Bricks or Blocks? 5

[Bamsi786]

Hey everybody, i'm from Pakistan, where bricks have been the conventional material for load bearing walls in residential homes, as blocks were non load bearing and needed frame structure which would increase the cost of the house. Bricks here are normally 1000 PSI, recently i have been working and researching, i have a few residential projects in line, and i have found some one who can make hollow blocks which are load bearing and have double the strenght of bricks (2000 PSI), now my question is, load bearing walls here are made from bricks with a thickness of 9 inches (2 brick thick wall, as 1 brick is 4.5 inch thick), the hollow concrete blocks are 6 inches thick but are load bearing and double capacity. So moving from 9 to 6 inch, is that okay?
Secondly, no reinforcement is used in brick masonry here, so should i do the same with the hollow blocks? I also have solid block with same PSI strenght as an option, but hollow for better insulation of heat as it gets really hot here. Sorry for the long post.

 

[Bamsi786]

So question 1 was, the decrease of 3 inches in external walls, making them 6 inches thick, is that structurally okay?
2nd: im using them without the frame structure purely as load bearing as an alternate to the brick masonry, is that okay?
3rd: someone advised me to add reinforcement vertical bars after every meter horizontally, and a steel mesh horizontally after every 1 meter in height for better resistance against earthquakes, is that important? as i was gonna go for solid concrete blocks first. But hollow were cost effective and had the option of reinforcement, so the money i was gonna save from the hollow blocks was going to be used in the steel reinforcement, is that a good decision?
Please really need the help,

 

[Bamsi786]

Last thing people, why am i changing the conventional way? Because of climate change as bricks kilns here contribute to the biggest smog, thick polluted fog, disaster of this area, search for smog issues in new delhi and lahore, brick kilns are damaging the environment and we want them banned here, i want to introduce a greener substitute here, plus brick kilns here involve child labor where poor families sell their children on contract to kiln owners to work which is also a very big problem, i have aimed to fight these blackmailers and get our people out of this problem, it would be really helpful if you guys would help me out and contribute to this cause, thanks!

 

[strucbells]

Sounds like a great cause, but I think you're going to be hard pressed to get meaningful advice here because:

1. Most of the frequent posters here don't have any experience working in the market you are in. It's hard to give advice when we have no familiarity with local building practices, governing code, typical manufacturing and construction quality control, material availability, etc.

2. It sounds like you don't have a very developed understanding of structural engineering, so it's challenging to give advice that would be meaningful and not at risk of being taken dangerously out of context.

It sounds like you are either a builder or a young engineer fresh out of school. I recommend finding an experienced local structural engineer who can either provide professional advice to you on these projects or who can mentor you as you develop your career.

 

[r13]

A block wall is much versatile than brick wall. Suggest to get technical information from NCMA, then compare with the local practice.
Link

 

[dhengr]

Bamsi786:
Your thinking about climate change, the environment and child labor or all very good and laudable. But, when you combine too many things like these along with other things it seems you need to learn, the sum becomes an insurmountable problem. First, you have to trying to learn Structural Engineering well enough, so that when you design a building or a structure it is strong enough for all of the loads imposed upon it, and is resilient enough in an earthquake or winds, etc. so that it doesn’t fail and kill a bunch of people. Your double wythe brick bearing wall seems to be your local standard, with much history, time and building experience involved in its development and execution during the building process. But, you should also have learned from earthquakes (EQ’s) over the last few decades, that it is not a very resilient building method when subjected to these dynamic/lateral loads. So, there could be plenty to do to improve that system if you are going to continue using it. As I understand it, one of your other local stds. is a gravity frame (concrete or steel) with block, brick, or clay tile walls as infill. The infill walls offer some lateral strength, but not enough to meet today’s stds.

One of the first things you should have noticed in comparing the older 2 wythe, 9” brick bearing wall and the newer 6” block bearing wall materials (units) is that you are reducing the wall thickness by one third. And, wall strength is dependent on the wall thickness or h/t ratio (height to thickness ratio), almost as much as the unit bearing strength. A 6” conc. block wall is not very amenable to reinforcing, and both the old and this new system are calling for that in your country, because of EQ’s. You really need a min. 8” conc. blk. to develop a proper, easily built bearing wall, of any significant height. And, as an aside, cement manufacturing does not get a good environmental grade. Then, it and the sand aggregate to make the blocks probably has to be transported some distance, to a plant which might use child labor in your country.

