Expert: Dan Griffin - 12/31/2009

Question
Dan,
I'm using Armstrong materials for a drop ceiling using 2' x 4' panels. The problem is the 4' cross sections lock into the main section but rest on the wall perimeter. I would like to secure it some how. It's not long enough to rivet. The cross sections fall out very east when trying to finish the grid. Any ideas?

Thanks,


Mike

Answer
Mike, it sounds like you off to a bad start.  All drop ceilings are laid out to create even borders at each end of the room.  There will be matched border at each end of the mains and a different matched border at each end of the cross tees.  It would be an extremely rare room that came out on even feet, and if it did, you would still lay out the room to have a border.  The system of mains and cross tees in the middle of the room all lock together to create the "field".  It is your job to make sure that the grid is square and secure.  very few rooms are truly square.

You need to determine how large the border will be before you start.  Make a sketch of the room and do several lay outs on paper to get the idea.  You will either have a main at the center or you will have a full tile at the center of the room, it always possible to do either one.  In commercial work, the determining factor is the light lay out.  Draw the room with a main down the center, draw in the other mains at 4' on center.  Lets assume the mains are going the long dimension of the room and the room is 15'-6 x 21'-3.  There will be 20' of full 2' tiles along the mains leaving 1'-3, divided by two giving you a 7 1/2" border on each end of the mains, you need to cut the end of the main so that the first cross tee will occur 7 1/2" from the end.  There will be 3 full 4' tiles going the other way, leaving 3-6", divided by two making a 1'-9" border at each end of the cross tees.  Set the first main 1'-9" from the corner with the cut end sitting on the wall angle.  Hang main number two 4' further.  Use spring clamps to hold the mains to the wall angle.  Install the cross tees locking these two mains to each other.  The first cross tee goes in the 7 1/2" slot and then every two feet.  Stretch a string line from end to end of the room - it is easiest to make the string run at the center slot of the cross tees, so 3'-9" from the corner.  Cut a cross tee the correct length to hold the slot at the string - use a spring clip to hold the cut tee to the wall angle and maintain the slot at the string.  Cut several cross tees to straighten the main.  Check one of the grid rectangles for square, holding a tape measure and getting the same reading on each diagonal.  Move one of the mains by loosening the spring clamp to adjust for square, make sure to check that you still are true to the line.  Once the grid is all sanpped together and square, o will pop rivet one end of each main and one wall's worth of cross tees.  DO NOT pop rivet both ends in either direction as slight movement must be allowed for expansion/contraction.

I've not read any of these, but some may have better illustrations as I'm sure my text has not been easy to follow:
http://www.google.com/#hl=en&source=hp&q=how+to+hang+drop+ceiling&aq=0&aqi=g1&oq...


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