Warping MDF boards!

[Spax]

Hello,
I've made 3 sliding doors out of MDF about 210x103 cm.
These have been wallpapered on the front side.

Unfortunately, they have started to warp

Now the question is why? Could it be because they are only wallpapered on one side, making it sealed while the backside still absorbs moisture?

Could it then be remedied by simply painting the backside?

Or is it so bad that they are warping from humidity :eek:

Do we have any MDF experts out there

 

[v-g]

MDF should always be secured or stabilized using, for example, regular wood.

Think about Billy where it's essentially the veneer that prevents the shelves from sagging, a wooden shelf never sags as much.

Humidity is not good for MDF either; it absorbs everything, as anyone who has tried to paint it knows.

 

[Spax]

But what can I do about it now?
The doors are completely finished.

What do you think about the theory that they are only wallpapered on one side?
All 3 have bent in the same direction.

 

[v-g]

Paper is quite strong in tension, so it is entirely possible.

 

[Spax]

Yesterday I painted the back of one of the doors, let's see what it gives!

More suggestions?

 

[Maba]

I read quite recently that you should wallpaper on both sides.

http://www.garderobspecialisten.com/gds/Garderob.pdf

 

[Spax]

Yes, that's what I suspected!
Let's see what the painting yields.

The next step will be to wallpaper the back!

Hope it's not too late......

 

[Zodie]

God, how boring, hope it works out...

 

[Spax]

I have now painted all the doors and so far they are holding their shape, knock on wood....
We'll see what happens when the air gets drier outside

 

[Tiger79]

Have they straightened out again?

Going to start building sliding doors soon...

 

[Spax]

I placed them on sawhorses. First for 4-5 hours without support in the middle. Then with support for about a day. I had noticed earlier that they "shape" themselves. Then I painted each door twice with ceiling paint. The first door has been hanging for about 2 weeks now without moving significantly.

But I recommend painting or wallpapering on both sides from the start.

 

[MB77]

I read quite recently that you should wallpaper both sides.

It's true, if you want ex. wallpaper then you need to have it on both sides. This applies to all wood fiberboards.

 

[JanneSjo]

what thickness did you have on the MDF boards

 

[pbengtsson]

Painted an MD door against the underfloor heating panel (about 70X80 cm) yesterday. The MDF was 19mm thick and I had read this thread before painting. I painted the back once and painted the front 2-3 times. Now I immediately see that the door is warping after a day. During drying, I placed it upright. I'll see if it straightens out once the paint has dried properly. The warping is happening towards the side I painted the most.

 

[Spax]

Even mine were 19 mm. When I wallpapered mine, they hung. They bowed inward. Like a U, where the opening of the U points outward from the wardrobe (if you understand )