Part 1
Having followed this forum for a while now and gained some really useful knowledge along the way, I thought it only fair to share my workshop build with others. I’ll be documenting the build as I go with photos and drawings, hopefully to help others and also to receive constructive feedback and maybe a little encouragement along the way.
The Plan
To construct a timber framed workshop measuring 5.4 x 4.2m at the rear of the garden as close to the boundary as possible. The back and sides will be clad in metal box profile sheets and the front face slatted timber (tbc). The roof will be a warm roof with an epdm covering. The workshop will be divided into a small storage area and the rest will be used as home office.
View down the garden. A little bit over grown, but mostly all clear now.
Planning permission drawings.
Rewind to June 2021 - The Base
I would have liked to construct a concrete base, however with no access to the garden other than through the house, along with constraints with parking, etc. this just wasn’t an (easy) option, so instead I settled on a timber framed base sat on top of concrete piers. I watched a lot of tutorials on this technique which seems to be widely adopted in the US, but less so in the UK.
The thinking behind using this technique for the foundation;
1. Less concrete, so I could mix up small batches, just enough at a time to fill each pier.
2. All materials could be brought through the house in small quantities.
3. Whilst maybe not as good a concrete slab base, it would still be very stable and not succumb to rot / damp.
4. The piers could be raised out the ground slightly to provide air flow and keep the timber away from the floor.
5. I wouldn’t have to completely level the garden which slopes from its highest point (top right) down to the lowest point (bottom left) by about 40cm.
After clearing the garden and marking out the size using string lines, I then marked out where and how far apart my concrete piers would need to be. 16 piers in total, 4 across and 4 deep. The maximum span between two piers across being 1.8m.
I levelled out the area roughly and then using an auger I drilled down as far as I could in each of the 16 pier locations. Approximately 1m deep. I’d seen in the US that they use a kind of cardboard tube that’s then filled with concrete and this had been my intention, however after more thought I was concerned that the diameter of the holes which was restricted by the size of the auger wouldn’t be sufficiently wide enough.
In the end I dug out each of the holes to approximately 40cm square and using scaffold board as shuttering, constructed a square frame around each opening, ensuring the tops of each one were level with one another.
With the holes for the foundation piers dug and the scaffold boards level, I then laid out the framework on top, ensuring it was square and level and temporarily fixed the frame together with each timber sitting centrally over the holes.
With the frame in place, I then drilled through the timber frame in each of the pier locations ensuring the hole was centred on the dug hole below. Once all drilled, I dropped in a steel threaded rod through the drilled holes in the frame and into the hole below. Each rod was held in place with a couple of nuts from above.
Next I poured concrete into each hole creating the piers. Once dry, I removed the frame and now had 16 concrete piers, each with a steel threaded rod sticking out the top.
With the frame removed, I used polo-shaped rubber rings that are typically used under plant pots to raise them off the ground and placed these over the steel rods. These would sit between the concrete pier and the timber frame stopping any moisture or water sat on the piers from rising up into the timber.
Model of pier construction.
Actual pier construction.
The frame then went back on and was secured in place with washers and nuts that sat just below the top of the timber. Any protruding steel rod was cut level with the timber using a grinder.
The frame was constructed with 4x2 C24 treated timber with the outer frame doubled up and bolted together. I should have probably used a bigger timber here to reduce flex, however as I wanted to keep the height low, I opted for doubling up the timbers and there doesn’t appear to be any flex across the spans.
Using mini joist hangers, I placed floor joists at 400 centres and then inlaid rigid foam insulation and foil taped the joints. These were sat on timber battens beneath the frame to stop it slipping out.
The next step, which I wasn’t sure about, but had seen someone else do it and seemed like a sensible idea, was to lay breather membrane over the top. This was laid with the outer face, facing downwards to hopefully reduce any moisture coming up through the frame. Not sure this was necessary as theoretically there shouldn’t be any moisture rising up, but thought it wouldn’t do any harm.
Over this I laid 22mm P5 tongue and groove chipboard, secured with screws and 5min wood glue.
View of base prior to overlaying breather membrane and tongue and groove chipboard.
Change of plan
After I constructed the base, I re-thought about the overall design. I initially wanted to build the workshop under permitted development, however I really wanted a warm roof. Due to the size of timber I need for the roof span, plus the thickness of the insulation on top and the raised timber base, keeping within the permitted development height of 2.5m would create a very low internal ceiling.
As a result, I decided to apply for planning permission so that I could maintain a decent internal height and keep the warm roof. This is a fairly simple process and easy to do if you have some drafting / drawing experience. As I had built the base I applied for part-retrospective permission. Although an extra cost, for the extra head height I think it’s worth it.
Six weeks later I got confirmation that my planning permission had been granted. They didn’t even come out to visit, just asked for some photos to be sent to them.
Fast forward to March 2022
After being granted permission, I covered up the base with tarpaulin and didn’t touch it until nearly a year later and it’s from this point that I’ll be documenting the build on the forum.
All wrapped up ready to begin again nearly a year later. PS. Tarpaulin isn't water proof!
