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Basement Performance Levels - What is dry?

GRADE OF BASEMENT RELATIVE HUMIDITY TEMPERATURE PERFORMANCE DAMPNESS LEVEL OF WETNESS
Grade 1Basic Utility >65% Normal UK External Range. Car Parks: Atmospheric, Workshops: 15-29 degrees C. Mechanical Plantrooms 32 degrees C Maximum at ceiling level. Visible damp patches may be acceptable. Minor seepage may be acceptable.
Grade 2 Better Utility 35-50%

Retail Storage: 15 degrees C Maximum.

Electrical Plantrooms 42 degrees C Maximum.

No visible damp patches, construction materials to contain  less than the air dry moisture content. None Acceptable.
Grade 3 Habitable

40-60%

55-60% for a restaurant in Summer

Offices: 21-25 degrees C. Residential 18-22 degrees C.

Leisure Centres:

18 degrees C Spectators.

10 degrees C Squash Courts.

22 degrees C for changing rooms.

24-29 degrees C Swimming Pools.

18-25 degrees C Restaurants.

 

None Acceptable: Active Measures to Control internal humidity may be necessary. None Acceptable.
Grade 4 Special

50% for art Storage.

>40% for Microfilms & Tapes

Art Storage 18-22 degrees C.

Book Archives 13-18 degrees C.

Active Measures to control internal humidity probably essential. None Acceptable

 

Grade 1 - Some water leaks may be permissible. No requirement for relative humidity control.

Grade 2 - No leaks Permissible. There will seldom be a need for relative humidity control.

Grades 3 & 4 - No leaks permissible. Relative humidity to be kept to a level appropriate for the usage of the basement.