Build a flat roof yourself

It does not always have to be a complicated steep roof with a roof truss. On different buildings you can also build a flat roof yourself. The important thing is to stick to the basic rules that apply to a flat roof. In return, you will receive detailed instructions for self-construction of a flat roof.

Here you can build your flat roof without hesitation

There are numerous smaller buildings and constructions on which you can put a flat roof yourself.

  • garage
  • carport
  • terrace roof
  • canopy
  • toolshed
  • garden shed

Accordingly, the flat roof can therefore be placed on a beam structure or a building. Consequently, we explain below the self-construction of the flat roof without the respective substructure. In the version (roof pitch angle) it must always be the same anyway.

The roof pitch angle at the flat roof

Even if the flat roof is called "flat roof", it should never really be completely flat. In Germany flat roofs are considered from a slope angle of two degrees as a flat roof and reach up to 25 degrees. In Austria even only up to five degrees.

Keep minimums

The flat roof should have a minimum inclination angle of two degrees. However, a roof pitch of at least five degrees is recommended. Because the steeper the flat roof becomes, the worse water can collect on the roof and runs much faster.

Instructions for self-construction of a flat roof

  • Beams as a warehouse for the rafters
  • rafter
  • battens
  • Tongue and groove boards
  • Wood preservatives
  • roofing felt
  • Pappa nails, galvanized
  • possibly Traufleisten
  • Nails or drywall screws
  • Bolts with nuts and large washers for the beams
  • suitable hand saw
  • miter
  • alternatively miter and chop saw
  • spirit level
  • corner
  • Cordless Screwdriver
  • drilling machine
  • Holzbohrer
  • hammer
  • chisel
  • possibly guideline
  • Site manager or easel

1. Preparatory work

First, you must set the roof pitch angle. In order to avoid having to wait too long, you can calculate 5 cm incline per depth meter (from the front, eaves, back, ridge) and fasten the chalk line accordingly.

In addition, all wood needs to be treated with wood preservative. Different systems can be used for this.

2. Attach the beam bearings

Now you have to fasten the beam bearings across the roof. Of course, the distance depends on the size of the building. For most buildings, however, you should calculate a distance of 80 to 100 cm - or divide the roof depth by the minimum number of rafter storage required. Although you can nail the bearings, however, glands are always preferable.

3. Attach the rafters

Now place the rafters lengthwise on the bearing beams. Now mark the support points and prick them out with the chisel so that the rafters lie flush on the bearings. Where you connect bearings and rafters, drill the connecting holes with the wood drill. Then screw the rafters.

4. Attach the roof battens to the rafters

Now you can relocate the roof battens on the rafters, ie from left to right. Again, the distance should be between 50 and 100 cm, depending on the size of the building.

5. The roofing with tongue and groove boards

Now lay the tongue and groove boards along the roof. Screw or nailing each board with two screws or nails per rafter.

6. Seal the roof with roofing felt

Finally, the roofing felt is used. If necessary, you can attach eaves moldings to the verges. At the eaves, you should attach the Traufleisten on the roofing felt. Also on the ridge, let the roofing felt overlap accordingly.

They start with the bottom row of roofing felt (at the eaves). Allow the roofing felt to protrude 5 to 10 cm from the verges and the eaves. Lay the next track with an overlap of 20 to 30 cm. If you later want to install bitumen shingles, use as few nails as possible.

Now push the overhanging roofing felt around the corners and fasten.

Tips & Tricks

The larger the roof pitch angle, the lower the overlap of the roofing felt.

You can preferably use boiler-impregnated wood, which they additionally admit or seal.

If you want to further seal your own flat roof, you will find numerous articles in the house journal. For example, to the bituminous membranes welded on the flat roof or to [roof shingles laying on a flat roof].

Video Board: Garden Room Workshop: Part 9. Flat roof structure