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Garage - Rotten Roof Rafters + Support Beam. Time to Replace (Diagram Inside)

Garage - Rotten Roof Rafters + Support Beam. Time to Replace (Diagram Inside)

Old 06-20-14, 07:22 AM
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Garage - Rotten Roof Rafters + Support Beam. Time to Replace (Diagram Inside)

Great. So I was have a 115 year old garage that is in worse shape than I originally thought. Please bear with me as I'm going to describe the whole story as best I can. I'm sure this will be entertaining for some of you and cringe worthy for others.

Basic Construction:
It is a 20 x 20 garage with a single garage door. It has a slanted roof with a pitch somewhere between 1.5/12 and 2/12. The back of the garage is about 7' high and the front is about 9' high.

The roof rafters are rough cut 2x6's that run the length of the roof from front to back. They are 21.5' long end to end including the overhang. Yep, that's right....21.5' long 2x6's. The rafters are approximately 24" O.C. There is a support beam in the middle of the rafters made out of 3 2x6's with a post holding it up in the middle.

The Problem:
I knew I needed a roof. The 3/4" planking is showing some dry rot and there are a few minor leaks on the inside of the garage. The fascia boards at the back side of the garage were starting to get soft.

My intent was to finish up the existing vinyl siding project, and then start on the garage roof. What I found was truly disturbing. I took the fascia boards off and nearly lost my lunch! The RAFTERS are rotted starting near the top plate of the back wall all the way through the overhang. It looks like someone had mickey moused it before as there were some 2x4's nailed to the old rafters to give the fascia something to connect to.

How Did this Roof Not Collapse???
Are you ready for this? Now that the fascia was off I could take a peak at the roofing. 5 LAYERS OF ROOFING MATERIAL!!!!
- Two layers of rolled roof on top of the 3/4" planks.
- A layer of shingles on top of the rolled roof.
- A layer of plywood on top of the shingles.
- Then the existing shingles now. MY GOD!!!!
Not to mention the back wall is not properly framed. The studs are 48" O.C.!!! How did this not fall down? Especially with 4' of snow on top?!?!?

Okay. I was already planning to re-frame the back wall so the studs are 16" O.C.. Prior to discovering the rotten rafters I was just planning to rip the existing roofing off and replace it with plywood and rolled roofing. Now it seems I have to replace the rafters also.

If you are still awake....here are my questions:

The support beam that supports the rafters needs to be replaced. It is currently three rough cut 2x6's that are nailed together. They are starting to split and are now warped after a 100 years holding 70 tons of roofing material.

My question is....what is the best way to construct a beam that needs to be 20' wide? Get custom 20' length lumber and basically replace whats there or can I sandwich some store-bought 16' sections and make something work? Since it is a slanted roof, what is the best way to make the beam conform to the angle of the rafters? Here is a diagram of what I'm trying to describe:
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The roof rafters are 21.5' long including the overhangs. Do I need to source 21.5' lumber or can I make this length by combining two 2x8x12's since there is a support beam in the middle? Another diagram:
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Sorry for the long winded post. What went from a simple roof job quickly turned into a rehab job that would require fixing 115 years of mistakes. So what do you think? Thanks in advance!!!
Old 06-21-14, 04:31 AM
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For beam I would check out a few options, LVL's, glulams or paralams. Deal with a lumber yard that can have their supplier size the beam based on your accurately supplied information.

You can use the two piece rafter method. Many guys would not deal with the issue of having full support for the rafters at the beam but you can put the beam in with a flat top and angle cut a piece of framing lumber to attach to the top which would allow you to have full bearing from the rafters.

How is the existing beam supported and do you have any idea what the posts are bearing on in terms of a proper footing/foundation.

I deal with many old structures that were under built , nevertheless, have stood for a century plus.
Old 06-22-14, 11:42 AM
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Thank you for the response! After further inspection, the triple 2x6 beam isn't in as bad a shape as I thought. There is a slight crack in one but it isn't a stress crack, its more of a slight crack due to drying of the wood over time.

Since this is a glorified shed, not a two car garage attached to a house I am trying to keep a somewhat affordable budget. Are glulams, LVL's, or other engineered beams somewhat price comparable to using a bunch of 2x6's?

I'm thinking I might be able to save the existing beam structure. The post that supports the beam isn't quite centered on the beam. It is about 12' from one wall and about 8' from the other. The beam has a light sag in the 12' section. And actually the sag is only on 1 of the 2x6's as only one actually makes contact with the rafters.

The beam is supported on each end by a 6x6. The foundation is field stone and the sill is a 6x6 beam.

After I remove the 20 tons of roofing I will put a new 6x6 post in the middle of the beam to better support it. I can probably straighten the beam out by jacking it up under the sag and once it is level I will attach some additional 2x6's to each side. Then send some bolts through it all to hold it together.

Sound like a plan?

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