how to extend timber uprights

[tryingitathome]

Someone gave me a pre-owned "kit" cubby house. As you can see from the photos, the uprights -- once concreted in -- are not at the same height. (The three posts in the middle are supposed to be a lot higher than the others; it's a basic gable roof.)

20221112_102904.jpg


Initially, I thought I'd just cut them down to the height of the shortest post, but I think that might make it too small/low for my kids.



Next, I thought I'd cut them down to the height of the shortest post and attach post stirrups on the top (y'know, the kind used on verandahs), but that wouldn't be very strong going into the end-grain on the posts.



Then, I wondered whether I could:

• cut them down to the height of the shortest post
• drill a hole about 250mm into the top of the post
• insert some rebar
• then, get another post the same diameter
• cut lengths to the desired height (I'd say probably 600mm)
• drill a hole down the centre
• slot it onto the rebar
• and add bracing/strapping on four sides about 200mm on each side of the join.

My latest hair-brained idea is to "sister" them in some way... not sure how... perhaps cut away half the top of the post (say, 500mm), do the same with the extension piece, then drill two or three holes through both and bolt them together with M10 or M12 bolts.



That all sounds rather complicated, though... surely there must be a simpler way?

Thanks very much for any advice you can offer this stuck dad.

[rwbuild]

3 pieces 50 x 6 flat bar 600 long per post (300mm lap on post and extension) , 2 bolts 10mm dia each post, total 4 bolts per piece of flat bar, all galvanised because you are dealing with treated pine

[tryingitathome]

You, sir, are a champion. Thank you!

[tryingitathome]

One question, though, Ray... why three pieces per post?

[rwbuild]

Anything in a triangular configuration is the strongest, forces equal in all directions
So 3 pieces 120deg apart on circular posts = 360deg
Instead of bolts use 50mm x 10mm coach screws, no problems of alignment that way

[tryingitathome]

It worked like a charm, Ray. Thank you!