Pier, pile, slab or strip foundation for a new build?

[rocketlad78]

Hi all,

 

Looking to use 4 X 40ft shipping containers for a building project (2 ground floor, 2 upper). It's my first time doing this, so excuse my ignorance.

 

Slab foundations seem to be a popular choice in Thailand, but expensive. Pier foundations seem ok for a container build but it's 2 floors and slab seems safer.

 

Does anyone have any experience with laying a foundation (not necessarily using a shipping container!) and if so, what was the cost of hiring the company to dig, steel it up, fill up with concrete, etc?

 

18ft by 42 ft long is a rough estimate. 

 

Thanks in advance ????

 

 

[Joinaman]

so 14m x 3 m slab is 42 m sq

at 4", or 100mm thick is 4.2 cubes of concrete

At 6" or 150mm thick, is 6.3 cubes

At 1,800 baht a cube means concrete is 7,560 baht, or 11,340 baht

If 4 " then possibly some reinforcing mesh or bars, depending on the ground ( firm undisturbed, or infilled )

6" can miss the reinforcing 

I have 4" drives and slabs, with no reinforcing, and have loaded concrete trucks drive over them with no bother 

Time to lay ( depending on the ground) 3 men one day to shutter and pour, one man next day to strip shutter

So labour maybe 2,00 baht ?

A container is a spread load, so weight is distributed across the slab, rather than point loaded, so less pressure on slab

 

 

[Artisi]

Depends  on ground conditions, best bet is to ask the local builders what is the best system, my single level house is on 57 6m piles plus pile caps and strip foundation to suit the underlying ground conditions. 

[sometimewoodworker]

10 hours ago, rocketlad78 said:

Looking to use 4 X 40ft shipping containers for a building project

Unless you already have the containers you are likely to find them difficult to buy at a price you want to pay specially at the moment when they are in short supply. Also you will find that building with normal materials is probably a similar price or lower, as there is a lot of fitting out to a container build. 
 

If you have the money to make a fashion statement they are an option. If you want an economic build they are a poor choice in Thailand.

[rocketlad78]

54 minutes ago, sometimewoodworker said:

Unless you already have the containers you are likely to find them difficult to buy at a price you want to pay specially at the moment when they are in short supply. Also you will find that building with normal materials is probably a similar price or lower, as there is a lot of fitting out to a container build. 
 

If you have the money to make a fashion statement they are an option. If you want an economic build they are a poor choice in Thailand.

I have found these guys who fit out containers for a very reasonable price with wiring included. After foundation and plumbing costs (including septic tank), I'm still looking at a cheap alternative. I'm looking to build a business, not a home, and the beauty of these is that you can move them like Lego!

 

https://www.boxfactory.co.th/

[sometimewoodworker]

12 minutes ago, rocketlad78 said:

I have found these guys who fit out containers for a very reasonable price with wiring included. After foundation and plumbing costs (including septic tank), I'm still looking at a cheap alternative. I'm looking to build a business, not a home, and the beauty of these is that you can move them like Lego!

 

https://www.boxfactory.co.th/

Do you have the containers yet?

“the beauty of these is that you can move them like Lego!” before modifying yes, after?

Edited July 27, 2021 by sometimewoodworker

[Saanim]

The foundation size depends on the quality of the soil. If quite a compact soil I would make a  trench 50 x 50 cm under each outline (12.5 x 2.5 m - outline of the trench), lay in a rebar structure (4 x d.6 mm) and fill in concrete. That's what people in a village can do for you.

  

[DaLa]

 

13 hours ago, Artisi said:

Depends  on ground conditions,

This is the only factor you should be taking into consideration.  There will be no point loading and a 40ft container weighs between 3.8 to 4.2 tonnes (slightly heavier for HC's).  Thus if you spread the whole weight ( empty) of the part that rests on the ground ( the 2 side rails and the front and rear cills) that will equate to approx. 2.2 lbs. per sq. inch. Atmospheric pressure on the ground is 14.7 lbs per square inch.

 

Reinforced concrete slab would be my solution unless I was placing them in a marsh.  In fact where I have built in the past, I'd just buy some railway sleepers and plant them on those.

 

 

Note.  Just read your post again and realised you plan for 2 storey. Thus you can double the load calc I just posted. That  is 4.4 pounds per square inch. .

Edited July 27, 2021 by DaLa
Corrected calculation.

[DaLa]

Just also want to point out that the compressive strength of concrete is in the range 2,500 - 10,000 pounds per square inch.   It's what the concrete is placed on that dictates how useful those numbers are.

[bbko]

I would think the foundation depends a lot on container weight and how much you plan on putting inside and the ground below.  My carport slab is 10 cm in depth and supported the weigh of a large crane we called in to help cut down coconut trees, average soil, not clay or marsh.

