Supporting Information for Dormer Extension of 11 Copster Drive, Longridge PR33SH Author: Jack Sharples Date: 01/01/18 Document Ref No.: PR33SH11-003
PR33SH11-003
01/01/18
Contents Overview.........................................................................................................................2 Construction Overview.....................................................................................................3 Floor Construction............................................................................................................6 Wall Construction.............................................................................................................7 Roof Construction............................................................................................................8 Appearance...................................................................................................................10 Similar Properties...................................................................................................................10
References....................................................................................................................14
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Overview The intention of the supporting document is to summarise the intended construction methods and standards used for the construction of the front and rear dormer extension of 11 Copster Drive. This will be broken down into the main construction elements and will describe all necessary details required to adhere to all required standards. With references to standards and prescribed requirements where available. This should be used as a quick reference and should any further details be required contact the appropriate persons as detailed in the submission which this document accompanies.
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Construction Overview The intended construction of the extension is a flat roofed, full width dormer consisting of the following main elements: –
Floor
–
Walls (both internal load bearing and external load bearing)
–
Roof
The rear dormer and front half dormer will increase the roof space by an estimated 30.7 cubic metres which is lower than that prescribed maximum allowable of 50 cubic metres in the Department for Communities and Local Government; Permitted Development Rights (PDR) for householders technical guidance document (issued April 2017). Although this extension will not be carried out under the PDR this document is worth noting for its reference to changes to roof space volumes. The dormer will extend from the gable end to the party wall across the rear of property, leaving a minimum of 200mm (0.2m) of roof tiles from the innermost eaves at the back of the house and the gable end. To the front of the property the dormer will cover the inner half of the building running from the party wall out the the internal supporting wall and from the ridge to a purlin at roughly 3.2m forward of the ridge, which is roughly 1.5m from the the front innermost eaves.
Extract from Drawing PR33SH-002.pdf – Proposed Dormer
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Rear Dormer and Front Half Dormer The following calculations are an estimate of the volume increase as a result of the dormer extension, as previously described.
Extract from Drawing PR33SH-002.pdf – Upper Floor Plan
Increase in Roof Space
= New Roof Space - Existing Roof Space = 103.6m3 – 72.91m3 = 30.69m3
Existing Roof Space
= (He x Wge x Lge / 2) + (He x Wpe x Lpe / 2) = (2.25m x 3.16m x 11.55m / 2) + (2.25m x 3.16m x 8.96m / 2) = (82.12m3 / 2) + (63.70m3 / 2) = 41.06m3 + 31.85m3 = 72.91m3
New Roof Space
= Front Slope Roof + Rear Dormer Roof + Front Dormer Roof = 18.23m3 + 62.19m3 + 23.18m3 = 103.6m3
Front Slope Roof Space
= Existing Roof / 4 = 72.91m3 / 4 = 18.23m3
Rear Dormer Roof Space = HDR x WDR x LDR = 2.25m x (3.16m+3.05m+0.1m) x 4.38m = = 62.19m3 Front Dormer Roof Space = HDF x WDF x LDF = 2.25m x 3.16m x 3.19m = 23.18m3 See next page for abbreviations.
