Large crack in new kitchen extension

Wailin

Kitchen extension was completed last May and about 2 weeks ago I noticed the large crack shown in the pics below. Should I be worried about this? Rang the builder who said it's nothing to worry about, just settling. Said he'd have a look but I reckon we will find it hard to get him back out. Thoughts folks?

Four Phucs Ache

I'm no expert but it looks like that is where the parapet dpc would be placed. Maybe the mortar hasn't taken to it and wind has weakened the join ?

Wailin

You could be right, but I don't think there is dampcourse along that line if I remember correctly. Removing and re-mortoring the blocks is a no no though as the fibreglass roof runs up that inner parapet and would be a major job to sort. I wonder would just sealing the crack be enough?

Metric Tensor

What is the wall buildup in the extension Wailin?

Blockwork and insulation - in what order and what thicknesses?

And also: What is the structure of the roof? Fibreglass on top of what else?

Wailin

Cavity block with plaster on outside as you see in photos, inside walls are battoned and then insulated plasterboard. No cracks at all on the skim inside.

The roof was a plywood (I think) structure with the fibeglass then coated over a mesh.

A photo of the roof:

Squatman

fwiw, im no expert, but i would say you need not worry. doesnt look like an issue

Metric Tensor

Bearing in mind that I'm going on a few pictures my guess would be that the crack is caused by expansion/contraction of the roofing timbers as they dry out.

That's only a guess though.

Best advice with cracks is always to monitor them over a period of time to see if they are changing size. You can purchase a cheap device called a "telltale" to do this.

Wailin

Cheers lads, I'll just keep an eye on it. I'm not worried about the thing collapsing...more about water eventually getting in through the crack if it expands more.

Bonzo Delaney

Where did you get the roof lights looks fairly cool

massy086

Bonzo Delaney wrote: »

Where did you get the roof lights looks fairly cool

Not sure about that zoom and and you can see the inside was never plasterboarded .Op why did the builder not finish it ????

Bonzo Delaney

massy086 wrote: »

Not sure about that zoom and and you can see the inside was never plasterboarded .Op why did the builder not finish it ????

I understood it as a pic taken during the build

antiskeptic

Wailin wrote: »

Cheers lads, I'll just keep an eye on it. I'm not worried about the thing collapsing...more about water eventually getting in through the crack if it expands more.

I'd guess osb sheeting was nailed to the upstand blockwork to form a substrate for the fibreglass. The hammering dislodging the blockwork.

Dont imagine itll collapse but expansion/contraction will make sealing up tricky.

Perhap cut a strip of render to expose the mortar line then cut out the mortar in short section and refill, let dry, do next short section. That just deals with the outside mortar line. You could drill across each block web (with a mortar depth diameter drill) and ram mortar down to tie across the block. Alternatively, inject chemical anchor glue down the same hole, ramming it as you go.

Then re render

Wailin

massy086 wrote: »

Not sure about that zoom and and you can see the inside was never plasterboarded .Op why did the builder not finish it ????

Taken during build last May, plasterboarded and all painted. Lead flashing also not done in that picture.

DOCARCH

Wailin wrote: »

Lead flashing also not done in that picture.

Noticed that!

Just wondering were the parapet walls built up in timber stud? Is cracking due to different materials/substrate.

Wailin

No as far as I can remember it was built with 9" blocks on the flat, on top of the cavity blocks for the walls.

Carpenter

We're the roof lights off the shelf.

Wailin

No idea, builder supplied and fitted them.