You insulate a sloping roof in a fixed sequence. If you want to insulate the inside of the roof, follow the following steps: increase the rafter depth, apply insulation material, apply vapor barrier and apply a finishing layer. You ensure that the insulation material fits well against the roof and the finishing layer. Only then will you have maximum efficiency of the insulation material. You can buy different types of insulation material. Nail flange blankets work the most convenient.
Insulate the inside of the roof
Before you start you should check that the shelter is vapor permeable. If the underroof consists of fiber cement sheets or microperforated foil, the underroof is vapor permeable. You need to check this because the moisture that can collect on the insulation must be able to escape to the outside.
Insulate pitched roof sequence
The insulation proceeds according to a number of fixed steps. You start by increasing the rafter depth. The rafter depth is the distance from the shelter inwards, say the depth, between the beams. If enough space has been created, you can apply the insulation material between the rafters. The inside of the sloping roof is finished with a vapor barrier and a finishing layer on the battens.
- increase rafter depth
- apply insulation material
- apply vapor barrier
- apply finishing coat
Increase the rafter depth for roof insulation
Depending on the thickness of the insulation wool, it is in some cases necessary to adjust the rafter depth. This is necessary to properly apply the insulation wool. You can adjust the rafter depth in two ways.
Adjusting the twill depth way 1
You can screw extra battens (rafters) onto the existing twill to create more depth. The advantage of this way is that the existing roof structure is reinforced
Twill depth adjustment way 2
If there are only purlin beams on the roof, you can decide for yourself at what width and height the battens should be placed between which the insulation material is placed. If you work with beams, apply them with galvanized corner brackets (against rusting).
Attach insulation wool
When the rafters have sufficient depth, you can start attaching the insulation material. The insulation wool is placed between the rafters. There are two ways to attach the insulation wool, between rafters with regular spacing and between rafters with irregular spacing.
Install insulation material between rafters at regular intervals
Working with regular spacing between the rafters is easiest. You can buy insulation material with a standard width of 35 cm, 45 cm and 60 cm at the hardware store. The simplest are nail flange blankets. You can easily cut these with a sharp knife along a metal lath.
Apply the insulation against the underroof between the purlin beams and the rafters. You start on the side at the wall, left or right doesn’t matter. Make sure that the material fits well against the underroof. Also, there should be no gaps between the beams and the insulation material, fill this with small strips. The insulation material must be of sufficient thickness to fit well against the underroof and the finishing layer.
Cover all seams with aluminum tape or damp-proof plastic tape. This is important to avoid condensation. In addition, with sealed seams, you have a maximum return on the insulation applied.
Apply insulation material between rafters with irregular distances
In principle, this is done in the same way as described above. However, there is one difference: you can use different material. Because you are dealing with irregular distances, nail flange blankets with standard dimensions cannot be fitted. The easiest thing to do is to buy insulation boards that are cut diagonally. You then have two triangular plates that you can fit better between rafters with irregular distances. First measure the distances carefully for each plate to be fitted.
Apply vapor barrier
When insulating a pitched roof, it is important to apply a vapor barrier over the insulation material and the rafters. Use damp-proof PE foil with a thickness of 0.2 mm for this. You can easily staple the foil to the rafters. The different strips of foil must overlap each other by about 10 cm for a good vapor tightness.
After applying the insulation foil, place battens at right angles to the rafters. Take into account any cables and recessed spotlights that have to run along the back. So take sufficient thickness slats. The easiest way is to lay some PVC pipes at the back to be able to pull cables.
Apply a finishing coat
If you have attached the battens at right angles to the rafters, you can finish the sloping roof with plasterboard, for example. You can choose to leave the purlin beams visible. Leaving the purlin beams invisible significantly simplifies the finish.
Tools and materials for sloping roof insulation
To be able to insulate a sloping or sloping roof, you need certain tools and materials. This list of basic materials and tools should in principle be sufficient:
- insulation material
- sharp knife
- metal lath
- stapler
- staples
- hammer
- wood screws
- drywall screws
- wooden slats
- tape measure or folding rule
- adhesive tape, aluminum or plastic
- screwdriver or cordless screwdriver
- 0.2mm thick vapor barrier foil