I'm trying to understand what size block to use to construct some internal walls at MiL's house, 7cm, 9cm or 14cm, here's the deal:

 

MiL's house is 17 years old and and sits on raised concrete posts that provide a large shaded area under the house for sitting/washing machine etc. The concrete posts are spaced (from memory) about 3 meters apart and are steel wired at the base, the concrete floor contains steel mesh and is strong.

 

A bathroom was constructed at ground level using 7cm block, one wall runs from post to post but the other walls stop short of the posts so are unsupported. Over 17 years, the frequent opening and closing of the door has caused the door opening wall to shift and badly crack, this has started to crack and weaken the two side walls. There is no lintel above the door! The concrete floor is intact and show no sign of cracking or weight damage. Floor to ceiling height appears to be about 2.5 meters.

 

The project is to remove the three bathroom walls, reconstruct them more solidly AND to build a second adjacent room for storage. all walls will run post to posts and both doors will have lintels installed above. The exception to this MAY be the bathroom door wall which will be sited some 60cms back from the posts but the supporting end walls at each end will run post to post, hence the door wall will be supported.

 

The existing walls appear to be 7 cm block. It looks like that may be OK if walls are run post to post and are supported, as long as the wall doesn't contain a door, otherwise  X mm block should be used. What is the value of X, please, I think 9 may work (it seems 7 cm worked OK for at least a decade)? I know that 14cm will be ideal but this is not my project and MiL's budget is tight, 14cm block is 20 baht vs 7. 

 

TIA

 

 

 

1 hour ago, nigelforbes said:

7mm, 9mm or 14mm

mm??? Don't you mean cm???

1 minute ago, 2baht said:

mm??? Don't you mean cm???

Well spotted, thank you, I'll fix that. :))

buy the blocks that fit her budget
unless you want to be forking out the extra

 

8 minutes ago, nigelforbes said:

I know that 14mm will be ideal but this is not my project and MiL's budget is is tight, 14mm block is 20 baht vs 7.

you sort of already answered your own question

1 minute ago, patman30 said:

buy the blocks that fit her budget
unless you want to be forking out the extra

 

you sort of already answered your own question

I will intervene if I have to, the money is not an issue for me but I do want the job done properly. If 9cm will work, great, but if it really should be 14, somebody will hopefully know and say.

Concrete filled 14cm blocks for strength and insulation. 

The smallest blocks should be fine if you render on both sides, the rendering adds a lot of strength.

 

I would make the concrete lintel run the full distance from post to post with re-bar the full length.

Just now, 2baht said:

Concrete filled 14cm blocks for strength and insulation. 

The insulation part is not nece3ssary since these are under-house rooms that are well shaded. I agree concrete fill will give superior strength but is almost certainly overkill.

1 minute ago, Crossy said:

The smallest blocks should be fine if you render on both sides, the rendering adds a lot of strength.

 

I would make the concrete lintel run the full distance from post to post with re-bar the full length.

I like that idea, thanks, it works for me. We are planning to render both sides but the full length lintel had escaped me, brilliant.

28 minutes ago, nigelforbes said:

I like that idea, thanks, it works for me. We are planning to render both sides but the full length lintel had escaped me, brilliant.

 

I admit it's not my idea.

 

When we built the house our contractor put full width lintels above all the doors and above and below the window openings. 12 years later nothing has moved or cracked ????

 

Something like this.

You can buy QCon ready made lintels.

 

21 minutes ago, CharlieKo said:

Something like this.

That's helpful, thank you.

I had and have 10cm internal walls in my condominium.

If I would decide from scratch then I would use thicker walls. The reason are electrical boxes and any pipes.

If the walls are too thin, then if you install something on one side of the wall you have to be careful what you install on the other side of the wall. And later, if you drill a hole in one side, you have to doublecheck also the other side of the wall.

I am no builder and this is only based on my one time renovation.

2 minutes ago, OneMoreFarang said:

I had and have 10cm internal walls in my condominium.

If I would decide from scratch then I would use thicker walls. The reason are electrical boxes and any pipes.

If the walls are too thin, then if you install something on one side of the wall you have to be careful what you install on the other side of the wall. And later, if you drill a hole in one side, you have to doublecheck also the other side of the wall.

I am no builder and this is only based on my one time renovation.

A valid point, duly noted. I think we're probably safe on this because the two rooms in question are a bathroom and a storage room so there wont be much by way of power etc or drilling of walls, at least there better not be! 

The beam or lintel from post to post across the top of the wall is highly recommended.  It is fairly common practice to put a smaller steel reinforced beam about half way up the wall for added strength, not expensive.  This would be a beam similar to what Crossy mentions having above and below windows.

Block size in this situation is not a major factor as it's not load bearing. The key here is make sure you use block tie straps from the existing posts to new block to ensure a strengthened tie in and prevent any sideways movement. Then make sure you use a lintel over the door. Those to things will eliminate any side movement to the new  wall.