Land Retaining Wall and House Build - Kalasin

[GarryP]

My wife has a small piece of land in north Kalasin province and we are planning to build a house on the land (land size 15m x 40m). However, we will also need to build a land retaining wall on three sides of the land. The land has already be filled and raised above the surrounding land and left for about 8 years so the land is solid but we will still need a retaining wall. At the rear the land plot is about 1.8 meters above the surrounding land but the difference decreases heading towards the front of the land. 

 

My questions are:

 

Should the retaining wall and the above ground part of the retaining wall be built before we start with the house build or after (noting that the land size is only 15m wide so the walls of the house will be only about 2 m from the walls at each side)? We have received differing opinions on this from Thai builders, namely, before, after or it doesn't matter. 

Can anyone recommend a builder/construction company in Kalsin, Udon or Khon Kaen for the retaining wall build? The local builder we have been talking to and who has visited the site seems to be a bit untrustworthy, although his other projects seem to be well done.  Thus, we would like to obtain quotations from a few others before making a final decision. 

 

    

[eyecatcher]

Actually it very oftrn does matter.

 

Building the wall first is going to contain the already compacted ground and help minimise any settlement on the house.

 

Without the wall in place the tendency will be to excavate anf distribute beyond your boundary and Totallly restrict activity on a wall later on.

Always take you house foundations below the level of your retaing wall not the other way around.

[GarryP]

1 hour ago, eyecatcher said:

Actually it very oftrn does matter.

 

Building the wall first is going to contain the already compacted ground and help minimise any settlement on the house.

 

Without the wall in place the tendency will be to excavate anf distribute beyond your boundary and Totallly restrict activity on a wall later on.

Always take you house foundations below the level of your retaing wall not the other way around.

Thanks. That makes sense to me. But I was concerned that if the retaining wall is done first, the construction of the house may lead to damage to the wall when the house is constructed. 

 

My idea was to build the retaining wall, bring in additional earth for filling against the retaining wall as needed and even out the the land, then leave to settle for another few years before building the house.  But my head started spinning when others said "Do the house first", or "It doesn't matter". 

 

As to the house foundations, the land at the moment is pretty rock solid so it could be a bit of a task taking the foundations below 1.8m (the height of the land above surrounding land). Also, here (the area concerned) they do not seem to go with driving piles, but simply dig down about 50cm and place footings and foundations at that depth. Seems way too shallow to me.   

[grollies]

1 hour ago, GarryP said:

Thanks. That makes sense to me. But I was concerned that if the retaining wall is done first, the construction of the house may lead to damage to the wall when the house is constructed. 

 

My idea was to build the retaining wall, bring in additional earth for filling against the retaining wall as needed and even out the the land, then leave to settle for another few years before building the house.  But my head started spinning when others said "Do the house first", or "It doesn't matter". 

 

As to the house foundations, the land at the moment is pretty rock solid so it could be a bit of a task taking the foundations below 1.8m (the height of the land above surrounding land). Also, here (the area concerned) they do not seem to go with driving piles, but simply dig down about 50cm and place footings and foundations at that depth. Seems way too shallow to me.   

You don't need foundations 1.8m deep but your house concrete post holes do need to go that deep, at least to the original ground. 1.8m isn't that deep.

 

Your retaining wall I've used 'H' posts and concrete panels. Posts 3m long x 8" square, panels 2m long. If just a retaining wall I'd take the posts down with the tops to your house ground level. I've seen retaining wall posts way too shallow and the wall just leans. 

[GarryP]

8 minutes ago, grollies said:

You don't need foundations 1.8m deep but your house concrete post holes do need to go that deep, at least to the original ground. 1.8m isn't that deep.

 

Your retaining wall I've used 'H' posts and concrete panels. Posts 3m long x 8" square, panels 2m long. If just a retaining wall I'd take the posts down with the tops to your house ground level. I've seen retaining wall posts way too shallow and the wall just leans. 

Thanks.  I want to go with the H posts and precast panels. At the rear 1.8m would bring it to the level of the land the house will be on and I want to have another 2 meters above ground. They would have to build internal support arms (don't know what the technical name is) for the retaining wall. Hopefully, that would help prevent the walls leaning. But is is also a concern of mine. Hence the questions.

[grollies]

14 minutes ago, GarryP said:

Thanks.  I want to go with the H posts and precast panels. At the rear 1.8m would bring it to the level of the land the house will be on and I want to have another 2 meters above ground. They would have to build internal support arms (don't know what the technical name is) for the retaining wall. Hopefully, that would help prevent the walls leaning. But is is also a concern of mine. Hence the questions.

Talk direct to the company making the posts, they could probably make you posts to order, 4.8m long posts would give you a 1.8m high wall. For asthetics you could use wood panels atop the concrete retaining panels......in fact, you've just given me an idea....

[Fruit Trader]

Idea for retaining a deep fill before construction.

