When installed however the shingles overlap doubling the thickness.
Flat roof joist thickness.
This sizing guide for roof rafters will help determine what you need for your small project.
Usually 400 450 or 600mm but any value can be used up to 610mm max 1 2 timber strength class and joist size automatically calculate sizes suitable for supporting the loads below.
Buildingregs4plans flat roof guidance provides information on flat roof deck design and materials including timberboarding plywood oriented strandboard.
The joists will normally be placed at 400mm centres but no more than 600mm centres.
As opposed to old built up felt roofing with joins new single ply waterproof membranes are now most commonly used.
Also available for the android os.
Notches are not to exceed 0 125 of the depth of the joist and are to be located between 0 07 and 0 25 of the span from the support.
Laid with the edges of the board corresponding with joists or noggins.
Weather you re building a shed roof or adding a dormer to your second story it is important to choose the proper size rafter.
Double nailed at each joist.
Standard asphalt shingles add very little thickness to the roof because a standard three tab shingle is about 3 16 inch thick.
Maximum clear span of flat roof joists in metres for sc3 timber spacing between joists size.
As the single ply roofing association spra points out this type of flat roofing is strong durable completely sealed and usually lasts at least 25 30 years.
Wherever possible joists should span the shortest distance.
A minimum thickness of 18mm these will be able to span up to 600mm.
Ceilings and roofs excluding trussed rafter roofs for dwellings or ask your lbc surveyor for advice.
Common joists sizes are 200 x 50mm 175 x 50mm and 150 x 50mm.
This is the distance between joist centres.
There are several variables to consider when determining the proper rafter size.
There are two types of flat roof.
Span calculator for wood joists and rafters also available for the android os.