Wall Expansion Joints How Create Movement Joint
Thermal movement is not normally allowed for in internal brick walls. Temperature will also cause brick to expand and contract. This can be done by knowing the coefficients of expansion of the brickwork and the parameters of its environment. In effect, tensile stresses act against the weakest property of the concrete material. When cracks are held tightly or remain small, the aggregate particles on the faces of a crack interlock thus providing load transfer across the crack.
The concrete has still cracked which is normal behavior, but the absence of random cracks at the concrete surface gives the appearance of an un-cracked section.
Joint spacing that is greater than 15 feet require the use of load transfer devices (dowels or diamond plates). In hot weather, concrete might crack if joints are not cut within 6-12 hours after finishing concrete. Under carpet areas the joints won’t have a chance to telegraph through vinyl areas. Most plans don’t have joint spacing marked on them.
BIA Architectural Video Series.Expansion Joints Control Joints – Masonry Wall Expansion Joints
Waterstops run from the footing continuously to the top of the wall, where they are covered by a coping or other flashing. Those below grade must be soldered. Separate copper flashings are inserted, wedged, and sealed into each reglet. Thermal movement is reversible and on-going. Very roughly, one third of the total longterm movement occurs in the first six months, the next third within five years, and the remainder over hundreds of years.
Therefore some relief is gained by storing the bricks for six months or so before use, but this is not a cure for the problem.
The important factor in allowing for brick growth is determining the coefficient of expansion (the e-value), which represents the likely permanent unrestrained growth over the first 15 years of the brick’s life.
Therefore a non-loadbearing wall in a framed building will have to cope with a slight shortening in the columns when further storeys are added above.
Expansion joints should be located where stresses or cracks are likely to develop in brickwork. Saw cutting cuts joints as soon as the concrete is hard enough that the edges abutting the cut don’t chip from the saw blade. Planning the joint pattern can sometimes eliminate re-entrant corners. There are two basic strategies to control cracking for good overall structural behavior. The most widely used method to control random cracking in concrete slabs is to place contraction/control joints in the concrete surface at predetermined locations to create weakened planes where the concrete can crack in a straight line.
The longer the first pass for jointing is delayed the more difficult it will be to shape clean straight line joints. Joints may also be sawed into the hardened concrete surface. This means that any cracks that occur before the concrete is sawed will render the sawed joint ineffective. Joints should be sawed as soon as the concrete will withstand the energy of sawing without raveling or dislodging aggregate particles. Early-entry saws are available which may allow cutting to begin within a few hours after placement.
For convenience, these values are usually rounded down and rationalised to suit the layout of the actual building. When the wall relies on a structural frame for stability, joints located close to the corner allow both parts of the wall to be tied back to the column.
The maximum distance from the corner is half the normal spacing. Other joints in a long wall might be concealed behind downpipes, or in a re-entrant corner as shown in the diagram. However, it should be noted that some closure of the door openings may occur. This is not a major problem with conventional timber doors and frames, but with close-fitting metal-framed doors in metal jambs (where it isn’t possible to just take a shaving off the edge of a door!) some other provision might be required.
Walls that are supported on a steel or concrete frame require a joint at the top, to allow for all the influences described above.
Because of the shrinkage and creep characteristics of concrete, which don’t apply to steel, the allowances are greater when the frame is reinforced concrete than if it is steel.
It may not be feasible to use these bricks in that situation, since horizontal joints can only be located immediately under the beam or slab at each floor level.
With low-expansion bricks and a steel frame, it should be possible to locate an expansion joint only every second storey, if that works with the other details.
Therefore a gap is needed at the top of these walls. An easy way to achieve this is to place a 20 x 110 timber board in the joint as the brickwork is laid, and remove it after the mortar is sufficiently set.
If sliding ties are needed across the joint, say every 600mm in height, the boards could be cut to 590mm long to fit between ties.
It will start as 20mm thick and may end up 5mm thick.
How do you create a movement joint in a solid
The backing rod is necessary to allow the sealant bead to be formed properly. If the wall is required to be fire-rated, a fire-rated sealing system will be required instead. If the joint occurs below a shelf angle, the thickness of the angle will be added to the height of the joint.