Bob's Blog

Low height at house attachment

PROBLEM:
The roof eaves are very low on my house.  With a 12ft projection and  ½” drop per foot I will need 6″ of fall. This will make the header at the edge of the concrete slab  too low.
what other options are there?
SOLUTION:

There are a few options available and a few things to consider when you are faced with a low attachment height at the house.
You will need a minimum of 6′-8″ clearance under the header, 6′-6″ is allowed with some building authorities, usually you just have to ask.

Laguna Lattice covers are easiest to work with when you have a low mounting height at the house for two reasons:
1. You do not need 1/2″ per foot of fall for rain runoff
2. You may “reverse mount” the header, putting it on top of the rafters and “hanging” them from the header.

The Newport Solid covers must have fall for the rain to run off and the header must be placed under the roof pans.

When calculating the fall for the solid roof at 1/2″ per foot you need to take into account the fall of the concrete, usually 1/4″ per foot, but this slope may vary greatly from job to job.  This can be added into the equation to gain your minimum slope of 1/2″ per foot.

You can simply use one of the side rafters, place it perpendicular to the house with one end touching the house (for an eave attachment place the rafter at the appropriate distance from the wall).  Place a level on top of the rafter and lift the rafter until it is level.  Measure your slabs “fall” at the post location.  Subtract this number from the total fall needed.

ex. If you have an 7′-6′ high wall attachment (bottom of Alumawood roof) and a cover with a 15′ projection then your posts will be somewhere between 14′-6″ and 13′.  For this example we will mount the posts at 14′. We will need 7″ of fall from the attachment at the house to the posts and header.  If we have 1/4″ of fall on our concrete slab then we have 3-1/2″ of fall in the slab and we will only need an additional 3-1/2″ of fall for the cover itself.  We also need to deduct 8″ for the header.  8″ + 3-1/2″ = 11-1/2″.
Our height at the wall of 7′-6″ – 11-1/2″ = 6′-6-1/2″ which is a bit low.
We can substitute a double 2×6 header for the 3×8 header which will give us more headroom under the header.  6-1/2″ + 3-1/2″ = 10″.  7′-6″ – 10″ = 6′-8″ and this will work for our headroom.

The final option available its to roof mount the patio cover.

This is much easier on a composition shingle roof as opposed to a concrete or clay tile roof.  On a comp roof you simply mount 8″ L-brackets with lag bolts through the roofing into the house rafters.  The bolts will need to be sealed with roof mastic or similar. You then need to bend the leg of the L-bracket that is sticking up to a vertical position.  Your ledger board can then be mounted to these L-brackets and your patio cover attached to this.
On a tile roof we recommend have a roofing contractor install the L-brackets.
As always check the engineering, available at www.alumawood.com on the resources page.  There are limitations to all applications as specified in the engineering.
You may always email questions to info@alumawood.com

or call us at 1-888-alumawood (258-6296)

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