Cracks in domestic house. How serious ?

What is the criteria for deciding how serious are external cracks in a domestic ? At what stage of cracking is underpinning required. Would be delighted to receive any information on this subject.

Describe the cracks?

Perhaps you need to find a good engineer to inspect and advise.

Cracks are in the external plaster, running both vertically and diagonally. In one case the crack is also evident in interior wall , presumably it has gone right through the wall. Cracks are all in the same plane. Maximium crack width about 3mm. Hope this information helps.

The fact that the crack is evident in both interior and exterior (presumably in the same location) suggests that serious subsidance/settlement may be taking place.

You need to find a structural engineer to inspect. Not an architect, mind.

Mojos,

you need to put a "tell-tale" gauge on the crack as soon as you can. Think you can get them in Brooks. Get about 4 of them and secure them to the wall. They are fairly evident when you see them....they measure the relative movement across the crack and have a sliding scale to show you.

A 3mm gap is very significant. Water could ingress and cause a lot of damage. If the crack is not moving I suggest you put some waterproof expanding sealant in the joint temporarily until the gauges have had a week or two to turn up anything.

Are any of the windows or doors not closing? That would indicate differential settlement and would impair the use of the building. Don't panic though...houses rarely fall down!!!! But the main thing is not to let water get in.

Come back in a week and tell me how you're getting on. Post a reply and PM me cos I don't get on here that often but I will pick up PM.

If you are filling up the cracks try this system which allows for movement.
Get a spray can or windolene bottle and spray water into the cracks.
Then fill up the cracks with expanding liquid foam which comes in a can, same stuff they use when they fit windows or filling holes in a wall. It is better to buy the foam with the seperate re-usable gun for more control over your work.
When the foam goes hard cut off the excess with a knife. 1-2 hours.
Plaster over the foam with flexible floor tile adhesive normally used for tiling onto a plywood floor.
Then plaster over the tile adhesive inside the house with Gyproc joint filler (comes in a bucket ready to use normally used for filling the gap between two plasterboards) and smooth off with sandpaper.
All of these products can be dry in a few hours ready for painting the same day.
Paint your undercoat onto the plaster and if you see any uneven-ness, plaster over the paint until it is smooth and sand again.
The undercoat and the plaster are similar chemically and can be used like so. plaster-paint-plaster-paint.
For sandpapering it is better to use a sandpaper pad attached to a pole.

Many thanks for all the advice given. Will test first to see if cracks are progressive using "tell-tale" gauge. If not, will seal cracks using the methods suggested.

Have a look at this thread on Boards.ie - it discusses a similar problem to yours - with pictures so it might be useful.

Is it just me or is boards.ie painfully slow most of the time?