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SkyMan

Compaction?  We don't need no stinking compaction....

Ok, so we finished the wall and another project so now I'm thinking about house building.  We're going to dig down into the limestone so would compaction for the slab even be necessary?  I suppose if we dug too deep and had to fill back in that would be a good idea but I don't see that as likely.  I'm also thinking it would be a good idea to spread a couple inches of crushed rock before the slab pour.  Would that need to be compacted?  I could probably rent a compactor but I'm also thinking maybe I could weld up a flat plate to attach to my jackhammer for that.  And then I'd have that for whatever future structures I might build.  Experienced thoughts?

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Paddy

Some interesting information here (also use the menu to look around). 
 

https://www.concretenetwork.com/concrete-subgrades-subbases/

I couldn’t find anything in there about the base being limestone, however, I think that’s going to eliminate the issue of getting the underlying soil “just right”.

A gravel layer, compacted, is a good idea if there is any concern about drainage. 

A vibrating compactor is better for area compaction. Your jack hammer contraption would likely be better in confined spaces. 
 

Proper compaction is important and, of course, mainly ignored here in Masbate. I have yet to see any work crew using a vibrating compactor (saw them and used them myself in Canada).

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Headshot

Limestone is bedrock. You don't have to compact bedrock. However, if there is any loose material on the surface, you may want to compact that (or you can just let it settle for a while, and gravity will compact it for you ... especially if the loose material is anapog (crushed limestone)).

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fred42
Posted (edited)
1 hour ago, Headshot said:

Limestone is bedrock. You don't have to compact bedrock. However, if there is any loose material on the surface, you may want to compact that (or you can just let it settle for a while, and gravity will compact it for you ... especially if the loose material is anapog (crushed limestone)).

Only thing that worries me a bit is how waste water pipes behave during even the slightest of under floor settlement. 
We bury the pipes in a trench shrouded in gravel. Thus far,no issues touch wood.

Edited by fred42
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SkyMan
11 minutes ago, fred42 said:

We bury the pipes in a trench shrouded in gravel. Thus far,no issues touch wood.

That's the correct way.

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yingy52

Similar to a French Drain maybe?:1frog:

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SkyMan
18 hours ago, yingy52 said:

Similar to a French Drain maybe?:1frog:

Technically a French drain is a channel with large rocks in the bottom and progressively smaller rocks on top.  But this is pretty the same with a pipe surrounded with gravel.  In the US it's common to do this around the bottom of basement walls with flible HDPE pipe with holes in it to collect water, then a few pipes under the basement to move the water to the sump pump to eject the water to a safe area.

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to_dave007
1 hour ago, SkyMan said:

Technically a French drain is a channel with large rocks in the bottom and progressively smaller rocks on top.  But this is pretty the same with a pipe surrounded with gravel.  In the US it's common to do this around the bottom of basement walls with flible HDPE pipe with holes in it to collect water, then a few pipes under the basement to move the water to the sump pump to eject the water to a safe area.

But a French drain might be used more in a place without great drainage..  Surely your location.. with the natural gradient.. should make it pretty easy to get good drainage.  

As for your compaction question..  Not sure how you are going to build your house.  Most houses here have a foundation pad at the bottom of each column.. and I should think that if the column is directly on bedrock.. or with just a small leveling layer (of sand or aggregate) under each pad, then I shouldn't think compaction will be a big issue.  But your opening post talked about a foundation "slab"..  which makes me wonder exactly what you mean.  If you are planning that that slab will eventually be tiled for your 1st floor I wouldn't want it to be far below grade.

At my place I remember one day during construction when we had a typhoon.. and a LOT of rain.  And we have quite an upslope behind the house.. and the whole muddy mess flowed right down the hill..  and in the back door through the dining room and living room and out the front.  No damage though..  we weren't far enough along..  Just a mess to clean up.  But after that I planned a canal along the back of the house to channel water away..  But it doesn't LOOK like a canal.. it looks like a sidewalk and a planter.  But it's primary purpose initially was to prevent a repeat of that flood.    

But if you are planning a floor slab.. In your location I shouldn't think you'll be far above the limestone bedrock.  You likely should consider how far above it you are.  How DEEP will the material be that you need to compact, And what material will you use.  How "compactable" is it?.  

One compaction job we had here was when I built the rainwater tank.   The tank is about 5300 gallons..  So the water would weigh about 22 tons.. plus the tank itself. By the time we built the tank we'd been in the house for a couple of years, and I noticed how much vibration we could feel from heavy vehicles on the road when they pass by about 30 meters away.  that.. plus earthquakes..  made me a little concerned about how to ""shake proof" the tank.  So we dug down in the earth about 4 feet..  to a layer that included  ONLY rocks that had been water smoothened..  so clearly at one time under water.  Given that we are 25 feet or more above sea level I think it's safe to say the earth we dig down to had not been disturbed in 10,000 or more years. We compacted a thin layer.. just a couple inches..  of sand on top if this..  more to level it than anything. Then we poured a thick and well reinforced foundation slab for the tank, about 2 feet bigger than the tank needed to be on each side.  And then we added the tank..  All the pipes have a zig-zag to allow some flexing in an earthquake.  After 4 or so years.. no problems.

