Concrete is one of the most simple and best known building materials and probably the most vital for the strength of the constructions of your building, parking lot, patio, garden wall, paths etc. That is why it is important to know how to properly mix and pour concrete.

Concrete contains only the following ingredients: cement (Portland), gravel, sand and water. When cement is mixed with water a chemical reaction takes place. The cement does not simply “dry” it reacts with the water binding the materials in a concrete mix firmly together and harden into an incredibly strong rock like mass.

Gravel and sand are called also aggregate and all you need to know how to mix concrete properly is the correct aggregate to cement ratio. The more cement the stronger the concrete.

The strength of a concrete mix is measured in grades. There are different concrete grades for example C15, C20, C25. The grade of the concrete means the concrete compression resistance after 28 days. It is done in Newtons per square millimetre. A concrete of Grade C15 means that the concrete will have a compresion resistance (withstanding a compression) of 15 N/mm2 per square millimetre in 28 days.


Proportions for different grades:

1:2:5 for grade C15(general purpose concrete)
1:2:4 for grade C25(strong)
1:2:3 for grade C30(very strong)
Remember the proportion is done in terms of volume.


Volume measures for cement, gravel and sand:
Cement (Portland): 1506 kg per cubic metre (
Gravel (loose, dry): 1522 kg per cubic metre
Sand (dry): 1602 kg per cubic metre

Pressure calculators: 1 Newton (N)= 0.1019716 Kg force
1 Pascal = 0.1019716 Kg/m2= 1 N/m2
1 Megapascal = 101971.6 Kg/m2 = 0.1019716 kg/mm2 = 1 N/mm2
1 Megapascal = 145.0377 psi = 10.19716 kg/cm2

The usual required strenght of the concrete are:
For C30: 30 Megapascal(N/mm2)=4351 psi = 305 kg/m2;generally 4500 psi
For C25: 25 MP (N/mm2) = 3625 psi = 255 kg/m2; generally 4000 psi
For C20: 20 MP (N/mm2) = 2900 psi = 203 kg/m2; gen. 3000 psi
For C15: 15 MP (N/mm2) = 2175 psi = 152 kg/m2; gen. 2000 psi

Another factor which determines the strength and hardness of the finished concrete product is proper mixing of the ingredients. If the ingredients are not thoroughly mixed there will be differing degrees of hardness in various parts of the finished product. Needless to say this is something to avoid at all costs.

Cement can be mixed by hand by a reasonably fir person, by a cement mixer or it can be ordered to be delivered ready mixed.
Mixing concrete by hand is exhausting and can be done only for small quantities - max. 1 cu. metre. For larger projects it is better to be be delivered ready to your site.


While it is very easy to order concrete you have to know what to oder:
- how much concrete (how many cubic metres)
- what grade
- time of the delivery

Once you have the concrete is delivered you have to be prepared to handle it. You should also consider access for the lorry, and you should be aware that the driver won’t be willing to wait long. That is why you should be fully prepared for the concrete also considering that concrete is getting hard pretty fast and you will not have more than 1-2 hours to handle it

How to mix concrete by hand

1. Select mixture formula from the table above. A 1:2:3 (cement:sand:gravel) is also a bullet proof formula.
2. Use a shovel to mix to ingredients in a wheelbarrow or on a large plate of sheet iron on the ground.
3. Add some water and continue mixing by hand. Use minimum volume of water possible. The less water the stronger the concrete.
4. While keeping water minimal be sure that there are no dry areas in the mix
5. Work fast as concrete dries out fast.

Tip

• You can also buy pre-mixed bags of ready-to-mix concrete at DIY supermarkets and lumber yards. These require water and mixing; the measuring is already done for you.
• If you have doubts about your ability to “work” and “finish” concrete, hire professionals. Any job over a few square feet in size may be more than the average homeowner wants to tackle.

