IMPORTANCE AND APPLICATION OF HARDCORE TO A BUILDING.

 

Question:

Oga, I have done casting and filling with laterite, do I need to use hardcore again or bricks before german floor. Is thought is just ramming the laterite.

Hardcore application in the building process is also as important as any of the key stages . Hardcore is reffered to as some measures of large aggregates of stones used as part of the foundation in a construction project. To simple put is bigger aggregates of what you call granites on site. Though some uses broken blocks /bricks, these are however not recommended because of their strenght, people only use them to save cement during casting of oversite/german concrete which is not advisable.

Hardcore is applied after you have filled the internal part of your foundation with laterite or sharpsand as the case may be, rammed and ready to apply iron rods/wire mesh and concrete. In the usage of hardcore, the textbook application is as shown in the image 1 below, there is a space entirely left for the hardcore as specified by the professional before the space for the concrete, this is standard or you call it textbook application, but getting the accurate thickness during construction for portion of concrete  is not always common because of crude method of construction, level of skill of the builder and the settlement pattern due to nature of soil. So what most people do onsite is as shown in image 2-the hardcore takes a portion of the concrete space so you only needs to fill the remaining parts with concrete.(Is not what is recommended but is what most do)

 

IMPORTANCE

(1)Hardcore strengthens or solidifies the base which the german concrete will sit on, thereby helps in resisting pressure of dead and live loads on the ground floor.

(2}It gives good base for building

(3)Is also part of foundation

(4)In the image 2 type of application, it helps to save cost of construction, the volume occupied by the hardcore if it were to be concrete it would have cost more.

(5)Is a gap between the german floor /oversite concrete and the earth so it helps to reduce movement of water up to the ground floor

(6)The air in between the hardcore if there is any will also help to reduce movement of water.

(7)In case of image 2, it reduces the time of casting because you are using lesser volume of concrete to when you are casting the entire mass.

An architect with decades of experience

43 Comments

  1. Dear Sir,
    Pls what is the quantity of Hardcore per square meter.

    Thank you and best regards

    1. Depends on what you have to do to get the area filled, sizes and space will affect area so is not easily determined.

  2. Yes thanks hardcore fill is vital in floor slabs. But what is recommed thickness of the stones and how many layers. Regards Abdimalik

  3. Tanks 4 enlitement us god bles u sir, hw can we calculate 4 d volume of hardcore req. 4 a building…

  4. Pls sir,I’m abt ??? do plasrerng ?f 2 _3b/rm FlAt ?n a?? single bUilDing.What A??????????????? ? mAtErials NeedeD ??? complEtE both inSide ????? outside.?»?·???·?????????????????????k????·???·???«?? ??U?????????·???·???«?? ????????????????·???·???«?? ?U?????c?????·???·???«??

  5. hardcore is about 224.6kg/m2 and density of 2931kg/m3 the size is from 75mm upwards so you can calculate your quantity required. Most quarries will sell per ton so 1000kg = 1ton

  6. please kindly send some technical drawing of your buildings to me i will to see some of them
    thanks

  7. Thanks a lot for your advice.I am just working on the foundation of my building.I intend to build a 4 bedroom bungalow using mud bricks. Do i really need to use iron rods/wire mesh as part of my foundation?

  8. Hardcore is also used to make up levels in raised floors. It saves cost and prevents capillarity rise which could cause nuisance to your walls.

    I will also add that immediately after the hardcore is compacted, a layer of sand bedding is spread on it followed by a dpm. A concrete blinding is spread on the dpm to prevent the dpm from punch when the reinforcement is laid. After the rebars are laid, the concrete can be casted. Curing is a Must to prevent cracks.

    The hardcore shall also be free of weeds, roots, vegetable soil, clay, black cotton soil or other unsuitable materials.

    Please always make sure the soil beneath is treated against termites. Otherwise you might be inviting termites during the ocuupancy of the building.

