form screeds and granolithic finishes
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Transcript of form screeds and granolithic finishes
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form screeds and granolithic finishes
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• Learning outcomes
• The purpose of damp proof membranes
• The recommended area of separate construction flooring that can be laid without an expansion strip?
• The thickness of a Monolithic floor
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The materials used in granolithic work include granite chippings 6 mm to dust, and Ordinary Portland CementGranite chippings and cement are mixed by volume in the ratio5 parts to 2
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Question
The purpose of damp proof membranes is to:
Answer
prevent damp rising through the structure
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What is the recommended area of separate construction flooring that can be laid without an expansion strip?
Answer
14 square metres
Expansion strip
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form screeds and granolithic finishes
• Monolithic 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 within 3 hours of the base being laid
• Monolithic thickness is from 20mm
Monolithic
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• An unbonded floor is where no bond to the concrete base is possible owing to its condition. Minimum thickness is 75mm.
• 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.
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• Floating screed • • An Floating screed floor is
where no bond to the concrete base is possible owing to its condition. Minimum thickness is 65mm.
• • 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
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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
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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, which is know as laitance
Poor curing. Weakens surface.
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• Learning outcomes• The use of a storey rod • How to form Granolithic coves• Why riser boards are cut to a splay:
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Nosing line
Floor line
Spirit level
Storey Rod
Straight edge resting on nails
Nails
Tread Riser
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Fix riser into position
Fix bottom riser
Use a long straight edge to line in other boards
Total Going
Total rise
Treads and risers are in the ratio of 2:1
I.e. for every inch you rise you tread,2inch
Riser of 6” = tread of 12”
Total going equal the proposed length of travel
Total riser equals the distance travelled from the floor
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Stringer
Struts used to wedge stringer into position
Riser board
Fixing blocks
Fixing riser boards
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Laying a granolithic staircase
• Set out• Fix riser boards and
stringer• Working on alternative
steps• Fill in the treads with
granate and trowel to a smooth finish
• When material has dried remove riser boards and fill in the missing treads
• Face up the risers
Struts
Stringer
Struts
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• Coved cement skirting can be formed in cement/sand screeds and granolithic screeds. They are usually formed by running using skirting or coving trowels in conjunction with battens or screed grounds.