12 Ways to Fix Lath and Plaster Ceilings: Complete Do-it-Yourself Guide for Homeowners by Ian Anderson

Author:Ian Anderson [Anderson, Ian]
Language: eng
Format: epub
Publisher: handycrowd media
Published: 2015-04-28T00:00:00+00:00

NOTE: although some conservation pros advocate the use of a proper ‘mortar mill’ for lime mortars, a conventional cement/ concrete drum type mixer is perfectly good enough for smaller quantities. I prefer the electric versions because you can easily switch them on and off making it easy to test for consistency, add hair, and cleaning out afterwards etc. You can even use a mixing attachment on a powerful drill and a bucket for small amounts.

First Coat

Before applying the new plaster to the laths, make sure they look damp but are not actually dripping.

Push a first coat (called the ‘pricking up coat’ or sometimes ‘scratch coat’) of haired lime mortar up, onto the lath and through the gaps using a plastering trowel and a hawk.

Ensure around half the mortar goes through the gaps in between the laths (thus forming a strong mechanical key), half will then go underneath the laths and half will go on the floor, (I know, I know; that doesn’t add up, but I’m just telling you how it feels, you’ll know what I mean once you get started!).

For the best quality work place small dabs or strips of plaster at intervals, carefully measured and levelled beforehand. These act as ‘screeds’ to work from.

Work on small areas radiating out from your first area. It’s not critical to get this coat perfect, just aim for a consistent thickness straight from the trowel. Aim for 10mm (3/8”) or so underneath the laths. Flatten the plaster out as you go but don’t over work this coat as you might damage the sensitive ‘green’ keys you’ve pushed through the laths.

Once this first coat has started to harden off (time varies on temperature and humidity, a few hours generally), gently scratch up the surface to provide a key for the next coat. You can use a special ‘comb’ type pronged scratcher, or make one from stiff wire or by nailing three short lengths of lath together after cutting one end of them to a sharp point. Spread the laths out like a small fan and gently create wavy lines in the surface of the mortar at 45 degrees both ways to the laths, creating a rough diamond shaped pattern. Not too deep and never through to the laths. Adjust the laths to ensure all three are creating the same depth scratches.

Allow the scratch coat to dry out. This varies and can take up to four weeks, depending upon temperature and humidity. A week or two is normal. Don’t worry about any light shrinkage or cracking and don’t try to ‘correct’ them, there’s no need and you’ll likely damage those all-important, delicate keys on top.

Slow is good when allowing the scratch coat to dry out. Keep humidity high and draughts out.

It’s ready when you can’t dent the surface with your thumb. The surface should still be slightly damp and usually only needs a fine spray of water from your garden sprayer before applying the second coat. If too dry keep wetting it until the surface stays damp looking.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.