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Calculation abbreviations for roof space:
He = Existing Height of roof space, Wge = Existing Width of outer half of roof space (gable end half), Lge = Existing Length of outer half of roof space (gable end half) Wpe = Existing Width of inner half of roof space (party wall half) Lpe = Existing Length of inner half of roof space (party wall half) HDR = Rear Dormer Height WDR = Rear Dormer Width (incl. Wall thk) LDR = Rear Dormer Length HDF = Front Dormer Height WDF = Front Dormer Width LDF = Front Dormer Length
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Floor Construction The floor will consist of the following elements; –
Joists
–
Hangers
–
Floorboards
–
Plasterboard
Joists The joists will be constructed from 175mm x 75mm C16 grade timber or 175mm x 50mm C24 grade timber; whichever is regarded most cost effective at the time of construction. This depth of joist has been chosen to maximise the head room in the upper floor. The joist span tables in reference item 1.1 show that the chosen joists will suffice. Joists will be pitched at 400mm centres perpendicular to the party and gable end walls, resting on both and a central brick wall across a maximum span of 3.16m. The maximum deflection for the chosen beam and grade is 3.5mm (C16) and 4.3mm (C24) under live loads. Given that a maximum permissible deflection under imposed loading is given as 0.25% of the length “L x 0.0025” with a maximum imposed load of 1.5kN/m2, equating to 7.9mm over a span of 3.16m, the deflection calculated is within tolerance. Note: - A personal preference to use a deflection limit of 0.25% of the Length (L x 0.0025) is quoted, despite the standard engineering value normally used which is 0.3% of the Length (L x 0.003) or 12mm whichever is smaller. See table in reference item 1.2 for more information.
Hangers The joists will be hung from steel hangers attached to a joist which will be resin bolted to the walls at the the party wall and the gable end wall. In the rear of the building the beams will be trimmed into steel beams either by tailoring the beams or by hangers on an inserted backer plate.
Floorboards Floorboards will be 22mm thick chipboard and will be laid perpendicular to the joists and glued and sealed with appropriate glue as recommended by manufacturer.
Plasterboard Plasterboard will be standard 9.5mm thick plasterboard installed using plasterboard screws to secure to underside of the joists.
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Wall Construction The internal central wall will be extended up from the existing wall using AAC (Aerated Concrete) blocks, which will support the remaining existing roof structure and the new Dormer roof structure. The proposed dining room and kitchen area will have a new wide archway (1.9m wide) the structural wall above this will be supported by a steel beam. A standard uniform beam of dimensions 178mm x 102mm x 19kg/m (Height x Width x Weight) will be used. The calculations in reference item 2.1 and structural simulation in reference item 2.2 show that the maximum deflection likely to be seen under live load will not exceed 0.25% of the length (L x 0.0025). The deflection calculated is 0.453mm (maximum allowable: 4.75mm). The specified limit of 0.25% is below the 0.28% (L/360) specified by Eurocode 3 National Annex NA2.23 (BS EN 1993-1-1:2005, 7.2.1(1)B). Given the industry preferred method of calculating the deflection and stress is to use the mathematically calculated deflection and the fact that the mathematical deflection is greater; the simulated deflection shall be considered as a reference only in support of the calculated values.
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Roof Construction The floor will consist of the following elements; –
Joists
–
Outer Skin
–
Insulation
–
Plasterboard
Joists The joists will be constructed from 150mm x 75mm C24 grade timber. The reason for the narrower depth is to maximise the head room in the upper floor. The joist span tables in reference item 1.3 show that the chosen joists will suffice. Joists will be pitched at 400mm centres perpendicular to the party and gable end walls, resting on both and a central brick wall across a maximum span of 3.16m. The maximum deflection for the chosen beam and grade is 2.5mm under live loads in the preferred orientation. Given that a maximum permissible deflection under imposed loading is given as “L x 0.0025” with a maximum imposed load of 0.75kN/m2, equating to 7.9mm over a span of 3.16m, the deflection calculated is within tolerance. 150mm x 50mm C24 will also be within tolerance in the preferred orientation with a max deflection of 3.8mm. In the alternative orientation (running from ridge beam to outer wall) the same grade and size of beam deflects 9.9mm which is also within the permissible deflection tolerance defined above (11.2mm over a span of 3.16m). Note: - A personal preference to use a deflection limit of 0.25% of the Length (L x 0.0025) is quoted, despite the standard engineering value normally used which is 0.3% of the Length (L x 0.003) or 12mm whichever is smaller. See table in reference item 1.4 for more information.
Outer skin The roof boards will be 18mm thick plywood board (preferably marine ply) below a GRP constructed outer layer.
