One for the Construction Meister

[CNC Paul]

This is for Mike Garnham our resident construction meister. 8)

I do rent a workshop but I would like to add to my workshop at home, the existing structure is in 225mm Solar blocks. My plan is to manufacture the addition in modules 600mm wide by 150mm thick by what ever height fits in with planning regs, they would be constructed in 18mm structural plywood cut on a CNC router and assembled with annular ring nails then filled with something like Warmcell. The exterior would be covered in Housewrap with 20mm vertical battens and then then finished with feather edge Larch or similar.

I hope you don't mind me asking.

My questions are? Is the method of constructon viable, do I need any additional vapour barrier and how would I determine the load bearing capabilities of the modules.

 

[MikeG.]

Paul,

no problem, of course I don't mind.

The big question is whether this build will require Building Regulations approval........because if it does this frameless construction is going to be be a job for a structural engineer to calculate. The other problem that springs to mind is how you propose to join these panels.......unless you build them as 5 sides boxes, join them together, then insulate, then add the final face (with the danger that you have contorted things and the face won't fit properly).

I understand why you plan to use this technique, but even with getting free use of the CNC kit, I still reckon it would all be a whole lot quicker and easier with a soft-wood frame. But we'll push on with it for the time being......let me know about the regs thing, because that will be a huge stumbling block.

Mike

 

[CNC Paul]

Mike, thanks for the reply.

My mistake, it should have been Planning Regs not Building Regs, I plan to keep it within permitted development. Would I still need Building Regs ?

My building method would be exactly as you described, because of the accuracy of the panel as long as they are fixed level and straight the inside panels should fit (hopefully). The top and bottom panels would be inset by 18mm to form a recess to take a long 18mm plywood sole and header plate to keep the panels aligned.

I hope I have made myself clear, I now will have to find a tame structural engineer.

 

[jasonB]

Would it not just be easier to use SIP Panels?

Seems like you are putting a lot of work into something that is like a SIP but not as good.

Jason

 

[CNC Paul]

Jason,

It might be easier to use SIP's but they cost approx £60 per Sq Mt, on top that I would require a very large crane because of the distance from the highway, my method would only cost me the raw materials at approx £18-20 Sq Mt

 

[MikeG.]

Paul,

if this is small enough to fall within Permitted Development (ie not require Planning Permission), then unless it is close to a boundary it shouldn't require Building regulations approval. If no BR required, then no Engineer required............I think that you know as I well as I do that this will be strong enough, and the problem of finding an engineer who agrees with that has now gone.

A couple of suggestions. Firstly, the standard........raise it on a low masonry plinth and tis will last an age. Put it straight on the ground/ slab/ wooden floor it will last 5 minutes. Secondly, I would look to squeeze some silicon between the panels, because you could have a good draft forcing its way between your nice warm panels. Thirdly, I suggest using mineral wool ("fibreglass" or "Rockwool") insulation rather than Warmcell. They are thermally very similar, and economically very different! I would make the internal dimension of the box 75 or 100mm to suit the insulation. Finally, 'twere it me I might consider having a "noggin" or internal horizontal member at half-height, to take some of the bounce out of the ply faces.

I like your head and sole plate idea. Tyvek Housewrap would be ideal around the outside.

The next big question is what load it bears. Will it have roof rafters sitting on the top of the panels, or are you planning a similar panel construction for the roof? Rafters would worry me a bit, with point loads potentially falling between the verticals with the potential for some bowing or deflection.


Mike

 

[CNC Paul]

Mike,

I will be keeping the structure just over 1m from the boundary, would that include the roof overhang?. You made me very happy with the comment "No Engineer", that means no steelwork. LOL

I take your suggestion on the mineral wool especially as the price seems to have come down recently. I had planned on two plywood vertical spacers in the center of the panels, they would also help to support the mineral wool.
The modules would be 150mm thick giving an internal size of 104mm, so I could reduce it to 100mm internally or go for a 150mm internal with 150mm mineral wool.

Noggin/spacer

Header plate

The roof panels would be the same construction.

Thanks for the advice

 

[CNC Paul]

I forgot,

I was hoping to raise it off the ground slightly and use the old Walter Seagal method of 75mm shingle over a weed barrier with the rim joists supported on legs set on pad stones.

