Upper Floors

Upper Floors

1. Overview

   • essential primary element of a building
   • must be able to minimise passage of sound from one floor to another

2. Durability Function

   • acts as a diaphragm or lateral restraint members
   • designed as compression ties due to effect of wind loading
   • introduced to reduce bulking between walls
   • Allows walls to maintain their dimensional stability

3. Functional efficiency

   • carry load imposed on them
   • minimise the passage of sound
   • stop or prevent the spread of fire
   • contribute to thermal performance

4. Types of Upper Floors

   • Timber (most common)
   • Concrete
     • Insitu
     • Pre-cast

5. Separating Floors

   • Common to two separate dwellings
   • Also called Party floors
   • Treated as isolating elements as by design, separate different occupancies
   • Isolating structural elements

6. Old Upper Floors

   • Timber built into the wall
     • mainly to improve load bearing
     • overtime bending movements between vertical and horizontal structural elemtns meant that any slight differential movment led to severe damage
     • mositure migrates throught he wall onto timbers - wet/dry rot
     • Structural damage will result in excessive failure in strength of timber floors and walls
     • Half brick joint will fail

7. Modern Timber Upper Floors

   • Construction
     • same way as timber floors at ground level
     • joists sizes are determined by uninterrupted floor span and anticipated use
     • End supports for hjoiusts and hangers spaced and positioned along the load bearing intermediatry walls to receive structural timber joists
     • When extra strength is required within the floor, joists should be doubled for added support
   • Timber Joists
     • Modern upper floor timber comprises of a series of 150mm x 45mm joists at 400mm centres
     • Planning joist spacing, a clearance of 25mm to 75mm between first joist and wall face should be allowed - help with fixings/ services
     • Not built into the wall
     • Ensure they are supported on steel joist hangers
     • 50mm gap should be left between the wall to allow for services runs and fixing of the decking
     • Noggins and blocking should be provided round the edge of the floor to support floor decking and ceiling boards
   • Support to timber floors
     • Strutting
       • helps distribute loads and limits movement
       • floor joists need strutting to minimise the buckling movement
       • helps entire floor attain rigidity
       • Types of Strutting
         • Herringbone
           • providing extra restraint to the floor joists
         • Horizontal
           • restrain a hjoist with a wider contact area
           • wider contact area for flooring
           • Not ideal for timber due to long term shrinkage
     • Restraints using sealed straps
       • 30 x 4mm Galvanised mild steel straps required to provide lateral restraing of floor relative to the run of external walls
       • Provided at 2m centres
       • Straps run perpendicular over 3 joists and bent over the internal leaf

8. Concrete Upper Floors

   • Concrete hollow planks -advantages
     • fast to erect
     • higher resistance to fire
     • cut down on labour costs
     • added long term durability
   • Pre-stressed plank floor
     • planks are capable of longer spans
     • planks are easy and quick to install
     • Must be well grpouted...
       • stiffen and prevent sound leakage
       • imrpoves fire protection
       • ready for variation of floor finsihes
   • Regulations
     • Any floor spearating one dwelling frpom another one or from another part of the same building, shall resist the transmission of air bourne sound
     • A floor above a dwelling separate from another shall resist the transmission of air bourne imapct
   • Advantages
     • lighter in construction
     • pre-fabricated off site
     • services canb be channeled through the voids
     • Provide good fire proof construction

9. Acoustic Issues

   • Timber Flooring
     • Timber bearers provide a highly effective method of reducing impact and air bourne transmission through concrete party floors as part of dry floating floor construction
     • Dry floating floors eliminated delays caused by drying of the screeds and can accomodate the services running under the floor
   • Concrete Flooring
     • uneven so a levelling screed is needed
     • flanking strip is used
     • screed isolated from hollow core planks
     • Insulation should be abutted against a 10mm perimeter edge isolator
     • Vapur check layer before concrete is poured
   • Factiors which create faiure
     • Inadequate mass
     • Plain edged boarding gaps
     • movement gaps create problems

10. Remedial of old upper floors

    • change to tounge and groove flooring
    • strip floor to bare minimum
    • use correct tools
    • use netting to avoid air gaps