Urgent: Q-con vs red brick double walls

[Resa]

We have met 4 Thai architects / builders today and everyone recommended us to go for red brick double walls instead of doing the walls with q-con blocks. Their main arguments were that double walls protect better from the heat, are stronger to put up built in furniture and that the weight doesnt really matter in our first one storey house.

We are about to let one of them do the drawings for our house and have to make a decision. What do you guys think? I was really set on using the 20cm q-cons but not sure now...

[jbrain]

Why not use 2 x 7 cm Q-con with a cavity between ?

[cooked]

Anything involving a double wall is much more labour intensive. A double wall must also be drained at the bottom - they have the advantage that you can hide conduits in there. Nothing wrong with Q-con, I would do it with that, as I will be doing on my own build soon.

I am a bit suspicious about the 'stronger to put up built in furniture' bit, this suggests that the architects don't know about the special fixings available for aerated concrete and are maybe a bit nervous about using a material they aren't really acquainted with.

[Resa]

Thanks, yeah on another house building forum people also said q-con can actually hold decent loads if you use the right fixtures.

[jbrain]

Now also keep in mind that the majority of the heat doesn't come through your walls, but through the roof. That is if you have roof overhangs to keep the sun of the walls.

[bankruatsteve]

Sounds like they just want to use what they know. Q-con/SuperBlock/etc. are wonderful building material in my view. Good insulation, easy to construct/cut/etc., and absolutely no problem with "strength" for whatever. In my opinion.

If you get them to try it, they will probably be converts.

[Resa]

Yep for the roof we will go for glasswool insulated white colorbond with proper overhangs to keep the heat in check.

[Ackybang]

Hello Resa -

It's your dollar at the end of the day, so all parties involved would have to follow your wishes, if you really have your heart set on the Q-con.

I went with a cavity wall in red brick, without anyone's recommendations, after weighing up the qualities of the Qcon, and a couple of variations of them.

I'm not so sure about what they're telling you about the thermal properties of red brick vs Qcon - as far as I know, the insulating properties of Qcon are supposed to be very good.

From my own experience with them, you can't use normal render with Qcon, and are limited to a very thin coat of boon gow, which is a ready mixed concrete, which may cause problems later, in terms of overall strength / drilling into them - not sure how they'd stand up to a shoulder test..

Having said that, you can buy everything bespoke to use with those particular blocks, for fixings, lintels, etc, but strength wise, I'm not so sure.

The builders might favour red brick, as they are a bit more forgiving in terms of rendering after - don't need any special tools or training - you don't need to be so precise with your shuttering and pours, or the laying of them - you can always get everything more or less square after with a good layer of render, using basic brickwork and lintel pours.

There are a couple of alternatives available - one is called clc block, if I remember correctly - very lightweight, and you can use normal render and concrete with them - they claim to get stronger over time, once plastered. The only drawback with these blocks is you must render within a certain amount of time after laying them, otherwise they become compromised with the elements.

In short, I chose red brick, because that's what I trusted to be strong, without any shadow of a doubt, after looking at, and getting a sample of all the alternatives - you know the saying 'built like a brick shit house' - well, it's true. I've just had all my walls rendered, and they are now around 10 inches thick - and extremely strong. I want to be hanging furniture, water tanks, TV's, etc, and I want to be able to drill into my walls without having to worry about using special fittings, or weight issues.

The cavity should mitigate any heat issues, but remember this is only one line of defence amongst quite a few others that your architects should be employing to keep your house cool and energy efficient (Raised up off the ground, shading, insulated and breathable roof, UV reflective windows etc). The cavity should also insulate against sound. My house is surrounded by trees, but certain parts of the house do receive direct sunlight at certain times of the day - my walls are cold to the touch inside.

If you go for red brick - order them from Ayudhaya - best in the Country. Also, make sure the builders put breather pipes in all of your lintels to mitigate the heat upwards, otherwise there's no point, and all your rendering will crack over time.

If there's anything you want to know - please ask.

Good luck.

[bankruatsteve]

^ I'm pretty sure the only diff in building with aerated cement blocks is that a "glue" is used vs. mortar. From my observation, rendering is the same. And, so far, it has held everything I have drilled anchors for.

[Ackybang]

^ Not true for Qcon.

