Reed Board

[KelvinM]

This is my first post on the forum although it has provided me with a wealth of useful information for the last few years since I purchased my Listed property.

I have a question about reed board. Just as a bit of background, I own a 300 year old, 3 storey timber framed house. We purchased it just over 3 years ago and have been gradually renovating the place. The property wasn't looked after by the previous owner, so most of the time so far has been spent simply getting the basics done so that the house is totally water-tight (reparing roof, electrics, rotten windows etc...). Fortunately we are now in a position to start more cosmetic works on the house and have just received LBC for quite a lot of work.

We have a room at the top of the house that will become the main bedroom. The ceiling of the bedroom was originally lathe and plaster. The plaster is no longer there but the lathes remain (although not in very good condition). At some point somebody has plasterboarded over the lathes. When we arrived there were two huge water tanks above the ceiling (they have now been removed). The weight of these we think has caused the plasterboard to crack. We have agreed with the Conservation Officer that we can remove the plasterboard and replace with reed board with lime plaster. The old lathes will remain. The CO was quite pragmatic and was quite impressed by the reedboard suggestion.

Essentually my question is whether anybody can see any issues with tacking the reed board straight over the lathes and then plastering onto the reed board. Any general experince with installing and/or platering on reedboard would also be useful, although I have already read some previous posts that have touched on the subject.

Thanks in advance for any help/advice/comments.

 

[Penners]

Hello Kelvin, and welcome.

As your first respondent, I'm not going to be much good to you, because I've never used reed boards. However, I've come across the following two data sheets that might have a nugget or two of handy information for you:-

http://www.womersleys.co.uk/pdfs/reedboards.pdf

http://www.constructionresources.com/products/pdfs/envelope/Claytec%20reed%20mats%20&%20boards.pdf

As a matter of general principle, I think the only point I can add is one with which you may already be entirely familiar. With any plastered surface (using any material... lime, gypsum, clay, etc), particularly a suspended structure like a ceiling, rigidity is important to its long-term stability. Removing the weight of the water tanks sounds like a good move, but if the joists are still a bit flimsy and "live" this is going to make it more difficult to plaster without hairline cracks, and will increase the likelihood of long-term cracking of the surface - particularly if the space above the ceiling is going to be used for storage, or walked on for any reason.

So if the joists are flimsy, you will probably do yourself a favour if you reinforce them, or add further joists between them.

Other than that, I hope that others with real experience of your planned project will give you more useful comments than mine.

Good luck, and do keep us in touch with your progress.

 

[Flyfisher]

Welcome to the forum Kelvin.

It sounds like you've been doing much the same thing as me for the past few years - getting your house watertight and repairing years of neglect. I hope you're finding it as rewarding as I do when it pours with rain and the house remains dry inside!

We also have a fair bit of plasterboard that has been used in the past to repair/replace areas of lath and plaster and have also found our CO to be eminently sensible and pragmatic about how to deal with it. I think the rationale is that where the original fabric has already been lost then (within limits!) it doesn't really matter what is used to replace it. Plasterboard has the advantage of being an 'honest repair' and is clearly a contemporary material that is unlikely to be confusing to future property historians, but there are also performance and aesthetic considerations as well.

I've no experience of reedboard but I wonder if fixing it against existing laths might prevent the plaster from fully penetrating around the reeds and perhaps affecting its adherence? Also, if you are leaving the original laths in place is it not possible to plaster on to them directly, after suitably repairing/replacing any in particularly poor condition? In our house, we seem to have more problems with laths coming away from beams due to the nails having rusted away than the laths themselves failing.

It certainly sounds as if your house is now in good hands though!

 

[inwood]

Flyfisher, don't get confused between reed board and reed matt. Reed board is a rigid board with densely packed reed (i.e. several reeds deep). As such these can be fixed to backgrounds using screws and large plastic washers. So for reedboard there's no issue about laths getting in the way of the plaster.

Reed matt, essentially lath on a roll - these are single strips of reed held together with galvanised wire, each reed has about a fingers width gap between to hold the knib of plaster that hooks over it.

Either way I think it would be more prudent to remove the lathes before fixing to the joists. That assumes, as Flyfisher states, that they are in a very poor state. If you only have small sections of lath that need replacing it would be easier, cleaner and cheaper to re use the existing laths (assuming the fixings are in a good condition).

I've no direct experience with reed board, although have seen it fixed up. I always wondered what was used (if anything) to joint the edges between boards to prevent hairline cracks, does anyone know?

