A solid slab is either solid concrete foundation or a flat solid wood door as opposed to a hollow core or a panel door.
What you need to do first is to check if you have that room near the threshold of the door for that extra concrete(which is minimum of 3.5" inches) then you need to remove the top surface of the old concrete to be rough surface don't break too much just about an 1"wash clean and let it dry and only then to install the new concrete.
drill holes and insert a concrete lag that follows layout for the door and then attach to the door casing.
action an reaction
If the concrete roof is on a brick load bearing wall you cannot open up the wall unless you have a concrete-steel beam below it . If you want a small door or window as opening you can open up the wall (not completely) but lay a beam under the wall for strength .
The recommended rough opening size for a 30x80 door is 32x82 inches.
Rough opening are 2" wider and 2-2 1/2" taller than than the door itself. 2/8" door needs a 2/10" wide opening.
The standard size for a rough opening for a door is typically 2 inches wider and 2 inches taller than the actual door size.
Rough opening is an opening in a wall, or the framework of a building, into which a door frame or window frame, subframe, or rough buck is fitted.It is a measurement that a manufacture needs for installment of their component applications.
The rough opening of an interior door is two inches wider than the width of the door and two inches higher than its height. Thus your rough opening width is 38". A typical interior door has a height of 80" which would require a rough opening height of 82" but check your door to ensure that is theheight.
The recommended rough opening size for a 30 by 80 inch door is 32 by 82 inches.
The rough opening required for a 30-inch door is typically 32 inches in width and 82 inches in height.
The standard size for a double door rough opening is typically 60 inches in width and 80 inches in height.
The standard rough opening size for a bypass door is typically 2 inches wider than the width of the door and 2 inches higher than the height of the door.
For a 30" door, the rough opening would be 32" in width and 82" in height. Check with your local building inspection department just in case a larger door is required.
The standard size for a rough opening for an exterior door is typically 2 inches wider and 2 inches taller than the actual door size.
The standard size for a rough opening for an interior door is typically 2 inches wider and 2 inches taller than the actual door size.