Some types of new block are compatible with normal render, as I said, but not Qcon - not without some serious prepwork and totally different methodology - they float in and don't absorb water - so there is no way you could render them the same as redbrick.

The render Qcon recommend is applied 3-10mm, which in building terms is not a lot of tolerance.

Check it out on the web, and check out many builder's opinions of it. Many wouldn't use it for exterior walls - many say it cracks very easily around doorframes etc, and is a pain to use all the special fittings, etc.

I don't think they're something your average Thai builder would know how to use properly.

I trusted my own instincts and wanted to go with aac myself at first, but in retrospect, I'm glad I didn't - still, each to their own.

Edited October 1, 2013 by Ackybang

[bankruatsteve]

OK. Didn't know that. We used "Superblock" and that rendered normally with no issues at all. The cement guys love it b/c it's so easy to work with.

[David48]

What size and what did you pay per block with the 'SuperBlock'?

Thanks

[cooked]

You want to go to a builders merchant to ask about prices. Definitely worth buying by the pallet, much cheaper.

[bankruatsteve]

The Superblock bricks I got from Global were 20x60x7.5cm to wit and average cost was 19 baht. I went with double brick walls and no cavity. That was about 3 years ago.

[crazykopite]

Why not use 2 x 7 cm Q-con with a cavity between ?

Anything with a cavity is an open invitation to unwelcome guests Termite and rats just to name a few Q-Con is extremely good however if you are hanging kitchen units you need to ensure you use the proper plugs/screws otherwise they would fall away Most Thai houses are rendered so why not use the very large grey breeze block In the western world if you were building in Breeze block you could build up to 5/6 courses per day as the mortar need time to dry with Q block there is no limit as you have to use a special adhesive however I have seen Thais putting mortar in between which is incorrect. Q block is new in Thailand even in the Western world a lot of builders shy away from it because they are to set in there ways !!!!!!!!

[kannot]

Anything involving a double wall is much more labour intensive. A double wall must also be drained at the bottom - they have the advantage that you can hide conduits in there. Nothing wrong with Q-con, I would do it with that, as I will be doing on my own build soon.

I am a bit suspicious about the 'stronger to put up built in furniture' bit, this suggests that the architects don't know about the special fixings available for aerated concrete and are maybe a bit nervous about using a material they aren't really acquainted with.

A double block wall needs to be sealed as the air is the insulator, labour is the cheapest part of a build in Thailand in fact probably only 20%

[kannot]

Hello Resa -

It's your dollar at the end of the day, so all parties involved would have to follow your wishes, if you really have your heart set on the Q-con.

I went with a cavity wall in red brick, without anyone's recommendations, after weighing up the qualities of the Qcon, and a couple of variations of them.

I'm not so sure about what they're telling you about the thermal properties of red brick vs Qcon - as far as I know, the insulating properties of Qcon are supposed to be very good.

From my own experience with them, you can't use normal render with Qcon, and are limited to a very thin coat of boon gow, which is a ready mixed concrete, which may cause problems later, in terms of overall strength / drilling into them - not sure how they'd stand up to a shoulder test..

Having said that, you can buy everything bespoke to use with those particular blocks, for fixings, lintels, etc, but strength wise, I'm not so sure.

The builders might favour red brick, as they are a bit more forgiving in terms of rendering after - don't need any special tools or training - you don't need to be so precise with your shuttering and pours, or the laying of them - you can always get everything more or less square after with a good layer of render, using basic brickwork and lintel pours.

There are a couple of alternatives available - one is called clc block, if I remember correctly - very lightweight, and you can use normal render and concrete with them - they claim to get stronger over time, once plastered. The only drawback with these blocks is you must render within a certain amount of time after laying them, otherwise they become compromised with the elements.

In short, I chose red brick, because that's what I trusted to be strong, without any shadow of a doubt, after looking at, and getting a sample of all the alternatives - you know the saying 'built like a brick shit house' - well, it's true. I've just had all my walls rendered, and they are now around 10 inches thick - and extremely strong. I want to be hanging furniture, water tanks, TV's, etc, and I want to be able to drill into my walls without having to worry about using special fittings, or weight issues.

The cavity should mitigate any heat issues, but remember this is only one line of defence amongst quite a few others that your architects should be employing to keep your house cool and energy efficient (Raised up off the ground, shading, insulated and breathable roof, UV reflective windows etc). The cavity should also insulate against sound. My house is surrounded by trees, but certain parts of the house do receive direct sunlight at certain times of the day - my walls are cold to the touch inside.