 

Below shows SCG wall system on top of reinforced lower retainer. The lower retainer is pinned below the neighbouring land level using the standard pad footing where half of the pad will reside in the neighbouring land. Side load is taken by the lower retainer and lean is prevented by the pad footings.

 

A regular column and block could be used instead of the precast system.

 

[eyecatcher]

As Grollies suggests for a panel retaining wall  2-4m high it would be typical to use a pile driver to send the H sections into the ground.

You are thi king of small buttress stays to stabalise a wall, which you would do for a wall over 2m high in your garden.

 

Tbh I would trust the strength of a pile driven panel wall before Somchais labourers with rebar concrete and blockwork

[Fruit Trader]

I guess if the OP's pockets are deep enough and his neighbours don't mind a little shaking on the 15 x 40 plot.

 

 

 

 

And finally Somchais labourers doing a grand job.

 

[GarryP]

Attached is a poor drawing of the land we will be building on. Can't find any photos at the moment. As you can see, it is higher than the land around it, more so at the rear of the land than the front. As there will be no earth against the outer side of the retaining wall, I think that driving the piles in would be better than a shallow footing. 

 

[grollies]

2 minutes ago, GarryP said:

Attached is a poor drawing of the land we will be building on. Can't find any photos at the moment. As you can see, it is higher than the land around it, more so at the rear of the land than the front. As there will be no earth against the outer side of the retaining wall, I think that driving the piles in would be better than a shallow footing. 

 

What's wrong with digging post holes with a mini excavator? Hell of a lot cheaper.

[lanng khao]

Put a reinforced concrete strip footing in, and use 2 skins of concrete block with a 100 mm cavity, build both skins up a meter and fill will rebar and concrete and tie wires holding the 2 skins together, then add another meter on top and do the same.
Put a nice coping stone on the top, can tie in block size pillars every ten block for extra strength, better than having a load of piles on show on the farmland.

Sent from my SHT-W09 using Thailand Forum - Thaivisa mobile app

[GarryP]

1 hour ago, grollies said:

What's wrong with digging post holes with a mini excavator? Hell of a lot cheaper.

Concerned about the strength. But we also have cost concerns so may have to do it that way. 

[eyecatcher]

Unless you are building your house right upto the high point, then why not grade the land back down to the original and just put up a regular wall.

2m height is nothing to get rid of. two metres in and grade at 45 degrees, 3m in and grade at (sine opposite hypotenuse, or is it tan opposite adjacent!!!) say 30 degrees, plant it up or be creative with it.

it may even be a nice solution to lose rainwater from the plot.

I think you can quite easily design it out with slopes, or a path, steps and save yourself a hell of an expense

 

[grollies]

8 minutes ago, eyecatcher said:

Unless you are building your house right upto the high point, then why not grade the land back down to the original and just put up a regular wall.

2m height is nothing to get rid of. two metres in and grade at 45 degrees, 3m in and grade at (sine opposite hypotenuse, or is it tan opposite adjacent!!!) say 30 degrees, plant it up or be creative with it.

it may even be a nice solution to lose rainwater from the plot.

I think you can quite easily design it out with slopes, or a path, steps and save yourself a hell of an expense

 

Nice idea but you are not supposed to loose your rainwater onto the neighbour's land.

[GarryP]

17 minutes ago, eyecatcher said:

Unless you are building your house right upto the high point, then why not grade the land back down to the original and just put up a regular wall.

2m height is nothing to get rid of. two metres in and grade at 45 degrees, 3m in and grade at (sine opposite hypotenuse, or is it tan opposite adjacent!!!) say 30 degrees, plant it up or be creative with it.

it may even be a nice solution to lose rainwater from the plot.

I think you can quite easily design it out with slopes, or a path, steps and save yourself a hell of an expense

 

Because the land is only 15m across and the house we are planning to build will be @10 meters across. Giving us only 5m to be shared between each side. 

 

The quote we have got so far is just over 300k but the piles aren't being driven in. Just concrete footing with wall posts and internal buttresses or retaining arms (not sure what they are called) on every other wall post.    

[eyecatcher]

1 hour ago, GarryP said:

Because the land is only 15m across and the house we are planning to build will be @10 meters across. Giving us only 5m to be shared between each side. 

 

The quote we have got so far is just over 300k but the piles aren't being driven in. Just concrete footing with wall posts and internal buttresses or retaining arms (not sure what they are called) on every other wall post.    

I am referring to the back only so 5m each side makes no difference plus as you drew it, it tapers back from 2m back to nothing.

 

300k i hope isnt just for the 15m stretch at the back.?

 Using concrete ties is the unengineered approach to retaining walls, just let the customer pay for more poured concrete.

 Dont be afraid to approach your local tessaban engineer for his opinion and maybe some suitable contractors

[GarryP]

2 hours ago, eyecatcher said:

I am referring to the back only so 5m each side makes no difference plus as you drew it, it tapers back from 2m back to nothing.

 

300k i hope isnt just for the 15m stretch at the back.?

 Using concrete ties is the unengineered approach to retaining walls, just let the customer pay for more poured concrete.

