Hey all,

I have a detached garage for my workshop. It's 24' by 38' (interior dimensions) concrete block structure with a flat roof, three parapet walls (sides and rolling doors side) and the flat roof overhangs the fourth side opposite the rolling doors. The parapet walls stick up about two to three feet above the flat roof, and the roof itself is 2x12" joists on 16" centers, approximately 28' long. The ledger boards are bolted to the concrete block walls, presumably with J-bolts that were set into the block when the workshop was built, and has some kind of tie where the roof hangs over the wall, and the spaces between the joists are filled in with bird-boards. The flat roof is finished in foam. I presume that the roof weighs around 8,000lb.

I'm curious about having the roof physically raised up higher relative to the parapet walls and having a metal framing structure put in on the overhung wall. Right now the unfinished ceiling is 9' from the floor excluding the HVAC duct hanging down in the middle, and that's really too low for a practical vehicle lift. If I can get in excess of 11' then a lift may be possible.

I expect that in advance of a contractor I'd have to do the following:

empty out the shop
unhook the HVAC duct from the air handler
Take the 8' lightbulbs down from the ceiling fixtures
remove any hooks screwed into the beams by the previous owner
remove the PVC air lines (that I plan to replace anyway)
disconnect electrical wiring where the wall meets the roof


I expect the contractor would have to do the following:

cut away the roofing foam where the roof meets the walls
identify the maximum desired height for the roof
design the support structure for where the roof hangs over the one wall, and possibly manufacture
support the weight of the roof structure on cribbing and hydraulic jacks
cut the J-bolts between the ledger boards and the walls
hydraulically lift the roof to the desired height
Install the support structure where the roof hangs over the wall
drill into the concrete block walls to install anchors to support the ledger boards on the three parapet walls
seal up the edges of the roof against the parapet walls
foam parts of the roof that require it and finish it


Then I have to reconnect my electrical, possibly using junction boxes and some extra wiring of the same gauges, add sheet metal to connect the HVAC duct, put the lightbulbs in, and putting windows in among the support structure.


If I've left anything out please say so! Also, any thoughts as to how expensive this would cost? I expect that thousands of dollars could be spent easily, but would it be $3,000? $5,000? $10,000?!!

 

You made one mistake & it's on one of the things you said the contractor would have to do.

"design the support structure for where the roof hangs over the one wall, and possibly manufacture"

Don't leave it to a contractor to do a design like that. Have an architect look at it first. If he says it can be done, let him draw the plans. Then you show the plans to a contractor & get a price.

 

Okay, I'll bear that in mind.

Theoretically it shouldn't be any more difficult than four 10' 4x6 timbers cut down to 38' length for the span to support the roof, some 2x6 or 2x8 timbers to sit on the top of the wall, and some 4x4 timbers cut to stand vertically in the gap between them, spaced evenly or at a a standard window size. A metal frame might look better but might be more expensive. It'd have to be constructed in advance probably, unless one could be quickly fabricated on site to be made for the space.

 

And suggest to the architect you hire that he use a licensed engineer to crunch the numbers. Architects are paid to make things look pretty, while engineers are paid to make sure those things don't collapse while looking pretty.

If it were mine, I'd prefab the support structure before the first lift. Doing so saves the down time the contractor will be charging for any of his crew just standing around waiting for things to be built. Also, in the event you have trouble finding conventional contractors willing to bid the job, consider using either house-movers or even a bridge contractor experiencing some down time. Many of the latter have worked with heavy lifts, often having all jacks tied to a manifold system, and everything raised simultaneously and at the same rate. Last job of mine we used it on was a 16" raise, total lift weight of just under 620,000 pounds--not a single crack in the deck as a result of the lift (I lost a 6-pack on that one, betting the contractor he'd crack the deck in at least one place--darn me!).

 

The part of Phoenix I live in is retiree-trailer-park central, and I work for an organization with probably 500 portable classrooms that are moved by outside contractors, so I can probably find a local heavy-lift company through one of those means or another. Come to think of it, since they're used to splitting those portables on their factory seams and reassembling at the new jobsite, getting them straight and level, they might be able to handle getting it even and correctly sloped relative to the existing three parapet walls. What they might not be able to do is to fab up a permanent support or to foam the roof correctly.

I'll see if I can get operations to give me the names of some contractors.