Concrete BuildingsCity of Alameda

Concrete Coalition Toolkit

Dave McCormick

Number of hazardous concrete buildings in California.

1. Estimate number of pre-1980 concrete buildings in specific jurisdictions.◦ Capture buildings constructed with 1973 UBC or earlier

2. Extrapolate to estimate number in state.

3. Perform studies to determine which are most hazardous. (PEER)

What Are We Looking For?

Category NumberTotal Number of Buildings ATotal Number of Concrete Buildings BPre-1980 Buildings CPre-1980 Concrete Buildings D

What to Count?

Concrete Building Types Count Data

Optional – Other Databases Available1

Do Not Count Data

City Buildings XCounty Buildings XState Buildings XPost Offices XCounty and State Courthouses XFederal Office Buildings and Courthouses XHospitals Regulated by OSHPD XUtility-Owned Bldgs. Including Substations XGrade K-12 Public Schools XUC and CSU XCommunity Colleges X

1 volunteers must indicate if they counted these building types

Concrete Building Types Count Data

Optional – Other Databases Available1

Do Not Count Data

Prisons XSpecial Districts including Pump Stations and Buildings at Treatment Plants

X

Churches XPort Buildings XRegional, County, and city Parks X

1 volunteers must indicate if they counted these building types

Concrete Building Types Count Data

Optional – Other Databases Available1

Do Not Count Data

Concrete Frame with Masonry Infill XWood-frame residential on Conc. Podium X1-Story Cast-in Place Concrete with wood Roof (including walls with pilasters)

X

Concrete Shear Wall with Steel Gravity Frame XMixed Construction2 XTilt-ups XDual System with Concrete Shear Wall3 XParking Garages XBuildings Whose Concrete Elements are Limited to Fire Walls Between Sections

X

Buildings Whose Concrete Elements are Limited to Basement or Retaining Walls

X

2 Includes horizontal additions of concrete as well as buildings with concrete lateral load systems in one direction only.

3 Do not need to make exceptional efforts to verify whether a building has a dual system or not, but if you know, don’t count it

Concrete Building Types Count Data

Optional – Other Databases Available1

Do Not Count Data

Retrofitted Buildings4 XAbandoned Buildings XBuildings in Areas Scheduled for Redevelopment

X

Building-like Nonbuilding Structures5 XNonbuilding-like Nonbuilding Structures6 XConcrete Structures Supported on Piers or Wharfs over Water

X

Buildings used for storage – No Occupancy X

4 Obtain approximate retrofit date is possible.

5 Includes campanile, substation and pumping stations.

6 Includes silos, tanks, bridges, canopies, covered walkways and monuments.

Do not include concrete block buildings without concrete walls.

City of Alameda

Strategy “Walk” the City (bike ride actually)

◦ Focus in commercial districts and where larger buildings are located Used knowledge of City Alternate approach would be to use Google

Contact Building Official and ask for help◦ Assessor data◦ Zoning map◦ Sanborn maps

Visit library Re-walk part of the City Review Sanborn maps again Walk small part of the City one more time

Walk the City “Walk” the City

◦ Use knowledge of the City to: Identify the buildings already known to be concrete Look in likely locations like commercial districts

◦ Record data on form that would provide more than information currently required by the Coalition including photograph

◦ Troublesome areas: No access to some military installations Some buildings are conglomerations of building types Modified buildings

Supplies– Map– Clip board– Camera– Previous lists– Panniers

Envisioned Survey FormAddress Number

of Stories

Torsional?

