Damp joist why and what can I do about it?

[BathDIY]

I have a 1970's house brought about 6 years ago.

Just had the radiator replaced and noticed damp on all the joist ends along the entire length of our dining room. It's on the external wall, at ground floor.

Outside the DPC is about 5 bricks above path level.

Any idea of what's causing this, and what might be done about it?

 

[tell80]

So the joist tails, like the one in the pic, are going into pockets in an outside wall?
There's a DPC showing below the blockwork and the joist tail.
Assuming you have a cavity wall with brick on the outside skin, can you post a pic of the outside at low level showing the ground and the DPC?
Do you have any signs of water damage inside along the dining room?
Have you tried to probe the damp areas on the joists to look for wood rot?

Its possible that the staining that looks like damp could be preservation fluid painted on each joist tail before installation?

 

[catlad]

Is it damp to the touch, it doesn't look too bad.

 

[BathDIY]

So the joist tails, like the one in the pic, are going into pockets in an outside wall?
There's a DPC showing below the blockwork and the joist tail.
Assuming you have a cavity wall with brick on the outside skin, can you post a pic of the outside at low level showing the ground and the DPC?
Do you have any signs of water damage inside along the dining room?
Have you tried to probe the damp areas on the joists to look for wood rot?

Its possible that the staining that looks like damp could be preservation fluid painted on each joist tail before installation?

Thanks for getting back to me...

No sorry, it is a cavity wall, by external wall I meant it's not internal to the property.

Can't see any signs of dampness inside the dining room.

Cant detect any rot on joists, perhaps seems damp to touch it's hard to tell.

Outside pictured below as requested, the path is crap, I know.

I do know we have insulation that's blown in (the bead type) am assuming this could cause issues in the DPC area?

 

[^woody^]

If not that pipe leaking, you have a cavity bridge. Deal with it from the outside, remove some bricks, clear the cavity.

 

[JohnD]

To my eye, the internal wall looks wetter above the DPC than below, which is unusual. I wonder where the water is coming from? Is it mostly wet beneath that window, or near the pipe, or the same all along?

Watch to see if it gets worse after a rainy spell.

Please stand back and take a wider pic, including gutters and any pipes in the wall.

 

[BathDIY]

If not that pipe leaking, you have a cavity bridge. Deal with it from the outside, remove some bricks, clear the cavity.

It's not the pipe it's all the way along across all joists.

The challenge is we have loose insulation blown into the cavity (done before we brought the property) so if I remove bricks this will pour out.

Also, should bricks be removed above or below the damp proof course?

To my eye, the internal wall looks wetter above the DPC than below, which is unusual. I wonder where the water is coming from? Is it mostly wet beneath that window, or near the pipe, or the same all along?

It's the same all along, even where there is no exposure to rain on the outside (where the extension comes into play).

When I look around other houses in the area, you can see real differences between newer brickwork and old, the bricks seem to get really porous over time.

 

[JohnD]

Blown mineral wool does not pour out. Polystyrene balls can.

The water looks to me like it is lying on top of the DPC, as if it is getting into the cavity

 

[BathDIY]

Polystyrene balls can

Yes, that's what we have, sorry for the confusion.

What do you suggest I do to fix the issue?

 

[JohnD]

You could drill a 1" hole from the inside, just above the DPC. That will tell you if it is full of builders rubble (or maybe water will run out)

If only balls, stick your finger in the hole.

I've cleared sand and rubble out of a cavity, raking and using a builders vac with metal extension tubes. A remarkable amount came out.

I don't know a solution to running polystyrene. Tip in some more in the loft?

 

[BathDIY]

You could drill a 1" hole from the inside, just above the DPC. That will tell you if it is full of builders rubble (or maybe water will run out)

How close can I get to DPC a couple of cm above?

Is this a potential fix or just diagnostic?

 

[JohnD]

Diagnostic.

If it full of water you want to find out why.

If it is full of rubble you want to rake it out.

Drill just high enough not to damage the DPC. Maybe at a mortar joint. Or the blocks will be fairly soft.

 

[BathDIY]

Got it thanks, that's very helpful will give it a go.

 

[^woody^]

Beads don't fall out like an egg-timer. You take out one brick, the upper most and and then pack the cavity with a rag or bag, then the same for the other bricks.

 

[BathDIY]

Beads don't fall out like an egg-timer. You take out one brick, the upper most and and then pack the cavity with a rag or bag, then the same for the other bricks.

Thanks for the reassurance, will do as you suggest.

Excuse my ignorance am assuming I remove the bricks from the outside below the DPC say at least a brick course below to avoid damaging the DPC?