Insulation In order to achieve the required insulation levels a foiled rigid phenolic insulation board will be used. There will be a 100mm thick section between each of the roof joists positioned flush with the lower edge, with a further 25mm thick section below the joists perpendicular to the joists. This will provide the 125mm thickness required with a 50mm ventilation clearance above.
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Plasterboard Plasterboard will be standard 9.5mm thick plasterboard installed using plasterboard nails to secure to underside on joists through the lower section of the insulation.
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Appearance The Exterior of the dormer extension will be clad in a brown exterior, most likely a UPVC fascia cladding or a wooden equivalent constructed using stained hardwood. All window frames and guttering will match in colour. The roof will be constructed using a GRP coating which will be grey in colour; to match the remainder of the roof tiles.. These styling/appearance choices have been selected so as to match the appearance of the majority of properties in the area. As stated in the Construction Overview section the front dormer will extend to roughly 3m forward of the ridge of the roof. This is roughly equivalent to 4 roof tiles in from the innermost front face of the property.
Similar Properties There are also a number of properties in the neighbouring area with similar extensions to the upper floor in the form of a dormer and the following images of these properties are intended to support the application by means of proof of conforming to existing styles.
7 Copster Drive Number 7 Copster Drive has a rear dormer extension that conforms to the permitted development rights allowing properties to be extended without planning permission. The intended extension to the rear of number 11 Copster Drive will very closely resemble the rear dormer at number 7 Copster Drive. This dormer extension is clad in brown UPVC cladding with matching window frames and guttering. A GRP roofing system has also been used.
No. 7 Copster Drive (from rear)
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14 Copster Drive Number 14 Copster Drive which is situated opposite number 11 has a front and rear extension. The front dormer extension protrudes to roughly 5 full rows of roofing tiles from the innermost front face of the property. This property is clad in a brown stained wooden exterior.
No. 14 Copster Drive (right)
No. 14 Copster Drive (right)
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No. 14 Copster Drive (right) & no. 16 Copster Drive (left)
16 Copster Drive Similar to number 14 Copster Drive number 16 has a front dormer extension which also protrudes to roughly 5 full rows of tiles from the innermost front face of the property. It is also clad in brown stained wood. This property is next door to number 14 and is the property to the left as pictured previously.