This is an interesting topic, well worth your study. But, you also need considerable Structural Engineering study and knowledge, and a local mentor who can guide you in your development on these newer construction methods. You won’t pick this up in a couple internet forum chats. You would do well to study the International Building Code (IBC) on these design and building matters. Also, look at what Brick Industry Association (BIA) Tech Notes and the National Concrete Masonry Association (NCMA) as Retired13 suggested. They both have very good stds., details for construction and the like, which you might adopt.

 

[Lomarandil]

Let's slow down a little bit guys. This is a big issue to tackle, I agree. But it is an achievable goal, happening in lots of places around the world (including where I live).

Lots of layers to this, so I'll try to separate them as much as I can.

Unreinforced concrete masonry hollow blocks can be used in a very similar way to unreinforced bricks. However, as dherngr points out, wall strength is mostly controlled by the stability and slenderness (especially for "out of plane" loading), not by unit strength. So while it's possible that 6" hollow units can be used in place of 9" solid walls, that will only work in some cases and not in others.

As you've noted, a substantial advantage of hollow blocks is the possibility for vertical reinforcement. As Dhengr also pointed out, it is challenging to successfully reinforce 6" hollow bricks, because the voids are small and it is difficult to grout well around the reinforcement. However, it can be done with careful planning, workmanship, and quality control. A 6" reinforced wall will be superior to a 9" solid brick wall in most situations.

Structures can be designed using masonry load-bearing walls, with masonry infill of a structural frame, or with "confined masonry" working together with the structural frame. Knowing which is best for your local context depends on many factors, but the masonry infill and especially combined masonry are most common in other countries with economic factors and seismic activity similar to Pakistan.

About the environmental impact of brick, CMU block, and other materials (AAC block) -- it is a complex issue. However, you're right that brick factories do disproportionally impact families and children and lead to some pretty bad situations in that regard (at least that's how it is here). I do not see child labor, debt indentured workers, etc in the block manufacturing operations the same way.

I'm happy to connect you with additional resources on these topics. I know a few people in India who are working in these areas, and they may have connections inside Pakistan as well.



----
just call me Lo.

 

[Bamsi786]

Hey Lo, please do connect me to the people, i am based in lahore, where there is less sesmic activity compared to our northern mountains, in islamabad for example we have to use confined masonry and use frame structure as well, blocks or bricks, but in lahore homes are only made on load bearing brick walls with no columns, and i also have an option of 6 inch solid concrete load bearing blocks, if hollow ones are a problem. And please give me your contact too whether facebook or instagram or whatsapp

 

[Bamsi786]

And i am an architect graduated from CUNY New York, an Overseas Pakistani, who came to the country to serve fellow country men in an industry which caters most of the poor people, if you construct one house here you are actually contributing in a 100 households while doing so, have been into the construction business since last 5 years, here since last 2 years our prime minister Imran Khan, has been shutting down byeick kilns in Punjab region, in october due to the smog they create in November, it has been working actually as smog has been reduced, but the kiln owners take advantage of it and increase their rates making brick prices to shoot up, and affecting the end consumers, they balance out their loss with this and blackmail customers as we have no ithter choice here, so its a war against them, secondly i also need other green construction eco friendly ideas, please help me out there aswell

 

[Bamsi786]

And yes i have been consulting with local structural engineers, and everyone i have met have given me a go ahead with the solid concrete blocks even if they are 6 inch, but no one has given me an example of a home made like this.

 

[Bamsi786]

Im going for hollow instead of solid because of the reinforcement i can do

 

[Bamsi786]

 

[Bamsi786]

 

[Bamsi786]

The house i shared was to let you guys know how homes are built here you can see there are no columms in the house apart from the 2 that are in the garage porch

 

[CivStruck]

Bamsi786,

Thanks Lomarandil for informing me of this interesting topic.

Based on my experience in this region the building you have shown is pretty typical, but that does not mean it will be very safe, particularly in the case of an earthquake. Even if it is common, it probably would not meet local building codes for earthquake design. I'm not familiar with the codes in Pakistan, but in India the construction can be very similar and the codes are often still not followed. Without some vertical and horizontal reinforcing elements, this building would have trouble resisting the lateral forces of an earthquake.

