Converting Log Cabin into Granny Annex - Insulation Advice Needed


Postby jim the plumb » Mon Aug 11, 2014 7:26 pm

Hi all.

In the garden we have a 6m X 3.6m summer house. It was here when we bought the house and has over the last 3 years been mostly a dumping ground and junk shop.

I was planning to knock it down and build a timber framed replacement as a granny annex for my parents who one day will find themselves alone.

So I then began thinking of costs - I already have a fully built timber frame building - watertight, dry and full of spiders!
What if I just converted the existing building?

So. My plan is as follows-

1. the 2 inch single skin walls will become internal walls.

2. Wrap the entire building in IKO breather membrane.

3. Fit 90mm ecotherm insulation to outside walls.

4. External wrap of plywood.

5. Second layer of IKO.

5. 25mm timber battens to create air gap between second IKO layer and final cladding which will probably be Cedral weatherboard from Marley Products.

What do you think? Any holes in my project?

Thanks for looking, jimbo.
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Postby welsh brickie » Tue Aug 12, 2014 10:53 am

how about spray foam the inside, and clad the inside with tongue and groove timber,
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Postby jim the plumb » Tue Aug 12, 2014 2:30 pm

Thanks Welsh brickie.

I've never thought of that before. It seems messy though.

I plan to plasterboard the internal walls and don't want to reduce the internal dimensions by too much. I'm doing it like a timber stud frame building except I'm working inside out, rather than outside in. If that makes sense.

The log cabin will need to be raised onto concrete beams with a dpc on each beam to protect the timber bearers from rot.

Once it's finished, you'll never know it was once a log cabin. It will have a warm insulated metal roof and kitchen and shower room.

I'll try and do a blog once we start. I'm just getting info on the insulation so that I do it correctly.

Jimbo
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Postby welsh brickie » Tue Aug 12, 2014 5:05 pm

its not messy, and a cheaper option, the U value is high its only 20mm thick, waterproof, and with the timber clad internally condensation issues wont affect it. Try sales@foamseal.co.uk
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