How to build a garden room- flat pack or scratch?

[mallangong1]

We want to knock down the small existing shed in the garden and replace it with a garden room. Am I best:

a. Buying an off the shelf timber "garden room", probably 33mm or 44mm T&G - which sometimes pop up second hand on eBay. I would then insulate and plasterboard it.

b. Build one from scratch?
If building one from scratch is the solution would I be best making a frame from 4x2, covering with breathable membrane, batons and cladding, then internally fill the frame with cellotex, cover with non-breathable membrane and then plasterboard?

c. Use SIPs - if so, how easy are these to use?

Sorry if this is very basic - just trying to work out the best approach early on.

 

[ntb]

It depends...

You will have to weigh up the costs of each option vs your skills and free time to do the work.

I would use plywood in preference to plasterboard if building it myself.

 

[mallangong1]

Thanks NTB. I'm fairly good at DIY and keen to get stuck into a project. How difficult are SIPs to work with and is there any reason to use them over the other options?

 

[AronSearle]

The point of sips is to make an well insulated and airtight build, whilst maintaining a thin wall.

If you plan to use celotex the difference won't be that significant, depending on build quality.

The biggest weakness of using celotex is workmanship related, and gaps in the insulation.

You can either make the wall panels on the floor, butting up the studs to the insulation to ensure a tight fit. Or erect the frame, insert the celotex between the studs, and use expanding foam to fill the gaps. The first option is better as the expanding foam is not as good as the celotex, but frankly this is passive house type stuff.

And it's basically a shed.

If you buy a 'log' cabin and insulation it, ideally you insulate the outside, batten out for a cavity, and install cladding. If you do this then think about the roof overhang, and how much this allows you to bring the wall build-up out by. Insulation on the inside is not recommended, due to the risk of moisture penetrating the 'log' structure and being trapped.

The only difficult thing about sips is how you join the panels, and it's not that difficult, just needs more precision and thought to do a good job.

The below shows corner and panel joints.

http://www.hemsecsips.com/downloads/SIPs_Typical-Details_2013-Flat.pdf

 

[ntb]

Sips are completely over the top for a garden room imho.

If you are up to building it yourself then you can have exactly what you want to the dimensions you desire (subject to planning) and will get a great deal of satisfaction from doing it. You will probably find another pair of hands useful at times so rope a mate in if you can.

I wouldn't bother with the extra expense of celotex. EPS70 polystyrene will be fine bonded around the edges with expanding foam - but buy a foam gun rather than using the hand held cans. Far easier and wastes a lot less foam.

 

[NoniMK]

I am also building a garden room/posh shed with sips and would love to know how you got on with yours