If you go for red brick - order them from Ayudhaya - best in the Country. Also, make sure the builders put breather pipes in all of your lintels to mitigate the heat upwards, otherwise there's no point, and all your rendering will crack over time.

If there's anything you want to know - please ask.

Good luck.

The ground under a house sat on the ground is cooler than the air blowing under a raised house although concrete paths around the house and joined to it would transmit that heat.

[trogers]

Hello Resa -

It's your dollar at the end of the day, so all parties involved would have to follow your wishes, if you really have your heart set on the Q-con.

I went with a cavity wall in red brick, without anyone's recommendations, after weighing up the qualities of the Qcon, and a couple of variations of them.

I'm not so sure about what they're telling you about the thermal properties of red brick vs Qcon - as far as I know, the insulating properties of Qcon are supposed to be very good.

From my own experience with them, you can't use normal render with Qcon, and are limited to a very thin coat of boon gow, which is a ready mixed concrete, which may cause problems later, in terms of overall strength / drilling into them - not sure how they'd stand up to a shoulder test..

Having said that, you can buy everything bespoke to use with those particular blocks, for fixings, lintels, etc, but strength wise, I'm not so sure.

The builders might favour red brick, as they are a bit more forgiving in terms of rendering after - don't need any special tools or training - you don't need to be so precise with your shuttering and pours, or the laying of them - you can always get everything more or less square after with a good layer of render, using basic brickwork and lintel pours.

There are a couple of alternatives available - one is called clc block, if I remember correctly - very lightweight, and you can use normal render and concrete with them - they claim to get stronger over time, once plastered. The only drawback with these blocks is you must render within a certain amount of time after laying them, otherwise they become compromised with the elements.

In short, I chose red brick, because that's what I trusted to be strong, without any shadow of a doubt, after looking at, and getting a sample of all the alternatives - you know the saying 'built like a brick shit house' - well, it's true. I've just had all my walls rendered, and they are now around 10 inches thick - and extremely strong. I want to be hanging furniture, water tanks, TV's, etc, and I want to be able to drill into my walls without having to worry about using special fittings, or weight issues.

The cavity should mitigate any heat issues, but remember this is only one line of defence amongst quite a few others that your architects should be employing to keep your house cool and energy efficient (Raised up off the ground, shading, insulated and breathable roof, UV reflective windows etc). The cavity should also insulate against sound. My house is surrounded by trees, but certain parts of the house do receive direct sunlight at certain times of the day - my walls are cold to the touch inside.

If you go for red brick - order them from Ayudhaya - best in the Country. Also, make sure the builders put breather pipes in all of your lintels to mitigate the heat upwards, otherwise there's no point, and all your rendering will crack over time.

If there's anything you want to know - please ask.

Good luck.

The ground under a house sat on the ground is cooler than the air blowing under a raised house although concrete paths around the house and joined to it would transmit that heat.

House on ground have problems with moisture, insects and dust - esp in rural areas where the surroundings are not paved or landscaped.

Built-in furnishing should be fixed on timber runners, and not directly onto walls, be they red brick or Q-con. These runners will spread the load.

[cooked]

Anything involving a double wall is much more labour intensive. A double wall must also be drained at the bottom - they have the advantage that you can hide conduits in there. Nothing wrong with Q-con, I would do it with that, as I will be doing on my own build soon.

I am a bit suspicious about the 'stronger to put up built in furniture' bit, this suggests that the architects don't know about the special fixings available for aerated concrete and are maybe a bit nervous about using a material they aren't really acquainted with.

A double block wall needs to be sealed as the air is the insulator, labour is the cheapest part of a build in Thailand in fact probably only 20%

The wall will insulate whether sealed or not, elementary physics.The gap needs to be drained and aired.

[canopy]

double walls protect better from the heat...I was really set on using the 20cm q-cons but not sure now

Ask your architects look up the facts and send you the data comparing the two so that they can learn the truth. I have looked it up and a 25cm block has 3 times the r-value of a red cavity brick wall.

red bricks are stronger to put up built in furniture

There is no real world strength advantage of red brick that I have seen. You can hang heavy cabinets with q-con and use the thick blocks for load bearing walls! q-con blocks are a German design and built to exacting quality specifications to withstand real world needs. So this whole strength argument is like saying don't use red brick because a half meter thick reinforced concrete wall is stronger. Yeah sure it is, but it has absolutely no real world strength benefit.

