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Preach_2 08-12-2009 05:56 PM

How to connect new deck roof to house
2 Attachment(s)
I am installing a flat roof over an existing deck and woul lkie to know if I can install a 2X8 ledger board on the existing exterior wall of the house and nail joist hangers on it to support the 2X8 rafters that will be on 12"oc and will have a free span of a little less than 16'? I am attaching pictures of the existing overhang that I intend to cut back to the wall. I could rest the rafters on the wall plate but would have to cut the roof back further during construction and would prefer to only cut it back flush with the wall until I am ready to install the roofing material.

Scuba_Dave 08-12-2009 06:46 PM

Where are you located?
Heavy rain or snow area?

Ledgers must be attached with lag bolts or thru bolts
What are you thinking of nailing the ledger to?
Just the rafters?

Preach_2 08-12-2009 06:58 PM

To the end of the rafters and the double 2X6" plate at the top of the studs. The house has 2X6" walls with a double plate at the top.

Preach_2 08-12-2009 07:01 PM

Once I cut off the rafters even with the house there will still be about 4" of the resting on the plate and the ledger will be a 2X8 so there will be 3 1/2".

Gary in WA 08-12-2009 09:32 PM

No, you cannot bolt the ledger to the top plate, without engineering done. A much better way is to rest (bear) the new rafters on the top plate of the wall. Especially for a flat roof, which you may want to check and see if it is even legal with your local Building Department.

Your picture shows the roof/wall flashing has no kick-out at the bottom. All the water is running into the stucco and framing below. Someone tried ineffectively to caulk it but still mold will grow.

If your house is similar to your neighbor's, you may want to check the venting requirements. He has about 60% of what he needs. Unless that is a ridge vent on top, adjoining the pot vent. Your insulation was effectively blocking your venting needs, also.
The mold on your stucco above the roof/wall flashing is because the stucco was installed too close to the roof surface. On a patio, it's 2" minimum to stucco. Be safe, G

ARI001 08-13-2009 08:30 AM

First if you are using 2 x 8 rafters you will need a 2 x 10 ridge/ledger board. Second no, you can not attach it to the tails of the existing rafters. You can bolt it to the wall framing but not the top plate and rafter tails. If it where me I would do a "California roof" and match up the roof lines to keep it architecturally pleasing to the eye.

Preach_2 08-13-2009 12:57 PM

Why do I need a 2X10 ledger for 2X8 rafters? What is a "California roof"?

ARI001 08-13-2009 02:37 PM


Originally Posted by Preach_2 (Post 313932)
Why do I need a 2X10 ledger for 2X8 rafters? What is a "California roof"?

You need a 2 x 10 so the heel cut on the rafter will rest completely on the ridge/ledger board. A California roof (also known as a blind valley roof) is a simpler method of framing a roof that is at a lower level then the existing ridge. Instead of altering the existing framing and installing valley rafters you frame on top of the sheathing.

The flat roof in one way or another will cost you more than building a shed roof (more typical for roofs over porches where the main structures roof is a story above the porch) assuming you can even do so in your locality. I don't think you could get enough pitch on a shed roof in this situation without sacrificing headroom. The California roof will tie into the rest of the structure and keep the roof lines clean. In turn it will be more aesthetically pleasing to the eye. If you're going to put it under roof do so in a way that adds to the structure and is not an eyesore.

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