Damp Ingress - Solution Needed

[Skavenger]

Hi;

So I have built a block and timber workshop in my garden up against an existing single skin block wall (border of the garden - my wall). The problem I am having is I am still getting damp ingress in part of the wall and cannot really use the workshop until it remains dry as it will be used for electronics and 3D printing.

After clearing away the back side of the wall and re-pointing and repairing some cracks it was still letting damp through so I thought the solution would be to render it on the outside.

To waterproof the wall I applied a Scratch Coat of Sharp Sand, Cement and Water / Plasticiser on the back side of the wall a couple of weeks ago and have been keeping an eye on the wall but it is still getting damp in the same upper area. I intend to put the top coat on when the weather picks up.

In the same location on the back side of the wall is a an extra course of blocks used to form a buttress. I did not render this thinking that the additional thickness of extra block would be sufficient but I am now thinking that water is seeping through the first and into the second course.

If I render the buttress and then put on the second coat of render over the entire wall do you think that this will solve the problem.

There is no way water is getting in anywhere else as far as I can see as the roof has now had the first stage of FiberGlass and a full facia board.

This affected wall faces West which gets all of the prevailing weather.

Some pics:

As hot from inside showing the damp area back left, the top two rows of blocks were added by my to bring the height of the wall up to that on the R/H side. I used Medium Density blocks.
The darker damp area appears to be in line with the buttress.

The back of the wall showing the scratch coat and non rendered buttress:
At the base of this wall when finishing off the rendering I will bevel out the bottom of the render to avoid water sitting on the bottom blocks that the wall appears to be sat on.

Other areas of the wall remain nice and dry:

 

[Doggit]

Where's your DPC

 

[^woody^]

Where's the roof drip?

Looks like it coming off the roof

 

[Ian H]

I think you would normall have an angled piece of plastic under the fibreglass that goes into the gutter, if you aren't having a gutter the fibreglass would have an angled piece under the top to stop water running off.

 

[Skavenger]

Sorry but the picture of the rear of the wall may be a bit confusing.
The FiberGlass Roofer has not yet finished, he has put on the Edge and Drip Trims, laid one layer of Fiberglass and fiberglassed where the trims join. The run off is from the rear to the front so what you can see in the pic is the rear Edge Trim. The Drip trim is on the opposite side of the roof and will run into a gutter.

What looks like a drip in the middle is dried fiberglass.

Where's your DPC

In this existing wall there is probably no DPC at the bottom but I have run a DPC along the top of the wall between the Block and the Wall Plate.
At the bottom where there is no DPC I will be laying some render angled out to deflect any water run off away from the base of the wall.

Where's the roof drip?

Looks like it coming off the roof

I don't believe it is coming off of the roof, as explained at the start of this post the Roof Drip is on the opposite side of the roof (out of picture). The render appears to be dry.

I think you would normall have an angled piece of plastic under the fibreglass that goes into the gutter, if you aren't having a gutter the fibreglass would have an angled piece under the top to stop water running off.

That's at the front on the opposite side of the roof.

 

[Doggit]

I think you need to pick up a cheap damp meter, and asses the levels in the wall to determine the highest areas; that'll give you a better indication of where it's coming from. You've rendered the outside, but might need to put a waterproofer in the top coat - Woody can advise better on that I suspect. As the wall was an original one, it wouldn't have had a DPC in the base to stop rising damp, and whilst the concrete blocks would be okay it can rise through the mortar joints, so you might need to look at injecting a silicone dpc in the lowest course. I haven't been able to look back on your earlier pictures, but did you put a fillet on the 3 rear edges of the roof to direct the water down towards the front, or at least on the sides.

 

[^woody^]

I don't believe it is coming off of the roof, as explained at the start of this post the Roof Drip is on the opposite side of the roof (out of picture). The render appears to be dry.

And yet the damp blocks and white salts go right up to the roof!