HomeMy WebLinkAbout07092008 BSC Agenda Item 4
EXCAVATIONS AND UNDERGROUND STRUCTURES
The key issues regarding excavations and underground structures are as follows:
1. A. Should the underground structure project into the yards and if so, then how much?
Should the excavation area be allowed to project into the yards? (ZPC)
Table 7-6 of the Zoning Regulations lists t:liose iterns allowed to project into the regulated
yards. Underground items are not restricted at all as to the l.irnits of their encroachment
into these yards. Conceivably, a basement would technically be allowed to span the
er:ttire building site from property litre to property line unrestricted.
B. Should underground structures be allowed on narrow lots taking the 3/7 alternate side
yard exception?
Narrow lots (Less than 55' wide) are given an option to use alternate side yards. This i.s
allowed to cn.courage rear situated gara>es. If a structure built underground on a narrot~-
site is constructed when taking the alternate side setback allowance, should there be
limits and restrictions on the proximity of the basement wall and the excavation to
adjoining property lines.
2. If an underground structure is allowed in the yard areas, should there be special rules for
lot drainage regulations? (BSC)
Chapter 1.13 provides regttlation.s for building site drainage and controlling the runoff rage
based on a F per hour rainfall. Slabs on grade will provide a srnall arnoun.t of pervious
area iinderneath the foundation for water absorption. If a full basement is built. will this
impact the drainage in a significant enough manner to require additional drainage
measures not specified in Chapter 18?
3. Underground structures in the 100 year floodplain are strictly controlled. Should there be
additional regulatory language controlling the basements outside the 100 year
floodplain?(BSC)
Enclosed portions of structures located in the 100 year floodplain which are below the
lase flood elevation are not allowed unless they meet criteria established in Section 8323
of' the 2003 IRC and Chapter IS :Article IX of the city"s Code of Ordinances. There are
no similar regulations for structures outside the floodplain.
4. Should there be additional engineering criteria for the foundations of underground
structures? (BSC)
M
Appendix C of the Code of Ordiriances deals with the 'Technical Codes rind amendments
to those codes. West. U has anrendrnents dealing with regt6reme.nts for different types of
foundations. Basement walls are not addressed in this arnendrnent. Section 8403 of the
2003 IRC addresses sorne aspects of basement construction, but does not tiddress
proximity to tidjitcent sites, depth of excavation, etc.
5. Should the area included within the walls of an underground structure be counted toward
framed area? (ZPC)
Framed area definition in Article 2 of the Zoning Regulations lists basements of a certain
depth. and less than 8' ceiling, height as an exemption to inclusion in the framed area
calculations.
6. Should the area included between the floor and ceiling of an underground structure be
counted as a story? (ZPC)
The current definition of a story in the zoning regulations would include the basement as
a story for compliance with the. 2 1,~z story rule. If certain basements do riot count toward
f'rarrred area, then shotdd they be counted as a story'? Or if we count the basement area as
a story, should it be counted toward the niaximttzn allowable framed area?
7. What types of uses of an underground structure will be allowed? (ZPC or BSQ
Any enclosure located below base flood elevation is limited to barking, access to the
structure, and story Te. We could. limit a basement to these uses only sand riot allow- any
habitable areas in a basernent.