gates
Below is the 1000 words picture. How do I cover that empty space?
The hinges are at the opposite end of the gate
How about this:
This will be done by ripping of a post in half (45%) and then that will be attached to the existing post. On that I will screw small horizontal boards made of the remainings of the 6×8 cedar boards that I used to build the gate
Rule of thumb is that 1/3 of the post should be in the ground. A 6' fence should be sunk into the ground 3', so you'd need 9' posts.
As Shirlock states, even that won't likely support an 8' wide gate. Two 4' gates would definitely be a better option.
Perhaps the easiest solution, however, is to not even make a gate. Instead, build your fence and then make this an 8' panel that is attached with temporary fasteners...such as bolts. On the rare occasions that you need access, unbolt the fence panel and remove it completely--thereby negating the need for the two posts to cary the load of a cantilevered gate.
On the plus side, it's less gate hardware you need to buy and deal with.
In an attempt to answer some of the questions raised in your posting let me respond in answer format.
1) It can be advantageous in some situations to affix a timber post to the brick or concrete posts/walls in either side of the gate opening. This post can then serve as a better medium into which to attach hinges and latches.
2) A 3.8 meter wide gate will develop a huge amount of lever arm out at the latch end of the gate and this needs to be taken into account when developing the gate design.
3) The size of wood used can play a big part in how heavy the gate will end up being. The type of wood can play a role as well. This is one reason that boards are often used for gate facing instead of thicker planks. Cedar wood is also much lighter than hard wood like oak and thus becomes a popular choice for gates.
4) Adding appropriate bracing into the design of the gate will keep the gate from sagging.
5) Successful wide gates can often benefit from making the aforementioned side posts much higher than the gate opening and then using a cable from the top down to the end of the gate away from the hinges to help support the weight of the gate. Sometimes you can see the tops of the two higher posts connected across by a horizontal member. This provides support from post to post to keep the weight of the gates from pulling the posts to the sides.
Best Answer
Rip a 45 degree notch down the center of a post (4 x 4 x hgt of gate) and install into a post anchor bracket and than afix to the brick mortar joints with TapCon screws. Or TapCon a 2 x 4 to one edge of the corner and cap the edge with another 2 x 4 on the other corner edge. If you can dig a hole sink a metal or wooden post and attach a fence board to it. Pour a cement footing and build a brick pillar with those left over half bricks. Attach a dog-eared fence board to the edge of the gate. Or install 2 angle brackets, bent to 22.5 degrees, to the mortar joints of the brick wall (with TapCons) and attach fence board to the bracket. Or pour a footing and install concrete block on edge, wrap extruded metal lathing around it, and trowel on a stucco finish.