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2 Copster Drive Number 2 Copster Drive has a front facing dormer over the larger part of the roof which protrudes to roughly 3 full rows of roof tiles from the innermost front face of the property, however this particular dormer still has a further 4 rows of tiles immediately in front of the extension. Whilst this property's extension is different to the others in position, it is worth noting for its difference in appearance using white UPVC cladding as opposed to brown UPVC or wooden cladding and the distance from the front of the building. This particular extension has utilised a GRP roof system, similar to that of number 7 and to the intended design for number 11 Copster Drive.
No. 2 Copster Drive
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References 1.1 - Joist Span Tables for Floors (TRADA Span Tables rev. 2) 1.2 - Joist Loading calculations (floor) 1.3 - Joist Span Tables for Roofs (TRADA Span Tables rev. 2) 1.4 - Joist Loading calculations (roof) 2.1 - Steel Beam Loading calculations 2.2 - Steel Beam Loading Simulation
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Ref 1.1 – Joist Span Tables for Floors (TRADA Span Tables rev. 2)
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Ref 1.2 – Joist Loading Calculations (Floor) LOAD CASE
Fd Fd + Fl (N/mm2)
Ax
Ay
INPUTS b
(mm)
CALCS
h (mm)
E (N/mm2)
A1.1 A1.2
0.0005 0.0005
0.002 0.002
400.0mm 400.0mm
3160.0mm 75.0mm 175.0mm C16 OPT 3160.0mm 50.0mm 175.0mm C16 OPT
A1.3 A1.4 A2.1 A2.2
0.0005 0.0005 0.0005 0.0005
0.002 0.002 0.002 0.002
400.0mm 400.0mm 400.0mm 400.0mm
3160.0mm 3160.0mm 3160.0mm 3160.0mm
C16 WOR C16 WOR C24 OPT C24 OPT
5800 5800 10800 10800
A2.3 A2.4 B1.1
0.0005 0.0005 0.0015
0.002 0.002 0.003
400.0mm 400.0mm 400.0mm
3160.0mm 75.0mm 175.0mm C24 WOR 3160.0mm 50.0mm 175.0mm C24 WOR 3160.0mm 75.0mm 175.0mm C16 OPT
7200 7200 8800
B1.2 B1.3 B1.4 B2.1
0.0015 0.0015 0.0015 0.0015
0.003 0.003 0.003 0.003
400.0mm 400.0mm 400.0mm 400.0mm
3160.0mm 3160.0mm 3160.0mm 3160.0mm
C16 OPT C16 WOR C16 WOR C24 OPT
8800 5800 5800 10800
B2.2 B2.3 B2.4
0.0015 0.0015 0.0015
0.003 0.003 0.003
400.0mm 400.0mm 400.0mm
3160.0mm 50.0mm 175.0mm C24 OPT 3160.0mm 75.0mm 175.0mm C24 WOR 3160.0mm 50.0mm 175.0mm C24 WOR
10800 7200 7200
Live Load Safety factor Total Dead Load
Fl (N/mm2) =
0.001500 1.5kN/m2
Fds (x1.25) = Fd (N/mm2)=
0.000505 0.5kN/m2 0.000404
component 22mm chipboard flooring 22kg per 1.4m2 board
F (N/mm2)
F (kN/m2)
15.7kg per m2 plasterboard services
0.000154 0.000130
0.154 0.130
(lights/wires/pipes) carpet
0.000100 0.000020
0.100 0.020
75.0mm 50.0mm 75.0mm 50.0mm
50.0mm 75.0mm 50.0mm 75.0mm
175.0mm 175.0mm 175.0mm 175.0mm
175.0mm 175.0mm 175.0mm 175.0mm
KN/m2 ==> N/mm2 1.0 0.0010 1.5 0.0015 2.0 2.5 Nominal Extreme
8800 8800
Ymax
I
(mm)
(mm4)
87.5mm
33496093.75
87.5mm
22330729.17
87.5mm
33496093.75
87.5mm
22330729.17
87.5mm
