SIPS Garden Office Project

[Ferdinand]

I'm building one!

 

Previous thread for reference:

 

The project is an 8x12 garden building to be used as a standalone utility room for a small house.

 

The ground conditions are solid - outdoor loo removed decades ago, and used as a parking space, then various bits of limestone and concrete put on there over the subsequent 3-4 decades. I personally had two lorry loads of stone put on that side. Approx half is over an existing estd. 100mm concrete slab.

 

Elements (and budget):

 

1 - Basic building. A SiPs kit from Simply SIPS, which gives an insulated 8x12' kiosk faced with OSB3, with a 5ft wide doorway for £1335. 97mm SiPs with U value of 0.3. Thicker panels not required as it is not designed for full day occupation in winter. Need to fetch it from Spalding - allow £100.

 

 

2 -  Doorway. I will pay between about £600 and £800 for a custom made and fitted PVCu door and glass side panel to a pair of French doors for that gap, including locks and fitting, with a U-value of 1.5 or so.

 

3 - Base. Either 2" concrete slabs - £1 per square foot = £100, or 2" concrete slabs on Adjustable Support Pads which will allow me to adjust things after it is built if anything moves by changing the heights. 25 support pads ~ £100.

 

4 - Rainscreen Cladding. Box section plastisol coated corrugated at £10 per sqm including overlaps. Area required for walls ~ 25sqm => £250. Trims and special screws and things add £100 => £350.

 

5 - If I choose to batten out the corrugated for air circulation then approx 50 CLS length at £1.80 each => £90 plus £10 for bits and pieces ~ £100.

Or 125m of roofing lath 30p per metre ~ £50. May be a better option as this is tanalised.

 

6 - Roof. It comes with a 1:40 fall towards the back. EDPM membrane. Say £150 including adhesive and trims etc.

 

7 - Captain Belt 'n' Braces may suggest a breathable membrane round the walls under the battens. 25sqm => not very much to buy. 

 

So for the groundworks and the building we are now at £2750 or so.

 

In addition and not included:

 

8 - Electricity supply requiring FCU and switch in house, then about 2m of armoured cable, garage CU for lights, a ring main to power 3/4 double sockets, a small water heater, potentially a small fan heater for short periods, and a ventilation fan. Need a real electrician as it is for a rented house.

 

9 - A path down the side.

 

10 - A privacy fence across the front.

 

11 - 2 men approx 2 days to build it.

 

12 - I hope to build it such that it can be easily dismantled and relocated.

 

The only fly I have in the ointment is, I think, that I need to watch the height carefully wrt permitted development.

 

Ferdinand

 

Edited July 15, 2017 by Ferdinand

[Ferdinand]

The things I would welcome advice on, in addition to general comments are:

 

1 - EDPM roofs. Quality, trims, how easy they are to work with, and how do I detail the overlapping down the sides?

 

2 - What breathable membrane to use under the rainscreen?

 

3 - What type of ventilation. I am thinking of a Vent-Axia Lo-Cardon Tempra P - which is a heat recovery fan with a boost cord and trickle mode that can be set to run permanently for about £5 a year. Would a trad bathroom fan with backdraft shutter be better?

 

4 - Given washers etc should I do the interior with exterior varnish so that moisture goes through the ventilation setup?

 

Cheers

 

Ferdinand

Edited July 15, 2017 by Ferdinand

[Tennentslager]

2 hours ago, Ferdinand said:

The things I would welcome advice on, in addition to general comments are:

 

1 - EDPM roofs. Quality, trims, how easy they are to work with, and how do I detail the overlapping down the sides?

 

2 - What breathable membrane to use under the rainscreen?

 

1. EPDM is just like the stuff an inner tube from a tyre is made of, basically a big sheet if rubber, so it's soft and easy to fold, tack and stick.

I sheeted my roof in 22mm OSB and then screwed through the OSB to attach lengths of 4*2 underneath, on the edge. I then lapped the EPDM around and under the 4*2 so there was a drip bead. you can also add a trim on top of the edge for a nice finish.

Its very easy to work with and if you use contact adhesive on the edges like Evostick it will be there forever. For the main part of the roof (i.e. not the last 200mm at the edge) you use latex adhesive which is cheaper, more watery but not as much bond strength. This can go on with a cheap roller or brush. Use a cheap roller or brush because you will be throwing it away afterwards!

2. I use any stuff you can get from Gumtree or cheapest...the rainscreen is keeping 99% of water off so the membrane is not doing much. Cross battens will leave a good gap and plenty of room for air flow.

[Ferdinand]

5 hours ago, Ferdinand said:

2 -  Doorway. I will pay between about £600 and £800 for a custom made and fitted PVCu door and glass side panel to a pair of French doors for that gap, including locks and fitting, with a U-value of 1.5 or so.

 

Looking around, I may be able to get a good set of French Doors in the right size from ebay for about £100-200. Save 20% on the project.

[lizzie]

This is a very interesting thread. Following. Thank you