Hello!This is DIY Renova.

For those of you who enjoy renovations and DIY, have you made good measures to address the "spring land" of your current home or the home you are planning to renovate?Many people may hear the term "ground subsidence" and think, "We may not be that bad."

However, in fact, once ground subsidence (non-uniform settlement: a phenomenon in which only part of a house sinks), it can become a hotbed for any kind of trouble, such as building tilt, cracks, and even leaks and poor drainage.

Check the usual hidden parts, such as the condition of the soil, the foundations and the surrounding area under the floor, to prevent major problems in the future.

In this article, we have organized the DIY methods for checking ground subsidence and points to be careful about, so that even beginners can understand.

We hope that you can properly understand the risks and help you keep your precious home comfortable for a long time.

This article is a long article, but please read to the end to give you a comprehensive understanding of the risks of "spring ground."

So, here you go.

1. What is "Spring Land Bread"?The problems and risks

"Pressed land" refers to the ground that has been reclaimed and converted into residential land in places with low terrain, sloped areas, or valleys.This is a method of artificially raising soil, but it actually involves the following risks:

• "Compact settlement": Suspension occurs when the added soil tightens over time.
• "Drainage poorly": The drainage inside the ground is poor, and it is likely that rain and groundwater accumulates easily.
• "Shallow support ground": The depth to the original solid formation is not sufficient, and the building load cannot be fully supported.

In particular, in residential areas that are old and old, there are cases where the ground has not been improved properly due to insufficient technology and supervision at the time.Be careful if there are no records of improvements or construction photos left.

If the "sized land base" is insufficiently solidified or no drainage measures are taken, the chances of sinking gradually increase over several years to decades.This is the major risk of "ground subsidence (or non-uniform settlement)."

2. Mechanism and causes of subsidence

Even though we simply say "ground subsidence," there are various causes and mechanisms.Generally, there are the following mechanisms:

1. "Compression of soil"

• The filling area and the clay layer, which were originally soft, are gradually compressed due to long-term loading.
• Moisture is lost or the soil tightens due to vibrations (earthquakes, car traffic, etc.)

1. "Pumping groundwater"

• If groundwater is used excessively in industry or agriculture, the gaps in the soil will decrease and the ground will subside.
• It is more likely to occur in residential areas where deep wells are used, or in areas where the ground is easy to maintain moisture.

1. "Issues and drainage defects"

• Drain pipes are damaged or the land drainage plan is insufficient, causing water to accumulate in the soil and weaken the ground.
• It also affects high groundwater levels.

1. "Liquefaction caused by vibrations such as earthquakes"

• When the soil containing a lot of moisture such as landfills or sandy soil shakes greatly, liquefaction occurs and the building sinks.
• In cases where a major earthquake occurs, the number of cases falls suddenly several tens of centimeters.

As far as amateurs can understand, it is a good idea to gather as much information as possible, such as "How was the ground originally created?", "Has ground improvements been made in the past?" and "Is the drainage situation appropriate?"We also recommend checking the ground survey report from the time of the new building and the hazard map.

3. Basic stance of DIY checking: How much can you handle yourself?

There are cases where checking ground subsidence is sufficiently possible with DIY, but if "repair" or "significant improvements" are actually required, specialized knowledge and equipment are required.The main things you can do with DIY are "early observations, small adjustments, and reinforcements."

• "The extent to which DIY can be done"
• Level checks on exterior and interior, visual checks of cracks that occur on the foundation and under the floor
• Small-scale reinforcement such as replacing bundles and installing steel bundles
• Simple repair of cracks caused by sealing
• "The scope to which you should ask a professional"
• Large-scale ground improvements (surface layer improvements, columnar improvements, chemical liquid injection, etc.)
• Jacking up the highly tilted foundation and sinking correction work
• Construction to the level that requires earthquake-resistant reinforcement of the housing structure itself

First, use the DIY check method introduced in this article to identify the problems and calmly determine whether major repairs are really necessary.

4. [Exterior check] Don't overlook any abnormalities in the fence, walls, dirt floors, and drains

Subsidence caused by the land plating causes clear symptoms not only inside the building but also on the exterior.Please check the following points to make sure you don't miss out on them.

"The height and tilt of fences and block walls"

• Are fences and block walls that should have been installed straight or not partially low or inclined?
• Using a "laser leveler" or "longer leveler" makes it easier to see subtle differences
• If the exterior itself is tilted, it is likely that the entire earth has subsided.

"Cracks and steps in concrete floors"

• Do you have large cracks in your parking space or in the garden?
• Hair cracks with a crack of about 1-2 mm may be within the range of age, but if there is a step, it may be suspected of sinking.
• Areas where puddles are likely to form on rainy days may be a sign that the ground is sinking.

"Sinking drains and basins"

• Are the drains and rainwater basins on the premises sinking or warping compared to the ground?
• Check if you have symptoms such as difficulty opening the lid or rainwater reflux.