 Dont be afraid to approach your local tessaban engineer for his opinion and maybe some suitable contractors

300k is for two sides and rear. Totally 95m. 

[Yellowtail]

As someone else indicated, were it me, given the small distance from the house to the wall, I would incorporate the retaining wall with the building foundation and just backfill the exterior walls. 

[sirineou]

We used TC House Khon Kaen, and were very happy with the work they did and the Owner Dook, very professional, no drama, he was recommended to me by another forum member in the area and he was also very happy with their work. Of course past performance is no guarantee of future results but a good place to start.

https://www.facebook.com/search/top/?q=tc house khon kaen รับสร้างบ้าน&epa=SEARCH_BOX

This is a link to our build :

 

[sometimewoodworker]

On 1/25/2019 at 2:14 PM, GarryP said:

As to the house foundations, the land at the moment is pretty rock solid so it could be a bit of a task taking the foundations below 1.8m (the height of the land above surrounding land). Also, here (the area concerned) they do not seem to go with driving piles, but simply dig down about 50cm and place footings and foundations at that depth. Seems way too shallow to me.   

The ideal way to find the depth you need to dig is to have a soil bearing test done. That way you will know if you need to go down to the original, pre-fill, level or if the fill has compacted enough so shallower is correct.

 

Without that your only safe option is to go down to the pre-fill depth. With our house we did the test and didn't need to go that deep. Our fill had about 9 years to compact.

[GarryP]

2 hours ago, sometimewoodworker said:

The ideal way to find the depth you need to dig is to have a soil bearing test done. That way you will know if you need to go down to the original, pre-fill, level or if the fill has compacted enough so shallower is correct.

 

Without that your only safe option is to go down to the pre-fill depth. With our house we did the test and didn't need to go that deep. Our fill had about 9 years to compact.

The land was filled nearly 10 years ago. Once the retaining wall is built we would grade the land a bit more and get a couple more trucks of earth in. But this will only be on the surface to level it all out, should be no deeper than 30 cms in any part of the land. The land will be then left for another three years before we proceed with the house build.

 

I will look up "soil bearing test" as it sounds like something we should do. 

[sometimewoodworker]

13 minutes ago, GarryP said:

The land was filled nearly 10 years ago. Once the retaining wall is built we would grade the land a bit more and get a couple more trucks of earth in. But this will only be on the surface to level it all out, should be no deeper than 30 cms in any part of the land. The land will be then left for another three years before we proceed with the house build.

 

I will look up "soil bearing test" as it sounds like something we should do. 

I've just checked the building thread. We filled about the same amount as you did and our foundations only needed to be 1 metre deep House building thread. This first page shows the testing.

 

One extremely important point is, if you dig deeper than needed use the deeper hole DO NOT put any earth back in, sand maybe, if you compact it, but any earth put back will have at least 30% air.

[GarryP]

1 hour ago, sometimewoodworker said:

I've just checked the building thread. We filled about the same amount as you did and our foundations only needed to be 1 metre deep House building thread. This first page shows the testing.

 

One extremely important point is, if you dig deeper than needed use the deeper hole DO NOT put any earth back in, sand maybe, if you compact it, but any earth put back will have at least 30% air.

I have just run through your building thread. Your house looks a lot larger than what I intend. Also, I will probably go with a standard plan. I don't have anywhere near the skill set or background to get as deeply involved in the build as you did. But having a workshop, hmmmm?? That got me thinking. 

 

BTW your house looks really interesting, not least of which is the roof. I like the idea of not going with roof tiles,  to minimize potential leaks and also the insulation spray you used.  The problem with looking at threads like yours is that I see so many great things to do, but they would most certainly take me over budget.  I'm only planning on spending 1.5 to 2 million for the house build. 

[BurriAussie]

This wall is around 38mt, 1mt footing with beam top and bottom, cost me 40,000baht in labour and around 80,000 in material.

[GarryP]

30 minutes ago, BurriAussie said:

This wall is around 38mt, 1mt footing with beam top and bottom, cost me 40,000baht in labour and around 80,000 in material.

 

 

I note that you built your wall into the raised land. In my case we will be building the wall around the raised land. 

[grollies]

5 hours ago, GarryP said:

I note that you built your wall into the raised land. In my case we will be building the wall around the raised land. 

Yeah but same same, he looks like he's then infilled to the top of the wall. 

[GarryP]

I was planning on having the retaining wall built this year, but that may not be possible now. However, I have another concern. As the house we are planning to build will be 11 meters wide, this will mean that the piles on each side of the house will only be 2 meters from the retaining wall. As such, I wonder whether I should wait until the house is built before building the retaining wall. My concern is that driving the piles for the house might damage the retaining wall. I am assuming that the land is not solid enough for shallow footings and that I have to have piles put in which go deeper than the land fill of about 1.5 meters.

 

Alternatively, as Yellowtail suggested, should I go will incorporating the retaining wall with the building of the house?