Garage/Workshop conversion
Garage-workshop conversion
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HOME PAGEPHASE 1. Back door removal & window replacement.

PHASE 2. Construction of a stud framework supporting eight joists.
(This page)

PHASE 3. Plasterboard ceiling construction. PHASE 4. Partition construction with relocated door. PHASE 5. Construction of mezzanine floor. PHASE 6. Installation of wall insulation & OSB sheathing. PHASE 7. Electrical re-wiring.
Garage/Workshop conversion
Garage/workshop conversion
FITTING OUT PROJECTS WOOD-TURNING
PROJECTS
APPENDIX 1. Measurements & materials.

Phase 2. Construction of a Stud Framework Supporting Eight Joists.


Synopsis of Work.
The first stage was the construction of the stud framework on the workshop window wall. This was followed by building the studwork on the two side workshop walls. The final stage was the erection of the 9 joists spanning wall to wall across the workshop, supporting the plasterboard ceiling and mezzanine chipboard floor, with a sandwich fill of rockwool insulation. Pressure treated soft-wood was used for all the structural components.

Details

Wood for studwork delivered 8th June 2015 Wood for studwork delivered by Chiltern Timber 8th June 2015.

Pressure treated wood for the stud walling and partition wall frameworks, plus the 8 joists supporting the new mezzanijne floor and plasterboard ceiling. Not much room for manoeuvre!

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Designing a stud framework for sheathing. Designing a stud framework to support the wall sheathing

The design must take account of the maximum width of the sheathing which, for the OSB boards used in this project, have a width of 1,220mm. The vertical studs to which the sheathing is screwed should be spaced to accommodate the full width of the boards with the joins located in the centres of the studs. The exceptions are the first and last boards in a given run where the vertical board edges will locate at the edges of the studs. The arrangement is shown in the diagram.

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Marking the positions on the sole plate for the 70mm x 45mm vertical studwork Marking the positions for the vertical studwork pieces. 17th June 2015

Marking the positions on the sole plate for the 70mm x 45mm vertical studwork, using steel tape, pencil and set-square.

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Using a spirit level to ensure the studding is vertical Using a spirit level to ensure the studding is vertical. 26th June 2015.

The spirit level is held against the upright which is moved until the bubble is centred (as shown in the inset). Holding the wooden upright in its vertical position, The holes for the fixings are then drilled into the masonry using pre-drilled holes in the wood as guides.

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Diagram showing how studs are fixed to the garage wall Diagram showing how studs are fixed to the garage wall.

Sketch showing the hole sizes and depths for fastening the 70mm x 45mm studs to the garage walls.

The holes in the wooden stud were drilled first. A cut stud was put in place on the brickwork, and the position of the holes marked on the wood, ensuring as far as possible, that the fixings were in solid brick rather than in the encasing mortar. The stud was then placed on the drill table and a 16mm spade bit used to drill the 5mm deep clearance hole for the hexagonal head of the coach screw (also wide enough to accommodate the end of the 10mm socket on the end of the ratchet driver). The hexagonal heads of the coach screws had to be recessed into the studs to allow for the overlying OSB 3 sheathing. A 5mm wood drill was then used to drill the hole for the M6 screw body right through the stud. The stud was then placed in position and the 5mm holes in the wooden studs, used as guides for a 5mm masonry drill to drill pilot holes in the garage wall brickwork. The stud was then removed and the pilot holes in the brickwork progressively drilled, out with a series of masonry drills, to a final diameter of 10mm and 55mm depth. The 10mm plastic plugs were then pushed into the holes, the stud placed in position and the 90mm long M6 coach bolts screwed home using the ratchet spanner.

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Fastenings and tools for the 70mm x 45mm studwork Fastenings and Tools for the 70mm x 45mm studwork.

Ratchet spanner with 10mm diameter socket (for hexagonal headed coach screws); 10mm x 50mm long plastic plugs; M6 hexagonal headed coach screws, 90mm long; M6 diameter steel washers; 5mm diameter wood drill; 10mm diameter masonry drill; 16mm diameter spade bit for drilling a 5mm deep hole in the wooden studs to take the hexagonal heads plus washers on the coach screws.

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Jig used for accurate drilling of studs. 16th June 2015.

I could have used a power drill and unsupported drilling for this but I preferred to use a drill press for more accurate drilling. One end of the stud rests on the circular drill press platform whilst the other is supported using a combination of a sash clamp in a Black & Decker Workmate. The stud is levelled by means of the sash clamp and once level, it can be clamped (using a G clamp) in position on the drill press table. The drill is started with a 16mm diameter spade bit and brought down until the spade part of the bit is just beginning to engage with the wood. The drill is stopped but with the bit in the same position (the spade just engaging with the surface of the wood), the drill's depth gauge is then set to 5mm, the drill re-started and the hole drilled to that depth. Then, without unclamping the wood, the spade bit is removed and replaced with a 5mm twist drill bit. This is then used to drill right through the stud. Because the wood is still clamped, the 5mm hole aligns perfectly with the centre of the 16mm hole, and both holes are perpendicular to the stud.