Frame or Shear

Wall

Photo Other

1 Main 2 Yes, corner

building

Frame with

masonry infill

1, 2 Adjacent wood frame buildings with no gap at

property lines

2 3rd St 2 No Shear wall

3, 4 See what appears to be wall anchors at roof

66 Oak 1 Yes, open front

? 5, 6 It looks like concrete, should verify

53 Elm 3 No Frame 7, 8 Looks like first floor is soft story, much greater

floor height

Data Sheet Used

No. of Stories 1

Irregularities Open front

Occupancy Commercial

Adjacency One side

Condition No deterioration observed

Comments Verified concrete

Brick veneer

Parapet bracing

1538 Webster/Alameda Pizza +

Tricks to Identify Concrete Buildings Walk behind the building

– fewer architectural finishes◦ Look for form boards

Look inside Look for elevated

floor/cripple wall – probably wood◦ Vents

Knock on wall Differentiate from tilt-

ups Look for retrofit

1546 Park

Looks like brick in front

Concrete in the back

1328 Park

Concrete in the back

Tilt-ups

Look for joints or pliasters

Contact Building Official

Building officials generally have excellent information about their jurisdictions◦ Could ask him/her to estimate number of concrete buildings◦ Ask which areas are post-1980 construction◦ Where would older concrete buildings like be found?

Mr. Greg McFann was very helpful◦ Had member of his staff access the Assessor data

Total number of buildings in Alameda 18,868 Total number of pre-1980 buildings Alameda – 12,674

◦ Provided zoning map that helped identify residential districts that can be eliminated

◦ Provided access to Sanborn Maps

Zoning Map

Naval Air Station

Bay Farm Island

Oakland

Zoning Map

Skip one family residential – few in other residential areas

Area 5

20

Sanborn Maps• Used by the insurance industry and updated until

about mid-1980s in Alameda. SERENDIPTY!• Able to get through the book in about 4 hours with

assistance of Marguerite Bello, S.E.• Issues:

Some buildings uncertain, require field verification. Some buildings may have been torn down but

Building Official said that is a rare occurrence. Large portion of the City – Naval Air Station – not

covered by Sanborn Maps.

Sanborn Map

Sanborn Maps – Note Taking

What if Sanborn Maps Had Been Older?

Need to find an approach for estimating the number of concrete buildings not included on Sanborn maps that were constructed prior to 1980.◦ Use of historic aerial photos◦ Building department records◦ Guidance from building official◦ Judgment/Estimates

Library Search

Lots of historic buildings listed in studies.◦ Attempting to get buildings qualified for

National Historic Building Register Lots of studies authored by Woody Minor –

Architect Discovered lots of interesting things about

Alameda unrelated to the study.

Library Search Walking Tour of Alameda’s Historic Downtown & Civic

Center District. 1977 Unreinforced Masonry Buildings Survey. 1980.

Woodruff Minor California Department of Parks and Recreation –

Historic Resources Inventory. Webster Street Commercial Area.

Survey of Pre-1945 Commercial Buildings, City of Alameda. Woodruff Minor.

Historic Commercial Buildings of Alameda. 1993. Woodruff Minor.

A Guide for Historical Research in Alameda. The Alameda Architectural/History Survey. Woodruff Minor. 1979.

Alameda: The Island City. 1941.

Sample Data from Library ReferenceBuilding Name Historic Building Name Current Address # Address Street

Reinf. Conc. Age Stories Structure Type Comments

Gibson, William W., Machine Shop/Neptune Bowl Fred's Wrench-house 647 Buena Vista Ave Yes 1938, 1939 1 RC walls with corrugated metal roof

Two rectangular shapes built separately into one building

Alameda Printing Company Schroeder-Dent, Inc. 741 Buena Vista Ave Yes1933, 1964-

1965 1 RC with gable roof.Addition in back in 1964-1965 to house equipment

Neptune Court Neptune Court 600 Central Ave 1925-1926 4 Wood frame

Safeway Store/New Island Market Thrifty Jr. Drug Store 704-710 Central Ave Yes 1941, 1955 1 RC, probably with wood roof 1955 is CMU 2-story residential addition

Marina Court Marina Court 726-736 Central Ave 1918, 1923 Wood frame Group of 10 buildings of mixed use

Browning, Henry, Garage None 650 Haight 1916 Wood frame

Naval Air Lockers/Courtesy Cleaners Divers Exchange 649 Pacific Ave 1941 1 BrIck

Luben Bros. West End Livery Stable Hay Barn Tony's Body & Fender Works 651 Pacific Ave 1893 1 & 2 Wood frame 1 story garage and 2 story barn

Britt's Hotel/Encinal Hotel/Pioneer Hotel/Croll's Croll's or Croll Building 1400-1410/705Webster Street/ Central Ave

