How to repair Lath and Plaster Ceilings

Uh oh….. you’ve got a period lath and plaster ceiling that needs some ‘love’ hmm? I’ve been working with lath and plaster for more than 30 years so read on and learn what you can do to get years more life out of your plasterwork and what to do if it’s beyond economic repair.

(p.s. if you want to remove your lath and plaster ceiling, you can head over to the “” page instead).

Most people agree that traditional lath and plaster ceilings (and walls), really add charm and enhance the feeling of living in a period house. Eventually though, old lath & plaster is prone to cracking, sagging or even falling down. The good news is that it’s often possible to repair lath & plaster ceilings (and walls) and make them last a good while longer (if you like the look and feel). For those that have gone too far and need replacing with something else, we’ll look at the different options open to you.

What you choose depends on the look or feel you’re aiming for, your budget and your ‘tolerance’ of erm…..how can I put it; ‘rustic’ surfaces! It’s also a universal truth that the ‘flatter’ and most ‘long lived’ repairs cost more to carry out and the older your lath and plaster, the more work it’s likely to need.

OK, enough blurb, lets get started……

Here are the Top Ten Eleven Ways to Repair Lath and Plaster ceilings and walls

Pretty much in order of cost/complexity/longevity…….

Re-decorate the Plasterwork As It Is The most minimum work, arguably not even a repair but basic maintenance. Vacuum to remove dust, (wash down, if required) and then re-decorate, preferably with a lime based paint (if the ceiling is completely original) or most likely with suitable water based paint. Not a good repair if the plasterwork has gone beyond the cracking stage, i.e. sagging badly, so this depends on the plasterworks condition. Cost: Very economical and quick. Pros: Period charm in abundance. Ideal for very old cottages that don’t have a straight edge or surface in them. Shows imperfections. Cons: Possibly very short term solution for damaged plasterwork and even potentially dangerous if really bad! Not a ‘flat’ finish. Shows imperfections! Repairing Cracks in Lath and Plaster (Ceilings and Walls) If the plasterwork has cracked or crazed but is still firmly adhered to the laths then you could simply fill the cracks and blemishes and redecorate. First scrape out all cracksand vacuum out loose material. Prime the cracks with a suitable primer like unibond then fill cracks and small blemishes with decorators’ filler using a suitably sized scraper or drywall spreader. Push the filler in at 90 degrees to the crack and then press to flatten out and scrape off excess by running the scraper along the crack. Gently sand the filler flat if necessary (shouldn’t need much) and vacuum all dust away. Fine cracks could be filled with a flexible decorators caulk and smoothed over with a damp flexible scraper. Wash down if required and re-decorate. Cost: Economical repair. Pros: Retains period feel. Looks good initially. Easy and quick repair. Cons: Might only last a few years depending on plasterworks original condition. Repairing Loose and Small Sections of Missing Plaster Small areas of missing or loose plasterwork can be re-plastered, preferably using similar haired lime based mortars and plasters. If these are not available to you, then areas could be re-plasteredusing modern lightweight backing plasters and finish plaster (non protected ceilings only). Ensure that loose plaster and dust is removed and damp the area a little before re-plastering. Ask at your local builders merchant for suitable plasters. Cost: Economical to medium repair depending on size of area. Pros: Retains period feel. Fairly quick repair. Cons: Needs reasonable DIY Skills. modern plasters might be too ‘rigid’ alongside your old plaster leading to some cracking. Might only last a few years depending on the surrounding plasterworks condition. NOTE: It is popular to see folks recommending to completely ‘re-skim’ old plasterwork with a thin ‘veneer’ of modern gypsum based plaster, say 3 or 4mm thick. Whilst this can tighten up the plasterwork on an old wall, it can cause cracking later due to the relative stiffness of the new plaster in comparison to the underlying lath and plasterwork. Sorry! Using a Thick Lining Paper A sound (ish!) lath and plaster ceilings appearance canbe improved greatly by the use of a good quality, thick lining paper. Lining paper has the benefit of ‘tightening’ everything up and giving the ceiling an uniform look. It can then be decorated however you wish (ironically, some are painted to look ‘distressed’!?!). It can be a good idea to scrape out and fill cracks as No.2 before you glue a thick grade of decorating lining paper over the plasterwork, as lining paper will ‘shrink’ into any cracks and unevenness. Re-decorate as you wish. Cost: Reasonably economical repair. Pros: Retains period feel. Could gain many more years out of reasonable plasterwork. Cons: Relatively difficult on uneven surfaces. Won’t stop further cracking over time if surface is still moving. Using a ‘Glue’ System to Fix Sagging Plasterwork Plasterwork can be ‘glued’ back into place by drilling holes in the plasterwork, vacuuming out the dust and injecting a suitable tube type adhesive. The plasterwork is then gently pushed back into place and supported untilthe adhesive dries. There is even a ‘system’ available in the states called ““, or you can see an video that explains the principles here:- . A popular way is to drill 4mm holes, slightly countersink the holes, vacuum then squirt a thin adhesive into the hole followed by the drywall screw. Gently tighten the screw up into the countersunk plaster. Push up and support any sagging plasterwork first onto blanket covered lengths of timber gently wedged up to the ceiling. The guys at ‘Old House Online’ have a great artice that explains how to glue up a sagging ceiling perfectly… . Cost: Medium to high cost, depending on time taken and plasterwork condition. Pros: Medium term