Garage Roof

[Lobsterman]

At the moment I have a double sectional concrete garage.

It is two garages bolted together and has a dividing wall down the centre.

Overall width is 19ft and length is 18ft.

The existing roof has 4 x 2's resting on outer wall and inner dividing wall which are 9.5ft long each.

Covering is corrugated (Asbestos??) sheet running from front to back.

I want to remove the dividing wall and have one big open plan garage.

Problem....

The roof span will now be 19ft and I want to do it the cheapest and easiest way.

I have got quotes from Compton for "C" section steel joists (For a straight flat roof)which work out at £108 each...a bit too expensive for me

1) Is it possible to span this width with a wooden joist?.....8 x 2 ? at 900mm centres?

2) could I use two 6x2x 14ft joists bolted together to make a 19ft length?

Ideally I don't want to go down the pitched truss route.

The covering would be 2m x 90cm thin galvanised sheet.

Any ideas gratefully recieved

 

[Deluks]

I'm in a similar predicament. I have a standard 20x16 double sectional. My current plan is to raise steel beams onto brick pillars lengthways at each side of the garage, and sit a new timber roof on top of these. I am creating a music studio so require soundproofing, therefore a heavy roof is necessary.

So are you intending to have a flat roof? I think over that distance, an 8x2 will sag in the middle, causing a big puddle in your roof when it rains, and therefore leaks. A simple truss design spanning the full width is a better option. but you will still need a 19ft timber for the ceiling joists to keep the roof triangular. As your covering will only be steel sheet, you could probably get away with designing and building your own truss, as long as you do some homework on the subject. Get a good roofing book.

http://www.behmdesign.com/garageplans/480-1f.html

 

[Static]

19ft is at the limits of timber flat roof design, yes there are some real beafy timbers but it will probably end up costing you in materials. What are the current walls constructed off?
It may be simpler to replace the divisional wall with a steel at high level and put in a couple of brick pier at each end (if existing walls are brick).
Course your current timbers are small and can probably support little more than corrigated plastic roof. If you want a proper roof on youll need to increase their size some

 

[Deluks]

19ft is at the limits of timber flat roof design, yes there are some real beafy timbers but it will probably end up costing you in materials. What are the current walls constructed off?
It may be simpler to replace the divisional wall with a steel at high level and put in a couple of brick pier at each end (if existing walls are brick).
Course your current timbers are small and can probably support little more than corrigated plastic roof. If you want a proper roof on youll need to increase their size some

Static, his existing walls aren't brick, they are concrete panels, I see what you mean about the walls needing to be brick to take the outward forces of the roof triangle, however as he is only using steel sheet it should be ok.

I don't have that luxury as I'm building a double layer plywood roof (or possibly bitumen OSB/MDF sandwich), hence my need for steels on brick pillars, built on the inside of the garage, next to existing side walls.

The doorway will be blocked up with medium density blocks, with pillars built in to support steels, the other end of the garage will have 2 pillars to take other end of steels, and the new truss roof will sit on this.

I'm not sure of the exact method. The garage is at the rear of the property so no worries about removing the door, or I may even build the wall on the inside.

Have you ever gone about building a steel into a brick pillar before? I could use some tips.

Here is a pic of one corner of my garage, where I intend to build a pillar, and is probably the same material Lobsters is made of.

 

[Static]

Deluks your probably best posting a new thread as by the looks of it your garage is not idential to one descibed in the orginal post - your has a pitch roof etc..
Im not a fan of concrete sectional garages, they have a low design life and little stability.

Lobsterman:
Sorry missed that it was a concrete garage in your original post, removal of the division between the garages may still possible with a steel goal post option, unless you intend to form a double garage door in the middle.
Your existing timbers are only designed to take a lightweight plastic/steel material.

 

[Lobsterman]

Thanks for all the replies...it has me thinking now.

With reference to the existing timbers...they are going completely and I will essentially have a concrete sectional box with a dimension of 6M x 6M which will need a new roof.

The Steel "Goal post" idea has caught my eye and would probably be the easiest option for me.

One more question though...

What kind of size steel are we looking at?

Rectangle box section?...RSJ?...Angle Iron...3mm thick steel...5mm thick....100x100...70 x 70...???? not got a clue

I have browsed on the HY-Ten website and they can supply all I need (Local too) I just need to know sizes if anyone can help.

 

[Static]

Do you intend to keep the 2 garage doors with a pier between? Also what roof covering will you be using?

 

[Lobsterman]

I will be having one 14ft roller door at the front.

The "Goal posts" will go across the width of the garage so that the roof will slope from front to back.

I will be using thin steel profiled sheeting similar to that used on warehouses (See Cladco website) in 10 ft lengths so I will be having a goal post across the garage at approx 5ft centres

 

[Static]

So basically you are removing the majority of the front elevation as well as the dividing wall. Urm... 14ft roller door? do you mean an up and over door?

 

[Lobsterman]

Yep...One door at the front and it will be a roller door (Gliderol) not an up and over.

 

[Lobsterman]

So...what size steel would I need?...anybody???

 

[Static]

Hmm, basically your loosing the orginal structural form of the two garages - which had roof structure spanning left to right and changing it to a double garage with roof spanning front to back.
Your scheme lacks framing support, you will need something to support the new roller door and also a new lintel over the opening for the roof. Also i would worry about lack of wall in the front elevation. End result i would suggest creating a full steel frame internally, posts in all 4 corners, maybe mid way posts along the walls to reduce spans, then run perimeter high level steels to form a frame - then the old concrete walls are just cladding.