What is the typical thickness of insulation of fibre glass in flat roof?

Answer 1

The thickness of fibreglass insulation that can be put in a flat roof is governed by the roof timber size so if they are 6"x2" then the max that could have been put in is obviously 6". But maybe perhaps only 4" was put in. Nowadays a gap would have to be left above the insulation to allow for ventilation so in the case of 6x2's if using fibreglass a max. of 4" would apply. Because that would not give, by todays standards, adequate insulation, fibreglass wouldn't likely be used. Modern insulation boards that may be only 2-3" thick give the equivalent maybe of 6-10" of fibreglass, and still leave the required gap for ventilation.

Answer 2

It varies tremendously witht the age of the building and the climate "zone" you are in. If this is a new building, it must comply with local codes, and national guidelines, which are available at most home centers. If it's an older building, then it depends on the age and type of construction. Usually you can add more in an access area, or above the ceiling. In my area, the required insulation above the ceiling is R30.

Answer 3

if you're talking about rolled fiberglass also known as glass ply 4.first you need a hot tar kettle,you will also need either
30 lb or 43 lb felt for underlayment.Then you either nail or adhere underlayment using metal simplex nails or the hot tar itself then you apply the glass ply 4 either 2,3,4 layers.the lines on it is your guide on the layers after that you need to put on your drip edge metal i.e FHA with 3 in. face then cut two strips from the glass ply 4 on at 6 in. and one at 9 in. apply these around the edge 6 in first then 9 in let hang ove approx 1/2 in when done trim the excess of typically you should also roll on aluminum roof coating after about 2 wks.

Answer 4

12 to 15 in. Minimum national code is R-30 wich is 12 in.
But that also depends on where you live, because local codes take precidence over national codes

Answer 5

building regs say 250mm but most roofs do not have enough gap for that amount ..so use 125mm of polyurethane board ..like kingspan