effectiveness. Retains period feel. Cons: Arguably a specialised job and may be too fiddly for some DIY repairers. Removing the Whole Ceiling and Exposing the Existing Beams Completely remove the lath and plaster, de-nail and clear away. Wire brush all plaster marks off the joists. Re-route any wiring, if required andrepair any damage, holes in the timberwork etc. Clean up and vacuum all surfaces. Leave as is or decorate with varnish, wood stain, or paint. Often strips of plasterboard are fixed in between the joists on small lathes nailed onto the side of the joists to hide wiring and the underside of the floorboards above. Usually just used on ceilings (walls sometimes in the USA due to better sawn lath). Cost: Economical to medium depending on timberwork condition. Pros: All the old plasterwork is removed and finished with newly decorated surfaces. Cons: Different look and feel, arguably only suited to certain properties and owners. Difficult electrical wiring and limited choice of light fittings. Overboard with Plasterboard or Sheetrock A lath and plaster ceiling can be left in place and ‘over-boarded’ with plasterboard, using long drywall screws through the existing lath and plaster into the joists (not ideal but, quite commonly done). You will hear this option discussed a lot and for many itis considered the ‘only’ option, mostly to avoid the horrible mess created by complete removal! First you need to find what there is to fix your new plasterboards too. Usually ceiling joists or studs in a wall. Find them using the old way of drilling a line of holes 20mm (3/4″) apart where you suspect there is timber. You will feel the resistance when you hit wood, mark it and continue to find the other side of the wood. Now you know how wide the wood is and where it is. Next Mark their position on the wall, about 25mm down from the ceiling. Now you are ready to over-board with plasterboard (sheetrock) using long (60mm to 75mm) drywall screws into the timberwork where you have marked. Board joints are then taped and filled if tapered edge drywall is used or skimmed with finish plaster if square edged boards are used. An even better way to overboard a ceiling or wall is to ‘batten out’ first. Here, appx 25mm x 50mm battens are fixed flat, underneath the existing lath and plasterwork, byscrewing through it, into the existing ceiling joists. The battens could also be packed level/flat using thin plastic or timber ‘shims’ as they are screwed tight. Plasterboards are then fitted as normal, (often incorporating, new wiring, insulation and a vapour barrier). This becomes a good repair as the battens secure the old plasterwork and the plasterboard gives a ‘new’ finish, plus the convenience of easy cable runs for new lighting. Cost: Medium to high. Pros: Effectively a brand new surface is created out of plasterboard/sheetrock. Cons: Potential problems with adding additional weight or levels if there is a cornice. Loss of ceiling height. Loses that period feel. Replacing the Plaster and Lath with Plasterboard Completely remove the lath and plasterwork and replace with plasterboards / sheetrock. Once the existing ceiling is down and cleared away, mark the positions of all joists and timbers onto the walls. Then fix 12.5mm plasterboards to the underside of the original joistsusing 38mm drywall screws as normal. Use the marks on the walls to snap a chalk line onto the plasterboards, showing you where to place the screws. Board joints are then taped and filled if tapered edge boards are used, or skimmed with finish plaster if square edged boards are used. Cost: High. Removal of old material, new boards and finishing makes this one of the most expensive options. Pros: Plasterboards/sheetrock are stable and very flat. A permanent repair. Cons: Loses the period feel. Re-plastering with Traditional Lime Mortar and Plaster A rarer alternative to complete removal, is the removal of the sagging and broken plasterwork, repairing the existing laths (or replacing them) and re-plastering with a suitable two coat haired lime mortar and a third coat of lime finish plaster. You may need access to the top of the laths to clear away the ‘keys’ or mortar ‘snots’ that were pushed through the gaps in the lath the first time. Cost: High, due to special skills and materialsneeded. Pros: Good as new finish, that also matches the surrounding period work. Long term repair. Cons: Arguably not a DIY proposition due to work involving lime plasterwork. Fully Repairing a ‘Protected’ Lath and Plaster Ceiling Given enough time and money even the worst ceilings can be rescued, as you would  have to do to satisfy the authorities if your ceilings were historically valuable. Briefly, fully support the plasterwork from underneath on blanket covered timber on props or staging. Working from above, gently remove all the accumulated dust, debris and old loose keys or nibs that build up over the decades or even centuries (dust masks essential!) Repairs can then be carried out using one of the various lath and plaster repair systems available. Often using stabilizing chemicals, wire mesh and adhesives or plasters, with the aim of reattaching the plasterwork below. For example; one system involves fixing a wire mesh to the inside edges of the joists just above the plasterworkand then applying adhesive to the plasterwork embedding it into the mesh. Cost: Expensive due to extreme care needed and labour involved. Pros: Retains all original period features. Usually only used on plasterwork of significant historical interest. Cons: Complicated, expensive, and sometimes beyond even the average builder. Arguably not a DIY proposition due to care needed to preserve original features without damage. And That Just Leaves….Buy a Newer House. Maybe you are just not cut out for living in a period house and would be better suited to a mimimalistic pad with the latest in smooooth technology…. *laughing*. Cost: Horribly expensive, removal companies, estate agents, lawyers etc. Pros: No lath and plaster to repair. Cons: Everything is very, very flat, smooth and arguably…..boring.

