If conditions are right new shingles laid over old shingles can be just as attractive and durable as shingles laid on bare sheathing.
Roofing over tg sheathing.
It spans the rafters to support the roofing and in the case of panel sheathing such as plywood or osb it acts as a diaphragm with the walls to resist horizontal loads.
One of the keys to over roofing is to tie the air control layer of the roof assembly to the air control layer of the wall assembly.
If your roof was not a low slope roof if it was say a roof with a 4 in 12 pitch you could install metal roofing over purlins with roofing underlayment asphalt felt under the purlins and above the roof sheathing.
Product may vary by store.
Measure from the edge of the plywood outside of the wall over to whatever the overhang will be and square a line up to indicate the end of the truss tail.
Add an inch and a half for subfascia strike a line.
When the roofing material wore out new composition shingles would be applied over the original roofing system.
Osb is a material with high mechanical properties that make it particularly suitable for load bearing applications in construction.
On the gable ends this was pretty easy.
This type of roof has a secondary layer the roofing underlayment to catch drips and an air space to allow the drips to evaporate.
To stabilize the rafters support the roofing material and hold the entire roof together roof sheathing is installed.
Roof sheathing attaches to the surface of the rafters or trusses to form the structural skin of the roof.
We go in depth on how to install roof sheathing.
As more layers of roofing were added there would be little chance that water would work its way through to the roof deck.
It is common to find older homes with 3 or 4 layers of roofing over the original roof.
Starting with how to place the first row of sheathing we cover fastening methods the use of h clips stagg.
Add the thickness of the true fascia 15 16 in in this case.
On the front of the roof edges the original roof deck sheathing was cut back flush with the wall and the fully adhered membrane folded down around the rafter tails to catch the.
As more and more layers of the roofing kept being added there was a minimal chance that any water was going to be able to work its way through your roofing deck.
The fully adhered membrane wrapped down over the cut back roof deck to tie into the wall water control layer and air control layer photograph 11.
But you must take care to install shingles correctly so they lie flat.
Once this roofing material started to wear out composition shingles began being applied over the original sheathing.
