Brick/block shed renovate

[GB13]

Morning all, hope you're all enjoying the lockdown and getting lots done around the house !
I've got a brick shed (mainly dense concrete blocks) and I'm looking to convert it into a "summerhouse"
It's 5m long X 3m wide with pitched roof - all water tight. T'was build before I move in. Its down the end of my garden right next to boarder so don't want to knock it down and start again as I'll probably have to move it due to planning and would cost 20k for something new.

There's no DPC and I doubt the floor has a DPM either.

Plan is to put external insulation on - either batten, celutex, DPM and clad with wood or ........ block foam insulation (glue and special screws maybe 90mm) skim and then clad with wood ( I like the wood effect).

Inside put batten on floor and celutex then OSB then wooden floor ?

Issue/advice. Not sure about whether I need to "tank" the walls and floor. It does get a very small bit of damp in the cornered occasionally.
Should I tank walls and put DPM down before I put floor insulation down ?

Also re the external insulation anyone tried the batten, celutex and clad method. Not so sure about it.

Obviously I'll plaster inside and out celutex in-between rafters etc.

All advice welcome. I'm a novice but fairly handy at most things - plastering etc.

 

[JohnD]

If the floor has no DPM, damp will constantly rise through it and cause damp and condensation.

items placed on the floor will become literally wet underneath as it cannot evaporate, and this will cause wood to rot and metal to rust.

Is the damp corner near the leaking gutter or downpipe?

 

[GB13]

Thanks for the reply JohnD.
There are no leaking gutters.
I think the damp, of which there is little, comes from no DPC, so the damp is being brought in from the walls. I couldn't see myself digging up the floor and putting DPM down or retro fitting walls with DPC, hence why I mention the tanking and whether you can paint something on the floor that would do the same.
I've no knowledge around this area. You tube makes me even more confused but I'm sure it's possible to come up with a solution.
BTW there's very little damp but you could just lay a floor on top. You would have to treat the floor with something, then put a DPM down ?? Then batten and celutex, then OSB, then flooring. ?? Not overly sure.

 

[JohnD]

Where does the downpipe from the gutters go?

can you post a photo of the wet corner please, inside and out.

And photo of an external wall, showing at, and a foot above, ground level.

Is the concrete above external ground level?

Shed sounds fairly modern

 

[GB13]

The shed is about 15 - 20 years old. I moved in 10 years.
The gutter runs into a water butt on one side but the other side just drips off the side into the soil ! I see where you're going with this.
Same side I get a bit of damp.
No photos yet. Will take some tomorrow.