What is the white chalky substance on my walls?

County: Anderson TN
Clinton
Lake City
Norris
Oak Ridge

County: Bedford TN
Bell Buckle
Shelbyville
Wartrace

County: Bledsoe TN
Pikeville

County: Blount TN
Alcoa
Friendsville
Louisville
Maryville
Rockford
Townsend

County: Bradley TN
Charleston
Cleveland

County: Campbell TN
Caryville
Jacksboro
Jellico
La Follette

County: Cannon TN
Auburntown
Woodbury

County: Cheatham TN
Ashland City
Kingston Springs
Pegram
Pleasant View

County: Claiborne TN
Cumberland Gap
Harrogate
New Tazewell
Tazewell

County: Clay TN
Celina

County: Cocke TN
Newport
Parrottsville

County: Coffee TN
Manchester
Normandy
Tullahoma

County: Cumberland TN
Crab Orchard
Crossville
Pleasant Hill
Spring City

County: Davidson TN
Belle Meade
Berry Hill
Forest Hills
Goodlettsville
Lakewood
Millersville
Nashville-Davidson
Oak Hill

County: DeKalb TN
Alexandria
Dowelltown
Liberty
Smithville

County: Dickson TN
Burns
Charlotte
Dickson
Slayden
Vanleer
White Bluff

County: Fentress TN
Allardt
Jamestown

County: Franklin TN
Cowan
Decherd
Estill Springs
Huntland
Winchester

County: Giles TN
Ardmore
Elkton
Lynnville
Minor Hill
Pulaski

County: Grainger TN
Bean Station
Blaine
Rutledge

County: Grundy TN
Altamont
Beersheba Springs
Coalmont
Gruetli-Laager
Palmer

County: Hamblen TN
Morristown

County: Hamilton TN
Chattanooga
Collegedale
East Ridge
Lakesite
Lookout Mountain
Red Bank
Ridgeside
Signal Mountain
Walden

County: Hickman TN
Centerville

County: Jackson TN
Gainesboro

County: Jefferson TN
Baneberry
Dandridge
Jefferson City
New Market
White Pine

County: Knox TN
Farragut
Knoxville

County: Lawrence TN
Ethridge
Iron City
Lawrenceburg
Loretto
St. Joseph

County: Lewis TN
Hohenwald

County: Lincoln TN
Ardmore
Fayetteville
Petersburg

County: Loudon TN
Greenback
Lenoir City
Loudon
Philadelphia

County: Macon TN
Lafayette
Red Boiling Springs

County: Marion TN
Jasper
Kimball
Monteagle
New Hope
Orme
Powells Crossroads
South Pittsburg
Tracy City
Whitwell

County: Marshall TN
Chapel Hill
Cornersville
Lewisburg

County: Maury TN
Columbia
Mount Pleasant
Spring Hill

County: McMinn TN
Athens
Calhoun
Englewood
Etowah
Niota

County: Meigs TN
Decatur

County: Monroe TN
Madisonville
Sweetwater
Tellico Plains
Vonore

County: Montgomery TN
Clarksville

County: Moore TN
Lynchburg

County: Morgan TN
Oakdale
Sunbright
Wartburg

County: Muray TN

County: Overton TN
Livingston

County: Pickett TN
Byrdstown

County: Polk TN
Benton
Copperhill
Ducktown

County: Putnam TN
Algood
Baxter
Cookeville
Monterey

County: Roane TN
Harriman
Kingston
Oliver Springs
Rockwood

County: Robertson TN
Adams
Cedar Hill
Coopertown
Cross Plains
Greenbrier
Orlinda
Ridgetop
Springfield
White House

County: Rutherford TN
Eagleville
La Vergne
Murfreesboro
Smyrna

County: Scott TN
Huntsville
Oneida
Winfield

County: Sequatchie TN
Dunlap

County: Sevier TN
Gatlinburg
Pigeon Forge
Pittman Center
Sevierville

County: Smith TN
Carthage
Gordonsville
South Carthage

County: Sumner TN
Gallatin
Hendersonville
Mitchellville
Portland
Walnut Grove
Westmoreland

County: Trousdale TN
Hartsville

County: Union TN
Luttrell
Maynardville
Plainview

County: Van Buren TN
Spencer

County: Warren TN
Centertown
McMinnville
Morrison
Viola

County: White TN
Doyle
Sparta

County: Williamson TN
Brentwood
Fairview
Franklin
Nolensville
Thompson's Station

County: Wilson TN
Lebanon
Mount Juliet
Watertown