1879, 1907, 1908, 1978-

1982 Wood frame Multiple phases.

Black, Henry and Catherine, Rental House None 1423-A Webster Street 1895 1 Wood frame

Probst, Louis and Maria, Building Santos Liquors 1425-1431 Webster Street 1878-1879, 1907-1908 2 Wood frame Original plus addition

Stelling, Martin, Building None 1432-1436 Webster Street Yes 1941 1 RC and brick walls

Lucky Store No. 9 Grand Auto Store 1440 Webster Street Yes 1941, 1969 1 RCGutted by fire in 1967. Garage bay and fenestration added at that time.

Alameda/Savings Bank/American Trust Co./Wells Fargo Bank Trans Pacific National Bank 1442 Webster Street Yes 1917, 1946 Brick, RC Original brick, 1-story east addition RC

Stelling, Martin, and Scales, Dixie Building None 1443-1453A Webster Street Yes 1941 1 RC Piers with brick infill

Alameda Dairy Co. Tillies 1500 Webster Street Yes 1916, 1940 1 Wood frame and concrete Concrete storage room added in rear

Building List Developed list of buildings by combining

◦ List from initial walkthrough◦ List from Sanborn Map ◦ Lists from library research.

Number of locations where there were conflicts◦ 10-15% of buildings

Did some verification with Google maps

Re-walk the City Sanborn maps identified a large number of buildings I did

not observe during initial walkthrough◦ Some turned out to be demolished◦ Some were inaccurately identified by maps◦ Some were correctly identified – I missed them in walkthrough◦ Some were behind other buildings, often small garage type

structures for residences or canopies for multi-unit residences My initial walkthrough seems to have included 85% of final

total.◦ Probably good enough.

Revisit Sanborn Maps After re-walking there were still a number of

structures where my walkthrough disagreed with the Sanborn maps, but there was some uncertainty due to limited access. ◦ Made one more visit to the City to look at the Sanborn

maps. I noticed some things during the second review of

the maps that I had missed the first time.

I made one more trip to a few buildings to come to a final conclusion.

Added Up My Buildings There are a number of buildings that I did not

count because:◦ They were unoccupied storage buildings◦ They are wood warehouses separated into sections by

concrete firewalls◦ They are podium structures with concrete block shear

walls Southshore Center buildings extensive remodel –

best estimate is 6 additional pre-1980 concrete buildings.

Ended up with 24 pre-1980 buildings not sure about.

Summary of Alameda DataNumber Final Count

Total Number of Buildings 18,868

Total Number of Concrete Buildings 138 + k(24)

Pre-1980 Buildings 12,674

Pre-1980 Concrete Buildings 126 verified + k (24)(24 uncertain)

Tilt-up Buildings 68 (not included above)

Note: this is all we are asking be done. Lists and photographs are extra efforts that are appreciated but not necessary.If you count schools, etc. Identify them in your list.

Schools with Concrete Buildings

Chipman

Alameda High

Encinal High

…..

Summary Initial walkthrough identified about 85% of total

buildings Relying on Sanborn Maps alone would not have

been relatively accurate.◦ Error: inaccurate structure type assignment

Large military presence resulted in areas where Sanborn Maps did not address.◦ Identification of building age primarily based on judgment

Many of buildings counted are obviously not high seismic risks.◦ One-story, lots of shear walls.◦ Not your job to figure out now.

Summary Older buildings of mixed construction due

additions are problematic.◦ Counted buildings with significant concrete

portions. It is quite possible that a number of podium

type residential structures were missed (parking under wood frame residential structures).

Add photo

Summary

Southshore – main shopping, was constructed in 1950s, added onto and recently remodeled. ◦ The construction type is uncertain. ◦ Had to assume number of old concrete buildings. ◦ Theoretically if they are high risks they may have been

retrofitted.◦ Data should be available at City Hall

Summary Walking into a number of structures could

decrease the uncertainty in the number of structures.

Included count of tilt-up buildings for completeness◦ Problems with addresses changing in newer buildings

constructed in the 1980s. Concrete schools and hospitals were observed

and noted but not counted.