33496093.75
87.5mm
22330729.17
87.5mm
33496093.75
87.5mm
22330729.17
87.5mm
33496093.75
87.5mm
22330729.17
87.5mm
33496093.75
87.5mm
22330729.17
87.5mm
33496093.75
87.5mm
22330729.17
87.5mm
33496093.75
87.5mm
22330729.17
OUTPUTS DEAD LOAD DEAD + LIVE LOAD MAX STRESS MAX DEFL. MAX STRESSMAX DEFL. 0.65MPa 0.98MPa
0.88mm 1.32mm
2.61MPa 3.91MPa
3.52mm 5.29mm
0.65MPa 0.98MPa 0.65MPa 0.98MPa
1.34mm 2.00mm 0.72mm 1.08mm
2.61MPa 3.91MPa 2.61MPa 3.91MPa
5.35mm 8.02mm 2.87mm 4.31mm
0.65MPa 0.98MPa 1.96MPa
1.08mm 1.62mm 2.64mm
2.61MPa 3.91MPa 3.91MPa
4.31mm 6.46mm 5.29mm
2.93MPa 1.96MPa 2.93MPa 1.96MPa
3.96mm 4.01mm 6.01mm 2.15mm
5.87MPa 3.91MPa 5.87MPa 3.91MPa
7.93mm 8.02mm 12.03mm 4.31mm
2.93MPa 1.96MPa 2.93MPa
3.23mm 3.23mm 4.85mm
5.87MPa 3.91MPa 5.87MPa
6.46mm 6.46mm 9.69mm
Acceptable Live Load defl. (L*0.0025) = (L = Ay)
7.90mm
0.003*L or 12mm whichever is least
0.0020 0.0025 A – 0.5kN/m2 Dead Load and 1.5kN/m2 Live Load = Imposed Load of 2.0kN/m2 B – 1.5kN/m2 Dead Load and 1.5kN/m2 Live Load = Imposed Load of 3.0kN/m2
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Ref 1.3 – Joist Span Tables for Roofs (TRADA Span Tables rev. 2)
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Ref 1.4 – Joist Loading Calculations (Roof) Fd Fd + Fl (N/mm2)
LOAD CASE
Ax
Ay
INPUTS b
(mm)
CALCS
h (mm)
E (N/mm2)
A1.1 A1.2 A1.3 A1.4 A2.1 A2.2 A2.3 A2.4
0.00036 0.00036 0.00036 0.00036 0.00036 0.00036 0.00036 0.00036
0.00111 0.00111 0.00111 0.00111 0.00111 0.00111 0.00111 0.00111
400.0mm 400.0mm 400.0mm 400.0mm 400.0mm 400.0mm 400.0mm 400.0mm
3160.0mm 3160.0mm 3160.0mm 3160.0mm 3160.0mm 3160.0mm 3160.0mm 3160.0mm
75.0mm 50.0mm 75.0mm 50.0mm 75.0mm 50.0mm 75.0mm 50.0mm
150.0mm 150.0mm 150.0mm 150.0mm 150.0mm 150.0mm 150.0mm 150.0mm
C16 OPT C16 OPT C16 WOR C16 WOR C24 OPT C24 OPT C24 WOR C24 WOR
8800 8800 5800 5800 10800 10800 7200 7200
B1.1 B1.2 B1.3 B1.4 B2.1 B2.2 B2.3 B2.4
0.00036 0.00036 0.00036 0.00036 0.00036 0.00036 0.00036 0.00036
0.00111 0.00111 0.00111 0.00111 0.00111 0.00111 0.00111 0.00111
400.0mm 400.0mm 400.0mm 400.0mm 400.0mm 400.0mm 400.0mm 400.0mm
4460.0mm 4460.0mm 4460.0mm 4460.0mm 4460.0mm 4460.0mm 4460.0mm 4460.0mm
75.0mm 50.0mm 75.0mm 50.0mm 75.0mm 50.0mm 75.0mm 50.0mm
150.0mm 150.0mm 150.0mm 150.0mm 150.0mm 150.0mm 150.0mm 150.0mm
C16 OPT C16 OPT C16 WOR C16 WOR C24 OPT C24 OPT C24 WOR C24 WOR
8800 8800 5800 5800 10800 10800 7200 7200
Live Load
Total Dead Load
Fl (N/mm2) =
Fd (N/mm2)=
component 18mm Plywood 32kg per 3.05m2 board 10.5kg per m2 plasterboard GRP Roof Insulation
Ymax
I
(mm)
(mm4)
75.0mm
21093750.00
75.0mm
14062500.00
75.0mm
21093750.00
75.0mm
14062500.00
75.0mm
21093750.00
75.0mm
14062500.00
75.0mm
21093750.00
75.0mm
14062500.00
75.0mm
21093750.00
75.0mm
14062500.00
75.0mm
21093750.00
75.0mm
14062500.00
75.0mm
21093750.00
75.0mm
14062500.00
75.0mm
21093750.00
75.0mm
14062500.00
OUTPUTS DEAD LOAD DEAD + LIVE LOAD MAX STRESS MAX DEFL. MAX STRESSMAX DEFL. 0.63MPa 0.95MPa 0.63MPa 0.95MPa 0.63MPa 0.95MPa 0.63MPa 0.95MPa
