from where they came or come out the side, if they can - I’m using that rigid with the stucco coating on the one side from top of footing to 4’ above, termite barrier, then 1” regular xps rigid above. They do make a borate infused eps rigid foam board, which could be an option as well