If the span under your deck is 12 ft for example the purlin at the outer end of the deck should be 3 in.
How to install tin roof under deck.
Lower than the purlin along the house 12 x 1 4 3.
First mark all the purlin locations on the deck joists.
Mark the porch with a line parallel to the edge farthest from the house.
How to build a tin roof over a deck step 1.
Step 1 select a tin roof type.
For an r panel style you will need to install it with 5 16 inch lap screws.
Position the next panel further from the house but overlapping the first by at least 6 inches.
Place the first screw.
Mark the line 2 inches in from the.
Decide what type of tin roof you want by selecting either an r panel or v crimp style.
Align the first metal roofing panel so that it overlaps the edging by 1 2 to 3 4 of an inch and is square to the roof.
Install the roofing screws vertically along each rib in the panel.
Step 2 take measurements.
Be sure the larger edge is laid so that the small edge of the next panel will overlap it.
Secure it in the same manner as the first.
Install subsequent rows of panels working your way to the downwind side of the deck s lower surface until finished.
Measure the porch to find the best length and width for a tin porch roof.
For example assume the porch measures.