My house was built in about 1970 with a brick outer wall and breeze block inner wall. In one bedroom, there is a horizontal crack in the plaster at just about the level that I would expect to find the mortar joint underneath the top breeze block. The crack extends along one wall from a corner for about 8 or 9 block lengths. This wall carries the roof. Around the corner, the crack only extends about one block along. A few years ago, when only this one non load bearing block showed some cracking in the plaster, I investigated and found that the whole breeze block was loose and could be removed. I replaced it using some epoxy adhesive to try to re-join the original mortar joint and replastered that small part of wall.
I am now worried that the blocks in the load bearing wall are also loose, either because the original mortar was poor and has failed or because the roof is moving in some way and “rocking” the breeze blocks.
The crack is not wide and fades out within the length of 8 or 9 blocks mentioned above. There are no visible cracks in the outer wall.
I am interested in any thoughts on the problem that might relieve my worries or substantiate them but mostly I am wondering who is the best person/trade to come and look at the problem and give reliable advice on what to do about it. Would giving this advice be the role of a structural surveyor, or civil engineer or who. In the past, I would have talked to the local general builder but nowadays these seem rare around us. They are all either little better than odd-job men or part of some large organisation that is interested in large projects that make a lot of money. I am unconvinced that either are fit to advise on what could be a trivial problem or a major one and could bridge several areas of expertise.

  • Mark Brinkley


    It might be that the roof is moving and has pushed the bloc work out of position. There is a bit of ironmongery known as a wallplate strap which should in theory connect the timber wallplate on top of the load bearing wall with the blockwork beneath, usually going down three or four courses. I wonder if they got fitted?

    You don’t say if the roof itself is triangulated by a ceiling height collar, or if it’s a trussed roof. These roofs shouldn’t deform unless an extra weight has been placed on the roof (solar panels?). However if the roof has long rafters which aren’t tied into the main roof, it is possible for the roof to speed a little which can put a strain on the supporting walls. Usually this would show up from the ground – does the roof appear to sag at all?

    If you can’t reach a diagnosis yourself, then a structural or building surveyor is the person to hire.

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