Floor Screeding Lesson no 1

Learning outcomes by the end of this lesson you should be able to Identify the bonded floor screed Describe the monolithic floor screed Recognise a Floating screed

Types of floor screed systems Bonded. (Monolithic.) Un Bonded Floating screed

Bonded ( monolithic) floor screed Bonded systems tend to be the most common methods it fits better with the nature of construction and the set and leave approach of concrete. In this method a screed is applied to a previously laid concrete base Bonded thickness is from 25mm to 40mm

Bonded floor screed

Un Bonded floor screed An unbonded floor is where no bond to the concrete base is possible owing to its condition. Minimum thickness is 50mm. A number of different forms of floor construction are included in this type, and are often grouped on their own, e.g. laying a screed on a damp-proof sheet membrane.

Un Bonded floor screed

Floating floor screed Floating screed • An Floating screed floor is where no bond to the concrete base is possible owing to its condition. Minimum thickness is 50mm. • A number of different forms of floor construction are included in this type, and are often grouped on their own, e.g. laying a creed on a damp-proof sheet membrane, and laying a floor on a layer of insulation

Floating floor screed

Task 1. How much mixed material is needed to complete a floor screed 5.000 m long by 4.000 m wide and 0.050 m thick? Answer 1 m3

Task Tools and equipment for floor screeding will generally include: sweeping brush, trowel, float, mixer, shovel splash brush, small tool, gauger, trowel, float spirit level, trowel, buckets, mixer, float levelling equipment, trowel, float, shovel buckets, mixer Answer 4

Answer

Types of materials used Mixing is one of the most important jobs of the whole operation The quality of the sand is important and must be sharp,gritty and clean The mix ratio is 3 parts sand and 1 part cement

Types of materials used Some floors are laid using granite chipping On large work , a pump mixer can be used.this will increase productivity and ensure an even mix

Preparation of floors Remove all loose particles and high points on the floor Brush all the area to remove dust For certain floor surfaces , a mix of cement slurry and P.V.A can be brushed into the surface Smooth surface should be scrabbled to form a key

Question Plastic sheeting below the structural floor is the: damp proof membrane vapour barrier moisture trap aid to curing the floor Answer

Question The type of cement used in floor screeds is: Masonry Portland Extra Portland Rapid Portland Ordinary Portland Answer

Finishes • Floors are generally finished with either a floated or trowelled surface. • A wood fl oat produces a sand-faced texture. • Trowelling gives a smooth finish which closes in the surface of a wood fl oat finish. • Power floats, tampers and rollers can be used to assist the floor layer.

Finishes Float finish These are laid mainly to receive mastic asphalt, asphalt tiles, bitumen, concrete tiles and other heavy finishes. Trowel finish These are laid mainly to receive carpet, hardboard, vinyl and cork tiles.

Task make a copy of this chart CAUSE EFFECT Poor preparation of sub-base. Cracking and lack of bond. Mix too dry. Hard to lay; gives weak finish. Too much cement. Shrinkage cracks. Too little cement. Will break down when load applied. Too much water. Hard to form flat surface; may shrink and be weak. Poor material mix. Could leave pockets of sand with no cement, or vice versa. Over-trowelling/trowelling too soon. Brings water to the surface with cement. Poor curing. Weakens surface.

Questions What is one of the most important jobs in the whole operation Answer Mixing is one of the most important jobs of the whole operation What is the mix ratio of a floor screed The mix ratio is 3 parts sand and 1 part cement

Curing It is essential that sufficient moisture is available for the continued hydration, or setting action, between the Portland cement and water for up to seven days after laying. This is achieved by restricting the moisture loss of evaporation from the mix by covering the finished topping with: Building paper. Polythene sheets. Damp hessian sacks.

A floor scrabbling machine How do we key a smooth floor to receive a screed Answer With a scrabbling machine Basic floor Scrabbled floor Scrabbling machine

Grinding High Spots The screed is ground using a power operated grinding machine. Throughout the process the surface is kept wet. Any ground material is removed using squeegees or some modern grinders collect the material as they operate

Question How should we prepare the floor to receive a screed Answer Remove all loose particles and high points on the floor Brush all the area to remove dust

Floor screeding Floor area is calculated by volume i.e length x width x depth. Length = 29m, x width = 30m, x depth = 0.035mm, = 30.45 m3

Question How do we key a smooth floor to receive a screed Answer With a scrabbling machine

Monolithic floor screed Monolithic in construction terminology means 'one body' or 'laid as one'. That is to say when materials such as a concrete base and its screed are laid within three hours, they are deemed to be laid as one Monolithic thickness is from 10mm to 15mm

Question Name the three types of floor screed Answer Bonded (Monolithic) Un-bonded Floating screed

Floor screeding Monolithic thickness is from 10mm to 15mm Un-bonded thickness is 50mm Bonded thickness is from 25mm to 40mm Separate Minimum thickness is 40mm..

