Damp problem - new breeze block shed

bar_1

We built a breeze block shed (one layer of brick top and bottom), on a raised base at the back of our garden in the summer to use as a home gym. It has been plastered inside and has been scratch coated on the outside. However, whenever it rains we get damp along the bottom and tops of the walls, mainly along one walled in particular. It also appears around one of the windows too.
Will having the top coat of render on the outside solve this? We were told by our plasterer (my bother in law) the scratch coat would waterproof it and the top coat was more for insulation. If not do you know what other causes might be.

ariba10

A single layer of breeze block will be very difficult to keep dry in the sort of weather we have at this time of year.

The damp walls are probably facing the prevailing wind.

bar_1

Thanks Ariba 10. Does that mean we are going to have to replace bricks in the future? Are you saying the rendering will not help?
The walled mainly affected is not very protected from the weather at the moment but we can erect a fence to help.

ormus

think it would be better with a new render and then pebbledashed.
the flint pebbledash has very good waterproofing qualities.

bar_1

Hi ormus,

Thanks for the advice, I hadn't thought of that. So you do the render then leave to set then do pebbledash?

ormus

NO!:)

you do it at the same time. the plasterer will know how.
basically, you do an area and then chuck the pebbles at it with a shovel.

evilgoose

You could try something like thompson water seal on the worst effected walls - but remember this acts both ways - so as well as locking moisture out it can also lock it in, so if you have alot of condensation it could worsen that unless you have good ventalation.

benood

If it's a gym then likely as not it's condensation - heat and ventilation may cure it, or perhaps insulation we had damp/condensation problems on an old house and used a system called oldroyd plus extra insulation which solved it. Good luck.

owls

hi

im a plasterer by trade.

pebble dashing will not make any difference as regards making it water tight. the chap who has done it, is correct your waterproof agent for any external dashing/plainfaced render is mixed in with your scratch coat ie first coat,and your top coat is insulation

has the blockwork got a damp proof course? if so he should have set his bellcast bead [drip bead] above this damp course to prevent any mosture going up the render and being locked into the single cavity wall.so it could be rising damp with the bell cast being set up wrong or a number of external faults. or any internal condensation problems. it is obiously very diificult to make a jugement without looking first hand in person though.

as mentioned once rendered on a single cavity wall ie one thickness of blockwork, once it has been rendered leave for a few months to weather then silicone seal the external wall this will solve any external problems as once it has been sprayed on water will run down the wall as opposed to being absorbed through the wall.

bar_1

owls wrote: »

hi

im a plasterer by trade.

pebble dashing will not make any difference as regards making it water tight. the chap who has done it, is correct your waterproof agent for any external dashing/plainfaced render is mixed in with your scratch coat ie first coat,and your top coat is insulation

has the blockwork got a damp proof course? if so he should have set his bellcast bead [drip bead] above this damp course to prevent any mosture going up the render and being locked into the single cavity wall.so it could be rising damp with the bell cast being set up wrong or a number of external faults. or any internal condensation problems. it is obiously very diificult to make a jugement without looking first hand in person though.

as mentioned once rendered on a single cavity wall ie one thickness of blockwork, once it has been rendered leave for a few months to weather then silicone seal the external wall this will solve any external problems as once it has been sprayed on water will run down the wall as opposed to being absorbed through the wall.

Hi Owls

Thanks for the indepth reply. Is it expensive to silicone spray? I assume it is something we can do as non professionals? Is it something we can pick up at the local DIY store.

ps - thanks to everyone for taking the time to offer advice.

bar_1

Another thought I had after speaking with my dad about the problem yesterday was that the damp patches only appear at the top and bottom of the building or around the windows. Indicating that it is getting through gaps, so in this case water proofing the whole thing wont help..?

We have used stuff to seal around the windows and the roof and made a small concrete slop around the rim of the base for the water to run off.
Any suggestions?