lightweight blocks

[Joinaman]

Hi there

thinking of building a small 4m x 4m room using the lightweight blocks , 100mm thick , build off a concrete slab

Any reason why i need to use concrete posts on the corners, instead of just bonding the corners?

The roof will be a lightweight steel frame with steel sheets over, so no weight on the walls

Seems to be the norm to use either standard concrete posts, or to form reinforced posts on the corners and intermediates

Thanks

[sometimewoodworker]

The blocks are not structural, so that could be a good reason.

[Joinaman]

Just now, sometimewoodworker said:

The blocks are not structural, so that could be a good reason.

they are reasonably solid, unlike the cheap concrete hollow blocks, and are bonded with adhesives rather than sand and cement 

[OneMoreFarang]

8 minutes ago, Joinaman said:

Any reason why i need to use concrete posts on the corners, instead of just bonding the corners?

In my renovation the professional builders used no post at the corners. They used posts on the door frame. 

This is just FYI. I don't know the reasoning why they did what they did. 

[sometimewoodworker]

20 minutes ago, Joinaman said:

they are reasonably solid, unlike the cheap concrete hollow blocks, and are bonded with adhesives rather than sand and cement 

If you are talking about AAC blocks they are not structural until you get to 200mm this is not opinion, it is in the specifications 

[degrub]

The posts would be there to resist in plane of wall forces ie pushing from the end edges of the wall.  So wind pressure on the wall that is 90 degrees to one of the walls. Or seismic forces. Also, properly set against the column, the mortared block would resist wind pressure directly hitting the wall face due to a pinching effect between the column face and the block end face.
 

is rhe steel frame supporting the roof frame independent of the walls? Or is the roof frame resting on the walls ?

 

The columns on both  sides of a door are there to provide a secure anchor for  the door hinge and to transfer  vertical load from the lintel over the door opening.

 

Edited April 9 by degrub

[freeworld]

Don't know your layout or how the roof is supported.

 

100mm wide block is quite narrow so may because of stability and the joints are quite thin.

 

Here is a video laying qcon blocks, they show concrete posts at the corners and these look 100mm wide.

 

 

Edited April 9 by freeworld

[Joinaman]

3 hours ago, freeworld said:

Don't know your layout or how the roof is supported.

 

100mm wide block is quite narrow so may because of stability and the joints are quite thin.

 

Here is a video laying qcon blocks, they show concrete posts at the corners and these look 100mm wide.

 

 

100mm is standard bock size in many countries. especially the UK. So not sure why the need for a post on the corner when it would be cross bonded, which would be as strong, if not stronger then butting up to a post each side ? Ant the roof would be lightweight steel, mono pitch, bearing on to a steel wall plate, so spreading the light load ? No wind shear to factor in, wil be built between existing buildings, so sheltered from sun and wind 

[freeworld]

3 hours ago, Joinaman said:

100mm is standard bock size in many countries. especially the UK. So not sure why the need for a post on the corner when it would be cross bonded, which would be as strong, if not stronger then butting up to a post each side ? Ant the roof would be lightweight steel, mono pitch, bearing on to a steel wall plate, so spreading the light load ? No wind shear to factor in, wil be built between existing buildings, so sheltered from sun and wind 

Aware that masonry blocks come in 10cm width and various other sizes in many countries (qcon manual shows different sizes they have available)

 

Yes blocks can be interlocked to tie them together. Masonry butting up against concrete columns are usually tied together with metal strips affixed or embedded in/to the concrete columns at intervals. There are different ways to do it, depends on the purpose, support, design considerations, the manufacturer technical specs, cost and building regulations etc...

 

As for your design assumptions, no comment.

 

For info here some details and info from Qcon block manual (don't know which block supplier you have but you could check with them)

 

https://qcon.co.th/th/what-is-alc-block-/q-con-alc-block-manual#ขั้นตอนการก่อผนังอิฐ Q-CON

 

 

 

Edited April 9 by freeworld

[lanng khao]

4 hours ago, Joinaman said:

100mm is standard bock size in many countries. especially the UK. So not sure why the need for a post on the corner when it would be cross bonded, which would be as strong, if not stronger then butting up to a post each side ? Ant the roof would be lightweight steel, mono pitch, bearing on to a steel wall plate, so spreading the light load ? No wind shear to factor in, wil be built between existing buildings, so sheltered from sun and wind 

Why not put a extra block in each corner to give it a bit of strength that would also give you half bond on your second course, but you would have pillars on the inside, im a bricklayer and wouldn't bother with the 'sows', concrete posts at the corners, or maybe go for a 140 mm block and just bond the corners.

