When to use Iron rods in the oversite/german floor concrete of a bungallow.

Mr. Emma
Please find attached a quotation for foundation sent to me by a contractor. i have excavated the land and some part you will see that its water logged. a lake is behind my land at igbogbo ikorodu.
Another contactor said i do not need iron rod for foundation since its a bungalow?
Please advise.
Regards,
Chris

The recent flooding around has brought new challenges and raised questions on wether to use iron rods to support the german floor of a bungallow, especially in a seemingly solid soil or not.
Going by what I saw inspecting a 4 bedroom bungalow close to the Ipaja canal in Lagos state has reinforced my belief for a careful analysis of any buildings prone to flood in future.
In this case on a particular Sunday when there was much rain, the water overflew it’s banks and entered people’s houses. For the house in question it was originally raised high which was constructed by me for over 5 years now and there has never been any issue of concern until this prolonged rain and blocked drains that led to unusual flood . The soil itself is sandy and fairly okay stability wise, other buildings are also standing around but to save money as most will do which is very wrong, we raise d the blocks straight from foundation up to the roof without breaking it with german/oversite concrete at the foundation/dpc level, we only pour some volume of concrete after the building have been roofed without any iron rods or wire mesh to really sustain the compressive force of the concrete.
Now a problem was discovered after the flood incidence, there were visible cracks along the walls both laterally and vertically, suggesting that the walls might cave in anytime, there was also serious movements of the ground floor concrete depressing further down and leaving a thin line between the walls and the concrete at the edges of each room round. These happened because the concrete were poured separately on each room just to sustain the weight of the occupiers and we didn’t put into cognizance the pressure a flood in the near future may cause. Ordinarily a German floor with wire mesh/reinforcements or iron rods casted together at the dpc (foundation) level will have given us a well formed monolithic mass of concrete that will have served as a protection against water penetrating directly from the ground to the house.
The water that surrounded the building went to its foundation ,soften the sands underground, and when the water dried the next day the soil under the building was further compressed by the wetness, hence there was movement of the concrete in the rooms which made them to go down and thereby separating blocks from the concrete.
This problem could have been avoided if the German floor was done and the concrete was made to pass on top and round the entire stretch of the building block, however without reinforcements on the concrete with the situation at hand despite that is a bungalow , we would still have had the same experience.
So I recommend for a waterlogged area, or for a site very close to the water or prone to future flooding, it is better to go the extra mile and reinforce the oversite or german concrete with iron rods so that if there is a movement under the buildingthe foundation and the german concrete will be able to sustain the building.
However if you have encountered this problem already, don’t fret yourself, get a professional to suggest the best way the building can be reinforced and also protected against flooding.

An architect with decades of experience

31 Comments

    1. Tony,
      It is most unlikely. Your building has an oversite/german floor concrete though not reinforced but it has a very short span which the concrete can still sustain.

  1. My question is how come construction engineers do not encourage client to use moisture protection membrane under the German floor, especially in water log area. Does it not add any value?

    1. They encourage and people use it actually. Except in areas where you don’t have water problems which is very few in Lagos.

  2. Based on your information, I’ll save enough money before commencing the construction of the foundation of my building to avoid mishap in future.
    Thank you and God bless.

    1. Thank you too. Though saving enough money before starting is not always the case for every situations. Each sites has its own peculiarities.

  3. Thanks for your articles and God will enrich your knowledge(amen). I have a serious problem with a two stories building i bought few years back. The building is situated near a carnal and down side of a slope the problem with the house now is that the side near the canal is now sinking making the house to be tilt to one side and each time there is rain the house is always flooded with water coming from under the concrete into the rooms.I wish to correct this situation without demolishing the whole building, could your offer me your services or recommend the appropriate professionals who could do this job well.

    1. I will like to visit the site as well, but you need a structural engineer to look at it. I will get one for you. Saw the pics you sent to my mail.

  4. Dear br,
    At my site the we have is cracking,when the soil was dug the clay that was fd bcms marchy during the rain and bcms hard with sm cracks during dry season,WITH THIS TYPE OF SOIL WHAT KIND OF FOUNDATION WILL U RECMD.?

  5. Dear br,
    At my site the whole builds we have is cracking,when the soil was dug the clay that was fd bcms marchy during the rain and bcms hard with sm cracks during dry season,WITH THIS TYPE OF SOIL WHAT KIND OF FOUNDATION WILL U RECMD.?

  6. Mr emma, thanks 4 all ur response. Pls can someone attain nd operating wt many proffessions like engineer, architect and builders aswell

    1. Oh yes you are suppose to be operating with all but because of scale of project you can do with one or two for larger or multistorey buildings they are indispensable. I also use other professionals when I am giving a project too.
      Thanks

  7. I must commend your effort at educating the general populace-it is indeed very well appreciated.
    With a professional this very basic but fundamental issues would have been taken into consideration before starting a building project.
    In the short term hiring a professional to handle your building project may cost more in terms of the service to be rendered and the building to be delivered. But the long term benefits are indeed very cost effective. Imagine what you would have to go through living in a house where the floor is sunken into the ground and it can actually be much worse of!

  8. I too is building on a waterlogged area. I have done the raft foundation with enough iron rods and cement and sand, the raft of 2 coaches. please i want to find out if i still have to do this german floor with a wire mesh on top? I have already done 3 coaches after the raft found, the size of the block is 9 inches. thank you.

  9. Looking at your German floor, it ‘s not sitting on anything other than the filling.
    usually in Europe we have cavity walls, the concrete sits on the inner wall, the outer brick is to the height of the concrete, that’s how the floors are levelled.
    Re-bars are used if the ground is poor or your unsure or if your weight load is heavy or vehicles run on it. For most ground floor houses it’s not necessary. if in doubt put it in. again it must be put in properly and to the right spec. DO NOT presume because you’ve put re-bars in it OK, specs have to be used, Ideally in footings when you cannot complete the concreting in the same day.

  10. Good day sir. You are doing a great job. I have a foundation of a 2-bedroom flat and a mini-flat together, measuring 14m x 8.5m for plan of one-story building. The depth of the foundation is just about 500mm and not up to 650mm you advised. Secondly, the floor concrete thickness is about 76mm and not up to 150mm you advised. Although, the pillars are intact with space of 3.66m (12ft)from one another but the same depth with the floor concrete.It is dry land but a little bit sloppy as one side of the foundation takes 3 coaches while the other one takes 5 coaches.
    Can I still go ahead and make it a story building as planned? Thanks in anticipation. More power to your elbows.

  11. Building up a building by a professional is very very important to avoid any defect on a specified project. thanks for your professional educative advises.. cheers and more grease to your elbow.

  12. This piece is seriously useful.tnx 4 d good job. My own question is is; when planning ur over-site concrete, in a dry land, by that i mean not water logged, not in lagos, o u still need to use rods and iron mersh? 2. some peolpe say its wise to just fill, dont put the concrete, only pour the concrete either at roofing level before roofing, or after roofing, according to them this ensures the filling has compacted properly with u adding sand, to gude against the sand depressing and leave a hollow between the sand and the concrete. others say u do ur over-site concrete before u raise the blocks up, that this avoids cracking in future. Pls i really need to know. Tnxxxxx,

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