Supporting garage plywood roof.

[Deluks]

I'm planning to use my garage as a music practice room, so require good soundproofing of the ceiling. The existing roof is corrugated asbestos sheet, I had intended to board out underneath this with ply, but I don't think the flimsy metal truss will take the weight, plus I will have very little headroom, so I'm at a bit of a crossroads on how to proceed with this.

The garage is detached, 20x16ft, with bolt together concrete panels for walls.

A friend who is an experienced chippie has suggested a frame of steelwork, consisting of 4 uprights and an inner rectangle frame to sit timber trusses onto. This sounds like a great idea, but pricey, so I'm wondering if anyone has ideas to keep the costs down.

I had intended to built a wall of medium density blocks just inside the main garage door, spanning 16ft from wall to wall. This was to act as extra soundproofing and security against the flimsy metal door.

The main Q's I need suggestions/answers for are:

Would I be able to sit steel beams on this wall if I built pillars into it? ..and if so would it need a foundation dug, or could I fix it down to the concrete floor using another method? (metal stud or similar?)

Could I build a pair of brick pillars at the other end of the garage to take the other ends of the steels, (this would do away with the need for steel uprights altogether) If so what size would they need to be to remain stable?

If timber trusses are used, they would have to be scissor type, as to give more headroom, so would be pushing outwards, which is why I dont just want to build them onto the existing walls. The roof will likely be felted 18mm ply, with mdf or plasterboard fixed directly to the underside, as to improve soundproofing.

For the record I will be building an inner ceiling on inner walls for the main studio room. Following the mass/air/mass principle of soundproofing.

 

[JohnD]

There is a risk you will spend a lot of money upgrading it, but still end up with an asbestos-roofed sectional garage. It might be worth thinking about having a new one nuilt, rendered blockwork is surprisingly cheap.

 

[Deluks]

Well the asbestos will be long gone, the council take asbestos with prior notice. I'll use ply as the new main roof and felt over it.
So the new roof will cost the same whichever was I choose to support it, but I would've thought an internal structural frame for the roof would be cheaper than tearing down/disposing of and rebuilding again surely?

 

[Deluks]

*Bump*

More info in this post.

The pic shows rear corner of the garage, the window is on the back wall. I now think that I could raise this new roof up, so could use standard (triangular) trusses, therefore outwards force won't be such a problem.

I still need a structure to take the weight though, about 1500kg's of ply, timber and shingles.


I'm now still thinking of 2 parallel steels, just inside the side walls. One end sitting on the aforementioned bricked up door, and the other end supported on a couple of brick pillars (one of which would be located in the corner area)

Is this the best option, or would steel columns be easier or more cost effective?

Also would the new wall and brick pillars need a footing, or could I just build up from the concrete floor?

 

[JohnD]

I still think you might as well build a new one.

You are going to end up with a steel-framed building with no walls inside your old sectional garage.

 

[Deluks]

I still think you might as well build a new one.

You are going to end up with a steel-framed building with no walls inside your old sectional garage.

The thing is, I need 2 sets of walls for full soundproofing. The external existing wall is my second line of defence against sound leakage, despite it's age it's still good enough for this purpose. There will be a new inner wall built from mdf and plasterboard which will hide any structural supports or brickwork.

By now you'll be thinking, why doesn't he build new inner brick walls and sit the ceiling on that?

This would defeat any soundproofing, as sound inside the room would transfer up these walls and through the roof. It's a tricky one