[bankruatsteve]

Anything involving a double wall is much more labour intensive. A double wall must also be drained at the bottom - they have the advantage that you can hide conduits in there. Nothing wrong with Q-con, I would do it with that, as I will be doing on my own build soon.

I am a bit suspicious about the 'stronger to put up built in furniture' bit, this suggests that the architects don't know about the special fixings available for aerated concrete and are maybe a bit nervous about using a material they aren't really acquainted with.

A double block wall needs to be sealed as the air is the insulator, labour is the cheapest part of a build in Thailand in fact probably only 20%

The wall will insulate whether sealed or not, elementary physics.The gap needs to be drained and aired.

Wrong. Ventilation will defeat insulation effect.

[cooked]

Anything involving a double wall is much more labour intensive. A double wall must also be drained at the bottom - they have the advantage that you can hide conduits in there. Nothing wrong with Q-con, I would do it with that, as I will be doing on my own build soon.

I am a bit suspicious about the 'stronger to put up built in furniture' bit, this suggests that the architects don't know about the special fixings available for aerated concrete and are maybe a bit nervous about using a material they aren't really acquainted with.

A double block wall needs to be sealed as the air is the insulator, labour is the cheapest part of a build in Thailand in fact probably only 20%

The wall will insulate whether sealed or not, elementary physics.The gap needs to be drained and aired.

Wrong. Ventilation will defeat insulation effect.

yes indeed, the hot air disappears up through the top of the wall through the vents that you didn't forget to build in, insect proof of course.. You are talking to a qualified civil engineer here. Any heat penetrating into a room gets there through radiation, meaning the wall warms up and eventually starts radiating heat into the interior. So whatever the temperature is in the cavity, the insulation properties of the wall will hardly vary. Google 'cavity walls', you will find that weep holes are de rigeur as are metal ties and damp proof course.

[David48]

The wall will insulate whether sealed or not, elementary physics.The gap needs to be drained and aired.

Wrong. Ventilation will defeat insulation effect.

Hope you don't mind ... I fixed up the quotes to represent who said what.

bankruatsteve ... might I guess that you originally came from a cold climate?

I come from a subtropical part of the world, I'm an electrician by trade and have a Uni Degree in Property ... the cavity brick constructions (double brick maybe in your language) ALL have small vents which both all the walls to breath ... thus negating any condensation build-up.

I'm not saying that where you came from doens't have a sealed double brick walls ... just in tropicial climates, of which Thailand certainly is, it's desirable to have this feature.

.

[bankruatsteve]

I didn't comment on ventilation. My comment regarded insulation. I repeat: An air gap loses any insulation value it may have provided if ventilated. Personally, I find cavity walls insignificant for additional insulation value unless filled with foam or the like.

Edited October 4, 2013 by bankruatsteve

[jbrain]

I didn't comment on ventilation. My comment regarded insulation. I repeat: An air gap loses any insulation value it may have provided if ventilated. Personally, I find cavity walls insignificant for additional insulation value unless filled with foam or the like.

When an airspace is locked, the air inside will heat up during the hot time of the day, and not easily cool down at night.

When it is ventilated it will always let the hot air out that get's replace by cooler air. That is if it has ventilation holes at the bottom and top side .

[bankruatsteve]

So talk about ventilated spaces - they are NOT insulated spaces. Duh.

[jbrain]

So talk about ventilated spaces - they are NOT insulated spaces. Duh.

Cavity walls consist of two 'skins' separated by a hollow space (cavity). The skins are commonly masonry such as brick or concrete block. Masonry is an absorbent material, and therefore will slowly draw rainwater or even humidity into the wall. The cavity serves as a way to drain this water back out through weep holes at the base of the wall system or above windows.