Concrete Thickness

Recommended minimum thickness of the concrete for the following projects are:

• Footpaths - 75mm (3 inches)
• Patio - 100mm (4 inches)
• Driveways and Parking areas - 125mm (5 inches)
• Base of light structures - 75mm (3 inches)

Slope of the concrete

Water will gap in depressions without a slab and if there is no natural slab of the land it should be calculated.
Any concrete against a building or a garden wall must slope away from it. Here the reccomended slopes:

• Footpaths - minimal, just to avoid areas where rain water will collect
• Patio - 1:60 (16mm in 1 metre, 5/8in in 3 ft)
• Driveways and Parking areas - 1:40 to 1:60 (25mm to 16mm in 1 metre, 1in to 3/8in in 3ft)
• Base of light structures - 1:80 (12.5mm in 1 metre, ½in in 3 ft)

See full Metric system conversion tables (opens new window)

For further reading:
- Concrete mixing on DIYdata.com
- Mixing concrete on DIYdoctor.org.uk

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Many property buyers in Bulgaria look to renovate an old property in Bulgaria to make it a home to live in or to resell it. In our previous post we hafe informed you about the Potential of Renovation and Renovating in Bulgaria. In this post we will try to look at the best way to approach buying a run down old Bulgarian property with the intention to resale. Many of the points would be valid too if you are buying such a property for you and your family. Even if finance is no problem you should always keep an eye on the budget in case you have to sell the property later in the future.
Old buildings in need of renovation are to be find in the Bulgarian countryside in the smaller villages. Just a few kilometers from the sea you will find beautiful villages with lots of old houses. you’ll The British have long been advocates of renovation and usually do a great job in bringing back these buildings to their former glory in a sympathetic manner.

Can you handle it?

Improvements are certainly adding value to the property; the key is not to take on more than you can handle. A large renovating project in Bulgaria will cost you time and personal engagement. Unless you can do the design (select, source and transport materials) and manage a team of different builders it is advisable to hire a tradesman (small building company) to do most of the jobs for you. If the builder is professional he will take care for things to go smoothly and your job will be to observe the process. If you have no experience in renovations in Bulgaria this will save you time and money for sure.

Can you make a profit?

As in any other business you can make more profit the more you plan and organize your business. Property price is a function of location and type of property. Make sure you buy in the right location and you buy the right type of property. When buying an old property the price strongly depend on the expenses made to renovate the building. But nevertheless what you need is a property with charm that will suit your potential buyers. During the work you should always keep in mind who will be using the home and design it correspondingly.

Where to start from?

Select and research an area that you think has a potential. Research for old properties and get an idea about the asking prices. Prices of old properties in need of renovation vary in a wide spread but what you mainly should be interested in is how much would be total to buy the property and to renovate it. You should also do a research about the prices of similar properties on the market – new built or renovated. This will help you to determine a budget for the project. You are better off buying a smaller property in a good location than a larger property in a poor location.

Additional cost

There will be some extra costs to consider when working out your budget. There will be property purchase fees (about 4 %), solicitor cost, company formation & annual bookkeeping, property insurance, maintenance if you are not onsite and cannot sell immediately, transport cost (flights, car, gasoline). Also do not forget the real estate agent commission when selling the property plus any taxes on the capital gain.

There are many hidden things in one house that might need repair but are not obvious because there is no access to them. A roof is a good example – it might look OK or “not that bad” but you will be able to check its condition only when you “open it” and see inside.

The golden rule is, whatever you do, don’t be rushed into buying the property. Take your time and visit as frequently as you need. Take a builder to look at the property and give you a quotation, then make the math and take a decision. If the property is sold in the meantime do not worry – the next property will come. We have a saying in Bulgaria: “You never know what you win when you lose”

Hiring a Builder

If you are going to employ builders or a project manager, do check out the quality of their work and get in touch with past clients if you can. Check our guide: "How to find a good Builder in Bulgaria". Get all quotes in writing, together with a timeframe of the work to be undertaken and a payment plan. There should be penalties for late completion - but on the other hand, you could add in a clause for a bonus if they finish early?

Decorating and Furnishing

With a renovation project it is all too easy to see the money slipping away. It is really tempting to splurge on extras, particularly fixtures and fittings. Think carefully about where you allocate your money for maximum effect. When considering decoration, neutral is best - it is usually brighter and most buyers won’t object as they can then make up their own mind about colour.

Tip - if you can affford to furnish the house, do so as it is much easier to sell a furnished property than one with empty rooms.
We are wishing you luck with your renovation project in Bulgaria and would be happy to help you.

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