Outbuilding

[TK46]

Hi there, I have a large single skin brick-built shed with a sloping flat roof (felt) and a concrete floor that sits four courses below the level of the surrounding ground level. As a result damp is constantly penetrating through those four courses.

I intend to turn the shed into a liveable room for use as an office.
First thing then is to deal with the penetrating damp. I initially looked into applying a damp proof membrane paint to the interior of the bricks but upon speaking with Bostik was informed the product was unsuitable in preventing hydostatic pressure.

Next I researched a tanking slurry. I looked at the Sovereign K11 http://www.sovchem.co.uk/tanking/hey-di-system.html

and the much cheaper alternative KA tanking slurry http://www.randjbuildershardware.co.uk/ka-tanking-slurry-25kg.html

I had thought I had found my solution. A builder came around that I had contacted via checkatrade.com and he advised me against using a tanking slurry due to its ineffectiveness. He said I should building an interior wall (like a house) from thermalite blocks instead, cost £1500.
Apart from the cost, I'm not keen on losing so much space.

Another builder told me that I should dig out the surrounding ground and coat the OUTSIDE of the bricks with tanking slurry then backfill with dirt since he claimed that with the outside of the bricks being damp all year around and being very porous and the inside painted in the slurry, the bricks would crumble over time as the damp had nowhere to go.

Once I have the damp issues taken care of I was thinking of painting the exterior of the building with a clear brick sealer and then simply screwing battens to the walls, fitting insulation boards between, and then fixing plaster boards over the top of that.

Would this work? Would I get dampness behind the boards? Behind the insullation board? I was also considering eco-quilt as an alternative... http://www.ecohome-insulation.com/?i=1033453

What do you guys think, my head is spinning. lol

 

[fishcake]

Can you not just raise the floor level?

 

[TK46]

Can you not just raise the floor level?

Unfortunately no. Its the first thing I considered. The external height of the building is just over 2 meters. If I brought the floor to the level of the door threshold I would be bumping my head against the ceiling lights. I've also noticed that due to the uneven terrain the damp course rises and falls across the brickwork. So it runs under the door (the threshold is on top of the 2nd course) but at other areas the damp course it on the 5th course at its highest. This would actually be ABOVE the height of the proposed raised floor.

 

[Deluks]

Builder 2 is on the right track, dig it out and don't backfill it with anything but a couple of inches of shingle or gravel. Retain the soil somehow, something as simple as concrete gravel boards and angle iron hammered in. Or could use cut down concrete fence posts for a neater job.


Like this

If the ground isn't free draining and backs up with water, remove the gravel and install some perforated pipe, taking the water away to lower ground.

Guttering and a water butt would be useful too.

 

[TK46]

Builder 2 is on the right track, dig it out and don't backfill it with anything but a couple of inches of shingle or gravel. Retain the soil somehow, something as simple as concrete gravel boards and angle iron hammered in. Or could use cut down concrete fence posts for a neater job.


Like this

If the ground isn't free draining and backs up with water, remove the gravel and install some perforated pipe, taking the water away to lower ground.

Guttering and a water butt would be useful too.

I have to backfill with something, I can't have a mote encircling the building.

 

[dhutch]

I have to backfill with something, I can't have a mote encircling the building.

We dont know the layout, but its not uncommon to have a retaining wall around the building. If its not that deep, maybe only 6inchs wide, or if its more than about a foot, enough to get in to clear it.
- Obviously if the ground is higher on all sides, rather than say just round the back, you would then need to provide a way for the water to drain out of it, which may also include helping surface run of go around the retaining wall no over/through it to reduce flow.

The other way of doing it, and what was done on my parents garage, is to run a damp proof membrane up the wall, blockwork, perforated pipe at the bottom, and back fill.

But you can expect a single skin, also acting as a retaining wall, to remain dry on the inside!

Daniel