Movement joint

[WWilts]

1) Movement joint in SE design, one mistakenly omitted by builder (see diagram). BCO does not mind, apparently. 
Should the movement joint be included from now on? (accepting that the lowest 665 mm will have no movement joint)
Or should we insist that the movement joint be inserted in the 665mm height of masonry that has already been built without it? (context: junction of stone quoins and brickwork)

 

2) How to make movement joints airtight and weather proof? 
Expanding foam and silicon bead?

[Brickie]

665mm is only 9 courses of brickwork,can he not take it down & build the MJ in? 
Brickfill or similar should be used during construction & then mastic applied for weather tightness once finished. 

[saveasteading]

It may be only me but I question that movement joints are always needed. You build this perfectly goo traditional masonry wall, then insert weaknesses.

There are no such joints in old houses.

 

Bricks expand for a while after manufacture, while concrete blocks shrink, and the new walls can be very stressed. If you can afford to let the materials  sit on site for a few weeks in typical weather, then likelihood of a problem from that source is removed.

 

Not expanding foam (out of a tin) please: it seals but is not flexible, and tends to spread more than is desired. There are expanding foam tapes specially made for this: you squeeze them smaller then they gradually fill the gap tight. Then seal with , again, special mastic filler which are flexible and also grip the sides...the name's I can't remember at present.

[TonyT]

Can you not have your expansion joints behind your gutter down pipes?

helps hide them a bit!

[WWilts]

3 hours ago, TonyT said:

behind your gutter down pipes

Yes

[WWilts]

3 hours ago, saveasteading said:

I question that movement joints are always needed.

Insufficient knowledge here.

Our simple thinking is that they are deliberate & controlled cracks inserted in the structure, to reduce the risk of unpredictable cracks later.

Awaiting SE advice on whether that particular M joint can be omitted

[saveasteading]

1 hour ago, WWilts said:

Awaiting SE

Yes take their advice, as they will see the circumstances.  But they are not likely to say that they designed for a joint and now it doesn't matter after all.

My point I suppose, is that if you happen to know that the materials were already stabilised, then the SE might just think that could be ok.

(sometimes blocks arrive on site that were made the day or week before, and they are guaranteed to shrink, or bricks are still war from the kiln and guaranteed to expand.....and then there are problems without joints)

 

keep us informed please.

[Temp]

As I recall they are only needed in walls over 11m long. Thought they were normally put in the middle of the wall. We have one. Looks like its sealed with a foam sheet similar to perimeter insulation used around concrete floors.

[WWilts]

Outcome: Movement joint put in.
Reason: cosmetic, not structural. To reduce the risk of cracks developing in the stone around that area

[saveasteading]

59 minutes ago, WWilts said:

Movement joint put in.

You mean they have cut it in retrospectively?

[WWilts]

7 hours ago, saveasteading said:

cut it in retrospectively?

Yes

[George]

On 12/12/2021 at 12:10, saveasteading said:

It may be only me but I question that movement joints are always needed. You build this perfectly goo traditional masonry wall, then insert weaknesses.

There are no such joints in old houses.

 

Bricks expand for a while after manufacture, while concrete blocks shrink, and the new walls can be very stressed. If you can afford to let the materials  sit on site for a few weeks in typical weather, then likelihood of a problem from that source is removed.

 

Not expanding foam (out of a tin) please: it seals but is not flexible, and tends to spread more than is desired. There are expanding foam tapes specially made for this: you squeeze them smaller then they gradually fill the gap tight. Then seal with , again, special mastic filler which are flexible and also grip the sides...the name's I can't remember at present.

 

Old houses built using lime mortar don't need movement joints. 

 

While movement joints are something of a sledgehammer to crack a nut, there isn't a very good alternative, especially for cavity walls (lots of bed joint reinforcement or altering the layout to avoid the need).

 

The differing expansion/contraction is dealt with by wall ties inherent flexibility. The different direction of the movement and characteristics of brick and block means the spacing and type of movement joints are different.

 

It is something that requires an element of engineering judgement and builders aren't always the best at putting them in. But, better to put in MJs than be dealing with an unpredictable cracked wall in future.

Edited December 15, 2021 by George