Protecting shed walls from damp (Ed.)

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have a block shed with render on outside. the render at the bottom of wall has blown, letting in water. .will be knocking 18inchs of render of this weekend, is there anything i can paint onto blocks temporary to keep out water. will re render when weather improves. thanks.
 
Are the gutters and downpipes correctly leading water away from the shed?

Please post some photos
 
it,s on the side of shed, the roof slopes away, the render at bottom of wall sounds hollow when you tap with a hammer. this side does
get the worst of the weather.
 
photo as requested. its the bottom 18 ins that is the problem. after i remove the old render, is there anything i cat put on the blockwork before i re render the wall.
 

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The mark looks to me like water is dripping off the roof and splashing on the wall

Or less likely, a slope in the paving causes puddles to pool against the wall.

Is the render touching the ground?

Is the wall built of lightweight foamed concrete blocks?

Does water collect in that trough?

Where is the DPC?
 
the paving slopes along side the shed.
the render does not touch the ground.
wall built with concrete blocks..
water does not collect in trough.
dpc. unknown. shed was built on slab, bottom of door is slab /floor level.
this shed was built before i bought the property . thanks.
 
There must be a reason the bottom of the wall is so wet, but I can't see it then.

Would have been better with a couple of courses of bricks (unrendered) at the foot of the wall, plus a DPC (foamed blocks are like sponges) but a bit late now.

If you find a dpc when you hack the render off, use a stop bead to prevent your new render bridging it.

See if you can work out where the water is coming from, and put a stop to it. Waterproof coatings on the wall will just prevent it drying out. My suggestions are of common causes. I presume your shed has no plumbing that could leak.
 
the render at the bottom is cracked. i think this is how the water is getting in. this wall also gets the worst of the weather. with the water running down the wall. no plumbing in shed.
would it be worth using some sort of injection damp proofer on the bottom of wall before i re render. thanks.
 
No, injection doesn't stop damp and is a waste of money.

You could experiment by leaning a large board against the wall to shelter it.

If it is driving rain, shiplap spaced on battens will cure it, and the spacing, plus a kick-out at the bottom, will reduce splashing at the foot of the wall. It must not touch the ground or it will rot. My own shed has a 200mm strip of stainless steel, painted to match, at the bottom of the exposed end.

A cement plinth, or bituminous paint, is often tried, but just shifts the damp above the plinth. Try digging out the trench and filling it with pebbles or cobbles (not shingle). The large stones drain freely due to large irregular gaps so do not splash.

If wind is blowing rain off the edge of the roof, a gutter may help.
 
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