To what extent can you save money by renovating your home yourself? (Japanese wooden construction model 2, complete practical version) [DIY renovation]

10/11/2025

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Hello. In this article, we will explain how much you can save by self-renovating a wooden house (up to 2 floors) using traditional Japanese construction methods, from an engineering/quantitative perspective and down to the steps at the material level.
In conclusion, if you do everything from disassembly, groundwork preparation, insulation and airtightness, interior finishing, painting, and simple equipment replacement through DIY, you may be able to reduce the total cost by about 20 to 45%. Furthermore, if you have the skills and safety system to handle the outer skin of roofs, exterior walls, sashes, etc., it is realistic to reduce costs by up to 50% or more.

However, there are strong legal and safety restrictions when it comes to electrical work (additions/wiring), major relocation of water supply and drainage, and fundamental changes to the structure, so it is important to leave the planning, application, and supervision to professionals.

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!

This article is not a recommendation, so please read it for reference only.

So, here you go.

Table of Contents

How to read this article and its assumptions

Target audience: First-time DIY to intermediate users. This article is written so that you can understand the steps and the order of materials, tools, and work.
Expected house: 2-story traditional wooden building from the 1980s to 2010s, with a total floor area of 80 to 120 square meters (approximately 24 to 36 tsubo).
Purpose: Improve performance (insulation, airtightness, earthquake resistance, fire resistance) and safety while reducing costs.
Laws and Regulations: We will list important points in accordance with the Japanese context, such as the Building Standards Act, Energy Saving Standards, Electrician Act, Water Supply System Construction Chief Engineer System, and Sewerage Act (this article takes a ``Japanese'' stance).
Super easy memo of terminology
- Thermal resistance R (m²K/W): Thickness/thermal conductivity. The larger the size, the more effective the insulation.
- U value (W/m²K): Ease of heat dissipation. The smaller the size, the better the insulation.
- C value (cm²/m²): The amount of gaps throughout the house. The smaller it is, the more airtight it is.
- n-value calculation: A simple calculation used to examine the amount of load-bearing walls and joint metal fittings.

DIY vs. professionals: Which is “faster and cheaper” to leave to others? [Conclusion quick reference table]

The following is a decision-making map assuming a ``two-story conventional wooden structure of around 100 square meters''. We ``recommend'' the option with the lowest total cost (time + accident risk + rework), which includes not only costs but also regulations, safety, and rework risks.