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Drilling a 5mm pilot hole with a masonry drill. Drilling a 5mm pilot hole in the brick wall with a masonry drill. 17th June 2015.

With the wooden stud wedged in position on the wall, a 5mm masonry bit (used with a hammer drill) can be put through each of the 5mm holes in the studs to drill a series of pilot holes in the brick wall of the garage. Make sure the stud is securely wedged in position whilst drilling to ensure that the masonry holes are in exactly the correct position.

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Extending the 5mm pilot hole with a masonry drill to the correct depth. Extending the 5mm pilot hole with a masonry drill to the correct depth. 17th June 2015.

The wooden stud is then removed and the pilot holes in the brickwork extended to the correct depth ( > 50mm).

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Enlarging the 5mm pilot hole, with masonry drills to 10mm diameter. Enlarging the 5mm pilot hole, with masonry drills to 10mm diameter. 17th June 2015.

I find the easiest way to do this is to use a series of drills, each drill 1 mm larger than the previous. (6mm, 7mm, 8mm, 9mm & 10mm). This may be tedious but it ensures accuracy and minimises wear and tear on the masonry bits. The final 10mm diameter bit is shown in the photograph.

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Tapping the plastic plug into place into the hole in the brickwork. Tapping the plastic plug into place into the hole in the brickwork. 17th June 2015.

The 10mm diameter plastic plugs can be gently tapped into the drilled holes in the brickwork.

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Stud in place with coach screw ready for driving home into the underlying plastic plug. Stud in place with coach screw ready for driving home. 17th June 2015.

The stud is placed back in position on the brickwork and the coach screws driven through the stud (ensuring that the ends are aligned to engage with the underlying plastic plugs), ready for driving home with the ratchet spanner.

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Using a ratchet spanner to screw stud to the garage wall. Using a ratchet spanner to drive home the screws. 14th June 2015.

Using a ratchet spanner is much easier and more effective than using a power or manual screwdriver. Here the sole plate of the stud work is being attached at the base of the window wall.

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Completed studwork for the end (Window) wall, photo & drawing. Completed studwork for the end (Window) wall. 18th June 2015.

Photograph (top) of completed end wall studwork. The original drawing for the studwork is shown (bottom), to demonstrate a perfect match. This part of the stud framework was completed on 18th June 2015.

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Installing the Joists

Note added in response to Discussion of this project on the Woodworkers Institute Forum (November 2016).
I'm most grateful to Peter Hyde for pointing out the importance of using structurally graded and treated timber of the correct size and length for the load-bearing joists. The UK Building Regulations provide a good tabular guide for this, which is reproduced below.


Building Control Guidance Note:
Subject: DOMESTIC TIMBER FLOORS, Timber sizes and construction details,
(Issued January 2010).

The following table gives details of allowable spans and spacing between joists for the most common timber sizes used in floor construction. All the figures are based on normal domestic floor loadings where the floor construction is typically 18-25mm floor boards/sheets with up to 12.5mm thick plasterboard and skim underneath. For any other situation these tables may not be appropriate and you should refer to the TRADA Document Span tables for solid timber members in floors, ceilings and roofs for dwellings. When choosing a joist spacing, check that your floorboards (or sheets) are strong enough to span over the width chosen. As a general rule - floorboards should be a minimum 16mm thick for joist centres up to 500mm and 19mm minimum for centres up to 600mm.

FLOOR JOISTS SUITABLE FOR DOMESTIC FLOOR LOADINGS

Width x thickness of joists
in mm.

Maximum allowed clear span in metres for a joist spacing of:

400mm * 450mm * 600mm
97 x 47 1.93 1.82 1.47
120 x 47 2.52 2.42 2.05
145 x 47 * 3.04 * 2.92 * 2.59
170 x 47 3.55 3.42 3.00
195 x 47 4.07 3.91 3.41
220 x 47 4.58 4.39 3.82
145 x 75 3.54 3.10 3.10
170 x 75 4.14 3.99 3.63
195 x 75 4.72 4.52 4.13
220 x 75 5.15 5.01 4.67

Table assumes a minimum C16 structural grade timber - not all timber is structurally graded - ensure you purchase the right material!!


For this workshop project, the joists needed to clear an unsupported span of 2.58m. Looking at the above table, and checking the data against availability of wood from local suppliers, I decided to opt for pressure treated structural timber grade C16, measuring 45mm (1¾") x 145mm (5¾"), with spacing between the mid-points of the joists measuring 405mm (1' 4"). This being nearest to the dimensions in bold and marked thus * in the above table.