Having followed this forum for a while now and gained some really useful knowledge along the way, I thought it only fair to share my workshop build with others. I’ll be documenting the build as I go with photos and drawings, hopefully to help others and also to receive constructive feedback and maybe a little encouragement along the way.
The Plan
To construct a timber framed workshop measuring 5.4 x 4.2m at the rear of the garden as close to the boundary as possible. The back and sides will be clad in metal box profile sheets and the front face slatted timber (tbc). The roof will be a warm roof with an epdm covering. The workshop will be divided into a small storage area and the rest will be used as home office.
View down the garden. A little bit over grown, but mostly all clear now.
Planning permission drawings.
Rewind to June 2021 - The Base
I would have liked to construct a concrete base, however with no access to the garden other than through the house, along with constraints with parking, etc. this just wasn’t an (easy) option, so instead I settled on a timber framed base sat on top of concrete piers. I watched a lot of tutorials on this technique which seems to be widely adopted in the US, but less so in the UK.
The thinking behind using this technique for the foundation;
1. Less concrete, so I could mix up small batches, just enough at a time to fill each pier.
2. All materials could be brought through the house in small quantities.
3. Whilst maybe not as good a concrete slab base, it would still be very stable and not succumb to rot / damp.
4. The piers could be raised out the ground slightly to provide air flow and keep the timber away from the floor.
5. I wouldn’t have to completely level the garden which slopes from its highest point (top right) down to the lowest point (bottom left) by about 40cm.
After clearing the garden and marking out the size using string lines, I then marked out where and how far apart my concrete piers would need to be. 16 piers in total, 4 across and 4 deep. The maximum span between two piers across being 1.8m.
I levelled out the area roughly and then using an auger I drilled down as far as I could in each of the 16 pier locations. Approximately 1m deep. I’d seen in the US that they use a kind of cardboard tube that’s then filled with concrete and this had been my intention, however after more thought I was concerned that the diameter of the holes which was restricted by the size of the auger wouldn’t be sufficiently wide enough.
In the end I dug out each of the holes to approximately 40cm square and using scaffold board as shuttering, constructed a square frame around each opening, ensuring the tops of each one were level with one another.
With the holes for the foundation piers dug and the scaffold boards level, I then laid out the framework on top, ensuring it was square and level and temporarily fixed the frame together with each timber sitting centrally over the holes.
With the frame in place, I then drilled through the timber frame in each of the pier locations ensuring the hole was centred on the dug hole below. Once all drilled, I dropped in a steel threaded rod through the drilled holes in the frame and into the hole below. Each rod was held in place with a couple of nuts from above.
Next I poured concrete into each hole creating the piers. Once dry, I removed the frame and now had 16 concrete piers, each with a steel threaded rod sticking out the top.
With the frame removed, I used polo-shaped rubber rings that are typically used under plant pots to raise them off the ground and placed these over the steel rods. These would sit between the concrete pier and the timber frame stopping any moisture or water sat on the piers from rising up into the timber.
Model of pier construction.
Actual pier construction.
The frame then went back on and was secured in place with washers and nuts that sat just below the top of the timber. Any protruding steel rod was cut level with the timber using a grinder.
The frame was constructed with 4x2 C24 treated timber with the outer frame doubled up and bolted together. I should have probably used a bigger timber here to reduce flex, however as I wanted to keep the height low, I opted for doubling up the timbers and there doesn’t appear to be any flex across the spans.
Using mini joist hangers, I placed floor joists at 400 centres and then inlaid rigid foam insulation and foil taped the joints. These were sat on timber battens beneath the frame to stop it slipping out.
The next step, which I wasn’t sure about, but had seen someone else do it and seemed like a sensible idea, was to lay breather membrane over the top. This was laid with the outer face, facing downwards to hopefully reduce any moisture coming up through the frame. Not sure this was necessary as theoretically there shouldn’t be any moisture rising up, but thought it wouldn’t do any harm.
Over this I laid 22mm P5 tongue and groove chipboard, secured with screws and 5min wood glue.
View of base prior to overlaying breather membrane and tongue and groove chipboard.
Change of plan
After I constructed the base, I re-thought about the overall design. I initially wanted to build the workshop under permitted development, however I really wanted a warm roof. Due to the size of timber I need for the roof span, plus the thickness of the insulation on top and the raised timber base, keeping within the permitted development height of 2.5m would create a very low internal ceiling.
As a result, I decided to apply for planning permission so that I could maintain a decent internal height and keep the warm roof. This is a fairly simple process and easy to do if you have some drafting / drawing experience. As I had built the base I applied for part-retrospective permission. Although an extra cost, for the extra head height I think it’s worth it.
Six weeks later I got confirmation that my planning permission had been granted. They didn’t even come out to visit, just asked for some photos to be sent to them.
Fast forward to March 2022
After being granted permission, I covered up the base with tarpaulin and didn’t touch it until nearly a year later and it’s from this point that I’ll be documenting the build on the forum.
All wrapped up ready to begin again nearly a year later. PS. Tarpaulin isn't water proof!