DIY check tips

• Using the "Laser Leveler" you can irradiate laser lines to a certain height, making it easy to check the horizontal and vertical surfaces of the exterior.
• A simple method of placing a "marble" on the ground and observing which way it will roll is also effective.

5. [Confirming the building's outer perimeter] Cracks in the foundation, height differences, and tilt of the ventilation opening

It is important to check not only the exterior structure but also the condition of the building foundation itself.Let's take a look at the following items:

"Cracks in the foundation"

• Hair cracks (slender cracks with a width of less than 0.3mm) on the foundation surface can be considered to be aging that is typical of concrete.
• However, cracks with a large width (more than 1mm) or cracks that run diagonally are likely to cause non-uniform settlement.
• Check areas where stress is concentrated, such as corners of the foundation or under the sash.

"Measure the height of the foundation"

• Measure the height to the top edge of the foundation at multiple points, such as in the corners of a building or near the center.
• For example, if you check the height according to the outer periphery, such as an entrance porch, you will likely notice subtle differences.
• Laser levels allow for even more accurate measurements

"Slope or clogged ventilation holes"

• If you have an old-fashioned underfloor ventilation vent, do they be installed parallel to the ground or not tilted?
• If the ventilation vents are blocked due to poor drainage or inflow of sediment, moisture can accumulate and weaken the floor.

6. [Indoor check] Doors, windows, and cloths are misaligned and creaks on the floor

No matter how good the exterior and foundations seem, if there is any discomfort with the fittings and floors inside the room, the ground may be subsided quietly.Here we list the symptoms that are likely to be noticed in your daily life.

"The doors and windows are difficult to open, they close without permission."

• Doors, sliding doors, and window sashes do not open and close smoothly
• The fact that the open door moves on its own may be proof that the floor is tilted

"The sound of sinking and creaking on the floor"

• The floor is dented only where heavy furniture is placed, and the sound of claws when walking
• Even if you are building a new or newly built, the bundles and joists may be loose, so be sure to check them out.

"Cracks and peeling off"

• Diagonal cracks can be seen in the four corners of the room and in the battle between the walls and ceiling.
• When the house is warped, the seams are subject to stress, making the cloth more likely to tear or peel off.

"The level of furniture and appliances doesn't suit them"

• Be careful if there are many furniture such as refrigerators and shelves that require leveling.
• Place marbles in the four corners of the room and compare how they roll.

7. [Check under the floor and bundles] Please check when skeletoning

If it is in a skeleton state due to renovations, be sure to carefully check the entire floor.There may be hints of subsidence hidden in the areas that are normally hidden.

Checkpoint

1. "The sinking and tilting of the foundation stone"

• Is the foundation stone stuck in the ground or sinking diagonally?
• Be careful if there is a space between the foundation stones and the pillars.

1. "The state of wooden or steel bundles"

• Is the old wooden bundle corroded or loose?
• Is the adjustment screws on the steel bundle unlocked?

1. "Ground moisture, puddles, cavities"

• It is likely to show poor drainage or loose ground
• If there is a large cavity under the floor, there may be a possibility that soil may be leaking out.

1. "Damage or uninstalled moisture-proof sheet"

• There are cases where moisture-proof sheets that suppress moisture from the ground are full of holes or are not originally laid out.
• When moisture builds up, the wood and bundles will decay, and the ground will likely become softer.

Examples of DIY measures

• Add "recycled crushed stone" (crushed stone with uniform grain size) below the foundation stone, then rotate it firmly and then re-adjust the height with a steel bundle.
• If there is a lot of humidity, consider reinstalling a moisture-proof sheet or introducing a dehumidifier for underfloors.
• If ventilation is poor, you can install a "underfloor ventilation fan"

8. [Notes on land only] Risks hiding in land higher than the surrounding area

The land is often "artificially raised" to suit the surrounding terrain, so there are unique problems.

1. "The flow of rainwater and drainage is unnatural"

• Because the original terrain has been altered, the structure is likely to cause water to accumulate somewhere.
• Without an appropriate drainage plan, water will stay in the soil and become weaker.

1. "There is a step at the boundary between the neighboring area."

• In some cases, retaining walls are installed to prevent the filling area from collapse.
• If the retaining wall is old, there is a risk of cracks due to rainwater or earthquakes

1. "Construction records at the time of residential development are vague"

• In the construction of a few years ago, it is unclear what kind of material (in some cases industrial waste) was filled with, but it may be difficult to understand what kind of material it was filled with.
• If there are no records of ground improvements or ground surveys, consider requesting an investigation later.

It is often thought that the higher the ground, the better the area, but if the part that has been raised with the filling is not solidified, there is a higher risk of sinking.Be especially careful when using old land.

9. Practice with DIY!Specific repairs and preventive measures

Some people have checked this far and thought, "This might be a bit dangerous..."It is a high hurdle to request large-scale construction work right away, but please consider the following DIY-level measures.

