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!

[Saul]

The Builder did their own tests and the result have come back even worse! The at best sample showed mortar with a cement-sand ratio of 1:8.5 but it went as weak as 1:10.5. The builder is claiming this mortar was delivered to site from Marshalls ready mixed. They admit they made a mistake and ordered M4 when they meant to order M6. Clearly M4 which is typically 1:4.5 to 1:6 cannot spontaneously transform to 1:10.5. They subsequently tested 42 other houses and all have the exact same issue. They have begun repointing and were meant to rake out 68mm on the beds and perps across panels no wider than 1.8m. The builder said for safety they were ignoring the Structural Engineer’s Spec and did 60mm on beds and 10mm or perps however they then went much wider than 1.8m so that contradicts their safety argument. The Structural Warranty Provider has since said because this is a material alteration that the Structural Warranty below DPC is now Void but the rest remains. It has also been pointed out that even after remedial work the house now fails to comply with BS EN 998-2 because it is not 100% M6 and the residual mortar that was left has no relative compressive strength. We are about to engage a further investigation into the mortar used above DPC and on the Inner Leaf as we have been told that this was also Marshalls M4 but clearly something has happened post delivery to adulterate the mix. This is hugely stressful and I imagine we’re looking at demolition if the results above DPC and on the Inner Leaf do indeed match those shocking results from below DPC. 

[Chanmenie]

That’s awful, must be so stressful for you.

Sounds like demolition and rebuild is the only safe way forward. 

[Big Jimbo]

Might sound harsh, but can you ask for all your money, and fees back, together with some compensation ? It it a known / large developer ?

[saveasteading]

I agree with @ProDave. It's good to do the homework on the issues but being so precise is giving them something to argue back against. 

Not fit for purpose because it is falling out.

 

On the speculation front. I don't know what happens with premixed mortar. How is it delivered and stored? How long does it sit around before use.

It is possible that it had gone off by the time it was used.

[Saul]

Some samples taken to day from above DPC behind cladding and Inner Leaf by cutting through plaster board. Didn’t need power tools to remove as immediately disintegrated and as you can see looks like pure sand in the bags. Lab tests to follow. This will be put into the hands of professionals and lawyers to work on a proper resolution but looks like a pretty catastrophic problem for us homeowners, the developer and everyone else that lives here because you’d presume 42 houses being flattened would be a serious blight on the development. It seems crazy this could happen! 

[Chanmenie]

Yeah catastrophic sums it’s up.

there were over 80 houses demolished near Cambridge recently due to incorrect foundations 

 

I’m a bit shocked the brick layers didn’t notice ?

Edited February 23 by Chanmenie

[Nickfromwales]

9 minutes ago, Chanmenie said:

Yeah catastrophic sums it’s up.

there were over 80 houses demolished near Cambridge recently due to incorrect foundations 

 

I’m a bit shocked the brick layers didn’t notice ?

Trades on mass build site (sausage factories) are beaten up on price and don’t really care about workmanship. Just spend 30 mins on YouTube to confirm how these houses get built nowadays. 
 

The trades know they’ll never be held accountable so rarely give 2 hoots.

[Andehh]

Ah I'm sorry OP, that's a real shitter! Not being funny, but take comfort there's 50+ others in the same situation!!

 

Have you got legal cover on home insurance?

 

Please keep us updated... But good luck!

[SBMS]

Is this what build warranty is for? Can you use it?

[twice round the block]

4 minutes ago, SBMS said:

Is this what build warranty is for? Can you use it?

You can use build warranty for any structural build issues with your property including garages.

 

NHBC will back peddle as fast as they can and deny all liability.

 

You may need to employ a structural surveyor, one that's also handles litigation cases.

You can also use your insurers if you have building cover.

[SBMS]

10 minutes ago, twice round the block said:

You can use build warranty for any structural build issues with your property including garages.

 

NHBC will back peddle as fast as they can and deny all liability.

 

You may need to employ a structural surveyor, one that's also handles litigation cases.

You can also use your insurers if you have building cover.

Sounds like this is exactly what latent defect warranty is for. @Saul - completely feel for you, sounds awful. I hope it can be rectified without a demolish/rebuild. 

[Saul]

I discovered the issue with the mortar less than a week after moving in. It was therefore raised within the Defects Period which lasts for 2 years so Protek the Warranty Provider don't get involved. They cover the next 8 years. We are instructing a specialist Lawyer and commissioning Structural Surveys including extensive mortar tests above DPC and on the Inner Leaf. Bizarrely the Mortar Supplier has weighed in on this and said that they are happy with the Lab Test Results for the below DPC mortar which came back with ratios as low as 1:10.5. To suggest that such a mix could ever hope to achieve a compressive strength of 4N/mm2 is crazy and we are sure there is not a Structural Engineer on the Planet that would agree with that as an Expert Witness. I appreciate many Mortar suppliers do not adhere to NHBC Mix Ratios for Cement-Sand and instead use Design Mortars that aim to achieve compressive strengths set out in BS EN 998-2 but that surely means there is a range of mix within manufacturing tolerances that would never extend to the results we have back from the Lab so far. Regardless of ratio the lab state that on average over 90% of the material component of the sample was proved to be Sand leaving 10% for Cement, Lime, Blast Furnace Slag, Additives, Whatever. This is going to be a drawn out battle I am sure. Time for the professionals to take over!

[Saul]

Looks like I was wrong about there not be a professional on the planet that would assert that 1:10.5 could ever be used to build a house. They’ve found a mortar specialist Expert Witness that today said you could happily build a house with 1:12! He thinks that mortar test results are meaningless, that sandy mortar and erosion is normal for new build houses which use modern factory cement that contains special ingredients so erosion doesn’t mean it’s not strong enough on the inside. It’s no surprise that the builder is doubling down on their stance that they have used M4 regardless of the evidence. Lab results on my Inner Leaf and Above DPC have come back as 1:8. This is obviously going to end up in Court and be an Expert Witness v Expert Witness decider.

[bmj1]

1 hour ago, Saul said:

Looks like I was wrong about there not be a professional on the planet that would assert that 1:10.5 could ever be used to build a house. They’ve found a mortar specialist Expert Witness that today said you could happily build a house with 1:12! He thinks that mortar test results are meaningless, that sandy mortar and erosion is normal for new build houses which use modern factory cement that contains special ingredients so erosion doesn’t mean it’s not strong enough on the inside. It’s no surprise that the builder is doubling down on their stance that they have used M4 regardless of the evidence. Lab results on my Inner Leaf and Above DPC have come back as 1:8. This is obviously going to end up in Court and be an Expert Witness v Expert Witness decider.

Welcome to the most crooked and corrupt industry on the planet

[Mr Punter]

If there is a big concern regarding the mortar they will offer to rake out and repoint.  There is no way they are going to demolish and rebuild.  If you go to court, be prepared to spend many £1,000s.

 

The house will not fall down.

[saveasteading]

11 hours ago, bmj1 said:

most crooked and corrupt industry on the planet

I beg your pardon. I and many others on here have been in the industry for decades. I don't sell drugs or arms, or ever cheat people.

There are cheats in all industries. What is yours?

 

A joke is OK but not that.