Collision for 3D Modell

[Thendon]

Hello,

I'm trying to create a chair for a new addon but the collisions are weird.

[IMG]http://i.imgur.com/mtUXCEt.png[/IMG]
Edit: I am standing on the chair in that picture

This is my qc file:

$scale 0.4
$modelname	"project/chair.mdl"
$staticprop
$body chair "chair.smd"
$collisionmodel "chair.smd" {
 $concave
}
$surfaceprop "Wood_Furniture" 
$contents "solid" 
$cdmaterials "project"

Am I doing something wrong?

[Rubat]

Read on the $concave flag description please:
https://developer.valvesoftware.com/wiki/$collisionmodel