I also followed the Building Regulations recommendation: Where the joists span over 2.5m, strutting is required to prevent joists twisting when loaded. For spans of between 2.5 and 4.5m one row of strutting is needed, at the mid span position. The strutting was constructed exactly as recommended.

The timber for the joists and associated spacers, were delivered in 3.0m lengths. Each of the 360mm long spacing timbers were attached to the brick walls using a single 90mm long, 6mm diameter hexagonal headed coach screw in a 10mm diameter 50mm long plastic plug (as per the studs).

The joists were screwed to the spacers using 65mm long, 6mm diameter hexagonal headed coach screws (two screws at each end of the joist). Details follow.

Details of joist construction. Details of joist construction.

Drawing showing how the joists were constructed.

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Details of joist construction. Attaching a Spacer between the Joists. 6th July 2015.

This shows a spacer (between the joists) being screwed to the brick wall. The clamp is used to hold the spacer in exactly the right position as the screw is driven home using the ratchet spanner.

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Details of joist construction. Drilling attachment holes in a joist. 4th July 2015.

The joists were attached to the spacers using 4 (two at each end), 65mm long 6mm diameter hexagonal headed coach screws. Here the holes for two of the coach screws are being drilled, first with a 16mm diameter spade bit (so that the hexagonal head of the bolt can be recessed in the joist), and then using a 5mm diameter drill to make a hole right through the joist.

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Details of joist construction. Joist in position. 4th July 2015.

Joist in position, ready to be screwed to the spacer. Note the wide 16mm diameter recess at the top of the holes, so that the hexagonal bolt heads can be hidden within the joist to allow for the placing of the next spacer timber.

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Details of joist construction. Joist in position. 6th July 2015.

Joist in position, 65mm long 6mm diameter hexagonal headed coach screws ready to be driven home.

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Details of joist construction. Work in progress. 6th July 2015.

Work in progress installing the joists.

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Installing Strutting supports

UK Building Regulations state that where floor joists span over 2.5m, strutting is required to prevent joists twisting when loaded. For spans of between 2.5 and 4.5 m one row of strutting is needed, at the mid span position. Solid strutting should be at least 38 mm thick timber extending to at least three quarters the joist depth. Here the 145mm x 45mm joists have timber of the same width and thickness used as strutting.

Photo showing fixing of struts to the joists, 18th July 2015. Construction of anti-twisting strutting. 18th July 2015.

Photograph showing work in progress in fixing anti-twisting struts to the joists. Each strut measures 360mm x 145mm x 45mm. Two pilot holes 5mm in diameter, have been drilled through the joist for fixing the end of the next strut.

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Fixing a new strut in place, 18th July 2015. Fixing a New Strut in Place - 1. 18th July 2015.

In this photograph the new strut has been positioned between the two adjacent joists and temporarily jammed in place by applying pressure (to the two containing joists), with a sash clamp.

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Fixing a new strut in place, 18th July 2015. Fixing a New Strut in Place - 2. 18th July 2015.

With the strut jammed in place with the sash clamp, the pilot holes are extended through the joist and into the strut.

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Fixing a new strut in place, 18th July 2015. Fixing a New Strut in Place - 3. 18th July 2015.

With the strut jammed in place with the sash clamp, the 6mm diameter, 80mm long woodscrews are ready to be driven home. 18th July 2015.

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Installing Lighting Support Battens

Installing the strutting was also a good time to install the battens which will support the 4 foot long fluorescent light units. Details of how this was done follows.

Fixing a new lighting support batten in place, 18th July 2015. Fixing a new lighting support batten in place. 18th July 2015.

The same method as used for fixing the struts in position, was used to fix the battens for supporting the fluorescent lights. Here the two 6mm diameter fixing screws at one end of the batten are ready to be driven home.

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Fluorescent light showing the dimension needed between the two support battens, 18th July 2015. Fluorescent Light Fitting. 18th July 2015.

Fluorescent light to be used in the workshop showing the dimension needed between the mid points of the two support battens.

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A pair of fitted battens, 18th July 2015. A Pair of Fitted Battens. 18th July 2015.

A pair of fitted fluorescent light battens showing the correct dimension of 600mm between their mid points.

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Completed joists compared with original drawing, 18th July 2015. Completion of Joists. 18th July 2015.

Photograph of completed joists with strutting and fluorescent light batten supports. A screenshot from the original Sketchup drawing is shown for comparison.

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Details of Phase 2 construction. Completion of Phase 2. 18th July 2015.

Photograph of completed studwork compared with a screenshot from the original Sketchup drawing.

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Phase 2 completed 18th July 2015.

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