field/work	Conclusion	Key points of evidence
Interior demolition (gypsum board, fixtures)	Many people prefer DIY.	Work with a high labor cost ratio. The main cost is the unit price for man-made products and the price per square meter, and it can be significantly reduced by DIY if proper separation and curing are followed (market price: 20,000 to 30,000 yen/day for man-made, 15,000 to 50,000 yen per tsubo for interior demolition).Yu Home Co., Ltd.
industrial waste disposal	Depending on conditions (semi-DIY)	Reduce costs through thorough separation. Local permit collection, transportation, and manifest handling are handled by a contractor. DIY is a practical solution for sorting, transporting, and loading. Market prices tend to be included in construction estimates.Happy Sumu
Gypsum boarding, putty, painting	DIY is better (if you have time)	If you follow the correct screw pitch and joint treatment, the risk of re-construction will be low. Public manuals for construction standards are available free of charge (pitch, layering, and processing are clearly specified).gypsumboard-a.or.jp
Adjustment of indoor fittings, baseboards, and surrounding edges	DIY is advantageous	The cost of redoing in the event of a failure is low, and the learning effect is high.
Flooring (direct pasting/disposable pasting)	DIY is possible (takes time)	The requirements for construction accuracy are moderate. Reconstruction costs for failures are medium. Depends on the precision of the base.
Window insulation renovation (inner windows)	DIY can be profitable	Windows are the biggest source of heat loss. Internal windows are one of the most popular DIY projects because they are “cost-effective and easy to construct.” The importance of openings is repeatedly emphasized in policy and industry materials.Japan Sash Association However, depending on each local government, there may be large subsidies for energy-saving renovations. Be sure to check out the subsidies first!
Window cover construction method (sash replacement on the outside)	Professionals are often faster and cheaper	Redoing water shutoffs and rain closures is expensive. External scaffolding, storing of accessories, and waterproofing are the key points, and the professional setup is successful.
Roofing work (reroofing/covering)	Almost recommended by professionals = professionals are “cheaper as a result”	The biggest cause of fatal accidents in the construction industry is falls. Professionals have an overwhelming advantage in reducing accident risk and shortening processes by standardizing safety equipment and procedures.Ministry of Health, Labour and Welfare
External wall layering (ventilation rim + siding)	If second floor scaffolding is involved, professional	Rework is expensive due to multiple steps such as scaffolding, unloading, ventilation, accessories, and two-sided adhesive bonding of stickers. Great for professional productivity (team work).
Electrical work (new installation, expansion, branching, conversion to 200V)	Legally professional (qualified person)	Qualified as a Class 2 electrician or higher. DIY is limited to “equivalent replacement” of equipment. There is a high risk of illegality, fire, and invalidation of insurance.OFFICE110 It may be fine if you have the qualifications and are working on parts other than the main parts of electrical equipment such as breakers!
Water/hot water supply piping modification	almost legally professional	Many local governments have a “designated construction shop” system. Illegal construction risks fines and water supply suspension.plumber net
Drainage (minor indoor changes)	DIY is possible with some conditions, but be careful.	Damage caused by poor slope and water leakage becomes expensive. Basically recommended by professionals.
Bathroom waterproofing (conventional bathroom renewal)	Recommended by professionals = cheaper as a result	The damage caused by water leakage is enormous. Outsourcing the unit bath with clear process standards and clear demarcation of responsibilities for the waterproof layer is ultimately cheaper.
Demolition of suspected asbestos sites	legally professional	Mandatory preliminary investigation, notification, work supervisor, and isolation regimen are essential. DIY is not allowed.Ministry of Health, Labor and Welfare/Asbestos comprehensive information portal site

1. Three representative fields where “DIY is really advantageous”

① Interior demolition (removal of plasterboard, fixtures, and floors)

Why it's worth it: This is because demolition involves a large proportion of labor costs, and it is easy to replace "labor costs" with DIY. The market price is generally in the range of 20,000 to 30,000 yen/day for artificial materials and 15,000 to 50,000 yen per square meter/tsubo (up or down depending on building conditions).Yu Home Co., Ltd.
However, conditions: Do not neglect the basic operations of curing, separation, dust management, and electrical shutoff. If this cannot be followedIncrease in disposal costsoraccidentSo it ended up being expensive.
Time-saving tips:
- Removed in the following order: Fixtures → Equipment → Board → Insulation → Remaining nails and screws.
- Industrial waste isPlaster, wood, metal, vinylThe more you separate it, the more efficient it is.
basis: Refer to multiple published pages that clearly indicate market price information (artificial unit price and unit price per tsubo). Labor unit prices for public works projects (Ministry of Land, Infrastructure, Transport and Tourism) can also be used as a reference for determining the weight of labor costs (design labor unit prices are reviewed every year, and the national weighted average remains at an all-time high).Land transportation

② Gypsum boarding/putty/painting

Why it's worth it: It is a "standardized process" that can easily produce quality if the correct steps are followed, and the materials are made available free of charge by public organizations.Bis pitch/seam treatment/base conditionsis clearly stated, so reproducibility is high.gypsumboard-a.or.jp
Board main points: Pitch of 150mm around the perimeter and 200mm in the middle, avoiding T-joints, opening corner assignments, etc. (For details, refer to the relevant chapter in the Gypsum Board Industry Association manual).gypsumboard-a.or.jp
Putty/Paint: Joint tape → Undercoat → Intermediate coat → Finishing, observe the drying time. Material costs are the main cost, and labor can be replaced with "self-time".
Pitfalls: Skimping on dust countermeasures will increase health and cleaning costs. Prepare a dust collection/dust mask (DS2).

③ Window insulation renovation (inner windows)

Why it's worth it: Windows are the biggest source of heat in and out of your home.do the windows firstPublic and industry materials have repeatedly shown that this is highly cost-effective. Many of the existing houses are made of the old “aluminum + single glass”, and the interior windows areEasily effective and easy to install even by DIY.Japan Sash Association
Basis of numerical values (example): The Ministry of Economy, Trade and Industry conference materials show the 2030 target U value and the 2020 results, and improving opening performance is an important policy theme.Ministry of Economy, Trade and Industry
Practical points: Measurements are taken at 3 points each on the top, bottom, left and right.Understand distortion in numbers. The effect will be stabilized if indoor dew condensation and joint air sealing are also reviewed at the same time.

