change height on multiple objects at once

Ok so let’s suppose i have 2 buildings;first one’s height,let’s say,is 4m and the second one’s is 5m.Now i want to ad 2 meters for each building:first one to be 6m and the second one 7m,can this be done at one go?
For example to select both ones and ad 2m to each of them but in one go

Or maybe if i could merge the 2 buildings into one,like multypolygon,and then change the height for that “multipolygon”,i’ve tried it but it doesn’t work…my buldings are next to each other so i can’t even make a multipolygon

…hope it make sense

What editors did you try?


Ok maybe I could manage to create the multipolygon but then can i grow,like i said,these buildings with the same amount of height?

I don’t see an easy way to do this with JOSM, or the other editors I’m familiar with. JOSM lets you change tags on all selected objects, but only to a new value for all objects (“set height on all buildings to 10 m”), not relatively to the existing value (“increase existing height value by 2”).

Multipolygons aren’t really suited for this use case at all in my opinion.

What i it practically needed for?
I don’t JOSM plugins but I assume, a new plugin could do it:
increase or decrease x meter or percent

Thank You both of you!

Tordanik - yeah this is what i was think of too,unfortunately

karlos- I assume that this plugin doesn’t exist already,isnt’it?