<p>Sometimes a "roof" can be accomplished using the bridging feature of the printer. Depending on your slicer and on your printer's capabilities, the filament can extend from one edge of a structure to another without using support. The slicer will "recognize" the endpoints and the distance between and speed up the travel and possibly increase the fan cooling, allowing minimal sag between points. There are resources available on many model sites to print bridging test pieces to help determine the limits of your printer.</p>

<p>Expect some sag on the first layer, with a reduction for each successive layer. If you have, for example, five layers for the top faces, the last of the five may cover the sag of the previous ones.</p>

<p>Support is commonly used when there is no opposing endpoint to handle the bridging or when the distance exceeds the capabilities of the printer.</p>

<p>An example of a bridging test piece can be found on <a href="http://www.thingiverse.com/thing:476845" rel="noreferrer">Thingiverse</a>, although there are many to be found with a simple search.</p>

<p><a href="https://i.sstatic.net/BhWlz.jpg" rel="noreferrer"><img src="https://i.sstatic.net/BhWlz.jpg" alt="Bridging test example"></a></p>

CC BY-SA 3.0
2017-03-11T18:59:18.497Z
2017-03-11T18:59:18.497Z
fred_dot_u
<p>If you are printing a solid cube with infill, then the infill will support the "roof".</p>

<p>If you are printing a hollow cube, then indeed, you should enable "support" to print a support structure under any overhangs.</p>

<p>Depending on the angle, you may not need supports. Generally, FDM printers can print overhanging structures up to 45 degrees without the need for supports. The steeper (i.e. further from parallel with the print bed) the angle, the better the result.</p>

CC BY-SA 3.0
2017-03-11T16:53:08.247Z
2017-03-11T16:53:08.247Z
Tom van der Zanden
<p>I recently bought a 3d printer and right now i am printing a normal cube just to try it out. However I was wondering, when it has the last part left of the printing where it needs to create the roof, how will the filament stay there and not just fall down as there is nothing underneath?</p>

<p>Will I need to check the "Support" function in the print-settings before hand or is there something else i need to do?</p>

<p>Thanks a lot for the help/tips!</p>

<fdm><support-structures>
Is it possible to print an object that has a "roof" without anything under it?
user6365
# Is it possible to print an object that has a "roof" without anything under it?

(Asked by: username_0 on 2017-03-11)

I recently bought a 3d printer and right now i am printing a normal cube just to try it out. However I was wondering, when it has the last part left of the printing where it needs to create the roof, how will the filament stay there and not just fall down as there is nothing underneath?

Will I need to check the "Support" function in the print-settings before hand or is there something else i need to do?

Thanks a lot for the help/tips!

**Tags:** fdm, support-structures

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## 2 answers

### Answer by username_1 on 2017-03-11. Score: 4

Sometimes a "roof" can be accomplished using the bridging feature of the printer. Depending on your slicer and on your printer's capabilities, the filament can extend from one edge of a structure to another without using support. The slicer will "recognize" the endpoints and the distance between and speed up the travel and possibly increase the fan cooling, allowing minimal sag between points. There are resources available on many model sites to print bridging test pieces to help determine the limits of your printer.

Expect some sag on the first layer, with a reduction for each successive layer. If you have, for example, five layers for the top faces, the last of the five may cover the sag of the previous ones.

Support is commonly used when there is no opposing endpoint to handle the bridging or when the distance exceeds the capabilities of the printer.

An example of a bridging test piece can be found on [Thingiverse](http://www.thingiverse.com/thing:476845), although there are many to be found with a simple search.

[![Bridging test example](https://i.sstatic.net/BhWlz.jpg)](https://i.sstatic.net/BhWlz.jpg)


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### Answer by username_2 on 2017-03-11. Score: 2

If you are printing a solid cube with infill, then the infill will support the "roof".

If you are printing a hollow cube, then indeed, you should enable "support" to print a support structure under any overhangs.

Depending on the angle, you may not need supports. Generally, FDM printers can print overhanging structures up to 45 degrees without the need for supports. The steeper (i.e. further from parallel with the print bed) the angle, the better the result.


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