 

[Flyfisher]

Fair point and thanks for the correction. Does anyone know the difference in performance between read mat and board? Seems to me that tightly packed reeds would make it more difficult for the plaster to form a solid 'nib' around the reeds for a good grip.

But my only experience is of repairing reed/lime 'sarking' in a roof, where reeds were laid across the rafters and then covered over with a lime mortar. This acted as a 'sarking' layer underneath the roof pantiles. But of course, the lime mortar wasn't vertical as it would be on a wall, so grip wouldn't be quite so important.

 

[biffvernon]

Penners? Flyfisher? What's the matter with you guys? You have neglected to warn the poor chap about the danger of attaching lathes to the ceiling.

 

[JohnB]

Penners? Flyfisher? What's the matter with you guys? You have neglected to warn the poor chap about the danger of attaching lathes to the ceiling.

It saves floor space, but all the swarf would fall on the floor, and get trodden into those beautifully restored floorboards :lol:.

 

[Flyfisher]

Penners? Flyfisher? What's the matter with you guys? You have neglected to warn the poor chap about the danger of attaching lathes to the ceiling.

:lol: :lol: :lol:
Perhaps a smallish one would be OK?

 

[JohnB]

Perhaps a smallish one would be OK?

You'd need very high ceilings to avoid banging your head on it. I've got a neat little Unimat that would fit on all but the lowest of ceilings quite safely, and it's probably light enough not to bring the ceiling down .

 

[Penners]

Penners? Flyfisher? What's the matter with you guys? You have neglected to warn the poor chap about the danger of attaching lathes to the ceiling.

Well it did occur to me. But I resisted for fear that I might be thought pedantic.

I'd hate that.

 

[MdB]

Just for you Biff, some lathes stuck to the ceiling:

 

[JohnB]

Just for you Biff, some lathes stuck to the ceiling:

Is that one on the left treadle operated? How do you work it?

 

[Penners]

It seems that you need a ladder to reach one of them. But if they're on the ceiling I suppose that's not surprising.

I think we've teased Kelvin enough, don't you? We don't want to make him feel unwelcome.





Kelvin - just for your background information, this is an ongoing "in joke" on this forum. "Lath" (ie: strip of wood) is normally spelled without an "e", but many people add that last letter. So, whimsical pranksters that we are, we all make schoolboy jokes about it. Sorry!

 

[KelvinM]

Don't worry - although this is my first post I have been looking at the forum for quite a while so understand the sense of humour of some of the members!

Thanks for all of the useful comments. I take the point on the laths and utilising them. The issue is two-fold really. Firstly, they are not in the best condition so there would be some work to get them repaired. I wouldn't mind doing that, but the CO didn't seem to keen on that. The rationale for this was that the more "honest" option would be to tack over the laths with plasterboard as this would be a true repair. I raised the reed board as a middle-ground option as I felt that it was a good comprimise between the like-for-like repair and using materials that are consistent with a timber-framed house that moves quite a lot. The CO agreed with this as was happy so long as the laths remained and that a record was made of the reed board repair to help future historians. Additionally, I didn't want to push too much for the lath option as it was the beginning of the CO's visit and I had lots of other work that needed agreement!

 

[Penners]

[the laths] are not in the best condition so there would be some work to get them repaired. I wouldn't mind doing that, but the CO didn't seem to keen on that. The rationale for this was that the more "honest" option would be to tack over the laths with plasterboard as this would be a true repair.

I find that a very strange attitude by the CO. Surely the most honest approach would be to repair (ie: renew) the laths.

 

[inwood]

Either way I think it would be more prudent to remove the lathes before fixing to the joists.

The case for the prosecution rests m'lud

 

[LadyArowana]

[the laths] are not in the best condition so there would be some work to get them repaired. I wouldn't mind doing that, but the CO didn't seem to keen on that. The rationale for this was that the more "honest" option would be to tack over the laths with plasterboard as this would be a true repair.

I find that a very strange attitude by the CO. Surely the most honest approach would be to repair (ie: renew) the laths.

I have spent hours reviewing applications in our local planning area and there is not a great deal of consistency. Some things are allowed that seem to change the character of the building quite considerably ( removal of steps from street level to basement in one case ) whilst other more minor things are not approved.

I like the Japanese approach to conservation as expressed at Ise Grand shrine. That is rebuilt every 20 years, and has been about 60 times! so it's very old and very new all at the same time.