Door Frame Replacement

[ajk1]

As part of a general structural repair of a suspended structural slab with corroded rebar, we have been asked to also specify the replacement of metal exit doors and metal frame due to advanced corrosion of these members in the 40 year old public library building. The doors which are the entrance to a fire exit stair of the library have to be 2 hour rated.

Questions:

1. How should we specify that the new metal door frame be attached to the wall? The wall is 4" brick and 6" block cavity wall. Do they have to take down the masonry and rebuild it around the head and jambs of the new frame?

2. Does the 2 hour rating require anything special for the frame installation? For example, should the hollow space created by the frame be filled with grout? If so, I suppose it would have to be a liquid grout pumped in thru some access ports?

 

[jike]

The door frame can be anchored to the masonry with countersunk bolts into sleeve anchors (usually 3 places equally spaced over height). Door frames should be filled with grout. Check your governing code as to whether the lintel needs to have a fire rating.

 

[hope9010]

Thanks Jike - aren't the door frames made of relatively thin metal (20 gauge or so?) and as such I don't see how the bolt heads can be countersunk...unless you mean to fill the frame with grout and then countersink the bolt head thru the metal frame and into the grout?

 

[jimstructures]

In the door jambs we receive for installation in masonry the metal jamb is dimpled and then the dimple is drilled to provide a hole for the bolt to pass through. the dimple provides a recess for the countersunk bolt head to nest into. Thus a countersunk bolt. The bolt may be a tapcon or similar threaded piece, not a headed bolt.

I hope that was clearer than mud.

Jim

 

[ajk1]

Thanks jimstructures - that is very clear and well explained. Assuming that the frame has to be grout filled for 2 hour fire rating, how is that done? Do they drill hole near the top and then inject in a flowable cementitious grout into the frame head and jambs? Or is it not necessary to fill the frame?

 

[Ingenuity]

We fill the frame by leaving a 2"+ gap over the door frame to enable flowable grout to enter the two vertical spaces between existing masonry and new frame, then dry-pack overhead gap.

 

[ajk1]

Thanks Ingenuity. Much appreciated.