A gaps has developed where our extension meets the house?

[acknowledged74]

Hi

Please take a look at the images below. We had a 2 story extension done 5 months ago.

I would expect some cracking inside with the change of season etc, however vertically where 2 walls meet inside the plaster upstairs and downstairs has cracked right the way down. This on its own is not necessarily a huge worry but as you will see from the images the mortor join outside also seems to be 'pulling away' a little from the existing house. Its around 3mm when maybe 3 months ago it was 0mm.

I saw that the bricklayer used these strange brick tie things to connect the existing to the extension, and at the time it just seemed a really light weight way of doing it.

Basically there were strips fixed vertically to the existing house and these right angled ties clips into the vertical strips and between the mortor or around every 3 bricks of the extension.

Should I be worried?

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[RonnyRaygun]

Looks like a shrinkage crack, probably due to drying out of the brickwork in the recent hot weather.

The crack is pretty much uniform all the way up; would be more of an issue if it was wider at the top as this would indicate some rotation of the foundations.

The wall starters you describe are the correct method of tying new brickwork to existing and is designed to allow some differential vertical movement between new and existing.

 

[^woody^]

Looks like a shrinkage crack, probably due to drying out of the brickwork in the recent hot weather.

Its typical movement crack caused by differential movement/settlement of the newer addition

It will always occur and what should have been done is the joint pointed with a flexible mastic and not inflexible mortar.

On the inside, the joint should have been covered with plasterboard so that movement does not crack the finish where the old and new walls meet

 

[indus]

Looks like a shrinkage crack, probably due to drying out of the brickwork in the recent hot weather.

Its typical movement crack caused by differential movement/settlement of the newer addition

It will always occur and what should have been done is the joint pointed with a flexible mastic and not inflexible mortar.

On the inside, the joint should have been covered with plasterboard so that movement does not crack the finish where the old and new walls meet

Woody, if you were to use flexible mastic then wouldn't the joint line stand out like a sore thumb and draw attention to the extension being an add on?

Thanks

 

[HERTS P&D]

You wouldn't see it as it is behind the down pipe.

Andy

 

[cjard]

[quote="^woody^";p="2837162Woody, if you were to use flexible mastic then wouldn't the joint line stand out like a sore thumb and draw attention to the extension being an add on?

Thanks

More of a sore thumb than the Liberty bell there?

 

[^woody^]

Woody, if you were to use flexible mastic then wouldn't the joint line stand out like a sore thumb and draw attention to the extension being an add on?

Thanks

Mastic comes in lots of colours nowadays. It wont stick out more than a cracked joint!

But yes, as HD says, the downpipe could be fixed across the joint too

 

[maltaron]

Personally I would say that is a botch job. Wall starters are OK on the inner skin and where the outside is rendered, but with face brickwork the new wall should be toothed in to maintain the bond. The bricks don't match either.

 

[jay679]

Personally, if it was my extension then I would have wanted the outer brickwork toothed in. I would also be concerned that the downpipe does not appear to go into a drain, but just spills out onto the broken concrete, which in itself appears to be a bit of a mess.

 

[RonnyRaygun]

Personally I would say that is a botch job. Wall starters are OK on the inner skin and where the outside is rendered, but with face brickwork the new wall should be toothed in to maintain the bond. The bricks don't match either.

The main problem with toothing in is that there is still the risk of differential movement between the existing and new buildings. New buildings tend to have deeper foundations, trees may have been removed etc etc. If the extension moves vertically at a different rate from the original building there is still a risk of cracking at the join. It could end up looking more unsightly than wall starters.
It's more expensive too.

Agree though that the bricks should match, although it's often the case that they don't as searching out a particular brick can be time consuming and costly.

 

[dann09]

I find the point under discussion pretty interesting, and have often wondered which way to go: "starters" or toothing".

We've never had a call back from using either method, and back in the day, before starters became popular, it was all toothing (poor work was just butted up and pointed).

For sure, site conditions can determine if a choice is available, altho i'm inclined to starters and mastic/movement joint. Why? Because i've seen lots of examples (of work by others) of toothing cracking.

However, i do wonder about how in the trades we've come to place such reliance on "mastic" applications, and what this will mean down the structural integrity road?

Does anyone have examples of starters actually being pulled out by differential settlement, or rotation?

 

[^woody^]

Personally I would say that is a botch job. Wall starters are OK on the inner skin and where the outside is rendered, but with face brickwork the new wall should be toothed in to maintain the bond. The bricks don't match either.

No its not a botched job and is the correct way of doing this type of thing nowadays

The slightest bit of movement of the new work and toothing cracks - in fact cracks just like it has done in the photo

Also, matching bricks does not mean identical bricks. Even the same bricks would not be identical to the old ones and the mortar would be different too

 

[stuart45]

Extensions usually look better when set back from the facework 4 inches.
That way the joint does not show up as much. Also when building metric bricks against older imperial sizes you are not governed by the old gauge making the bed joints much bigger.
Wall starters are a real bonus nowadays compared to when we had to spend time toothing out.

 

[acknowledged74]

So we are basically happy that my house isn't falling down then?

They don't do the same brick any more, so it was either trying to get loads of replaimed or get as close as possible.

The guttering by the way is a dummy just to try and cover the join.

 

[simonjay]

Looks like a shrinkage crack, probably due to drying out of the brickwork in the recent hot weather.

Its typical movement crack caused by differential movement/settlement of the newer addition

It will always occur and what should have been done is the joint pointed with a flexible mastic and not inflexible mortar.

On the inside, the joint should have been covered with plasterboard so that movement does not crack the finish where the old and new walls meet

The correct way is certainly polysuphide mastic, but it is expensive in the quantities required to run a good deep bead up 2 stories, and I have never seen it used on domestic extensions. I have seen it a lot on commercial buildings though. If the new wall is a cavity wall, a slight crack in mortar will not cause much problem.