Subsidence or plaster issue

3 Apr 2020
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United Kingdom

I moved into a 12 year old house a couple of years back. Basic survey at the time came back clear.

Cracks appeared a year after moving in. I filled the cracks and house was freshly painted at the time but since then cracks have re-appeared in the plaster.

All cracks run horizontal from window ledge to window ledge. PVC windows. See photo.

I am considering paying for an advanced survey to rule out subsidence. An architect has told me it is noticeable where the blockwork was changed on the exterior walls. Would this be the cause? There are no visible cracks outside.

Is this just a weakness due to window frames? Blown plaster?

I should add - walls are cold and need insulated - could this cause it? There is a large tree in the garden - what’s the chances of internal-only cracks being subsidence?



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MikeTech12, good evening.

To be Subsidence then there MUST be external cracking as well as what you see internally.

The cracks in the posted images appear to be where two different substrate materials meet, such as two different types of block [say breeze and Thermalite?] or brick and block on the inner leaf only?

Yes there is a well known horizontal [generally] external crack where a crack forms horizontally, in this specific case the old iron wall ties are corroding, the rust build up actually forces the brickwork to separate and a horizontal crack occurs.

As an aside you did a good job filling the crack last time !

Any chance of an external image of the affected area?

Hi Ken,

many thanks for your reply. I will post a photo of the exterior but unfortunately I don’t think it will add any info to this. To me the exterior looks the same from top
to bottom. There isn’t a single crack on the exterior. However - an architect did comment and say that he could see where the brickwork was changed in the exterior mid-build. Not sure what that means.
Looks like a plasterboard crack. Is it plasterboard?

Horizontal cracks are not typical of foundation movement.
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I assume it’s plasterboard - how would I know for certain?

The cracks are mostly horizontal - from window to window although some slight vertical cracks - again from window. They only appear on the upstairs windows. No cracks at all downstairs.

if I can rule out subsidence then I guess the fix is for a full replaster job as patching it up each time will just mean the issue will re-occur
If you tap the areas of plaster above and below the crack line, if Plasterboard then you get a "hollow" sound, if the plaster is on to block work or brick then the sound is solid, not hollow.

As for a fix, depends on what noise you get when you tap the walls?

Would suggest you consider a plaster repair, but right over the junction of say brick to plasterboard you leave a slight gap, then cover over the crack with a surface mounted timber rail?? making it a Dado rail around the room??

Thanks very much for the advice.

Yes there is a slight hollow sound when tapping it.

Will see what I can do myself and worst case will get a plasterer.
Plasterboard cracking needs to be repaired with a mesh tape across the joint, else it just keeps on cracking afterwards.

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