C
I have built a treehouse
G
I have built a treehouse
Am
Nobody can see us
F
It's a you and me house


Same chord progression here, twice. A bunch of "ooooooh"'s for vocals.

C
I've been climbing rocks and stones
G
Been collectin' broken bones
Am
I've been swimming 'cross the lakes
F
Just to find this perfect place

C
I got lost into the woods
G
I got covered up in mud
Am
I've been going through a lot
F
Just to find this perfect spot


^Then you repeat all of that except for the "Ooooooh" section^

Then it goes into the section with the same lyrics as the chorus, only sung with a
rhythm. This is the only part where I'm not sure if the chord progression used in the 
of
song applies. There doesn't seem to be much instrumentation other than percussion and 
though.

The final section, the first 2 lines of the chorus only slower:

C           G
I've built a treehouse
Am            F
And no one can see us