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One- and Two-Family Dwellings (UDC) - Frequently Asked Questions


SPS 321

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Manufactured Home FAQ

Deck Codes SPS 321.225


Can we still use the UDC deck codes that we have always been using or is Appendix B the new code we have to enforce?   How does Appendix C affect decks? 


The department has determined that a deck can be built per the following methods effective January 1, 2016:



SPS 321.225 Decks. (1) Decks attached to dwellings and

any detached decks that serve an exit shall comply with the applicable

provisions of subchs. II to X of ch. SPS 321, including all

of the following:

(a) Excavation requirements under s. SPS 321.14;

(b) Footing requirements under s. SPS 321.15 (2) (f);

(c) Frost penetration requirements under s. SPS 321.16;

(d) Load requirements under s. SPS 321.02;

(e) Stair, handrail and guard requirements of s. SPS 321.04.

(f) Decay protection requirements of s. SPS 321.10.



SPS 321.225 (2) A deck that complies with the standards in ch. SPS 320-325 Appendix B, and ch. SPS 320-325 Appendix C, if applicable, shall be considered as complying with sub. (1).  Meaning, you would follow Appendix B and C exclusively.



Also, the department has determined that a deck designed and constructed to the DCA6 standard, (Prescriptive Residential Deck Construction Guide-2012 IRC version by The American Would Council,) would be considered code compliant.  The decision was based on several factors which included the following:

-Based on prior analysis by the department, the DCA6 standard met or exceeded Wisconsin Uniform Dwelling Code requirements. 

-The DCA6 standard is primarily based on NDS standards, which the Department also adopts in SPS 320.24

-Finally, utilizing the DCA6 standard would in fact be considered a form of structural analysis which is accepted under the scope of SPS321.02(2).  


NOTE: You may not “mix and match” the options, meaning take parts from Appendix B then use parts of SPS 321.225(1).



Garage Penetrations SPS 321.08


I am inquiring about holes in an attached garage.  Is there any code that requires the sealing of holes in the garage?  We do seal all holes and boxes on the common wall but we have been cited twice for not sealing in the garage.


Yes, holes created in fire separations dwellings and garages must be protected.  This includes holes that were drilled for wiring and not used.


SPS 321.08(1)(a) requires fire separation of dwelling units from attached garages.

SPS 321.08(3)(b) specifically addresses penetrations by electrical and plumbing components.


SPS 321.08(3)(b) (b) Electrical and plumbing components. Penetrations of a required separation by electrical and plumbing components shall be firmly packed with noncombustible material or shall be protected with a listed through−penetration firestop system with a rating of at least one hour.



Habitable Rooms in Basements SPS 321.05(2) & 323.02(3)(c)


I have a question regarding habitable rooms in basements without openable windows. In a rec room or theater room in the basement with no openable windows, SPS323.02 (3) (c) states a balanced mechanical ventilation system producing one air change per hour of fresh outside air while room is occupied must be provided.  Does a simple exhaust fan in the basement rec room qualify for this ventilation?


No, you cannot simply exhaust air from the habitable room.  There are two codes that require fresh outside air be brought in while in use for habitable rooms without openable windows.  Fenestration air through leakage does not apply towards this.  The codes are listed below:


SPS 321.05 Natural ventilation.

(2) VENTILATION. (a) 1. Balanced mechanical ventilation may be provided in lieu of openable exterior doors, skylights or windows provided the system is capable of providing at least one air change per hour of fresh outside air while the room is occupied.


SPS 323.02 (3) VENTILATION. (c) Habitable rooms.

Habitable rooms without openable windows shall be provided with a balanced mechanical ventilation system producing one air change per hour of fresh outside air while the room is occupied.


Is the required mechanical ventilation required to be tied into a light switch so it's on when the room is occupied?


The fan has to be tied to a switch that’s readily accessible however the code is silent as to whether it must be directly tied to a light switch.  We do encourage you to consider the use of an occupancy sensor tied to the ventilation exhaust/makeup air system.



Ramp Footings SPS 321.16


I am looking for clarification on whether or not a ramp requires frost protection for landings that are built into the ramp. When you read SPS 321.16 (1) it states landings  shall be placed below the frost penetration level or least 48” below adjacent grade. Do all landings require frost protection?


The code section below exempts the landings contained within the ramp. If the top of the ramp were to abut a landing or stoop with frost protected footing, then only that end of the ramp would need to comply.  The rest of the ramp does not.


SPS 321.16 Frost protection. (1) EXCEPTIONS.

(d) Subsection (1) (a) does not apply to the footing for a ramp and its handrail posts unless the ramp abuts a frost−protected stoop or landing, in which case only the footing for that abutting end of the ramp is required to have the frost protection under sub. (1) (a), such as by bearing onto the stoop or landing, so that a tripping hazard is not created.

Note: See ch. SPS 325 Appendix A for further information.

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