Doing a spare bedroom/storage attached to the house,size about 3x6m. Q: 1: Do i need rebar for the floor as it wont be any heavy load? Is 5 cm thick concrete enough/ok? 2: Using the cheap/standard 6 baht blocks for the walls,do i need to add steel/rebar to "lock" them in the ends(towards the columns)? 

%cm? Here and there it will be only 3cm. Personally, I would go for 12cm minimum, with rebar. I would also go 30cm deep at the places where the wall is going, which is in fact, a heavy load,  also with rebar. That way you can be sure it won't shift or crack. Where the walls meet up with the posts, yes it is advisable to bore a hole in the post and slip in a short piece of rebar, every 2 or three layers. Don't worry about the rebar, it's easy to put in place, just make sure it doesn't touch the soil. 

2 hours ago, sanook 1 said:

Q: 1: Do i need rebar for the floor as it wont be any heavy load? Is 5 cm thick concrete enough/ok?

Yes for the first part and no for the second. Without rebar it will definitely crack, and may do with rebar at that thickness.

18 hours ago, cooked said:

%cm? Here and there it will be only 3cm. Personally, I would go for 12cm minimum, with rebar. I would also go 30cm deep at the places where the wall is going, which is in fact, a heavy load,  also with rebar. That way you can be sure it won't shift or crack. Where the walls meet up with the posts, yes it is advisable to bore a hole in the post and slip in a short piece of rebar, every 2 or three layers. Don't worry about the rebar, it's easy to put in place, just make sure it doesn't touch the soil. 

Very clear,Thank you!  Do i need to "lock" the floor slab into the existing building/walls in some way? 

Another Q: The electric earth pole is going down in the soil in one of the corners where i doing the floor,is it ok to just leave it there and pour the concrete around?

On 12/28/2025 at 10:39 AM, sanook 1 said:

Very clear,Thank you!  Do i need to "lock" the floor slab into the existing building/walls in some way? 

I didn't. However, I did take care to lay the first layer of bricks into the wet concrete slab. Maybe you need to think about a damp proof course? Nobody was bothering with this 14 years ago when I laid my last brick so I didn't either. Regret it now. I would buy some robust plastic/rubber sheeting or a bag or two of asphalt.

14 minutes ago, sanook 1 said:

Another Q: The electric earth pole is going down in the soil in one of the corners where i doing the floor,is it ok to just leave it there and pour the concrete around?

Don't worry about it if it isn't in the way. Otherwise, you can easily buy a new copper rod at Thaiwatsadu.

On 12/30/2025 at 11:08 AM, cooked said:

Don't worry about it if it isn't in the way. Otherwise, you can easily buy a new copper rod at Thaiwatsadu.

Thank you!