As with any building element when designing a flat roof it is good design practice to follow and adopt relevant design guidance.
Insulating a flat roof with parapets.
For areas which do not need above cover hole with bug screen.
Soooo then install the same perimeter wood blocking right over the roll roofing to match insulation thickness 5 or so of polyiso.
The decks have been designed with parapets.
Parapets on modern roofs.
We also have a parapet on a flat roof and the ventilation solution is not through the cladding but the design flows air over the parapet.
A warm roof is defined as being when the all or the majority of the insulation is above the joists or deck.
Naturally there are many different types of parapets for all the different situations materials construction methods and climates out there.
By majority the rule of thumb is that in a domestic house not flats approximately a third of the total thermal performance of insulation can be placed below the deck with two thirds above the deck sometimes this is called a hybrid.
Max baker and stonewall jackson would be proud.
The roof itself is therefore kept warm.
The build is by mbc timber frame and it will be a cold roof construction.
Insulate within parapet wall cavity to depth of roof insulation if present.
When you sheathe inside the parapet hold the sheathing short enough at the top to install the same metal strip you use for gable vent.
Terminate roofing on parapet wall with mechanically fastened termination bar.
Then sheathe the deck right up to the parapet studs.
Roof membrane must lap up wall to minimum of 12 above roof plane or per specifications whichever is greater.
Screw it down and glue down a 45 mil epdm membrane.
Upstands at parapets and abutments should be protected by either.
I would switch to a warm roof insulation above the structural elements.
Parapets often go unnoticed on modern houses as they can appear as the line of a flat roof.
The parapet contains the sloped roof and frees up the architecture to have a perfectly flat profile.
The perimeter of the roof assembly insulation is wrapped to prevent interstitial airflow from the parapet into the multilayered rigid insulation of the field of the roof.
Parapets can be both a safety feature designed to stop falls from the edge of the roof and also a constructional and stylistic feature a large percentage of flat roofs also feature a parapet of some height.
The cure for parapetitus is continuity of the control layers and letting things move when they have to move.