9-1. Funded stones and underfloor reinforcement

• "If the sinking is minor"
• Lift the foundation stone once, add crushed stone or sand below, and rotate it to stabilize it.
• If there is space, replace it with a steel bundle and re-adjust the height.
• "If the bundle itself is degraded"
• Replace rotten wooden bundles early
• Using steel bundles makes level adjustment easier

9-2. Cracked sealing

• Minor cracks in foundations and concrete can be reinforced by injecting repair materials such as "epoxy resin"
• In the case of large cracks, simply sealing does not provide a fundamental solution, so consult an expert.

9-3. Reviewing the drainage plan

• If the drainage on the property is poor, consider adding drains or increasing the capacity of the rainwater basin.
• If drainage from the gutters tends to accumulate around the building, adjust the slope of the ground and inspect the drain pipes.
• Consider garden plants and planting plans to prevent water from accumulating

9-4. Improvement of the underfloor environment

• Keeping the floor dry by laying moisture-proof sheets, adding under-floor ventilation fans, and replacing insulation materials.
• Moisture countermeasures are also effective in preventing damage to white ants

9-5. Small-scale ground improvement

• The extent to which DIY can be achieved is to replace the surrounding soil or add crushed stone to transform it.
• If you rent a drum type "plate compactor" (small compression machine), you can rotate to a certain extent.
• However, if you need large-scale ground improvements, it is better to ask a specialist to do so.

10. Cases to consult with a professional and timing

What can be addressed with DIY is simply the case of "minor sinking" or "surface problems."In the following cases, consult a specialist (such as a ground survey company, contractor, architect, etc.) as soon as possible.

1. "There are big cracks in the foundation and foundation."

• It is likely to have a negative effect on the building structure itself.

1. "Step in a few centimeters on the floor and exterior"

• Visually it has subsided, or it may interfere with opening and closing the door.

1. "Serious cracks and tilts in the retaining wall"

• There is a risk of collapse due to soil pressure

1. "The N value (an indicator of the hardness of the ground) is extremely low in the results of the ground survey."

• Ground improvement and reinforcement work is essential

If there is a concern that a certain degree of subsidence is present in a swelled land, major reinforcement by professionals such as "ground subsidence correction work," "chemical liquid injection," and "pillar improvements."The cost is high, ranging from hundreds of thousands to millions of yen, but if left untreated there is a possibility of greater damage, so please get a thorough estimate and consult with us.

11. Summary: Now is the time to develop an "eye to see the ground"

Now that you've made your home into a skeleton, the foundations, underfloors and structures are exposed, making it a great opportunity to observe every detail of areas that are normally invisible.To avoid regretting later saying, "Oh, I should have looked closely at the ground back then...", be sure to use the checklist in this article to carefully check the parts you need.

Since "ground subsidence" often progresses slowly over the long term, by the time you notice it, the damage may already be widespread.However, on the other hand, if you detect abnormalities early and take measures, there are many cases where large-scale construction is no longer necessary.

• "Are there any cracks or slopes in the exterior or foundation?"
• "What are the levels of the doors and floors inside?"
• "Are the bundles and ground under the floor healthy?"

Don't miss these and check them out and take measures as soon as possible where you can reinforce them with DIY.And, if you suspect serious levels of sinking, we recommend that you do not hesitate to consult a professional.

Houses are sometimes said to be the biggest purchase of your life, but for those who use their own hands to renovate or DIY, they become even more attached to them.That is why it is important to develop a "eye to see the ground" to make your home last longer.

12. References and Videos

Below are some recommended sources to help you deepen your understanding of subsidence and fillings when writing the article.I will introduce it with respect.

• "Residential Manual for Residential Land" (edited by the Japan Architectural Center)
• It provides detailed explanations on the basics of ground investigations, types of ground improvements, and the causes of ground subsidence.
• Materials related to the Ministry of Land, Infrastructure, Transport and Tourism's "Regulation of Residential Land Development, etc."
• You can check regulations and safety standards for building soil and residential land.
• YouTube channel "A relaxed talk by a DIY-loving architect"
• The practical examples of underfloor inspections and foundation repairs are presented in an easy-to-understand manner.
• "Ground Safety Map" Websites
• You can view information by region, such as ground disaster risks and hazard maps.

This information will also help you gain professional level knowledge and will be very useful for DIY measures and inspections.Be sure to check it out.

Above, we have compiled a DIY checklist and key points to help prevent subsidence in houses with a swelled land.There's no need to worry more than necessary, but it's safe to check carefully with "Make sure you're careful."I hope your precious home will remain comfortable and safe forever.Thank you for reading to the end!

If you're wondering "How much renovation or remodeling can I actually do on my own home?" or "Where should I even start?", please visit this page. If you're looking to learn more about specific renovation processes or construction details, don't miss this page as well!