[sometimewoodworker]

5 hours ago, Joinaman said:

100mm is standard bock size in many countries. especially the UK. So not sure why the need for a post on the corner when it would be cross bonded, which would be as strong, if not stronger then butting up to a post each side ? Ant the roof would be lightweight steel, mono pitch, bearing on to a steel wall plate, so spreading the light load ? No wind shear to factor in, wil be built between existing buildings, so sheltered from sun and wind 

That is because the standard in the U.K. is not AAC. AAC, to repeat myself, is not rated for non post and beam walls under 2000mm. The makers all rate the thinner blocks for fill in walls. Exactly why the 2000mm limit is there I don’t know, it certainly isn’t for cross bonding, it is probably for compression but for information you should contact Habel the original makers, who by now have almost 100 years experience 

[Pogust]

I have built several small house extensions using 100 mm AAC blocks. A pump-house and a kitchen. No need for any posts. But do get a lintel above door and window. Doors and windows mounted with polyurethane spray foam, no need for mechanical fasteners.

 

If you ever tried to break down a 100 mm AAC wall you realize how strong it is.....

[Fruit Trader]

4 hours ago, sometimewoodworker said:

That is because the standard in the U.K. is not AAC.

 

I seek a lesson.

A little reading at the UK Forterra (block manufacturer) website shows their lightweight block includes autoclave time in the manufacturing process. 

 

What is the difference between the Thai autoclaved block and the UK autoclaved block? Compressive strength ratings are similar for the various standards available in each country.

 

Laying of these blocks also varies between countries, with some using a glue mix and others standard mortar mix bed on walls that appear to be carrying a second floor load. 

 

I include video showing the UK method of regular mortar bed. 

 

 

 

 

[sirineou]

If done properly 10cm AAC is load bearing,

having said that ,

I would not Recommend it  it.

The operative  phrase  here is "If done properly"  and the locals here are used to working with columns.

  In addition the slab would have to be reinforced which would negate the savings from  not using columns. Also you would have to pour a ring beam on top to attach the roof metal, and since the AAC block is soft it has little tension strength, (what makes it load bearing is it's compression straight).  So that would also eat on your savings from not run  columns.

If I was doing that I would also use galvanised straps to transfer the wind load from the roof to the slab. 

When in Rome do as the Romans do !!!

7.5 AAC costs 28.75   bht at Thaiwasadu , 10cm is special order and I found it at 43 bht  

So for almost the same price as a single  10 cm AAC  you can get 15 cm of AAC by using the double 7.5 s . Also you will get a cavity if you do wished (highly recommend it) and would hide your columns!!!! .

For your interior walls, single 7.5 is adequate for additional savings!!

Also since 10cm would have to be special order you will have to buy extra to compensate for waste.

7.5 is everywhere, probably 10 places have it in stock in your area. So you can get a little as you want and if you need more, drive to Thai wasady, or Do home and get some more. 

 

 

[sometimewoodworker]

6 hours ago, Pogust said:

I have built several small house extensions using 100 mm AAC blocks. A pump-house and a kitchen. No need for any posts. But do get a lintel above door and window. Doors and windows mounted with polyurethane spray foam, no need for mechanical fasteners.

 

If you ever tried to break down a 100 mm AAC wall you realize how strong it is.....

If a house has been successfully built using materials not rated for the use does not provide any proof that it is the correct way to do it, nor does it give any confidence that the structure is sound.

 

That the walls are difficult to break down doesn’t prove anything but the glue bond is strong. 

 

You can build a house using cardboard if you want and if properly waterproofed and sized it could be good enough for a pump house but you would not get me using it, the same is true of your 100mm load bearing wall house, it will work for a time but isn’t rated for the use.

 

I have found an AAC block that is load bearing at 125mm but not all AAC blocks are equal and the standard blocks used in Thailand have a lower limit of 200mm for load bearing use

 

 

[sometimewoodworker]

4 hours ago, Fruit Trader said:

What is the difference between the Thai autoclaved block and the UK autoclaved block? Compressive strength ratings are similar for the various standards available in each country.

