Covering up cracks in internal walls

[Cobber]

Rod - if its lathen plaster do you have any idea what to do with the corner sstrips that I have in a few of my rooms....they look awful. I'm inclined not to replaster as the condition is not too bad apart from the corner strips? I could maybe sand the strips or replace them. I'll take a photo on the weekend as i appreciate its a but hard to comment without a photo.

By the way whats makes you think its lathen plaster?

[rod@plasterbrok]

Lathen plaster is sand and cement render over wooden slats, with a skim coat of hard plaster over it.

The photo shows the slats.

Post a photo so I can get an idea of what you have got.

Cheers

[JIT]

Hi,

Here´s a picture of the cracks across the right side wall at the back of the house, where the living and kitchen area is. I think this area of the house was renovated many years ago by a previous owner. Makes me cringe whenever I see it...Any thoughts...

GSJ

[rod@plasterbrok]

They can be dug out and repaired

[Cobber]

Looks like a bit of work. I have cracks going all around the room in one line also. I will post my photo next week if i remember. If you can fix that then it gives me some hope.

I pulled off one of the corner strip bits and its definetely lathen plaster as there is 2 pieces of wood strips behind it and thick threads.

I am not convinced that the rest of the plaster is lathen though. Half of the house has been demolished I can see the plaster from the back of the exposed house....if it was lathen surely I would see all the strips. All I can see us a white lumpy sheet. The plaster has alot of threads hanging out of it not as thick as the ones from the lathen strip I pulled off.

Was there a plaster after lathen and before the modern plasterboard by any chance Rod?

Thanks

Cobber

[rod@plasterbrok]

Yes fibrous plaster sheet replaced the use of lathen plaster.

Then came plasterboard.

Fibrous plaster sheet typically was made in 2.1 m wide sheets so the join would be at door height and covered by the picture rail. It is a common practice when renovating to remove the picture rails and stop up the join.

We see it often where the stopping hasn't been done well in older renovations and the join cracks. Another problem is the sheet below the picture rail is often thicker than the sheet above giving you and uneven finish.

Cheers Cobber.

[Cobber]

Ah I reckon thats what I have then as there is a gap between or underneath the picture rails. That makes sense then. Fibrous plaster sheet with the horrible corner join strips.

Rod is it easy to fix cracks in fibrous plaster (as per lath plaster). I havent seen much on this website. Is it the same technique as your normal plaster sheets or lathe plaster as described in your website?

Thanks for your help.

Cobber

[rod@plasterbrok]

Treat cracks in the joins of fibrous plaster much the same way as you would a cracked join in plasterboard.

The only thing is the join in fibrous plaster is not rebated, so you can assume any previous attempt to fill them will cause a "lump" like a butt joint in plasterboard.

When fibrous plaster was jointed there was no tape the used to face scrim with hemp. So one way to get back to a reasonable flat surface it to get into it with some heavy duty sand paper and a belt sander. (just along the join and only if you really need to). If you hit fibre STOP. you cant sand any more. If you break through the to the fiber the sand paper will cause the fibres to raise up and it is very hard to coat over them.

If this happens, I have found scorching them is the best way to get rid of them. Take care don't burn the place down!

You will find a thread here on fixing cracks in plasterboard joins.

Cheers

Rod Dyson

[Cobber]

Thanks alot Rod. When I get around to doing it I am sure I will be asking questions. In anycase I'll post some photos at some stage soon.

cheers

Cobber

[johnc]

I don't think we are talking about lathe and plaster at all. If these houses are brick it may apply to the ceiling but the walls sound like solid plaster. Much the same job with a weak but thick base layer and a harder top coat. Look at what Tools said about bridging the gap, there is a product made for the job or bird wire can be used. Get someone in to have a look first, your jumping the gun talking about plastering over etc, when what it may need is a proper repair job. A straight repair will be a lot less fiddly, but may not solve the problem. Ground moisture, drainage etc may be causing a lot of the problem. Large trees, heavy clay soils or just a few very dry years could all be part of the problem.

I think everyone needs to take a deep breath some of the ideas such as sikaflex and plastering over may not produce a very appealing outcome.

John

[rod@plasterbrok]

I would still go with cutting out the cracks to the substate be it bricks or laths and fill them with cornice adhesive with top coat over.

The most important thing is to open the crack wide enough to get the material used to repair right in to the substate.

Using chicken wire or expanded metal, then rendering over is not required in most cases, of cracking in solid plaster or lathen plaster. Definitly not required for simple cracks but is useful if a larger area needs to be rendered, but even then a combination of cornice adhesive and perlite will adhere perfectly. We even make cornices institu, around curved walls to get a seamless finish, with this mix.

Chicken wire or expanded metal is essential if you are rendering over a non porous surface, where the render cannot bond. Eg, painted walls or glazed bricks etc.

Obviously if the cause of the cracking in the first place is not addressed, the most likely result is further cracking.

We did a major renovation of the historical society in melbourne that had very seveer cracking in the solid plaster walls.

They wanted the restoration to be original, as it was on of the oldest buildings in Melbourne and was where Burke and Wills left on their historical journey.

We had to reconstruct 1 meter wide cornices etc that had basically fallen apart.

The buliding had some under pinning done to stop the sinking at the junction of an old renovation. Once this was done we placed plastic tabs on the cracks with markers to see if over a period of time the cracking worsened. When satisfied that the building was secure we cut out all the cracks, removed loose and drummy plaster, repaired them all in the exact manner describe on our web side. For a fantastic result.

Needless to say the reason for the cracking in the first place should be investigated and the building made stable.

In most cases cracking repairs are done after reblocking etc.

[JIT]

Just a quick question, might be an obvious answer, but...why is plasterboard sheeting less likely to crack? Is it much more flexible, rather than "brittle", like other materials?

If I were to do this to the Victorian-era property mentioned at the start of this thread...would the plasterboard sheeting not just crack with further movement????

GSJ

[Ivan in Oz]

G'Day GSJ,

I'm thinking I've missed something.
Is the present cracking in BRICKWORK or
Rendered Plaster?

I'm thinking EPOXY Injection,
BUT
that would only transfer the cracking to somewhere else.

NEXT DOOR ??????

[myla]

hello,

cracking looks like through solid plaster to me and sure if drummy would need to be replaced

this is why a flexible sealant is an immediate fix, as provides continual movement if the "larger issues" are not resolved

as stated need seude effects or textured paint or around 4 coats of quality paint to cover and make presentable

I think GSJ's brief was for a cost affective "fix" and from memory is currently rented and therefore addressed with minimal fuss

thankyou
myla

[JIT]

Ivan in OZ

The cracking is on the plaster I think, cannot see the bricks on the inside, but on the outside walls there is cracking seen on the bricks...what is EPOXY injection?

GSJ