Floor Slab Isolation Joint

Joints are commonly spaced at distances equal to 24 to 30 times the slab thickness.

Floor slab isolation joint.

Joint spacing that is greater than 15 feet require the use of load transfer devices dowels or diamond plates. Isolation joint material should go all the way through the slab starting at the subbase but should not extend above the top. Expansion joints which are really isolation joints permit differential settlement of the wall and the floor. The idea is to reduce restraint so your slab doesn t crack.

Joint spacing in feet contraction joints may be tooled into the concrete surface at the time of placement. Expansion joints are used in pavements to provide for thermal and moisture induced movement of the slab. The joint free slab. A contraction joint is formed sawed or tooled groove in a concrete structure to create a weakened plane to regulate the location of cracking resulting from the dimensional change of different parts of the structure.

Maximum joint spacing should be 24 to 36 times the thickness of the slab. For a cleaner looking isolation joint the top part of the preformed filler can be cut off and the space filled with elastomeric sealant. Joints should be spaced about 10 feet and a maximum of 15 feet. Isolation joints are generally formed by casting against a compressible preformed filler material eg self expanding cork over the full depth of the joint to provide a complete separation.

If you don t have the clearance a layer of 30 pound roofing felt should work. Some proprietary joints come with removable caps to form this sealant reservoir. And rectangular dowels and for diamond shaped load plates are provided in aci 302 1r 04 guide for concrete floor and slab construction or aci 360r 06 design of slabs on ground. Saw cut joints should be done within 4 to 12 hours after the concrete has been finished.

Concrete isolation joints or expansion joints separate or isolate the concrete from other parts of the building structure like walls footings columns and piers. A concrete expansion joint is also used to separate a concrete driveway or patio from a garage slab sidewalk stairway light pole or any other point or restraint. Most details we ve seen recommend not placing the slab directly on the footing but if you ve got enough vertical clearance we think a inch layer of sand would work better than isolation joint material. The perimeter joint prevents this problem.

When using joint groove for contraction joints the joint should be a minimum depth of thickness of the slab. For a cleaner looking isolation joint the top part of the preformed filler can be cut off and the space filled with elastomeric sealant. Some proprietary joints come with removable caps to form this sealant reservoir. What is the difference between a contraction joint isolation joint expansion joint construction joint and a cold joint.

Isolation joint material should go all the way through the slab starting at the subbase but should not extend above the top.