2. 5 major areas where professionals are cheaper/faster

① Roof (reroofing/layer roofing)

reason: The biggest cause of fatal accidents in the construction industry is falls. Roofing work involves a combination of safety, setup, and skills, including ropes, full harnesses, temporary arrangements, storage of supplies, and rain protection, and has the highest learning cost and accident risk for amateurs. Construction by a professional team takes less time, and scaffolding costs are not delayed, which means it is cheaper overall.Ministry of Health, Labour and Welfare

② External wall layering (ventilation rim + siding), exterior painting on the second floor and above

reason: Rework is extremely high in multiple processes such as scaffolding, unloading, ventilation layers, accessories, and seals. Safety equipment is a prerequisite for high places, just like roofs. If the base is uneven or if you make a mistake in closing the rainwater opening, the repair costs will increase in the future. As a result, in most cases, professionals are faster and cheaper.

③ Electrical work (new installation/expansion/branching, conversion to 200V, change in distribution board capacity)

reason: Work area of legally qualified personnel. Activities that go beyond “equivalent replacement” of equipment are eligible. The risks of accidents, fires, and invalidation of insurance outweigh the price difference.OFFICE110

④ Relocation/expansion of water supply/hot water supply piping

reason: Many local governments have a “designated plumbing contractor” system. Illegal construction risks fines, water supply cutoff, etc. The damage caused by invisible water leaks is expensive. In the end, it's cheaper to leave it to a professional.plumber net

⑤ Demolition suspected of asbestos

reason: There are strict requirements such as compulsory preliminary investigation, reporting to the Labor Standards Office for operations over a certain scale, a work chief, isolation curing, and negative pressure dust collection. Please note that DIY is not allowed unless you are qualified.Ministry of Health, Labour and Welfare

3. Four representative fields of “gray zone (depending on conditions)”

① Drainage (indoor short route replacement)

Judgment axis: slope 1/50 to 1/100, minimum bending, joints chamfered, twisted, and fixed. The cost of redoing is high, so if you are unsure about slopes and leaks, go for a professional.
Why: Although the legal hurdles are lower than for water supply, the impact on livelihoods and damage is large.

② Replacement of kitchen/washroom equipment (do not change location)

Judgment axis: DIY is possible if you only need to replace the equipment without touching the piping. If position changes and circuit additions are involved, it's a pro.
why: When you start touching on water leakage and electricity risks, the risks suddenly become high.

③ Full flooring replacement

Judgment axis: If you have plenty of time and can strictly adjust the groundwork (unevenness and joist pitch), you can benefit from DIY. If shortening the construction period is important and the aesthetic appearance of the baseboards and fittings is important, hire a professional in a short period of time.
Why: Material costs are the same, the difference is in labor and consistency of finish.

④ “External” window construction (cover construction method)

Judgment criteria: Water stoppage, rain protection, and exterior tangles are involved, so if you can set up the exterior skin as a whole, you're a professional. By DIYing the inner windows and professionally covering the outer windows, it is easy to separate the windows in a cost-effective manner.
basis: The importance of windows (the main cause of heat loss) and the common view in policy and industry materials that the performance of existing windows in Japan is low.Japan Sash Association

4. “The reason why professionals are cheaper” is not just “labor costs”

Safety and process reduction

The initial cost of safety equipment is high for roofs and high places, and the proportion of falls is greatest. Professionals shorten the construction period with standardized procedures and team productivity, which reduces scaffolding costs and the risk of waiting for weather.Ministry of Health, Labour and Welfare

Areas where quality “rework” is high

When it comes to stopping water on the outside of windows, waterproofing bathrooms, and storing accessories on the outside walls, a single mistake can directly lead to damages of hundreds of thousands of yen. In the end, it's cheaper to be a professional who has a short battle and a clear scope of responsibility.