There are several, if not many, different grades of AAC blocks, the materials used vary as do the structural strength. There is not one standard, so without doing research into the details I can’t answer your question.

[Joinaman]

9 hours ago, Pogust said:

I have built several small house extensions using 100 mm AAC blocks. A pump-house and a kitchen. No need for any posts. But do get a lintel above door and window. Doors and windows mounted with polyurethane spray foam, no need for mechanical fasteners.

 

If you ever tried to break down a 100 mm AAC wall you realize how strong it is.....

thanks

putting lintols over openings is a given, standard practice 

used foam before with windows, due to fixing problems in the cheap concrete blocks

But rof will be a lightweight mono pitch steel roof, fixed to existing house wall, with steel wall plate at the other end+

its an extension rather than a separate building, tied two sides to existing building and one front wall with door and window +size is 4mx4m max, so not a large unit or large spans 

I have built a couple of dwarf walls using these blocks with 45 degree angles and surprised how strong the actually are when impacted 

[Joinaman]

7 hours ago, sirineou said:

If done properly 10cm AAC is load bearing,

having said that ,

I would not Recommend it  it.

The operative  phrase  here is "If done properly"  and the locals here are used to working with columns.

  In addition the slab would have to be reinforced which would negate the savings from  not using columns. Also you would have to pour a ring beam on top to attach the roof metal, and since the AAC block is soft it has little tension strength, (what makes it load bearing is it's compression straight).  So that would also eat on your savings from not run  columns.

If I was doing that I would also use galvanised straps to transfer the wind load from the roof to the slab. 

When in Rome do as the Romans do !!!

7.5 AAC costs 28.75   bht at Thaiwasadu , 10cm is special order and I found it at 43 bht  

So for almost the same price as a single  10 cm AAC  you can get 15 cm of AAC by using the double 7.5 s . Also you will get a cavity if you do wished (highly recommend it) and would hide your columns!!!! .

For your interior walls, single 7.5 is adequate for additional savings!!

Also since 10cm would have to be special order you will have to buy extra to compensate for waste.

7.5 is everywhere, probably 10 places have it in stock in your area. So you can get a little as you want and if you need more, drive to Thai wasady, or Do home and get some more. 

 

 

thanks

100mm is stock where i am, but could go to 125mm , just creates more problems around the door and window, which are 100mm 

not sure what you mean by ring beam for roof ? Its a mono pitch, fixed at the high point to the existing building, with the only light load being on the front wall, which would have a steel wall plate strapped down, which would spread the light weight on the full width

why the need or a concrete beam ?

where is the load bearing , apart from the front wall? which will have minimal load ? 

 

 

[Joinaman]

3 hours ago, sometimewoodworker said:

If a house has been successfully built using materials not rated for the use does not provide any proof that it is the correct way to do it, nor does it give any confidence that the structure is sound.

 

That the walls are difficult to break down doesn’t prove anything but the glue bond is strong. 

 

You can build a house using cardboard if you want and if properly waterproofed and sized it could be good enough for a pump house but you would not get me using it, the same is true of your 100mm load bearing wall house, it will work for a time but isn’t rated for the use.

 

I have found an AAC block that is load bearing at 125mm but not all AAC blocks are equal and the standard blocks used in Thailand have a lower limit of 200mm for load bearing use

 

 

so where is the load bearing on a small 4x4 extension ?

Two side walls will be tied to the existing building , with only two corners to form the front wall 

the only load onto the new walls would be on the front wall, which would have a wll plate fixed to fasten the lightweight steel mono pitch roof to , with the high point of the roof fixed to the existing building, so no load on the side walls from the roof 

are you saying 100mm oe 125mm blocks are not strong enough to stnd up and the bonded corners are not sufficient ?

Surely the bonded corners ar as strong as the clip or nails the use to tie the blocks in with ?

[sirineou]

1 minute ago, Joinaman said:

not sure what you mean by ring beam for roof ? Its a mono pitch, fixed at the high point to the existing building, with the only light load being on the front wall,

The roof would have to be attached to something.

