SIPS building and permitted development?

[rinseout]

I want to build a workshop in my garden (4mx6m roughly) and I was thinking of using SIPS. I don't think it will be too dissimilar in terms of cost compared to a timber frame building. Main reasons for a SIPS building is speed of construction and insulation. They are also supposedly stronger than a timber frame building. A few questions regarding that:

1. Just how much stronger is a SIPS building made of 100mm panels compared to a timber frame building made of 4x2's and osb sheets?

2. How much weight can I hang from the roof internally?

3. Would it be strong enough to support a beam trolley with a 250kg engine hanging off it?


My second query relates to permitted development. 30m2 is allowed, but it can only be max 2.4m in height. It also has to be 1m away from a boundary unless "constructed of substantially non-combustible materials".

4. I live on a hill and the far end of my garden is lower than the front. I can't find the relative information on the permitted development website, but i've read that the 2.4m height is measured from the highest point of the curtilage of the house. So assuming the far end of my garden (where I want to place the workshop) is 1m lower than the patio, I can effectively have a building with a height of 3.4m. Is that correct?

5. I saw someone building a shed on youtube. They were right up against a boundary, but claimed that cladding the shed on the boundary sides with steel sheeting would mean it complies with the regulation. Permitted development regs doesn't go into much detail about this so it seems like a bit of a grey area. Thoughts?

[roscopervis]

You’re confusing building regs with planning regs. Each are separate. You have to comply with both and they are not necessarily the same.

[rinseout]

Apologies, i'm not clued up with building and planning regs. Which part specifically have I got wrong?

[blueg33]

A SIPS panel is basically a closed panel timber frame and structurally there is little difference. It’s down to the size and quality of the framing material. Same materials = basically same strength. However, if you are buying SIPS off the shelf you can’t customise it as you could timber frame, especially if you are stick building.

In terms of load. 250kg is a lot. Where we are manufacturing floor cassettes for care homes etc that have hoist tracks a fair amount of extra material goes in. Unfortunately, I can’t give you the detail as I have engineers and technical managers that sort that stuff out.

[PhilboSE]

SIPs are great for what they are, but it’s quite involved to add additional strength to standard panels. I have no idea what the engineering tolerances of a SIP is but I doubt you’d be able to hang 250kg off one in a roof without significant deflection. Without re-engineering the SIP with additional strength, you would probably have to build a timber or steel frame inside the SIP enclosure.

I built a garden room and I needed a steel goalpost arrangement for some doors, and that with some other details meant I went down the stick build route rather than SIPs. There’s a thread on here about the build, I can dig it out if you’re interested.

You’re incorrect on point 4 about heights; it’s the highest original ground level adjacent to the building that you take, not the curtilage. So if the site you want to build on is sloping, it can work to your favour (as does understanding the exact points on the building that PD takes for height calculations).

Again, my site for the above building was sloping so I was able to build 600mm higher than usual under PD. Again, there was a thread on here about the principles, discussed in detail with a planning consultant who used to frequent this forum, and it was all ratified with Lawful Development Certificate by the Council.

Edited by PhilboSE on Sunday 10th August 07:20

Edited by PhilboSE on Sunday 10th August 07:21

[PhilboSE]

Re point 5 and building materials, there isn’t a precise definition of “substantially”. Fundamentally you can do what you want, until it’s challenged. If so, you’ll have to justify the materials in a way rather more detailed than “I saw a bloke on YouTube do it s as nd he says it was ok”. Easiest thing is to build 2m away from the boundaries, if you can.

[smokey mow]

rinseout said:

5. I saw someone building a shed on youtube. They were right up against a boundary, but claimed that cladding the shed on the boundary sides with steel sheeting would mean it complies with the regulation. Permitted development regs doesn't go into much detail about this so it seems like a bit of a grey area. Thoughts?

The YouTuber needs to understand the difference between “constructed from” and “clad in”. Steel is an incredibly good conductor of heat.

There is no steel cladding on the market that will stop a combustible building from catching fire if exposed to the heat of a fire.

[blueg33]

smokey mow said:

rinseout said:

5. I saw someone building a shed on youtube. They were right up against a boundary, but claimed that cladding the shed on the boundary sides with steel sheeting would mean it complies with the regulation. Permitted development regs doesn't go into much detail about this so it seems like a bit of a grey area. Thoughts?

The YouTuber needs to understand the difference between “constructed from” and “clad in”. Steel is an incredibly good conductor of heat.

There is no steel cladding on the market that will stop a combustible building from catching fire if exposed to the heat of a fire.

Steel generally performs less well structurally in a fire than timber.

[DonkeyApple]

Personally, I'd build the shed however you wish to give you the result that you desire. Timber frame is probably easiest if you have space to construct the sides on the floor but sips, especially if a kit will not be much different. I'd then just add a steel goal post internally exactly where I'd want to be hoisting and engine out but to be honest, using an actual mobile engine hoist seems more sensible as you can then move the engine away from the car opposed to having to move the car from the engine etc?