1:6 mortar used below DPC

[Saul]

Posted about this before but now extremely concerned so would appreciate comments / advice.

 

My house is built on a Piled Slab with Rendered Block Work. The Damp Proof course of S2F2 Bricks have been laid using 1:6 mortar as confirmed by Independent Professional UKAS certified Lab Report. To be honest you don’t need a lab report as the mortar is washing out every time it rains and if you tickle it with a screwdriver it falls apart like a sand castle on Margate Beach. The side elevations have stronger mortar in places so clearly different batches but the majority of the front and rear are extremely sandy. (Also a side note, not sure why the front protruding pillars are not sitting on the concrete base but appear to have some kind of pad stone below them.

 

The house was signed off by building control and has a 8 year Protek warranty that kicks in after the builders 2 year warranty. They are being very slow to act and insist this is 1:3 mortar but it very clearly is not. 

 

I’ve been asked not to contact my house insurance, mortgage provider or warranty provider until they have conducted their own tests.

 

I’m very worried the house has the structural integrity of a Kit Kat and that it will be condemned and need bulldozing and rebuilding.

 

Cheers

Saul

[ProDave]

Your complaint is not about the mix of the mortar, but the fact it is crumbling and falling out.

 

No point claiming it is 6:1 and they counter that it is 3:1, it is still crumbling and falling out.

[nod]

Bulldozing the house is unlikely 

More likely is the joints raked out and repointed with a stronger mortar 

[Chanmenie]

Even 1:6 mortar should not crumble, so it might be even weaker or there’s another issue causing the crumbling 

 

[Saul]

I thought building regs were 1:3. Their test will apparently be witnessed but I still need to ensure the sample taken is the one that makes it to the lab. But yes whatever the technical mix it clearly isn’t doing its job. The DPC was laid in April and I’ve been in 3 months. When it rains and bounces back up at the mortar it gets visibly wet and holds the moisture and then as it dries it sheds sand like in this photo. I sweep it away and then there’s more after the next rainfall. This gradual erosion is on top of the chunks falling out like in the vertical gap shown in original post. Hopefully they’ll agree to rake out and repoint. The DPC membrane is also recessed 25mm in several places. They scraped out some mortar for a small section and added a thin strip of membrane but watched them and it looked like a right bodge. The retaining wall behind the house was done with engineering bricks and grey mortar and is solid but that was a different contractor. 

[Chanmenie]

You are correct below DPC recommended is 1:3

thats what I used and you’d struggle to scrape it with a chisel, even when wet.

being that strong it also looks dark grey even though the sand was very light in colour, but I did use Mannok Cement which is quite dark, but even with normal Portland I’d expect it to look more grey in colour than in your pictures

[Saul]

I feel like the 1 part of the 1 to 6 was optimistic as it really does fall apart like a sand castle with very little agitation. A crack has appeared along the entire side elevation. I’m sure they’ll pass it off as just in the render and part of the process with a newly built property but I’m expecting to see more signs of instability given what the exterior wall is standing on. Photos of the block work internally show that the mortar is grey in colour so it’s just this DPC course of bricks that were laid a short time before the block work was done. Still waiting for the contractor to attend to inspect/carry out their own (“witnessed”) tests. Very stressful!