Tn 18A web-nov06. indd

1

/

4

 in. (6.4 mm).

Photo 1

Vertical Expansion Joint Construction

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VERTICAL EXPANSION JOINTS

Figure 1

 shows typical methods of forming vertical 

expansion joints with either a premolded foam pad, a 

neoprene pad or a backer rod. 

While generally limited to rain screen walls, a two-stage 

joint as shown in 

Figure 2 

can increase resistance to 

water and air infiltration. This type of joint provides a 

vented or pressure-equalized joint. The space between 

the sealants must be vented toward the exterior to allow 

drainage. This is typically achieved by leaving a hole or 

gap in the exterior sealant joint at the top and bottom of 

the joint.

Spacing

No single recommendation on the positioning and spacing 

of expansion joints can be applicable to all structures. 

Review each structure for the extent of movements 

expected. Accommodate these movements with a 

series of expansion joints. Determine the spacing of 

expansion joints by considering the amount of expected 

wall movement, the size of the expansion joint and the 

compressibility of the expansion joint materials. In addition 

to the amount of anticipated movement, other variables 

that also may affect the size and spacing of expansion 

joints include restraint conditions, elastic deformation 

due to loads, shrinkage and creep of mortar, construction 

tolerances and wall orientation.

The theory and equation for estimating the anticipated extent of unrestrained brick wythe movement are presented 

in Technical Note 18. Estimated movement is based on the theoretical movement of the brickwork attributed to 

each property and expressed as coefficients of moisture expansion (k

e

), thermal expansion (k

t

) and freezing 

expansion (k

f

).  As discussed in Technical Note 18, for most unrestrained brickwork, the total extent of movement 

can be estimated as the length of the brickwork multiplied by 0.0009. A derivative of this equation can be written to 

calculate the theoretical spacing between vertical expansion joints as follows:

 

 

 

 

 

 

S

e

 =

     w

j

e

j 

 

 

 

 

 

 

 

        

  

 

 

 

 

           0.09 

 

 

 

 

 Eq. 

1

where:

S

e

 = spacing between expansion joints, in. (mm)

w

j

 = width of expansion joint, typically the mortar joint width, in. (mm)

e

j

 = percent extensibility of expansion joint material

The expansion joint is typically sized to resemble a mortar joint, usually