Thermal Expansion Cracks

[Adrian80]

Hi Guys,

I have a 1960's semi which has some cracking on the inside of a south facing wall.

The cracks appear at the end of the lintels and underneath the window on the inside of the building no cracks are visible on the outside in these positions.

I also have a small stepping crack in the outside of the brickwork at the very top of the building on the corner.

I had a brief valuation report when i bought the place and they suggested thermal expansion.

However, what do i do to cure this expansion. I think in better designed buildings they have thermal expansion gaps built in. But my house doesn't.

Is there anything i can do to alleviate this expansion problem, or do i just have to live with it.

From a couple of pictures on websites i have seen top to bottom vertical cuts in the building back filled with a flexible filler at regular intervals. But i bet the bricks along the cuts have more wall ties. Could i do something similar retrospectively.

Thanks for your help in advance.

Adrian

 

[^woody^]

There can be several reasons why thermal expansion/contraction occurs in specific situations in a domestic property, but generally they are a 'once only' event and a more cosmetic issue than a structural one.

Treatment may be filler, replastering or plastering with mesh reinforcement. It depends on the location/severity

 

[Adrian80]

Hi Woody,

Thanks for the advice, the cracks are quite small on the inside (<1mm), but slightly larger on the external face (2-3mm).

I am doing a refurb at the moment so i just wanted to sort the problem out before replastering.

So i guess the solution is to hack off all the old plaster around the cracks, fix a wire mesh over the cracking and the bond and skim over the top.

Fingers crossed they have finished moving!

Cheers Adrian

 

[Shytalkz]

Presumably they're concrete lintels on a block wall? Dissimilar thermal movements, not structural, but may come back from time to time as there's no movement to stop as such (other than initial drying shrinkage that has long since ceased), the wall will always keep on heating up and cooling down. Just one o' dem tings.

 

[Adrian80]

Thanks for your input,

yes indeed a block wall with concrete lintels, then with a brick veneer.

So i guess the concrete, the steel inside the concrete lintels, the blocks (also concrete), and the brick veneer, will all be expanding and contracting at their own rate.

Cheers for all your input!

Adrian

 

[Richard C]

So i guess the solution is to hack off all the old plaster around the cracks, fix a wire mesh over the cracking and the bond and skim over the top.

Fingers crossed they have finished moving!

Cheers Adrian

I’ve had the same problem on practically every lintel in the 60’s property I’m currently renovating. Some huge cracks on the inside including the blocks but no cracks on the exterior brickwork; but I’ve got a top “soldier” course which seems to have been stuck well into the huge cast-in-situ lintels! I hacked it all back & laid on a 300mm wide strip of SS mesh but used a render base not bonding. The earliest cracks have been repaired & plastered for nearly 3 years now with no sign of further movement or even hairline cracking.

 

[Adrian80]

Hi Richard,

Can i ask why render not bonding. Is it that the render is more flexible, or just more durable.

Excuse my ignorance.



Cheers Adrian

 

[Richard C]

The original base coat is render & I’m aware it provides some flexibility; it just seemed to be the obvious solution to reinforce the mesh repairs around the concrete lintels to me. I have used Bonding over mesh on other cracks & they have not reappeared either so I’ve no idea if there is any logic behind my render approach; can anyone else advise if there is benefit in this over Bonding?

 

[Shytalkz]

If you were getting significant levels of differential thermal movement, it wouldnt matter what you used: with mesh, it would be just as likely to move the crack along to the point where the mesh stopped.

 

[Adrian80]

Thanks all for the advice.

I definitely going for the wire mesh, and then try and find a plaster with a bit of acrylic in it. Apparently improves the flexibility!

But as shytalkz says if its that bad it wont make a blind bit of difference. Saying that its got to be worth a shot, and hopefully i can leave the polyfiller in the bag.

If i remember i will report back in a couple of years to the whole world know about the state of my crack

cheers adrian

 

[henllys]

Hi

I was wondering if you have managed to find a solution to your issue with lintels and cracks.

We have just moved into a 1960 house with large windows, 2 - 3 metres in width, when the sun shines on the back of the house we get cracks starting at the top corder of the window casing and going upto the ceiling. The cracks are only on the first floor windows though not on the ground floor.

Once the sun stops shining the cracks disappear.

I am thinking of fitting some thermal cladding to see if that stops the expansion.

 

[Adrian80]

Hi,

No real solution, sorry.

However i did fit some expamet stop bead
http://www.expamet.co.uk/wider-wing-stop-bead

basically you fix the wing over the gap but only attaching it one side. The wall then moves behind the mesh.

It still cracks but just in a straight line. at least its neater and a bit controlled.

A