Garden Office project

22 Oct 2015
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United Kingdom
Hey all...

I'm in the process of designing a new garden office to replace an existing T&G Log cabin that's had it's time...

The office footprint is going to be 4.8m wide x 4.2m deep, and will come in under the 2.5m height for permitted development. I'm intending to add a small kitchenette and a cloakroom so that I can work down there all day without having to go back to the house for a brew or to use the toilet. :)
Under the existing log cabin is a 100mm MOT1 base, so minimal effort required there.

The main things I'm not sure on right now are
  • Timber frame vs SIPS.
  • Drainage.

Timber vs SIPS:
Based on a quote from SimplySIPs, it looks like a SIPS structure is going to be ~£1.5-2k more expensive...

Pro's I can see from going SIPS is that it's quicker to build, and potentially better insulated.
Con's are that it's more expensive, and it will also result in a sloped internal ceiling, whereas I'd quite like to have flat one. It will also make it difficult to install downlights, without battening out 50mm+ which eats into head-height again...

Any thoughts? Things I've possibly missed?

The rough design I'm looking at is:
Garden Office view.png

We're quite fortunate to have quite a long garden, at ~30m from house to bottom of garden.
The office will be sited at the bottom of the garden, so any drainage run will be around 30m. There's also not a direct line between where I want to install the toilet/kitchen and the closest sewer manhole. And to add to all that, the last ~3m of the run is currently concreted over, so will need to break through that aswell... :(
The fall should be OK, as the existing manhole is below the level of where the office will be.

This pic gives a better illustration.
Garden Layout - Base.jpg
The 2 brown X's are where the toilet and kitchen sink will be placed, and the brown square is the nearest manhole cover. Blue and Red are where I'm intending to run Power + Comms and Water feeds. Orange hatching is concreted areas.

My initial thought for drainage is this:
Garden Layout - Drainage 1.jpg
The only issue I can foresee is that I'm intending to build decking on the front of the Garden Office, which would potentially cover the manhole there. However I guess could build an access hatch into the decking...

Anything else I need to think of?

Thanks in advance.

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If you add a WC, won't you need Building Regulations approval at least?

if it starts to look like living accomodation, I have an idea you'll need PP as well.
If you add a WC, won't you need Building Regulations approval at least?

if it starts to look like living accomodation, I have an idea you'll need PP as well.

I hadn't thought so initially...

However just checked again, and looking at I might end up having to apply, due to both the internal floor area in relation to distance from boundary (18m2 and less than 1m), and adding a WC connected to mains sewer...

Looks like I need to do some more research on this area specifically...
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Timber frame. For sips you will need crane access.
I've got side access, so don't think getting the panels in will be an issue.

I'm inclined to go with SIPS currently, as saves a load of time getting to a waterproof shell. And I think the time saving is worth the £1500 price premium.
So things have moved on a bit since my last post, and I've put a deposit on the SIPS panels.
Main reason being that the price difference came down to ~£1k, which given the fact that it should be possible to build in a day, versus probably 4-5 days for a traditional timber framed construction is worth it to me.

So I've got just over 4 weeks to get all the services run in before the panels arrive...

Time to start a project thread I think :D

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