    As for the Mesh which is sometimes called thermal reinforcement, it is only used to prevent cracks on the german floor. It is not for structural purpose but for durability and serviceability reasons.

  9. Sir thanks a lot for your posts. Its normal for people to hoarde knowledge, but you’re different. As u continue to share ur knowledge I know God will continue to increase it- and also increase you in life. Thanks.

  10. I have some questions though. I thought a DPC was enough to prevent the rise of water- why use hardcore again?
    Also, I know a house been built in Lekki where hardcore was not used at all and rebars were not embedded in the oversite concrete floor. Is this house at risk?
    Finally, the floor of the bathroom of the house where I currently stay constantly spills water, not from d toilet, sink or bath, but seemingly from the sides of the tiled floor(where it meets a tiled wall). I know you’re not a plumber but is it there’s a broken pipe somewhere? Or is water seeping up from the ground(the house is in Lekki peninsula). Would the tiles on the wall need to be removed to see if water has seeped up the wall too?

  11. In my own opinion,

    1. after hardcore is placed and compacted to make up level, a sand blinding is spread on it followed by a DPM and then by concrete blinding… This way you have cut off water rise from ground.

    2. Some people even don’t use hardcore, they just fill up with filling sand (laterite), spread DPM, then concrete blind the surface to prevent the rebars from creating holes on the DPM…. There after lay the rebars and cast the german floor slabs….

    3. The fact is that if you know the functions of the different methods and what they can do, you can implement it in you own peculiar situation…

    I would recommend option 1 because from experience, if you directly lay the mesh (light rebars) on the hardcores chances are that the mesh that are supposed to be above the neutral axis (to prevent cracks) would bend and get displaced due to casting gangs stepping on the light rebars and also due to the heavy weight of the wet concrete… but if the hardcore is sand blinded it creates a base for the rebars and make casting better…In this case the hardcore is purely to make up levels.

    The goal in the above methods is to make up level and also prevent capillarity rise, so methodologies could differ.

  12. AM WORKING ON A SITE AND ON THAT SITE THE OWNER WANTS US TO COMPACT AND THEN USE IRON ROD THE USE CONCRETE TO POUR ON THE OVERSITE INSTEAD OF THE STONE BASE…OF WAT ADVANTAGE IS DIS AND WHY.

  13. A nice educating article here. But i have a question..what really is this ‘blinding’? And what are the uses to the foundation of a building?

  14. Really particularly laudable what is going on here. Impressive, actually, are Bldr. Kunifeds’ contributions.

  15. what are the qualities required for the hardcore materials ( What kind of stones are suitable for the hardcore?)…

  16. This site has been very helpful so far. With the help of this site I arranged my very first estimate and thank God I got the job. Soon I will start the job and I stumbled upon this article. Special thanks to bldr kunlefads. I think I will apply your method when I officially start the job at the eastern part of the country…God bless. More grease to your elbows

  17. The function opa wiremesh is to prevents cracking on the German floor and serves as serviceability and durability purposes.

  18. For your building design,site engr and contractor you can reach me (engr.yomi) on 08161911763. Am a civil engr by profession and not a quack or bricklayer but expertrait.

  19. Need some advise,wen I built my bungalow,my engineer really deal with me by cheating me,which I later discovered. Now I want to build a storey building. want to ask, can I give it to an experienced brickslayer?
    thanks so much

    1. No you still need an engineer with proper monitoring you should have a good project. Is like saying you won’t use a motor vehicle any longer because you witnessed an accident.

  20. Ok, good deal makes a good job. Thank you so much for given this big knowledge. It has well understood for the users.

  21. Thanks for your enlightment very educative to both laymen and professionals.For the production of your professional drawings,supervision,getting materials at very competitive prices I am @ your service.I have many years of experience in civil constructions(building and drainage).My contact number is 08028991675

  22. Pls I av an area of 137.66cubic metre to be fill with hard core pls how many ton will it be pls help me 08072722258

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