Important!
Unless otherwise stated here, the latest recommendations in AMA Hus (JSB.6) apply.
- The permanent surface layer determines the minimum roof slope for the underlay, but always at least 3° (1:18) for exposed but not battened roofs. When battening and exposing without the outer roof covering, at least 14° (1:4)! If battening is needed at a slope below 14° (1:4), it should be done directly in connection with the installation of the outer roof.
- When covering with flat roof tiles, the supplier's guidelines for the underlay must be followed!
For unsealed roof tiles or in wind-exposed areas (coastal), it is recommended to choose a more secure underlay such as T-Roof Epic. - The underlay should not be combined with surface layers that are hot air mounted (welded).
- For concealed fastening, carefully check the strength of the joint after installation. Consider adverse weather conditions and ensure any temporary securing of overlaps or protective covering until the permanent surface layer is installed!
- The adhesive edge has aggressive adhesion under normal conditions! In cooler weather (<+10°C) it can
Sometimes there is a need to improve adhesion. Use a heat gun and warm the adhesive surfaces
carefully. Press the joint together firmly! In cool weather, rolls should be pre-stored for at least 1 day in a warm storage
- Be mindful to gently load the surface and immediately repair any damage with roofing felt adhesive
Sealant K-36 or equivalent repair compound for bitumen waterproofing. For larger damage, use and
attach/glue a strip from the underlay fabric. - Mechanical fastening for concealed attachment should be corrosion-protected clamp type Rapid 140/10
or larger staples with leg length 12-15 mm, back width 12.4-15 mm (wire dimension 0.5 x 1.3
mm) alternatively roofing felt nails min 25x2.5 mm. For open fastening at the joint, hot-dip galvanized
nails must be used! - Always cover with the surface layer (tiles, sheet metal, etc.) as soon as possible to avoid exposure to sunlight and
poor weather conditions. During construction, the underlayment can be exposed to sunlight for up to
maximum 12 months. During the usage stage, the underlay must be protected by the outer roof covering. - Rolls should be stored upright on a flat, dry surface and protected from sun and precipitation.
- T-Roof Epic is diffusion-tight and when mounted on a wooden substrate, the space underneath should be ventilated according to
practice.
1. Installation
Installation is done with strips across the direction of the roof slope. Rolling is done from right to left so that the side
the top side of the roll is unrolled inward. The sheets are easiest laid from the bottom with overlapping subsequent upwards. The substrate should be dry, even, and stable to avoid deflection and movement. The surface layer determines the nature of the substrate and the minimum slope. For the minimum underlying panel thickness, see table AMA HSD. 1331/1 (AMA-Hus 24). For battened roofs, at least 20 mm clapboard wood panel, and for non-battened, at least 23 mm. NOTE! The space under the wooden base or above the insulation must be ventilated according to standard practice.
For roof slopes steeper than 18° (1:3), the underlayment can also be installed according to the roof slope, from ridge to eaves. Be extra careful to ensure the adhesive edges stick during installation.
2. Gables
Starting and ending against gables is best done with a triangular strip that angles the base upwards.
The underlay fabric is folded around the strip and fastened visibly on the outside.
3. Joints
The underlay fabric is mechanically fastened with roofing felt nails min 25 x 2.5 mm (according to fig 3.D) or double with staples corresponding to at least Rapid 140/10 (according to fig 2.B) alternatively with larger staples, leg length 12-15 mm, back width 12.4-15 mm and wire dimension 0.5 x 1.3 mm (according to fig 3.C). Mechanical fastening is done at the longitudinal edges hidden in the upper adhesive edge of the sheet. Open and visible fastening (through both sheets in the overlap) can alternatively be done with only roofing felt nails and at slopes from 14° (approx. 1:4) and upwards (for flat banded sheet metal, hidden fastening is required). The sheet is temporarily fastened at the top edge (approx. 1 m between fastenings) and adjusted at the bottom edge. Overlapped in a straight edge line, the protective films are then pulled away simultaneously with careful pressure afterwards. Overlapping occurs
with adhesive edge to adhesive edge corresponding to the recommended overlap. NOTE! In case of hidden mechanical fastening, carefully check the strength of the joint afterwards. Consider difficult weather conditions and ensure any temporary fixing of the overlaps or protective covering until the permanent surface layer is installed! Alternatively, battening if possible! At transverse joints, the overlapping sheet at the lower edge should overlap at least 150 mm and then be cut diagonally upwards so that the overlap at the top is as it
lower (150 mm) + 300 mm. The lower sheet is attached at the edge with mechanical fastening c- measure 60 mm (according to fig 3.A). Cross seams should be glued down with 3 strings of roofing felt adhesive equivalent to Sealant K-36.