I was going to use some neoprene strips set in a groove between the panel.

 

[MikeG.]

That all sounds fine to me, Paul. Technically, the 1m from the boundary rule includes everything, including the gutters......

Mike

 

[TEO]

I understand why you plan to use this technique, but even with getting free use of the CNC kit, I still reckon it would all be a whole lot quicker and easier with a soft-wood frame. But we'll push on with it for the time being......let me know about the regs thing, because that will be a huge stumbling block.

Mike

Sorry to butt in here; can you explain to me the advantages of this technique over a normal stud frame please? I'm guessing that it's to do with improved insulation but surely once you clad a stud with ply on the outside, fill it with rockwool batts and clad the interior with plasterboard or more ply...you get the same result? Don't you? And it's got to be way way easier and cheaper than the modules.
I'm intrigued....and probably a bit thick, what am I missing?
Cheers,
T

 

[MikeG.]

The advantage is that Paul works on a CNC router all day every day, and probably has access to cheaper ply than you or I could buy. This means that he can make a flat-pack extension, for not a lot of money.

It wouldn't be the case for most people!

Mike

 

[TEO]

The advantage is that Paul works on a CNC router all day every day, and probably has access to cheaper ply than you or I could buy. This means that he can make a flat-pack extension, for not a lot of money.

It wouldn't be the case for most people!

Mike

Thanks for the explanation Mike,
Cheers,
T

 

[CNC Paul]

Teo,

As Mike says it is very easy for me to put a sheet of plywood on the CNC press GO and get on with something else or sit in the office and drink coffee 8). The parts come cut and drilled ready to assemble, the modules are 600mm wide so they can be assemble in the workshop reducing the fixing time on site, you could not do that with a timber frame.

I look on it as like the old way of building a car with a chassis and a body compared to the new method with monocoque construction, all though it was pioneered in the 1930's

 

[wizer]

Will you build it with the thought of ever moving it, or will it be a perm structure?

 

[CNC Paul]

Will you build it with the thought of ever moving it, or will it be a perm structure?

Permanent

 

[TEO]

Teo,

As Mike says it is very easy for me to put a sheet of plywood on the CNC press GO and get on with something else or sit in the office and drink coffee 8). The parts come cut and drilled ready to assemble, the modules are 600mm wide so they can be assemble in the workshop reducing the fixing time on site, you could not do that with a timber frame.

I look on it as like the old way of building a car with a chassis and a body compared to the new method with monocoque construction, all though it was pioneered in the 1930's

Hey Paul

Well, much as I enjoy sitting around drinking coffee, I've yet to meet the machine that will make that possible by taking your beautifully cut boards, assembling them into the modules and then then erecting them all square etc.

I don't consider myself a luddite, in fact I've a project I'm trying to get CNC machining prices for now. And I'm certainly not trying to have a go but it's all too easy to get carried away with the toys when sometimes the older methods are just as if not more effective. I'm sure that a guy who knows what he's doing and a mate would have this done in less time than it will take with the modules.

Good luck with whichever method you choose, I'd love to see some pics if you go with the modules.

Cheers,
T

 

[promhandicam]

Paul,

Just a thought - what are you planning to do regarding electrics. Doing a timber frame (studwork and cladding) it would be easy to run the electrics in the cavity. This might be more problematic with the modules. Or perhaps you are happy to have the wiring in conduit on the surface.

Steve

 

[CNC Paul]

Steve,

The modules will have cable access holes in their edges, the internal panels are left off till the insulation and cables have been installed. The inner panel will have either a removable panel or the outlet boxed fitted directly to the panels.

 

[Steve Maskery]

This looks jolly interesting!
Paul, how are you going to avoid the boards soaking up moisture from whatever they are sitting on?
S

 

[MikeG.]

Paul,

that is not how I would recommend doing electrics in a shed. You are much safer to surface mount the cables, because everyone can see where they are then. Enclosed in the structure and sure as eggs is eggs someone will whack a nail straight into a cable sometime. Furthermore, buried cables are a nightmare if you need to alter the circuitry at any stage......adding sockets for instance.

Mike