 

Edited July 27, 2021 by bbko

[Yellowtail]

I see no benefit from a slab as the containers are supported by the corners anyway. 

 

I would just  pour/sink nice footings for each corner and raise it off the ground enough to have a crawl space.

[chilly07]

All of the above! Don't forget the rebar to link them all up. Perhaps an engineer can advise you?

[natway09]

Ensure you check with your local shire first.

Many have now banned containers (even new) 

As to what you sit it on it will depend on your local soil/clay type

I have insulated 5 for customers & to do a good R2.6 with no leakage expensive 

[Cake Monster]

49 minutes ago, Yellowtail said:

I see no benefit from a slab as the containers are supported by the corners anyway. 

 

I would just  pour/sink nice footings for each corner and raise it off the ground enough to have a crawl space.

Just put in 6 Footing pads with a riser to the height you want the floor level to be. 4 on the corners and 2 halfway down the long side.

Dig down 1. 5 Meters

Pad size 1.5 M x 1. 5 M x 200 thick and rebarred 

Risers 200 Square and rebarred

I have suggested 6 pads to compensate for any slight sag there may be in the weight of the Containers over that 40 ft length, as you are stacking them 2 high.

 

[Jen65]

21 hours ago, Joinaman said:

so 14m x 3 m slab is 42 m sq

at 4", or 100mm thick is 4.2 cubes of concrete

At 6" or 150mm thick, is 6.3 cubes

At 1,800 baht a cube means concrete is 7,560 baht, or 11,340 baht

If 4 " then possibly some reinforcing mesh or bars, depending on the ground ( firm undisturbed, or infilled )

6" can miss the reinforcing 

I have 4" drives and slabs, with no reinforcing, and have loaded concrete trucks drive over them with no bother 

Time to lay ( depending on the ground) 3 men one day to shutter and pour, one man next day to strip shutter

So labour maybe 2,00 baht ?

A container is a spread load, so weight is distributed across the slab, rather than point loaded, so less pressure on slab

 

 

sorry but ANY container has a 4 point load !!  I should know as carried millions around the globe !  On ships they are staked with interlocks sometimes 6,8,10 high ( you must have seen the high stacks on deck of container ships ) The corners take the load are made to support others.   

[The Theory]

This is basic raised footings for a 40ft. 
but foundation is just a beginning for a building by steel containers. Insulation is very important in hot climates, from inside and outside. If you don't want a big AC bill. 
One more thing could be "noise". Since they work like a drum. You need to consider all these factors. 
I attached 2 photos as basic ideas. 

 

[Kinok Powell]

11 hours ago, Cake Monster said:

Just put in 6 Footing pads with a riser to the height you want the floor level to be. 4 on the corners and 2 halfway down the long side.

Dig down 1. 5 Meters

Pad size 1.5 M x 1. 5 M x 200 thick and rebarred 

Risers 200 Square and rebarred

I have suggested 6 pads to compensate for any slight sag there may be in the weight of the Containers over that 40 ft length, as you are stacking them 2 high.

 

For what it's worth that is the way i'd go too.One on each corner+1 midcenter on all four sides if the containers are side by side,not forgetting the middle pad.But i'm only a retired,burnt out bricklayer.

Ps,might be a good idea to have the containers on site to double check your measurements.

Edited July 27, 2021 by Kinok Powell

[sometimewoodworker]

12 hours ago, Jen65 said:

sorry but ANY container has a 4 point load !!  I should know as carried millions around the globe !  On ships they are staked with interlocks sometimes 6,8,10 high ( you must have seen the high stacks on deck of container ships ) The corners take the load are made to support others.   

When intact and without compromised sides that is of course true.
 

The problem comes when you start chopping large openings in the sides and possibly the top. This obviously compromises the strength of the containers in rather unpredictable ways, so you can no longer just support the 4 corners and be sure they will not deform. 

[Saanim]

8 hours ago, Kinok Powell said:

For what it's worth that is the way i'd go too.One on each corner+1 midcenter on all four sides if the containers are side by side,not forgetting the middle pad.But i'm only a retired,burnt out bricklayer.

Ps,might be a good idea to have the containers on site to double check your measurements.

All containers are same, you can find the size by goggle. When bringing the container(s) on site  then it is good to have the foundation ready, with the same crane to place it in.

[Kinok Powell]

2 minutes ago, Saanim said:

All containers are same, you can find the size by goggle. When bringing the container(s) on site  then it is good to have the foundation ready, with the same crane to place it in.

Of course.

[Yellowtail]

[rocketlad78]

On 7/28/2021 at 8:37 AM, sometimewoodworker said:

When intact and without compromised sides that is of course true.
 

The problem comes when you start chopping large openings in the sides and possibly the top. This obviously compromises the strength of the containers in rather unpredictable ways, so you can no longer just support the 4 corners and be sure they will not deform. 