Usually it is welded to the rebar on the columns, the rebar transfers the forces from the roof  to the foundation

 Load, or compression is not the only force. Sure it can support the weight of the roof. when the wing gets under the roof where it extends from the wall (usually 1m) you have an upward load. (tension) .

If you are using AAC block all the way to the top . without columns, or a ring beam , the only thing that is holding the roof from blowing away is the top course of AAC block .

  First potential  issue is that AAC block is soft and your unchors could pull away especially after years of this happening repeatedly during windy season. 

  Second potential issue is that the block you have the roof attached too, could detach from the one below .

if you go without columns ,one way to mitigate this is a concrete ring beam , another way is to have straps from the roof to the foundation. 

  So true story. Me and my friend were visiting his uncle in Homestead FL  after hurricane David had hit there. His Development was situated around a home made lake . and almost every house was leveled except his. This is what he said, and how it was explained to him by the insurance adjuster. a couple of weeks before the hurricane, the unit next to him was burglarized. They went in through the window,  and my friends uncle went and had steel rolled down shutters installed to all of his windows . 

What the insurance guy said is,  that in situations such as a hurricane what happens is that the windows blow in first, the wind getch in the house and lifts the roof, without the roof holding the wall box together , the walls colapse outwards. 

Since then it is code in FL , that straps are installed tying the roof to the foundation. 

I hope this little story made what I tried to convey a bit clearer, 

If you look at the picture in my first post, you will see a ring beam 1/3rd the way up under the window .and then you will have a lintel over the window.  This is because I used double 7.5 cavity wall . 

it is more apparent in this picture. 

In this picture you can see that the AAC block goes all the way to the top, because my roof is welded to the rebar sticking out from the top of the columns. 

If you are making only one room , am I to assume it is and addition to an existing structure? if so, them you probably only need two columns, you could even buy the precast ones,  thy are very cheap  and easy to use.

I used them at my farm where I made a 4x8 meter staracture, and we had 6 precast columns up in one day . next day we poured the slab. One day we had the roof and the next couple of days block window and door.   

[sometimewoodworker]

11 hours ago, Joinaman said:

so where is the load bearing on a small 4x4 extension ?

If you have the standard posts, often at 4 meter centres and those have a ring beam it the top and if required part way down. The that structure is bearing the weight of the roof so is load bearing, for example like this

if you add fill in walls etc you have a small house, the roof is supported by the posts and tied down to them, FWIW the tie downs on a roof like this must be stronger than an enclosed structure 

 

If you don’t have posts supporting the roof then the walls are load bearing QED. Don’t forget that Thailand like other countries does have wind! Wind even if not a typhoon exerts force on roofs and walls these forces come in all directions from pushing down on the roof to lifting it up and of course pushing it sideways, post and beams are designed for these forces, Thai AAC over 200mm are also capable of withstanding these forces. Thai AAC at half the load bearing thickness however interlocked the corners are not rated for this use. Can you use them? Of course you can. Is it a good idea? Absolutely not. The cost difference in material between 100mm and 200mm blocks is an insignificant amount when compared to the overall cost of building.

 

all the talk of comparing Thai AAC 100mm (an unusual size) to UK 100mm blocks is totally irrelevant. The U.K. doesn’t use the same specifications of AAC blocks that are standard in Thailand. Thai AAC blocks are predominantly used in 75mm thickness and always as a fill in wall never as load bearing walls. It is foolish to think that a U.K. building practice can be transplanted to Thailand without all the other design elements surrounding it. 

Edited April 10 by sometimewoodworker

[Fruit Trader]

On 4/9/2024 at 7:17 PM, Joinaman said:

Any reason why i need to use concrete posts on the corners, instead of just bonding the corners?

 

Looking at even the lowest compressive strength value of AAC blocks available in Thailand, probably no when considering your light roof load.

 

 

But to keep everyone's nerves in check and avoid having to form columns, you could set two readily available precast columns into your slab to form the corners then fill in with lightweight blocks.

 

Photo of precast columns.

 

 

 

 

 

Or, keeping to the no column theme, consider the same method as our work sheds which were constructed on rafts using hollow blocks and bars in vertical downpours. Bit of an overkill for a 4x4 extension though.

 

Photo shows start of our smaller shed using 150mm blocks. The larger shed 8x20M uses 200mm blocks.