The science of cavity insulation

The reason cavity insulation keeps heat in is that the polymer and air in the cavity are good insulators. This is because the distance between the particles in the air is greater than in a solid. Other benefits of cavity walls are their resistance to moisture from the outer side to the inner wall and the increase of sound proofing.

http://en.wikipedia.org/wiki/Cavity_wall

Edited October 4, 2013 by jbrain

[passingas]

I used both AAC block with a red brick inner wall....have had no problems with anything trying to live in between in the void (varmits or mildew)...they do not have to be drained...and I am so glad I used it this way. Our house is like a thermos....that being said...I get up early in the morning, open all the windows, turn on the exhaust fans (mounted at ceiling height) get as much cool morning air I can (up until 9:00 am or so), close all the windows and doors and enjoy a very nice temp up until the late evening. By then is has started warming up inside, while the outside is cooling back down. Used in a double wall construction, you eliminate those damned inside columns every 3 m or so. I tried uploading some pics, but this won't happen for whatever reason. If you would like more info, PM me. pg

[kannot]

Hello Resa -

It's your dollar at the end of the day, so all parties involved would have to follow your wishes, if you really have your heart set on the Q-con.

I went with a cavity wall in red brick, without anyone's recommendations, after weighing up the qualities of the Qcon, and a couple of variations of them.

I'm not so sure about what they're telling you about the thermal properties of red brick vs Qcon - as far as I know, the insulating properties of Qcon are supposed to be very good.

From my own experience with them, you can't use normal render with Qcon, and are limited to a very thin coat of boon gow, which is a ready mixed concrete, which may cause problems later, in terms of overall strength / drilling into them - not sure how they'd stand up to a shoulder test..

Having said that, you can buy everything bespoke to use with those particular blocks, for fixings, lintels, etc, but strength wise, I'm not so sure.

The builders might favour red brick, as they are a bit more forgiving in terms of rendering after - don't need any special tools or training - you don't need to be so precise with your shuttering and pours, or the laying of them - you can always get everything more or less square after with a good layer of render, using basic brickwork and lintel pours.

There are a couple of alternatives available - one is called clc block, if I remember correctly - very lightweight, and you can use normal render and concrete with them - they claim to get stronger over time, once plastered. The only drawback with these blocks is you must render within a certain amount of time after laying them, otherwise they become compromised with the elements.

In short, I chose red brick, because that's what I trusted to be strong, without any shadow of a doubt, after looking at, and getting a sample of all the alternatives - you know the saying 'built like a brick shit house' - well, it's true. I've just had all my walls rendered, and they are now around 10 inches thick - and extremely strong. I want to be hanging furniture, water tanks, TV's, etc, and I want to be able to drill into my walls without having to worry about using special fittings, or weight issues.

The cavity should mitigate any heat issues, but remember this is only one line of defence amongst quite a few others that your architects should be employing to keep your house cool and energy efficient (Raised up off the ground, shading, insulated and breathable roof, UV reflective windows etc). The cavity should also insulate against sound. My house is surrounded by trees, but certain parts of the house do receive direct sunlight at certain times of the day - my walls are cold to the touch inside.

If you go for red brick - order them from Ayudhaya - best in the Country. Also, make sure the builders put breather pipes in all of your lintels to mitigate the heat upwards, otherwise there's no point, and all your rendering will crack over time.

If there's anything you want to know - please ask.

Good luck.

The ground under a house sat on the ground is cooler than the air blowing under a raised house although concrete paths around the house and joined to it would transmit that heat.

House on ground have problems with moisture, insects and dust - esp in rural areas where the surroundings are not paved or landscaped.

Built-in furnishing should be fixed on timber runners, and not directly onto walls, be they red brick or Q-con. These runners will spread the load.

Not when you actually put a plastic membrane under the concrete as I did and treat the ground with termite spray under that also vibrated the concrete added waterproofer and then compacted it all with a powerfloat

Edited October 5, 2013 by kannot

[kannot]

Anything involving a double wall is much more labour intensive. A double wall must also be drained at the bottom - they have the advantage that you can hide conduits in there. Nothing wrong with Q-con, I would do it with that, as I will be doing on my own build soon.

I am a bit suspicious about the 'stronger to put up built in furniture' bit, this suggests that the architects don't know about the special fixings available for aerated concrete and are maybe a bit nervous about using a material they aren't really acquainted with.

A double block wall needs to be sealed as the air is the insulator, labour is the cheapest part of a build in Thailand in fact probably only 20%

The wall will insulate whether sealed or not, elementary physics.The gap needs to be drained and aired.

http://www.thaivisa.com/forum/topic/432933-how-to-properly-insulate-ventilate-double-blockbrick-walls/