Fixing damp proof course which is leaking over the TOP

[Fromey]

Update:

I've sealed up the minor cracks and cemented up around the protruding railway line (some water was definitely getting in there as the cement was crumbling away around it in parts, so a bit of excavation, treating the metal, re-cementing, and then some sealant just for good measure).

Finally, I cemented up a few scrappy mortar joints in the damp course brick layer and ran a bead of sealant between the top of the DMC and the cement bricks.

It all looked fairly ship shape and water tight. Resisted some minor rainfall.

However, it's just chucked it down and again water is leaking in at the same spot #-o The good news is, it seems to be less =D>

Looking at the wall, there's no way water it's coming in from around the railway line or through the cracks. It might be generally penetrating through the paint as I've not been able to apply a coat of Thompsons yet (I'll hopefully be able to do that next week if it stops raining and the wall dries off enough). However, if it is that it seems a bit odd that the water should emerge on the inside at only one location.

There is still water pooling along the DPC directly opposite the leak point within the shed. Thus, I'm still wondering if wicking over the top of that is the cause. Next week, as a test, I'll pour water down the exterior of the wall in various places and see if I can simulate the rain leaking.

Does anyone know of a type of flashing or drip skirt that can be placed at the base of a wall so the water will run off a little away from the DPC?

 

[Graham Orm]

It's been mentioned earlier in the thread by Phil, you are describing a bell bead, this would go along the bottom of the render usually a course above the damp course to deflect rain out away from the base of the wall.

If you have a Selco near you they have Thompsons on offer for £9.90 plus VAT at the moment. You'll need to wangle a trade card somehow.

 

[Fromey]

Thanks Grayorm. That's my ignorance for not knowing what a bell cast is. Hmmm, that solution looks like it will then need some rendering done. I'll have to do some research. I wonder if rendering direct onto sandtex will work or if some of the paint will have to be stripped off first.

 

[Bod]

A bit off track.
All the gutters, and down pipes are in good condition?
Both on your building, and any others that could send water against the wall. (leaking water butts?)
The bricks, themselves, the type with holes in place of Frogs, could make internal passages, for water from roof level. Bit far fetched?

Bod

 

[Fromey]

Thanks Bod. The shed has no guttering along that wall. I considered that water might be getting in from the roof line and then dripping down, but for instance today's rain clearly showed that the roof overhang shielded the upper parts of the wall. Water had only touched the wall from about 2/3 up and then downwards. Thus, I'm fairly certain water's not getting in from the top level.

I'll see if I can replicate the effect by pouring water on the DPC and if that confirms it as the culprit, I'll evaluate if I'm skilled enough to fit a bell cast/bead/drip. If not, I'll see if a local tradesman can do it for me.

 

[Graham Orm]

Thanks Bod. The shed has no guttering along that wall. I considered that water might be getting in from the roof line and then dripping down, but for instance today's rain clearly showed that the roof overhang shielded the upper parts of the wall. Water had only touched the wall from about 2/3 up and then downwards. Thus, I'm fairly certain water's not getting in from the top level.

I'll see if I can replicate the effect by pouring water on the DPC and if that confirms it as the culprit, I'll evaluate if I'm skilled enough to fit a bell cast/bead/drip. If not, I'll see if a local tradesman can do it for me.

The reason that the DPC has to be 2 courses up is to avoid splash back from water falling on the floor next to it. If your roof drains directly onto the floor next to the wall that may be a symptom of your problem.

 

[MikeJhn]

It is a mistake to not have guttering on any roof that drains onto a wall, brick/blocks are not waterproof except for very dense engineering brick, but as an aside to your damp house problem, there is not such thing as rising damp, it's usually a different water source that is causing the problem, mostly leaking gutters, when was the last time you inspected your gutters in the rain.

 

[MikeJhn]

Thanks Bod. The shed has no guttering along that wall. I considered that water might be getting in from the roof line and then dripping down, but for instance today's rain clearly showed that the roof overhang shielded the upper parts of the wall. Water had only touched the wall from about 2/3 up and then downwards. Thus, I'm fairly certain water's not getting in from the top level.

Flawed thinking, water against the wall at any level will try to penetrate the substrata and eventually build up to show itself on the other side of the wall, you probably have a combination of things causing this problem, but saturation of the cracked and holed blockwork is a major factor and it may not be possible to 100% stop this from happening, long term solution is to divert the water internally to an external drain and build an internal skin if it bothers you that much.