It appears that Lahore is in an area of lesser seismic activity but that does not mean it is without risk. An engineer should refer to a seismic map of the country to determine what level of earthquake resistant design is appropriate. Delhi for example is also in a region of rather low seismicity compared to the Himilayas, however, compared to the rest of the world, it still has significant earthquake risk. Based on this seismic map of India, Lahore would appear to be similar to Delhi and in Zone III or IV per Indian Standards (Medium to High Risk):

https://bmtpc.org/DataFiles/CMS/file/VAI2019/map/eqmap/EQ_INDIA.pdf

Let me outline 3 types of masonry construction mentioned in the Indian Standards:
[ol 1]
[li]RC Frame with Masonry Infill Walls - This certainly common for larger structures, but smaller residential structures also. It consists of a reinforced concrete frame with infill brick masonry. This is widely used in the region and can be designed to resist earthquake loads, but the masonry is not a structural element in this case, or if so, only in a very localized sense (the wall supports itself, but not the structure). [/li]

[li]Minimally Reinforced Masonry with RC Bands and Vertical Bars - This seems to be the type of construction you are going for. This method still requires the use of reinforced concrete reinforcement to strengthen the structure for lateral loads (earthquakes). The structure does not so much depend on the width of the walls for resisting lateral loads as it does the whole structure acting together with the reinforced concrete helping it to behave as a unit. The hollow areas of your blocks could be used for adding reinforcing steel and concrete to form posts inside of the wall. As was mentioned by others, these gaps are rather small, so you may need to have multiple hollows adjacently used for this. Horizontal bands should also be incorporated into the design.
Useful resources:
[ul]
[li]IS 2572:2005 - Construction of Hollow and Solid Concrete Block Masonry[/li]
[li]IS 4236:2013 - Earthquake Resistant Design and Construction[/li]
[/ul]
[/li]
From: IS 2752

From: IS 4326

[li]Confined Masonry - Recent research and Indian Standards would probably recommend using Confined Masonry for this type of construction, especially if it is a zone of higher earthquake risk. Confined masonry can behave very well in earthquakes, even better than an RC Frame with infill walls. However, there can be limitations with this type of constrcution on the sizes of rooms and the height of a buildilng. But this should be very appropriate for most single unit residences.
Useful resources:
[ul]
[li]National Building Code of India 2016 Part 6, Section 4, Annex E[/li]
[li]This is a practical confined masonry guide for use in homes:

https://www.iitk.ac.in/nicee/IITK-GSDMA/ConfinedMasonryHouse_003_2013_31May.pdf

[/li]
[/ul]
[/li]
[/ol]

In all cases, it is important to utilize an architect and engineer for useful and safe structures. You don't want to invest so much in a permanent structure only to find it very inefficient (poorly planned) or laying on top of you in an earthquake. A good engineer will go beyond rough details and do actual calculations to meet the appropriate building code. Spend the extra time and money to do it right so you can sleep soundly at night.

If you are connected with this product you should really also try to meet whatever local specification is most relevant for this type of material. I believe the similar Indian Standard would be IS 2185:2005 (Part 1) - Concrete Masonry Units - Specification. Meeting the correct specification ensures that designers and contractors that use your material will be able to construct safe and effective buildings appropriate to the material.

I have a reference for a local construction company in Lahore that may be able to assist you in designing and constructing using your blocks. I will send you via PM.

Finally, I understand a bit of the context you are in and how poor the quality and safety of everyday construction is, so if you forgo all this advice given by professionals who are very invested in the safety and good practice of building construction, please AT LEAST do as was recommended to you and put in grouted vertical reinforcement regularly in the hollows of your blocks and horizontal mesh between layers (at the minimum: sill, lintel, and roof levels) and make sure to embed reinforcement that the roof can be rigidly fixed to in the vertical elements or roof beam. Lightweight but rigid roofs are preferable such as wood trusses with braces. These are recommendations that would often be used to retrofit low-strength masonry buildings in the Himalayan region. It should not be relied upon as "safe" but it will significantly improve the strength of the structure over that of an unreinforced masonry building without any larger connecting elements to make it behave as a whole unit.

 

[Bamsi786]

Thank you! Please share the number of the concerned person in lahore. I would be very grateful.

 

[Bamsi786]

Civstruck your postbwas really helpful thank you so much!

 

[CivStruck]

Bamsi786, you may refer to this company:

http://www.zor.com.pk/main/index.

I do not know them personally, but we have a mutual reference. See if they can help answer your questions regarding what is appropriate, and if I were you I would considering engaging them for architectural and engineering services.