Yes, this is what the plan is. Bottom floor will be glass windows across the whole length.

[driver52]

2 hours ago, rocketlad78 said:

Yes, this is what the plan is. Bottom floor will be glass windows across the whole length.

SO why don't you just use some concrete posts and forget about the whole 'metal box' idea? ????

[rocketlad78]

1 hour ago, driver52 said:

SO why don't you just use some concrete posts and forget about the whole 'metal box' idea? ????

Firstly, I'm trying to be environmentally conscious. The whole idea is that the build will have (a relatively) passive impact. Sustainability is part of my business focus.

 

Secondly, there may be a day when we have to move location and after it's detached from the foundation it can be lifted off onto trucks and moved. 

 

I'm also useless at design! The companies that create these containers have preset designs at a very reasonable rate.

[Yellowtail]

56 minutes ago, rocketlad78 said:

Firstly, I'm trying to be environmentally conscious. The whole idea is that the build will have (a relatively) passive impact. Sustainability is part of my business focus.

 

Secondly, there may be a day when we have to move location and after it's detached from the foundation it can be lifted off onto trucks and moved. 

 

I'm also useless at design! The companies that create these containers have preset designs at a very reasonable rate.

Will the people that design them not also install deliver and install them?

 

They would be the people to contact as far as what site-work and foundation is required. I assume they will provide a clear drawing set with the order documents so you are clear on all you will need to provide to facilitate the installation. 

[sometimewoodworker]

1 hour ago, rocketlad78 said:

there may be a day when we have to move location and after it's detached from the foundation it can be lifted off onto trucks and moved. 

As I mentioned to do that, with the compromised structures of the containers, it will not be a simple crane job, you will need a lifting jig to ensure the containers don’t deform. With normal container cranes they don’t use those as they are not needed. You may need to have one built for the job, not a difficult job but you need a structural engineer to advise on that.

[rocketlad78]

6 hours ago, Yellowtail said:

Will the people that design them not also install deliver and install them?

 

They would be the people to contact as far as what site-work and foundation is required. I assume they will provide a clear drawing set with the order documents so you are clear on all you will need to provide to facilitate the installation. 

Yes but also getting other opinions too. 

[Yellowtail]

14 hours ago, rocketlad78 said:

Yes but also getting other opinions too. 

 

Well, as I said, I would pour footings and support it at the corners high enough to have a decent crawl-space. Even if it settles a little, you can jack it up and shim it. 

 

You can also weld a structure directly to the container for awnings of if you want to shade the whole area, or better to support solar panels AND provide shade. 

 

The standard containers are very robust, and I would not worry about removing the corrugated from the sides, they can still be moved. 

[Dr B]

I am an engineer, and I specialise in foundations. Obviously I agree with the far greater experience of Jen65 that all of the load of and in a container is taken at the four corners. That is how they are lifted and stacked. They have a very strong frame consisting of the corner posts and upper rails, but most importantly the floor which can support about 23 tonnes, even when the container is hanging by the upper corners. The side panels are typically some sort of corrugated pattern, and will not make a significant contribution to strength. The basic container weighs about 36.5 kN. Floor area is about 12.4 m2 so you could allow another 31 kN for floor load. That is a typical code allowance so quite conservative. That comes to 67.5 kN total, or 17 kN per corner which is less than 2 tonnes. Apply a factor of 1.5 for safety.

Now what matters is how strong is your soil, and is it subject to shrink/swell with seasonal moisture content (do you see significant surface cracks in the dry season?).

If not, then you can dig down a reasonable distance, below roots and organic material, and do a standard heel test. Put on your best work boots and try to push your heel into the soil. If it goes in less than 10 to 12 mm then you can assume a safe bearing pressure of 100 kPa. That means that a pad 0.5 x 0.5 m will support 25 kN, which is the factored load. As suggested elsewhere put some rebar in the pad, and make it 200 to 300 mm thick. Build a short stub to support each corner, also about 200 x 200 mm as suggested with some rebar, to leave yourself a crawl space. Probably most imprtantly get a concrete vibrator. I bought one recently for less than Bt 3,000. Our workers had not seen one before but now they love it. That means you can vibrate the pads and the stubs, and any other concrete you choose to pour, and use that to stop them putting too much water in the concrete, which is the local alternative to achieve workability, because they have never been told that adding water increases water cement ratio which reduces strength directly.

If you do see lots of surface cracks around, you might need to dig deeper to below the depth of seasonal moisture variation, or just accept that that your container goes up and down during the year.

Good luck

[Saanim]

19 hours ago, Dr B said:

Floor area is about 12.4 m2

20 ft container inside floor area is 6x2.34 m=14 m2, outside it is more by the wall thickness.