Weak mortar used for house construction

[AACS]

In August we moved into a new build property and just prior to completion noticed that the mortar appeared very weak/soft. We mentioned this to the builders and arranged for a surveyor to vist. Before he came the builder repointed large parts of the house so there was little to see.
This has now weathered, along with the remainder which was not done. It is so soft that I can scratch it out with a brass door key without damaging the key and I have recently sawn out some lumps from some of think thicker mortar beds with a hacksaw blade to send away for analysis.
I would be very interested to know if anyone else has come across such weak mortar in their house construction and, if so, what was done to fix it.

[NewHomeExpert]

Yes I have come across it before. It ended up with a whole estate of Bryant houses having the brickwork taken down and re buillt on each house.

What you describe could be due to frost freezing the mortar during construction, insufficent cement in the mix, most likely if mortar is mixed on site, too much or incorrect additives being added to the mortar mix, or the use of old mortar that had started to set and was revived. Or any combination.

You need the mortar analyised before deciding on a further course of action.
Be prepared for a long hard slog to get this issue resolved and lots of being fobbed off by everyone from the house builder, his contractor, his engineer.surveyors, the NHBC and various other "experts".

At the end of the day it aint right and must be rectified and none of this is your responsiblity.

[AACS]

Hi, thanks for your reply.
We have now had the results of our mortar tests back and apparently the mix is up to spec. Even so, there is a completely different consistency between that used on the ground floor of the house to that above.
Our site manager has now looked at things and his reaction was it was it was due to freezing. The weather had been extremely cold around the time.
Does anyone know what that means in terms of how to repair things and the long-term outlook for our new home

[NewHomeExpert]

Proper job: The affected brickwork will need to be taken down and re built using the correct mix and protected from freezing this time!

Bodge job: The mortar joints to the brickwork will need to be racked out to at least half way and re pointed as above.

You will need to make enquiries about haveing the inner skin blockwork checked out too, unless you have a timber frame house. See your NHBC new home card for details or ask the site manager. The inner skin is loadbearing and weak inner skin could affect the support of floor joists and/or roof trusses.

On a good note, at least the site manager admitted that it was the builderr's fault. Get this in writing! if you havent already got it.

[AACS]

The story continues with slow progress. Taylor Wimpey have admitted fault and the bricklaying company (a subcontractor) have also admitted fault.
The solution proposed has been to grind out the mortar to a depth of 2-3 cm and repoint, even though the cement used is still extremely soft and can be scraped away without much effort as I stated in my first post.

At first this was done with a chisel in the garage as the grinders did not arrive on site. This is a single skin wall and in places caused the wall to crack all the way through into the garden side, as well as begining to push the mortar beds out of the wall in some places.

Further, where they have ground out on the house itself, the horizontal beds of mortar appear to be full thickness. They are unable to cut out the fertical beds at the end of the blocks, however, to the required depth, as when they do a hole opens up. The vertical joint is made to a thickness of about 1 inch. I have seen bricklayers working and they often appear to put a thinner skim of the front edge when laying the brick/block, but should the entire house be done like this.

[NewHomeExpert]

Not sure exactly what they are doing from what you say.

It does sound like when the joints are being racked out, more mortar than intended falls or is being pushed out.
This would suggest to me that the wall should be taken down and rebuilt as re pointing (what I think you are describing) is just a sticking plaster.
In the future, in an extreme case, a window cleaner may put his ladder up against the wall and push it in.

You really need to have the NHBC aware of this and making regular inspections.
You may even be wise to get your won expert surveyor to check what is being done with the remedial works.

Quite a few years ago a Bryant (a Taylor Woodrow company) development in Ashington, Sussex that has the same problem.
All the external leaf brickwork was taken down and re built using correct mix mortar.
A big job but at least it was re done properly.