Need More Information or Help?

Urban legend has it that you only need to read six books on a subject to be classed as an ‘expert’. So, here are some books I found interesting which will be useful to get you started! Or drop me a comment and ask a question.

All available from , (or here at for the rest of the world), just follow the links to have a peek!

• Not destined for the coffee table…….. :A Practical Guide to Care and Repair, by Roger Hunt and Marianne Suhr. Hardback. Don’t be deceived, this book may be at home on the coffee table, but it packs a lot of really useful information into its 208 pages. Passed and approved by my favorite ‘Institute’, the guys at , the Society for the Protection of Ancient Buildings. The book teaches you to work with your house, not fight it. Repair not restore or renovate. If you are into minimalistic, white flat surfaces and recessed downlights, this book may be a shock for you, as it educates us to live with a buildings character, not destroy it.
• maintenance of historic buildings by Jurgen Klemisch.A practical, hands-on guide to the maintenance of your older house. Based on many years of experience, this book teaches you the current best practices related to maintenance and is presented using a straightforward logical format. In two sections the book deals with maintenance for use by owners and how to conduct condition surveys. The book makes extensive use of helpful checklists, work cards detailing routine cleaning, deep cleaning, inspection, servicing and redecoration; and even spreadsheets to help plan your maintenance. Following the books recommendations would also (over time) build a useful record about your house, which will be helpful when deciding the timing of future repairs and allow you to assess costs accurately.
• A damp house is a dying house…… : A Guide to the Causes and Treatment of Dampness. By Jonathan Hetreed. Hardback. I thought that I would include this book because as the owner of an older property you will soon come to learn that water or damp is the mortal enemy of your house! Managing the moisture and water, on, in and around your home is vital in the battle to preserve and protect it. From the patio to the ridge, water is trying to get into your house and cause damage! Read Jonathan’s insights and learn how to keep it at bay.
• The Victorian House manual from Haynes By Haynes A no nonsense book that even Conservation Officers like and use! This book covers some of the most common problems found in houses built in this era, along with some of the more common misconceptions about some of the repairs commonly touted as being able to “cure all ills”. As you would expect from Haynes these books have great photos and easy to understand and follow instructions. A hard to beat primer for anyone owning or thinking of buying a Victorian (or Edwardian for that matter) house.
• Guide to using natural finishes Lime and Clay Based Plasters, Renders and Paints – A Step-by-step Guide By Adam Weismann Adam Weismann’s book is more specialized than those above and would suit the hard core enthusiast who wants to have a go at repairing their old walls and ceilings themselves. Kevin McCloud from Grand Designs comments that it is “A splendid book. A real addition to what’s out there and very complementary to the Society for the Protection of Ancient Buildings’ new technical manual on Old Building Repairs”.

Endnote….

Lath and plaster carpet

Bev Hisey was so inspired by the look and feel of the lath and plaster when renovating her home that she has dedicated a brand new carpet design to it! Click the image to see more…

Stay well Ian Anderson