Background for Floor Tiles

8/2/2019 Background for Floor Tiles

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Background for Floor TilesBackground for Floor Tiles


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Background for Floor Tiles

The previous notes covered the backgrounds to which wall tiles have to be fixed, concrete is the usual

background for floor tiles but we do get some variations in their construction.

Concrete FloorsConcrete is widely used in floor construction today, being extensively adopted in factories, offices, multi-storey

structures such as blocks of flats and in two-storey buildings.

In multi-storey buildings some concrete floors are cast in-situ others are precast, most are in the form of slab,

or beam and slab construction; the beams being provided where extra strength is needed. Another form

includes hollow clay blocks, with reinforcing rods between, concrete being poured over and around these

blocks.

The most important factor which the tile fixer has to consider is the extent to which the floor has undergone

shrinkage before the tiles are to be applied, therefore the laying of tiles and mosaics direct to concrete

base should be delayed as long as possible to minimize the disruptive effect of concrete,shrinkage on the

bond between tiles and bedding.

Timber Floors

On occasions the tiler has to lay tiles to timber floors; there are several factors to take into consideration here.1. Will the floor be able to carry the extra weight.

2. Is the floor well ventilated underneath, otherwise Dry rot may set in at a later date.

3. The timber may swell from the moisture from the tile laying. Therefore consider these points before laying

tiles to timber floors.


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Other types of base

On occasion: tiles are laid on asphalt. Examples include, its use for exterior verandahs, and asphalt employed

as 'tanking' in basements. Factors to consider; it may retard the drying out of bedding laid on top; variations in

the surface level, and tendency for plastic flow to occur in warm conditions.

Other surfaces on which a tile fixer may be asked to lay tiles include existing tiled floors, terrazzo, granolithic

and natural stone, and metal surfaces; these types of bases are only infrequently encountered, but the

procedure to be adopted is the same as described for wall tiles.


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12 25 mm

Fig 1

Monolithic Construction

Screed placed within 3

hours of base.

Not to scale

2. Separate construction

In this case the screed is laid after the base has set and hardened.

A minimum thickness of 40 mm is considered sufficient provided

the base has been adequately prepared to receive the screed.

1. Monolithic construction

This is a case where a screed is laid in-situ on a concrete base

before it has set (within 3 hours of placing) thus obtaining a

complete bond. A screed thickness of 12 mm is considered

adequate and layers thicker than 25 mm should be avoided.

40 mm

Fig 2

Separate Construction

Screed placed more than

3 hours after base.

Floor ScreedsThere are four types of screed for dense concrete.


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60 mm min.

Fig 4

Floating Screed

On Compressible material.

3. Unbounded construction

Where a damp-proof membrane is used or the concrete is

contaminated with oil or grease, or if it is weak concrete; the

minimum thickness for the screed should be 50 mm or if the

floor contains heating cables at least 65 mm.

4. Floating Screed

A screed laid on a compressible layer of thermal or sound-

insulating material should be at least 65 mm thick. The floating

screed is usually on 20-50 mm mesh wire netting resting on

polythene sheeting over the layer of insulating material.

If the screed is to contain heating cables then it should be at

least 75 mm thick.Mix proportion for screeding up to 40 mm thick should be 1;3/4

cement and sand. For thicker screeding fine concrete should be

used 1;1;3 (cement; fine aggregate : course aggregate). If

there is difficulty in finishing the concrete it can be topped up with

a layer of cement and sand about 5-10 mm thick placed before

the concrete has set.

Fig 3

Unbonded Construction

without Leading cables.

50 mm min.

Other Materials used for screeds

These include synthetic anhydrite, lightweight aggregate

concrete, and screeds, modified by the inclusion of polyacetate,

synthetic rubber, etc. Where tiles are to be laid on such screeds

then the suppliers of the screed material should be consulted, and

it should be established whether or not there is likely to be any

incompatibility with the proposed method of laying.


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Preparing and Laying Floor Screeds

Inspect and Prepare Sub-Floor for Screeding

1. Use lath axe.

2. Remove any cement or plaster droppings.

3. Brush off the area thoroughly with a stiff broom.

4. Wash off area with clean water.


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Mark Off Datum Line Using Straight Edge Rule

1. Check spirit level for truth by placing it on a level surface.

2. Mark off the position of the level and note the position of the bubble.

3. Reverse level end for end and note the position of the bubble. (If the level is correct the bubble

should be in the same position as before).4. Adjust level if required.

5. Mark off the position of the datum and with assistance hold straight edge to mark.

6. Place level on rule and adjust until bubble is in the centre of the level.

7. For long walls - reverse the rule end for end when taking the next reading.

8. Use this method to form the level marks on the remaining walls.

9. Take the chalk line and with assistance chalk the line.1. Line taut and in correct position, snap line. Repeat on walls if required.

The sketch below shows the method of using the rule and level.

Remember: the rule is reversed end for end for corner mark.


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1. Check water level is working correctly.

2. Note that the level of water in both tubes should be the same.

3. If not correct, there is an air-lock in the tubes.

4. Hold end of tube under the water tap and force water through the tube to remove the air-lock.

5. Mark off position of the datum.

6. With assistance, use the water level with the stoppers in.7. Hold one end of tube to the mark whilst assistant holds the other end in the approximate position where

level mark is required.