4. Eaves
At the eaves, the first strip is attached at the lower edge against the recommended eaves flashing with the adhesive edge
(Do not forget to remove the protective film!) and 3 sticks of roofing felt adhesive equivalent to Sealant K-36 (see fig 4). The end is positioned slightly up (about 20 mm) so that it is concealed by the protective surface layer in the usage environment. Adhesion should be done on cleaned metal. The eaves plate should be mounted on a strip of underlay above the wooden substrate (e.g., T-Roof Multi Strip).
For the surface layer of self-adhesive roofing felt, install the eaves flashing on top of the first layer of the underlayment.
5. Ridge ventilated
A ventilated ridge is arranged with an end at the wooden substrate's end towards the ventilated opening. Fasten at the top with roofing felt nails. Ensure that the ridge board is covered with an adapted strip of the underlay fabric down towards and out onto the top of the counter battens so that it is clamped by the topmost load-bearing batten.
6. Ridge sealed
At a tight ridge, make a pull towards the top edge of the ridge board and over to the other side, fasten mechanically with
for example, roofing felt nails. The covering of the ridge board is done from both sides of the roof and also constitutes the overlap of the underlay. If no ridge board is used, the overlap should occur from each side of the roof and total at least 500 mm. The lower sheet is fastened with, for example, roofing felt nails, and the upper is glued down with roofing felt adhesive equivalent to Sealant K-36. An alternative according to image 6.B alt, is done without a ridge board.
7. Valley
First ensure that the valley gutter has a stable and fixed base with a metal underlay (minimum 300 mm wide). The underlay should be provided with a strip of underlayment underneath. The underlay should be nailed to mechanically hold the roof sides together. In the case of a valley gutter with valley flashing, the gutter should be equipped
with a strip of the underlay fabric (see fig 7). The strip in the valley is fastened at the ridge and at the outer edges of
for example, roofing felt nails c-dimension 100 mm. Then let the connecting sheets from each roof side overlap the valley sheet by at least 150 mm. The fastening is done with roofing felt adhesive equivalent to Sealant K-36.
8. Pass-through options A, B, and C
A. For square pass-throughs (chimney, ventilation duct, etc.), the underlay should be cut, folded up, and nailed at the bottom (see fig 8.A). Then cover the fold with a strip of underlay fabric all around with an overlap (at least 300 mm high). Fasten with nails and glue (80 mm wide or 3 strings) or nail at the bottom. Nailing is done with a c-measure of at least 100 mm. Gluing is done with Sealant K-36 or equivalent. The corners are sealed extra with Sealant K-36 or equivalent sealant or with elastic durable sealing tape. Penetrations in battened constructions are finally provided with an underflashing of sheet metal at the bottom and all around!
B. For square pass-throughs and lower roof slopes (≤12°/1:5), higher safety and installation with glued collars are recommended (according to fig 8.B). Cut out four sides from the underlay (overlap 150 mm), trim and attach the bottom one first with the subsequent two sides, and finish with the back one towards the ridge. Gluing is done on all edges with Sealant K-36 or equivalent (80 mm wide or with 3 strings).
C. For round pass-throughs such as holes for ventilation pipes, etc., a collar like self-adhesive T-Collar butyl or full rubber collar (see fig 8.C) is used. The base of the collar is fully adhered to the substrate and the underlay. For full rubber collars, adhesion should be done with Sealant K-36 or equivalent. For a square base, one of the collar's corners should be positioned straight up towards the ridge during adhesion. The collar should be sealed at the top with a clamping ring or at least 2 turns of durable sealing tape.
9. Vertical connection (wall)
At the connection where the roof underlay at the top edge meets the wall (as per fig 9.A), an extension on the adjoining wall should be made, at least 300 mm. The extension is made under the facade and attached to the wind protection layer with roofing nails at 100 mm intervals and 30 mm from the edge. For battened outer roofs, the connection is provided with a metal flashing above the underlay (as per fig 9.B).
