Building materials used in property renovation

Little do you know if before you start your project, but these are the things you will come to love - builders materials. Types and colours of sand and cement; when to use lime; how to use plaster are all covered.

Even if you don't want to do the renovation yourself, after the builders have left you will probably still find lots of small things that need doing or finishing off. You may also be tackling a room or two yourself, where the work involved is not too great. If only you knew the best approach to use, and the appropriate materials to use...

This section looks at the different types of sand, lime, cement and plaster and the usual ways in which they are employed. Most of these products are available in small quantities at your local bricolage store, so you can avoid the need to purchase a 35kg sack of plaster just to fill a small hole or two. 

General Advice when Using these Products

Even for small jobs you should follow the same basic rules:

1) Work in a clean dust free space if possible

2) Use clean tools

3) Use clean water

4) Use clean dry materials

5) Mix your products in a clean, usually rubber or plastic, tray or bucket

5) After using them, clean your tools and organise them somewhere they can be found again easily

6) Clean up after you! - it makes work much more efficient, and of a higher quality, if you always start with a clear clean work area around you, rather than stamping through piles of dust every time you move.

You will have spotted a theme in each of these rules - 'clean'. Completely obvious, and often ignored. I have twice uncovered dead rabbits who had attempted to burrow into a sand pile during our own works. But this is not recommended good practice, or funny.

Check out the individual postings for details about sand, cement, lime and plaster.

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Materials

There are a few possibilities available when you are buying tools and materials for your renovation project. Most French towns have some kind of builders merchant where you can buy all the materials that you need. This is a good place to start - local delivery charges will be less or not apply at all, and if you go in and introduce yourself before you start your project, and explain that you intend to spend lots of money, you will possibly be able to negotiate a discount.

The staff in the shop will get to know you, which will make it easier to get free advice. But I have found that prices are not always very clearly marked.

(See our DIY shops in France section for a brief introduction to the DIY shopping experience in France.)

Keep an eye on the free brochures and magazines that come tumbling through your door.Most of the larger stores eg E Leclerc, Auchan, Gamm Vert etc which have large 'building' sections have occasional promotions. These promotions can save you a large amount of money.

As an example, when I needed to buy 250 square metres of plasterboard for building ceilings and walls, a local ELeclerc was offering a promotion price that amounted to a reduction of about 2 euros per square metre. Even after paying the delivery charge (40 euros) I saved a great deal of money.

Similarly, other expensive items, such as insulation, are often available at a reduced price at certain times of the year. Even if you don't actually need them for a month or two, consider buying them in advance and storing them.

Remember that the different jobs require different materials - plasterboard for a bathroom is not the same as plasterboard for a lounge, for example. So don't get carried away with bulk buying, only to find you are left with large amounts of unnecessary materials. It is worth buying materials accredited as Normes Francaises (NF) whenever possible, since these are certified as being of a certain quality.

When comparing prices between different suppliers, be sure you are comparing like with like - you can pay 5 euros or 25 euros per square metre of silver foil roof insulation, but they are not the same thing!

Buying tools

Always buy the right tool for the job. It does make a difference to the quality of the final result.

If you are starting a large project, buy good quality tools and electrical equipment at the beginning. These will cost several times as much as the cheapest available, but will actually last for the duration of the job, and make the work much easier to do. If you read the specifications on the boxes in the shop, it is unclear why you are paying extra, when they have the same speed, same pressure, same power and so on. Get home and use them and you will change your mind.

You have to trust me on this one - I don't buy expensive things because I have got too much money, but because there is no alternative if you want to do a professional job.

Typical examples are drills, jigsaws, air compressors, angle grinders, pressure washers etc. All come in cheap versions and expensive versions and you will regret buying the cheaper.

Sand

Sand comes in a wide range of sizes, colours and qualities. It is important to recognise these different types and the different projects that they are used for:

Building Sand

'Normal' grey building sand comes in two main categories. Sand to be used for making concrete contains a lot of large, very rough particles - strictly, particles larger than 6.3mm diameter. Sand to be used for mortar, as used for brick-laying etc has less of the large grit in it. Both of these types of sand are usually bought by the cubic metre, and are best suited to large building projects.

For smaller jobs, the choice is usually between medium, fine and very fine. These will have been carefully washed, dried and graded. The fineness of the sand used determines how smooth the resultant mix is, since neither lime or cement add to the graininess of the mortar used.

Very fine sand

Very fine sand comes from a quarry. It is very pale, with grains 0.1 - 0.3 mm in diameter. This sand is used occassionally for very fine cement work, but is used also for polishing and cleaning. There are few jobs which require a large quantity of this sand.

Fine sand

Comes from either a quarry or a river. Usually very pale brown, with grains 0.2 - 0.6mm. This fine sand is used for sandblasting and hydro-sandblasting (sandblasting with a mixture of sand and water), on materials such as wood and metal.

Sand for sandblasting is usually silicon rich - often labelled 'sable naturel a quartz' or similar.

Medium sand

Also from either a river or a quarry. Light brown, with grains of diameter 0.4 - 1.6mm. This is usually used for sandbasting stonework and masonry, when the wall is sufficiently stable to support it.