8. Remove stoppers and assistant adjusts the height of his tube until the height of water is level with the

datum mark

9. Assistant marks the level of the water in his tube.

10. Repeat process to all corners of the room.11. Snap lines to these marks by using the chalk line.

Mark Off Datum Line Using Water Level


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Use of Datum Line

1. Set out the datum line using a water level and chalk line.

2. Place a mark on a large square corresponding to the height of the datum line,

above the bottom of the lining.

3. Bed down dot laths and level both ways.


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1. Wood battens 20 mm x 50 mm to thickness of the screeding and cut to fit the length of the room.

2. Form bays about 1200 mm wide.

3. Ascertain the height of the floor screed from the bottom of the door lining, allowing for the thickness of a

tile and bed if tiles are to be laid later.

4. Make a pinch or gauge rod from say, a piece of batten 20 mm 50 mm, and mark on it the height of thefloor level to the datum line. (see illustration over page).

5. Brush cement slurry over the sub-floor where the rules are to be laid.

6. Place cement and sand in a layer 75 mm wide next to side of rules.

7. Rules are now placed on the top of the compo and bedded down into the material.

8. The pinch rod is now used to gauge the height of the top of the rule from the level datum line.

9. Use straight edged rule and level to level and straighten pinch rod in from this point.

10. Adjust the rules and consolidate the material at the sides of the rule by using he gauging trowel.

Lay Wood Screeds Beded in Cement and Sand

Levelled in from Datum


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Lay Wood Screed Rules

1. Height: finished level of screed

(a) Dot at door lining plus piece of

tile = floor level.

(b) Further dots - level in from datum dot using

spirit level and straight edges.

2. Screed rules

These can now be put in place, see slide 8 and bedded in as previously

described.

Use gauging trowel to consolidate material at sides of rules.

See illustration

below


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Make a Pinch or Gauge Rod

1. Take wood batten supplied end place on floor or bench.

2. Place one tile on batten flush with one end.

3. Mark off length of tile with pencil.

4. Place second tile on batten next to the first and mark off length of that one.

5. Hold second tile in position, lift the first tile and place next to second and mark that.Continue in this way until end of batten is reached. Square off the lines and make saw cuts to these marks.

6. Cut off any extra length of batten.

NOTE: Another method is to butt the tiles up to the rod as shown and mark the joints from there.

For floor tiles the joints must be 3 mm wide.


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Complete the laying of Floor Screeds

Screed Mix

1. 3 to1 or 4 to 1 - cement and sand - semi-dry mix.

2. Consistency: to hold together when hand squeezed.

Method

1. Screeding rules already in position.

2. Dump 3 or 4 bucketsful of screed as far from the door as possible.

3. Spread with trowel.4. Consolidate by heavy trowel just above rules levels.

5. Level off using straight edge rule - SAWING ACTION.

6. Finally, fill holes and marks and finish off with float.

7. Complete floor area by same method.

Note: Fix screed rules across doorways and leave in place to assist when screeding up outside rooms.Stop entry into room whilst screeds set.

Saturate screed next day to harden it off.


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Slurry Sub-floor and Use Thickness Rules for Screeds

Slurry Sub - Floor

1. Preparation

- clean and wash concrete sub-floor.

2. Key

- slurry over with sand and cement.

3. Method and mix

- 2 sand: 1 cement, mixed to thick creamy consistency;

- pour on to concrete and sweep with a stiff broom to a thickness of 2 mm.

Thickness Gauge Rules to Floor for Screeding

1. Level concrete floor

- screed direct using thickness rules instead of bedding in rules;

- rule to the thickness of desired screeding and not bedded in.

Lay direct to base and secure;

- length of rule approximately 2 m long;- fill in space formed after rules are moved.

Note: This method can only by used when the sub-floor base is level, or if the finished

floor is to be laid to falls, when the sub-floor is also evenly laid to falls.

Setting Out for Floor Tiling


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Setting Out for Floor TilingCheck Levels Prior to Starting Work

Datum Line Method

1. Check datum line is continuous at the angles; not one above the other.

2. Check lines are straight.3. Take timber gauge rod, place upright against one wall and mark one rod height of datum

line from floor.

4. Using rod in a like manner, check level of sub-floor and mark off high or low points.

Level and Straight Edge

1. Check level of floor from the door opening using a long straight edge rule,

3 m to 4 m long and spirit level. (see diagram) Mark off high or low points.


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Setting Out Using the Centering Method

1. Check walls for square.

2. Measure the centre of the back wall and the two side walls.

3. Snap lines on floor to these marks.

4. Use pinch rod and check how tiles will work out from the centre; first with the jointon the line and

then with a tile placed equally on the centre line.


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Setting Out Using the Working Out Method

1. Use the pinch rod made in last objective to see how the tiles will work out.

2. Start with a full tile, leaving a cut tile in the corner.

3. Check from adjacent wall to see if it works out better from that side, trying to avoid

narrow and unsightly cuts.


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Setting Out for Panelled Work

1. Check walls are square.

2. Check size of walls and tiles with the drawing supplied.

3. Mark off centre of walls.

4. Snap centre lines to these marks.

5. Mark off size of panel from the centre lines.

6. Use pinch rod to check setting out is correct.

7. If a diamond pattern is being set out, check that the diagonal of the small tile is

the same as the width of the large tile.

Setting Out Panelled Work Diamond Pattern


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Setting for Expansion Joints

1. Mark off the position of the expansion joint on the walls and draw vertical lines to these.

2. Snap lines to these marks on the floor.

3. Use the pinch rod and check the setting out of the tiles so that the joint coincides with theexpansion joint. Allow for the extra width in the joint.

Background for Floor Tiles

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