House columns and beams size.

[ilikethai]

I'm planning to build a house with some local and visiting friends.  I have a neighbor who does house building (that's what he's said). We're not engineers nor architects.  We're just coffee drinkers.  We're just planing out and talking.  Cut to the chase.  Simple 2 story house and maybe a small living attic with a dormer.  Usually houses here are in equal grid but this is not quite the case.  See pic.  He recommends the following.

-2 story house, modern shed roof to save on cost. all blocks no bricks.

-ceiling height 1st floor 3.5m.  2nd floor 3.2m

-1.5m deep hole footing. footing size 1.5cm wide and 50cm depth. (can this be 80cm wide and 50cm deep footing?)

-25cmx25cm column size with six 16mm rebars, 8mm ties.  (I think it's too much, I was hoping for 4 rebars)

-25cm width x 40cm depth of beam with three 14mm rebars on the bottom and three 12mm rebars on top, 8mm ties.  (that's new to me, it's always been all same size rebars)

-25cm width x 30cm depth of beam for very top where roof frame is. ( would 25cm x 25cm work?  because it needs to be lighter load)

-floor slab is pre-made but will be putting on wire mesh and pour concrete on top to get 8cm thickness. (can I just lay tiles

 on without putting on the wire mesh?)

 

what do you think? thanks in advance.

[Kwasaki]

Where we live drawings have to be presented to the local govt for approval before build.  

All above are familiar sizes but without calculations made and a proper layout also drawing to work from I couldn't help. 

[MikeN]

The depth and size of the footings is going to depend on the soil, but for a two storey house I would say the answer to your question will be “No!” 

If you are going to have 5m beams as in your pic, I wouldn’t be skimping on the size or the rebar.

[ilikethai]

Edit: I meant to say.

-25cmx25cm column size with 8 rebars 16mm diameter, 8mm ties.  (I think it's too much, I was hoping for 14mm rebars)

[prophet01]

On 3/31/2021 at 5:41 AM, ilikethai said:

We're not engineers nor architects.  We're just coffee drinkers.

 

1 hour ago, ilikethai said:

-25cmx25cm column size with 8 rebars 16mm diameter, 8mm ties.  (I think it's too much, I was hoping for 14mm rebars)

 

@ilikethai

If you're neither an engineer nor architect, just a coffee drinker, on what basis are you making your decisions in respect of the proposed structural integrity of a building?

[Toosetinmyways]

I have been out of the Thai house building and renovation for 20 years now so my knowledge is dated.

Firstly it depends on where you live as to what you will be able to achieve. All my projects were done to the local area standards and regularly inspected with no deviations from the submitted plans allowed without prior approval.

I feel you will be stretching some Thai builders comfort zone.

Attic living space with dormer window will require a non standard roof truss design. Not only will the truss's have to support the roof but  floor and walls inside the roof space with a greatly increased span.

I built a house with a mixture of 4 and 5 meter spans as I had a full sized snooker table. I do not recommend it. The 5 meter span beam is so much bigger ie. (taller and heavier requiring larger footings and posts) that you have to decide how to hide it. If you have a large false ceiling space you can drop the beam into the space and have a level first floor. If you want to keep a high ground floor ceiling then you will have have to put the excess beam height into the first floor floor creating a two level first floor .

Just a guess but I would say a 5 meter span beam would be around 80 to 100 % more expensive than a 4 meter span.

Most houses in Thailand are constructed on the 4 meter modular size as this is the most cost effective size.

[ilikethai]

35 minutes ago, prophet01 said:

 

 

@ilikethai

If you're neither an engineer nor architect, just a coffee drinker, on what basis are you making your decisions in respect of the proposed structural integrity of a building?

it's all about thinking and opinion ahead.  talking and talking.  all I can do is talk.

[sometimewoodworker]

5 hours ago, Toosetinmyways said:

 

I built a house with a mixture of 4 and 5 meter spans as I had a full sized snooker table. I do not recommend it.

Our living room is 8 metres by 7 metres and the room I use for woodworking is 7.5 metres by 11.5 m both of these are completely clear.

[Toosetinmyways]

The advice I was trying to give, was not to mix beam sizes in the same strucure .

I have a garage with 7x 7 meter unsupported spans, but all the post and beams are the same dimensions.

[sometimewoodworker]

1 hour ago, Toosetinmyways said:

The advice I was trying to give, was not to mix beam sizes in the same strucure .

I have a garage with 7x 7 meter unsupported spans, but all the post and beams are the same dimensions.

There is no reason (other than possible convenience ) to do that the sizes of posts and beams should be calculated correctly and rebar placed correctly. They have different loads, tension vs compression.
 

None of my beams are the same dimensions as my posts and there are various different sizes for both, but then they were designed for the loading that they have.

 

If your posts and beams are the same dimensions then the posts are seriously over built. Also if the rebar is the same in both then you either have far too much in some or very badly designed beams.

 

sure you can spec for the QEII on a rowing boat and it will probably still float but that just shows your level of competence not design ability and skill.

 

because a building is still standing only tells you it was at least strong enough, it doesn’t tell you about the level of over strength used in it.

Edited April 2, 2021 by sometimewoodworker