1.00mm 1.49mm 1.51mm 2.27mm 0.81mm 1.22mm 1.22mm 1.83mm
1.96MPa 2.95MPa 1.96MPa 2.95MPa 1.96MPa 2.95MPa 1.96MPa 2.95MPa
3.09mm 4.64mm 4.69mm 7.04mm 2.52mm 3.78mm 3.78mm 5.67mm
1.26MPa 1.89MPa 1.26MPa 1.89MPa 1.26MPa 1.89MPa 1.26MPa 1.89MPa
3.95mm 5.93mm 6.00mm 8.99mm 3.22mm 4.83mm 4.83mm 7.25mm
3.91MPa 5.87MPa 3.91MPa 5.87MPa 3.91MPa 5.87MPa 3.91MPa 5.87MPa
12.28mm 18.42mm 18.63mm 27.94mm 10.00mm 15.01mm 15.01mm 22.51mm
0.000750 0.75kN/m2
0.000356 0.32kN/m2 F (N/mm2)
F (kN/m2)
0.000103 0.000130
0.103 0.130
0.000023 0.000100
0.023 0.100
KN/m2 ==> N/mm2 1.0 0.0010 1.5 0.0015 2.0 0.0020 2.5 0.0025 Option Option
GRP Roof resin glass topcoat total
Acceptable Live Load defl. (L*0.0025) = (L = Ay) 0.003*L or 12mm whichever is least
A – Beams run from party wall and gable end to Central Brick wall B – Beams run from ridge beam to dormer front
18mm PLY 1.35 kg/m2 0.45 kg/m2 0.5 kg/m2 2.3 kg/m2 0.022555 kN/m2 0.000023 N/mm2
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22mm CHIP 32 22 kg 3.05 1.4 m2 10.4918032787 15.71428571 kg/m2 0.1028894426 0.1541045 kN/m2 0.000103 0.000154 kN/mm2
7.90mm A 11.15mm B
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Ref 2.1 – Steel Beam Loading Calculations INPUTS LOAD CASE A1.1 A1.2 A1.3 A1.4
q(d)
q(d) + q(l) (N/mm)
2.55 2.59 2.70 2.77
7.29 7.33 7.44 7.51
Span (mm) 1900.0mm 1900.0mm 1900.0mm 1900.0mm
H (mm) 178.0mm 178.0mm 178.0mm 178.0mm
CALCS
b (mm)
Joist Spec h (mm) Density max (kg/m3)
50.0mm 50.0mm 75.0mm 75.0mm
175.0mm 175.0mm 175.0mm 175.0mm
370.0 420.0 370.0 420.0
C16 C24 C16 C24
E (N/mm2) Steel Steel Steel Steel
14260.1N Live Load / mm Dead Load / mm
q(l) (N/mm) =
4.74 Ll x 2 / Span
4503.00 (Fl x Span x Room Length / 2)
Lj (N)= ((Span / Joist Spacing)+1) x Mass of Single joist / 2 Total – Lt (N)= Dead load – Ld (N)= Wall – Lw (N)=
Lj
I
(mm)
(N)
(mm4)
89.0mm
288.54
89.0mm
327.53
89.0mm
432.81
89.0mm
491.30
13560000 13560000 13560000 13560000
OUTPUTS DEAD LOAD DEAD + LIVE LOAD MAX STRESS MAX DEFL. MAX STRESS MAX DEFL. 7.56MPa 7.68MPa 8.01MPa 8.19MPa
0.160mm 0.162mm 0.169mm 0.173mm
21.60MPa 21.72MPa 22.05MPa 22.23MPa
Acceptable Live Load defl. (Span*0.0025) =
q(d) (N/mm) = ((Lt + Lj) x 2) / Span Live load – Ll (N)=
200000 200000 200000 200000
Ymax
2135.76 1516.01 Fd x Span x Room Length / 2 619.75 0.1m x ((Span / 2)^2) x 700kg/m3
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0.456mm 0.459mm 0.466mm 0.470mm 4.75mm
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Ref 2.2 - Steel Beam Loading Simulation This simulation was run in ANSYS Discovery Live design software. It shows the maximum deflection in a steel beam would be 0.33mm when the beam is loaded with half the calculated load (7130N) on both the lower flanges, as per the build intent. This equates to roughly 70% of the deflection predicted using the mathematical method (0.47mm).
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