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Alternative to PT sill plates

Discussion in 'Residential Foundation Codes' started by Jambe, Aug 13, 2018.

  1. Jambe

    Jambe Registered User

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    Just for the sake of discussion, what would be required for a sill plate on a concrete foundation wall to not have to be pressure treated? (Think untreated Timberstrand plate. Strandguard is getting difficult to obtain.)

    What could be placed between the concrete and the untreated plate to make it acceptable?

    How about a layer or two of water and ice shield, along with the sill sealer foam?

    Or some material like (1/8") plastic.

    I know, someone will say just use PT wood! But I would like to know what alternatives there are that would be allowed by code.
     
  2. cda

    cda Sawhorse

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    Welcome

    Give it a day or two for great responses
     
  3. ICE

    ICE Sawhorse

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    California residential code: R317.1
     
  4. cda

    cda Sawhorse

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  5. mark handler

    mark handler Sawhorse

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    You need pressure treated lumber when:
    Sills and sleepers on a concrete or masonry slab that is in direct contact with the ground unless separated from such slab by an impervious moisture barrier.
    This includes the footing.
     
    Keystone likes this.
  6. Jambe

    Jambe Registered User

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    Thanks for your replies.

    Is water and ice shield acceptable as an "impervious moisture barrier?
     
  7. Joe Engel

    Joe Engel Member

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    IMO, I would accept it along with products designed to seal the plate, but i'm having second thoughts now whether felt paper would be acceptable. What about beam or bunk wrapping material?
     
  8. mark handler

    mark handler Sawhorse

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    Ask the manufacturer.

    "Grace Ice & Water Shield" is for roofing applications. Due to product "off gassing", They had a big lawsuit when some were using it for windows under stucco.
     
  9. Pcinspector1

    Pcinspector1 Platinum Member

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    Sill sealer is a moisture barrier, also depends if your below grade.

    Borate treated lumber (Blue color) is available in some areas as an alternative to ACQ PT lumber.

    Not sure redwood is still allowed or not, $$$$
     
  10. tmurray

    tmurray Sawhorse

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    We sometimes see poly vapour barrier used for this purpose.
     
  11. khsmith55

    khsmith55 Bronze Member

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    I used Bituthene cut in 6" strips for decades until Grace came out with Vycor in 4"
    and 6" rolls, which I spec now, works great.
     
  12. conarb

    conarb Sawhorse

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    QUOTE="Pcinspector1, post: 185530, member: 161"]
    Not sure redwood is still allowed or not, $$$$[/QUOTE]

    "Foundation Grade Redwood" is no-longer milled, but I've had "Clear Heart Redwood" approved as an alternative with no problems. Seems a shame to hide beautiful wood like that, but if there are no acceptable alternatives what are you going to do?
     
  13. Francis Vineyard

    Francis Vineyard Sawhorse

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    "Jambe, post: 185496, member: 17827"]Just for the sake of discussion, what would be required for a sill plate on a concrete foundation wall to not have to be pressure treated? (Think untreated Timberstrand plate. Strandguard is getting difficult to obtain.)

    What could be placed between the concrete and the untreated plate to make it acceptable?

    R317.1 does not permit an impervious moisture barrier between the sill plate and foundation wall in lieu of preservative treated or naturally durable wood.

    The exception is for sills and sleepers on slabs. This manner of construction is prescriptively done with a "6-mil polyethylene or approved vapor retarder placed between the concrete floor slab and the base course or the prepared subgrade where no base course exists" in accordance with R506.2.3. The same applies to monolithic slabs for the footing (at which the rebar can no longer serve as a UFER!)

    The alternative for foundation walls is if the sill is at least 8-inches from the exposed ground. I believe you would be hard pressed to find an impervious moisture barrier that is approved directly under sills for this purpose. Additionally we may often see some sort of rubber or bitumen material under the ends of girders, it is not prescribed nor an alternative is provided if the clearance is less in item 4.

    R317.1 Location required. Protection of wood and wood based 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.

    1. Wood joists or the bottom of a wood structural floor when closer than 18 inches or wood girders when closer than 12 inches to the exposed ground in crawl spaces or unexcavated area located within the periphery of the building foundation.

    2. All wood framing members that rest on concrete or masonry exterior foundation walls and are less than 8 inches from the exposed ground.

    3. Sills and sleepers on a concrete or masonry slab that is in direct contact with the ground unless separated from such slab by an impervious moisture barrier.

    4. The ends of wood girders entering exterior masonry or concrete walls having clearances of less than 1/2 inch on tops, sides and ends.
     
  14. Jambe

    Jambe Registered User

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    Interesting.

    Just for the record, I am in Utah and have to adhere to the 2015 IRC, and will be putting the sill plate on an ICF wall. What I am hearing from Francis Vineyard is that the sill must be treated lumber—no alternatives are acceptable.

    I have to wonder what the code author was thinking when he said it is okay for wood to be separated from concrete on a slab by an impervious moisture barrier but it is not okay for wood to be similarly separated from the concrete of a foundation wall. In what way is the concrete different?

    Actually, on a slab the concrete can pick up moisture but it can't pick up moisture in an ICF foundation wall.
     
  15. my250r11

    my250r11 Sawhorse

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    All wood in these areas is to be treated. As well as in contact with masonry or concrete.
     

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