Sand colour

The colour of your sand is important when the final product will be visible - for example if you are repointing a wall. The colour of the sand that should be used is very specific to your immediate region so you will need to take advice from a local builders merchant.

Plaster

Plaster is bought in sacks as a fine white powder. It has the main characteristic that after being mixed with water it dries completely hard and unworkable very quickly. This happens much faster than lime or cement and sometimes within a few minutes (it well tell you on the sack an estimated time of use). Synthetic plaster is also available, but there is little reason why you would ever choose not to use natural / real plaster.

Unlike cement, plaster is used alone, simply mixed with water (follow the instructions carefully) - no sand is used in the mixture.

A couple of unexpected uses of plaster

One occasion when plaster becomes indispensable is when you are trying to hold tubing (gaines) for electrical cables in place, before you do the pointing of a wall. A big dab of plaster every metre or so will hold the tubing solidly in place, and the rapid drying time of the plaster means that within a few minutes you can let go of the tube and it will be held in place. Another time it is useful is when installing a bath. A big blob of plaster around the base of each of the legs will help hold the bath in place much more solidly than the legs alone.

Mixing Plaster - a race against the clock

Measure the quantities carefully, according to the instructions on the bag. It is not possible to add more water later without weakening or spoiling the whole mixture. Make small quantities, because of the speed that it dries.

To make plaster, the plaster powder must be sprinkled onto the water, rather than adding water to the plaster. Otherwise dry lumps will be present in the final mix. A plastic or rubber tray or bucket is best for this.If a small amount of lime (CAEB - add 15g per litre of water) is added to the mix, the drying time will be slowed a little.

The plaster should then be left for a minute or two before being vigorously stirred. Usually a drill with a mixer attachment is the most efficient way to mix.After standing for a further 10 minutes the plaster should be a thick mix, ready to apply. And 30 minutes later it will probably be unusably hard!

Other

Plaster can be combined with colourants to create interesting effects. This does require some skill and experience, since the plaster dries so fast.

Plaster will stick to cement, but cement will not stick on to plaster - there is a chemical reaction produced which stops it sticking properly.

Because (French) plaster is difficult to work with, most amateurs use it only for small repairs, using plasterboard for large areas of wall. It is also possible to buy tubs of ready mixed products which dry much more slowly and can be used, for example, for filling the gaps between sheets of plasterboard, or blocking small holes.

Cement

Cement is available in grey and white. White cement is often used where the colour of the finished product is important  - for example as a strenthening product in wall pointing mortar.

The normal building cement is 'Artificial Portland cement' (CPJ CEM II 42.5).

Cement should never be mixed with too much water, because this will reduce its final strength. 4 kg of cement should be mixed with up to 1 kg of water maximum (i.e. one 35 kg sack of cement should be mixed with slightly less than one bucket of water.

You can see the 'walls' page for a list of the differences between cement and lime when used for pointing and stonework.

Specialist cements

Specialist cements are usually sold in smaller quantities, typically 5kg. These are a very fine powder, and they contract and crack less as they dry. This makes them suitable for very fine cement and masonry work.

Uses of specialist cements (supplied by SB Mercier in DIY stores)

1. These can be used pure (3 volumes cement : 1 volume water), for very small repairs, or sprinkled on a screed floor as it dries to increase the strength of the surface.

2. Mixed with a 'resine d'accrochage' or simply with water (2 volumes cement : 1 volume water), to smooth the surface of an old concrete floor (although specific products are sold for this 'ragréage' and may be more suitable)

3. Mixed with sand and used as mortar (3 volumes cement : 6-9 volumes of sand : 1 volume of water). Again, if very small quantities are required it may be preferable to buy a sack of ready-mixed product.

Rapid drying Cement (Ciment Prompt Vicat)

This can be used for small repair work, for work that is exposed to water, and for erecting fence posts, for example, and also other work where a quick drying time is important.

Ciment Fondu Lafarge

This is a specialist cement that initially dries quickly, but doesn't then complete its hardening any faster than normal cement. It is extremely hard when it has finished setting, so can be used, for example, for garage floors which will be subject to high wear and tear, and for wall-supporting lintels.

Lime

Lime comes in various categories and types. Not all are commonly used in the DIY environment.

The lime used by 'amateurs' is the lime called (in France) 'chaux aerienne eteinte pour le batiment' (CAEB). It is prepared from very pure limestone, and is an extremely fine powder. It is sometimes also known as 'fleur de chaux'.

'Chaux hydraulique naturelle' is also sometimes used, but is less pure and has a slight grey tint.

Stand well back after emptying lime into a cement mixer. It tends to come back out in a fine cloud, coating you head to foot 'Laurel and Hardy' style, and making you choke at the same time.

Uses

There are several differences between cement and lime when used for pointing and stonework. Suffice to say here, lime has numerous advantages during the renovation of an old building, and few disadvantages.

The only general disadvantage of lime is that its ultimate strength is less than that of cement, so would not usually be used for bricklaying, for example, and likewise would not be used in lintels or in other work with a 'structural' factor.

It can (and should) be used in place of cement for rendering walls and pointing walls, although a small amount of white cement can be added to give extra strength.

 
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