legal costs

Legal restrictions determine the cost difference for electricity, water supply, and asbestos. Illegal construction may result in penalties, suspension of lifelines, and non-compliance with insurance.OFFICE110

Actual level of personnel costs

The Ministry of Land, Infrastructure, Transport and Tourism's design labor unit price (estimate standard for public works) is reviewed every year. It has been on the rise in recent years, and while DIY is more attractive in areas where you can "replace labor costs with your own time," it is difficult to match the productivity of professionals in areas that require specialized skills and temporary construction.Ministry of Land, Infrastructure, Transport and Tourism

5. “Winning” allocation when budget is limited

Core that should be on the DIY side:Interior demolition/gypsum board/putty/painting/inner windows/fittings adjustment/baseboards
Leave it to the professionals and proceed with “zero accidents and a short period of time”:Roof/outer wall (scaffolding involved)/new/expanded electrical installation/remodeling of water supply piping/bathroom waterproofing/suspected asbestos area
Gray is selected based on “time vs. rework cost”:Full flooring/Short distance replacement of drainage/External window covering method

With this distribution, it is easy to achieve "overall optimization" where performance (windows) and cost (demolition/interior) can be achieved through DIY, while accidents, regulations, and expensive areas of rework can be dealt with professionally in the shortest possible time.

6. Immediate implementation checklist (1 sheet operation)

① Color-code and write out “DIY”, “Professional”, and “Gray” for the plane and elevation.
② In the gray area, estimate the “damage amount when redoing” and “temporary construction/safety costs”
③ Windows are a priority: Improving the experience on the inner windows first → turning the outer windows over to professionals (shared scaffolding) in the later process. Prioritizing openings is also appropriate in policy and industry materials.Japan Sash Association
④ Develop your planning skills by doing DIY for interior demolition (DIY is also possible for just separating industrial waste).Yu Home Co., Ltd.
⑤ Consult with a professional from the beginning regarding electricity, water supply, and asbestos (with legal basis).OFFICE110
⑥ The roof and exterior walls will be a short-term decisive battle combined with the scaffolding plan (fall prevention and standardization of safety procedures).Ministry of Health, Labour and Welfare

Reference (ground/source)

Ministry of Land, Infrastructure, Transport and Tourism's "Public Works Design Labor Unit Prices" related materials (for understanding the structure and level of labor costs).Ministry of Land, Infrastructure, Transport and Tourism
How to think about market prices and estimates for interior demolition (cross-check market prices on multiple sites).Yu Home Co., Ltd.
Gypsum Board Industry Association "Gypsum Board Construction Manual" (standards for bis pitch, etc.).gypsumboard-a.or.jp
Ministry of Economy, Trade and Industry/Ministry of the Environment/Ministry of Land, Infrastructure, Transport and Tourism collaboration document/industry document: Openings are the biggest source of heat loss in houses, and window performance in existing houses is an issue.itakyo.or.jp
Ministry of Economy, Trade and Industry Council Materials: Window U value performance and targets (policy positioning for improving opening performance).Ministry of Economy, Trade and Industry
Ministry of Health, Labor and Welfare (Guide to fall prevention and roof work in the construction industry) - A system of safety measures is essential at high places.Ministry of Health, Labour and Welfare
Qualification requirements for electrical work (the scope of what can be done with DIY is limited).OFFICE110
Water supply equipment construction (designated construction shop system/limits and risks of DIY).plumber net
Asbestos (requires preliminary investigation, notification, work chief, etc.—DIY not possible).Asbestos comprehensive information portal site

Discreet leads of tools and materials (places where it is easy to insert affiliates)

Demolition: Reciprocating saw blade, multi-tool blade, industrial waste flexible container, dust mask DS2
Gypsum board: screws (for plasterboard), fiber tape, putty, roller/brush
Inner window: measuring tape, laser distance meter, sealing material, airtight tape

Summary (today's decisions)

Benefit from DIY: Interior demolition, plasterboard, putty, painting, interior windows, interior fittings, baseboards
Pros are faster and cheaper after all.: Roofs/outer walls (scaffolding involved), new/expanded electrical installations, water supply piping modifications, bathroom waterproofing, areas suspected of asbestos
Depends on conditions: Short-distance drainage replacement, full floor, external window covering method