When the house was built all the rooms were filled with rough sand and compacted before the floor was poured. Some of those were several feet of fil, which was compacted 6 inches at a time.

All the compaction was done "province style"..  with a heavy piece of wood.. a cylindrical piece..  with handles nailed to each side..  and manual labor to simply pound the whole floor.  Crude.. and labour intensive.. but it seems to have worked.  

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Headshot

If Skyman is building directly over bedrock, I'm pretty sure he doesn't need to worry much about settling. In addition, I'm pretty sure that he doesn't plan to build a "typical" Filipino house (at least not unless he has changed his plans since the last time we talked about house construction).

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SkyMan
On 5/23/2020 at 1:10 PM, to_dave007 said:

But a French drain might be used more in a place without great drainage..  Surely your location.. with the natural gradient.. should make it pretty easy to get good drainage.  

Yeah, we kinda got off topic with the French drain idea. I don't need it.

On 5/23/2020 at 1:10 PM, to_dave007 said:

Most houses here have a foundation pad at the bottom of each column.. and I should think that if the column is directly on bedrock.. or with just a small leveling layer (of sand or aggregate) under each pad.

Footers.

On 5/23/2020 at 1:10 PM, to_dave007 said:

But your opening post talked about a foundation "slab"..  which makes me wonder exactly what you mean.  If you are planning that that slab will eventually be tiled for your 1st floor I wouldn't want it to be far below grade.

I'm talking about the basement floor really and have no plans for flooring at this time. Most likely that floor and any column footers will be poured at the same time. I've seen this done in the US too, only with steel posts rather than concrete columns.  They dig the basement and then dig out an additional 'box' anywhere a load bearing post will go and extra rebar is added there. Then they pour the floor. You can do the same with concrete columns, just there will be rebar sticking up.

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to_dave007
7 minutes ago, SkyMan said:

I'm talking about the basement floor really and have no plans for flooring at this time. Most likely that floor and any column footers will be poured at the same time. I've seen this done in the US too, only with steel posts rather than concrete columns.  They dig the basement and then dig out an additional 'box' anywhere a load bearing post will go and extra rebar is added there. Then they pour the floor. You can do the same with concrete columns, just there will be rebar sticking up.

Sounds like you want your "basement" to open out towards the downhill side looking out eastwards towards the rising sun, while being below grade at the uphill side of the house. Is that right?

How much soil to you have over the limestone bedrock there?

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SkyMan
Posted (edited)

Yes, the east side. Will be less than fully below grade. Like HS said, the house is not typical local style. Mainly because of the basement. Locals don't like basements. Even my wife has expressed concerns. "It will get rats." Hahaha 

The ground floor will be the garage and laundry.  The living area above that.

Edited by SkyMan
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to_dave007
24 minutes ago, SkyMan said:

Yes, the east side. Will be less than fully below grade. Like HS said, the house is not typical local style. Mainly because of the basement. Locals don't like basements. Even my wife has expressed concerns. "It will get rats." Hahaha 

The ground floor will be the garage and laundry.  The living area above that.

then I don't really understand why you'll need compaction.  Surely if you have 1/2 of a floor below grade you'll be on rock already where you are. Won't you?

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Headshot
26 minutes ago, SkyMan said:

Yes, the east side. Will be less than fully below grade. Like HS said, the house is not typical local style. Mainly because of the basement. Locals don't like basements. Even my wife has expressed concerns. "It will get rats." Hahaha 

The ground floor will be the garage and laundry.  The living area above that.

She is likely more afraid of ghosts being in the basements than rats. However, as long as at least one side is above grade and opens to the outside, you might possibly convince her that it isn't really a basement. Filipinos are afraid of rats because they have no idea how to construct a threshold under their doors. The rats are able to just squeeze under the door (right along with the huntsman spiders, geckos and cockroaches). Put thresholds under your exterior doors, and that problem is solved.

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SkyMan
19 minutes ago, to_dave007 said:

then I don't really understand why you'll need compaction.  Surely if you have 1/2 of a floor below grade you'll be on rock already where you are. Won't you?

Probably not.  We'll know when we get down there.  Maybe I've watched too many videos.  Hahahaha

12 minutes ago, Headshot said:

She is likely more afraid of ghosts being in the basements than rats.

No, she doesn't buy into that momo horse hockey.  Just that basements are uncommon here and if we were near sea level I wouldn't likely consider it.  Rats (actually mice) get in some pretty small holes and will chew through some of the thin wood construction materials here.  There won't be any food for them in the basement or garage levels so if they want to go there to die, I guess I'm ok with that.

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