Task Now work in groups to answer questions 14-22 on pages 324 –326 of your work book

Floor Screed Lesson no 2

Floor screeding by the end of this lesson you should be able to Recall why we use a datum line, and how to set out levels Understand the term Curing Be aware of common faults that might occur when floor screeding

Recap on lesson no 1 Name four types of floor screed Answer Monolithic Bonded Un-bonded Floating screed How do we key a smooth floor to receive a screed Answer With a scrabbling machine

Recap on lesson no 1 How should we prepare the floor to receive a screed Answer Remove all loose particles and high points on the floor Brush all the area to remove dust

Datum line A datum line is a level line around the room This can be drawn by using a sprit level , or a laser level, or a water level. The height of the screed can be set from the datum line by using a builders square

Water level The green pipe is filled with water . Then with two operatives each take an end of the water level, By raising the end of the water level up or down they will both reach a point where both reading are the same At this point a mark will be made on the wall, this is a datum point,from which datum lines can then be drawn

Water level Setting datum level to wall areas Set the liquid container at a suitable height for working Set adjustable gauge to zero at the level of liquid in container

Water level Move instrument rod 3 from station point 1 to point 2,3,4 in sequence. Raise or lower the rod until liquid is at zero on gauge and then mark this datum point on the wall at each of the points 1 – 2 Join up station points to obtain level datum line

Water level

Water level

Laser level The laser level will project a level line around the room it is located in

Laser level

Laser level

Battens levelled in. Bays filled in working in chequer board batten. An initial trowel as work proceeds and turn back when floor has ‘picked-up’ and give final Trowelling up.

Dots levelled in. Screeds ruled off dots in order indicated. Bay filled in ruling off screeds. Rubbing up and consolidating with a wood fl oat giving sand faced texture or when trowel finish is required lightly Trowelling up fl oat finish.

Task 1 In your own word describe how to seta datum level for setting up a level floor Make a sketch of a water level

Tools required for the task You will need the following tools to carry out the floor screed: • Flooring trowel. • Large fl oat. • Spirit level. • Gauger. • Large and small straight edges. • Shovel. • Timber for dots. • Builders square. • Water or laser level.

Question What is a datum line Answer A datum line is a level line around the room

Curing It is essential that sufficient moisture is available for the continued hydration ,or setting action This is achieved by restricting the moisture loss of evaporation from the mix by covering the finish topping with Building paper Polythene sheets Damp hessian sacks

Task 2 Describe how to set up a floor with a fall

Common faults Dusty Floors This is a common problem. The surface of a floor begins to loose adhesion and does not resist abrasion well, the top layer of laitance (cement paste) turns to dust. This can be caused by :- a) Insufficient curing of dryer mixes b) Too much water in the concrete or screed mix c) Lack of cement in the mix d) Too much fine aggregate in the mix e) Weak aggregates in the mix

Question How do we let a floor cure Answer This is achieved by restricting the moisture loss of evaporation from the mix by covering the finish topping with Building paper Polythene sheets Damp hessian sacks

Question Give me two reasons why a floor screed may become dusty Answer Insufficient curing of dryer mixes b) Too much water in the concrete or screed mix c) Lack of cement in the mix d) Too much fine aggregate in the mix e) Weak aggregates in the mix

Task Now work in groups to answer questions1 –19 , pages 327 –335 of your work book Then complete the word search

Floor with a fall Fall are put in floor screeds to drain away water, i. e a shower room Achieving a fall on a floor screed is not as daunting as it may first seem. The secret is in the preparation of the dots used to control the levels and thus the falls for the screeded area.

Achieving a fall Achieving a fall on a roof screed is not as daunting as it may first seem. The secret is in the preparation of the dots used to control the levels and thus the falls for the screeded area.

Achieving a fall On roofs, dots are started from the lowest outlet position and worked back and lined in to an agreed fall. The best way of achieving this is by the use of a fixed length rule or straightedge of known length.

Achieving a fall For example, if a fall of 1:100 is required this is the same as 10mm in every metre. If you have a 3m straightedge, then place a packing piece 30mm thick (10mm x 3m length) below one end. You will find when you level the straightedge using a spirit level, this will mean that from one dot to another will rise by 30mm - simple ! This technique can be used for whatever fall you need, just calculate the packing thickness.