Repairing cracked plaster in victorian terrace.

[morrik27]

I'm having a deilema with replastering the front room of my grans house, it's not been used for a while and the plaster is only held on with the wall paper on the outer wall, in one corner the crack goes up onto the ceiling.

I'm fairly happy about taking it back to the brick and making it good on the wall.....

BUT, where the crack goes across the corner of the ceiling, and froms a small triangle, I start to worry!

I'm used to skimming plasterboards - but i'm guessing there wont be any on this ceiling, as it's not been looked at for about 50 years!!!

What should i expect to find under this if i take it (or it falls off)? would it be thin battons like wattle and dawb? if so could i just put over some bonding wix, then finish it, or would the whole lot need to come down and be reboarded?

 

[JohnD]

I expect the ceiling is Lath and plaster. a section of plaster has probably come away by the nibs breaking off. this is common from war damage. It is possible to re-stick the plaster, but you need access from above to remove the broken nibs, some of which will have got between the laths and the plaster.

Or you could pull it down (which makes a lot of dirty dust) and nail up p/board.

If you try to nail plasterboard over (under) the old L&P, you will probably have bumps unless you remove the loose nibs as above.

You can hire an industrial vacuum (like an oil drum) to do it quicker but need accces to the upper surface.

 

[morrik27]

Oh (rats!).

Would it be possible to remove the plaster to reveal the lathe....then (if all is good) go over with bonding mix? [might this be looked at as being a cowboy finish?]

Or if the nibs have broken off, take them back to the last joist and replace them? Or are them nailed in from above?

It may be worth mentioning that the triangle in the corner is a continuation of the crack along the wall, and that ( i suspect), the only thing keeping it attached is the paper on the ceiling...

 

[JohnD]

the "nibs" are where the fresh soft plaster has been pressed up against the laths, when the ceiling was made, Some of it squidged between the laths, upwards, then bulges or flops sideways. as it sets, these are the things that hold the plaster in place. If you go into the loft and look at the upper side of a ceiling you will see what I mean

You can't exactly "replace" nibs, but what you can do, is put a hard flat board under the sagging plaster, brace it to lift it back into place, then pour a runny mix of finish plaster down from above. It bonds with the plaster and also spreads over the laths, so that when hard it hold the plaster in place and you can take the boards away. I have done it out of interest in an old house. it is an old technique not often used now but you will find it in old plastering manuals, and in restorer's books.

You have to vacuum the upper surface of the ceiling to remove dirt and broken-off nibs. You have to pluck anything that's between the underside of the lathes nd the upper side of the old plaster. If any laths are missing, broke or eaten, you can screw Expanded Metal Lathing to the sides of the joists so that your pour will stick to it.

If the plaster falls off but the laths are in good condition I see no reason why you couldn't plaster up into them. You may need to find instructions on the mix and technique as it has not been common practice for 50 years or so.

If you are a pro plasterer and you learn these two techniques, you might be able to make money as a restorer of old ceilings, as you can repair ornate old ceilings using the "lift and pour" method. You have to support them so they don't fall down while you are working, though.

 

[morrik27]

Great! that makes it sound less harrowing than before... (I'm no pro plasterer - but i do love it, just so relaxing and rewarding), i digress!

Hopefully the lathes will be in ok nick (bearing in mind that this room has not been decorated in at least 60 years, and that the ceiling is probably original (189?).

If the lathes are eaten,broken, would it be possible to replace them from the last good joist? - is it likely to be an 8x2?

Would EML be suitable to patch over a small area of brocken lathes, run it across two joists - the crack that makes the triangle runs across the corner with the two wall side about 8inches long, so i'm guessing it might be about a square foot in the corner.

Would i need to mix something like horse hair into the mix when replacing the ceiling?

 

[Nige F]

I expect the ceiling is Lath and plaster. a section of plaster has probably come away by the nibs breaking off. this is common from war damage.
.

Do you live in der bombenn Alley I hav seen der failing plaster in der remotest parts of your shizen little island vere ve vould`nt haff vasted der luftenfuel it is your crapzen vorkmans und der pass age of time. Knauf for der ceiling

 

[JohnD]

maybe

but I grew up in London where most older houses had been shaken up by falling bombs and Vs. Hence cracked ceilings and trapezoid doorframes. No doubt it can happen even without war damage.

 

[morrik27]

This house is in an area, where there was very light bombing during our nations trouble history. In more recent years the council however decided to put in speed bumps, so that the student boy (and girl) racers, lorries and postoffice vans could scream down her road and use them as BMX ramps! One of these is about 4feet from the front of her house.

After looking into this i found a site (several references in fact), to the effect of " large diaganal cracks can be attributed to high loading, and areas of regular and strong vibrations.

Our city council is great! they sting people for all the money they... NO!! I WILL NO USE THIS AS A VENT FOR MY ANGER! sorry, but i love my granny!