Vaulted ceiling in a thatched property

[Ian15v]

hello , everyone.
I am new to this forum, but have found lots of the other posts helpful. We have recently purchased (18 months ago) a 17th century thatched property in Essex, as part of the restorations of the house, we removed a poorly installed ceiling in one of the bedrooms and exposed the joists and roof structure. To us (with no experience in thatched houses) the underside of the roof looked in good condition and we were wondering about vaulting the ceiling in the bedroom, however I have some concerns on how to do this with out causing damp issues / or damaging the structure.

Any help would be greatly received

Ian.

 

[Cassie]

Hi Ian, that looks like a beautiful structure! Is it listed? I have no expertise here, but just wondering-what was wrong with the ceiling before? Purely curious!

 

[stuart45]

What is the plan? Removing the ceiling joists and replacing with collars?

 

[Cubist]

That roof is indeed wonderful and I can well understand your desire to see more of it through vaulting the ceilings. Sorry if perhaps I sound a damp squib but...

Is the house listed in a conservation/heritage area?
Has your insurer specified any conditions concerning the roof?
When was the roof last fully thatched?
Was it merely coated?
When was the ridge last replaced?
How deep is the thatch?
What type off thatch is the main roof Straw, Reed?

 

[88v8]

Hello and welcome.

We have a room like that which one could describe as vaulted, in that the room is within what would be your attic.

Some of the rafters are wonky although not as much as yours and it would of course be a crime to cover them up.

The wonkiness which is their beauty brings with it difficulties if one wishes to plaster, because inserting plaster board or strawboard between them introduces a flatness which is completely at odds with the nature of the building.
What was done in our cottage, and it was probably done when the house was thatched which might be 200 years ago, was to lime plaster - lime goes without saying really - direct on the underside of the thatch.

The plaster is very thin, just a skim really, and the surface is smooth but not at all flat, lumpy bumpy might be a description. Above the plaster much of the base coat of thatch has rotted, not doubt due to lack of maintenace over the years, so the plaster is sitting over pretty much nothing and very fragile.... but beautiful.

Your first problem will be finding someone who is capable of plastering in lime, and without making it smooth or flat.
Your thatch looks very fresh, but the second problem is that when the thatch requires maintenance - reridge every ten years or less - complete recover perhaps thirty years - there is a very high risk that the plaster will suffer from the inevitable clambering and hammering and chunks will fall off.

You can see here areas of relative flatness where past damage has been repaired by plasterers who were not capable of replicating the original wonkiness.



So yes, the effect can be lovely but there will be periodic maintenance.

A pity btw that what looks to have been a very old ceiling had to be removed, and as already mentioned the Conservation dept will have views on the topic if the house is listed.

Ivor

 

[Ian15v]

Hi Ian, that looks like a beautiful structure! Is it listed? I have no expertise here, but just wondering-what was wrong with the ceiling before? Purely curious!

Hello, no the property is not listed which is partially the problem. The previous owners put up a bodged modern plasterboard ceiling which was falling down. Thus why we took the ceiling down and we were pleasantly surprised by the roof above.

 

[Ian15v]

That roof is indeed wonderful and I can well understand your desire to see more of it through vaulting the ceilings. Sorry if perhaps I sound a damp squib but...

Is the house listed in a conservation/heritage area?
Has your insurer specified any conditions concerning the roof?
When was the roof last fully thatched?
Was it merely coated?
When was the ridge last replaced?
How deep is the thatch?
What type of thatch is the main roof Straw, Reed?

 

[Ian15v]

Hello Cubist,
That you for your reply. Please see the answers to your questions below.

1) No the property is not listed;
2) my understanding is the house was last fully thatched 15 years ago;
3) I believe so;
4) last re-ridged 3/4 years a ago;
5) long straw;

 

[Ian15v]

What is the plan? Removing the ceiling joists and replacing with collars?

Hello,
We have no plans at all currently, we just removed a plasterboard ceiling that was failing down.
We do not want to mess around with the structure of the property. So no removal of ceiling joists.
We just wondered if it was possible to open up the ceiling and expose the beams/roof, but didn’t want to damage the property by causing other issues in to process.

 

[CliffordPope]

I saw an old cottage in Ireland at a preserved heritage village and the panels between the rafters appeared to have been covered with canvas tacked to the sides of the rafters, and then painted with some kind of sloppy emulsion or lime concoction.

 

[Zebra]

I don't know much about thatch. So I'm talking in general terms, but as I understand it, the issue with vaulting a loft space (same thing happens with loft conversions) is ventilation. With the conventional set-up, the loft space is ventilated at the eaves, and unheated. The ceiling forms the thermal barrier between the warm inside and the cold outside, thus the loft is cold, well ventilated, and both of these factors combine to keep it dry, and your rafters free from rot, mould, woodworm etc .
When the ceiling is placed at roof level, even if some ventilation is preserved at the eaves, the ventilation is much reduced. There is a rule of thumb for the minimum gap which must be maintained between ceiling (plus insulation) and roof, but I can't remember the number.
Also your roof space ends up warmer. Warm air holds more moisture than cold air, so this, along with the reduced ventilation, can cause increased moisture in the roof timbers.
A further issue is the cold bridging where each tie-beam (joist) passes through from the cold area to the warm area. The end of each beam is cold. Wood is a good insulator but nevertheless, each beam end as it passes through the plaster, will be a cold spot in the room. Cold spots attract condensation. Another risk of damp timbers.
I was going to do something almost identical to that in my bedroom. The ceiling was down, the tie-beams were beautiful, I wanted to see them inside the room, but having asked for advice on here, decided to put it back as originally designed, and haven't regretted it.
I'll see if I can dig out the forum post where I originally considered it.

 

[Cubist]

Hello Cubist,
That you for your reply. Please see the answers to your questions below.

1) No the property is not listed;
2) my understanding is the house was last fully thatched 15 years ago;
3) I believe so;
4) last re-ridged 3/4 years a ago;
5) long straw;

Thank you. You may be puzzled why I'm asking about the thatch when your question concerned vaulting the roof space, so here is my rationale.

There are some crude rules of thumb associated with thatch that are important to know and understand. The key ones being: -

• Long Straw has a mean life of circa 25-30 years between new thatch coats.
• The ridge is typically constructed on long straw even for reed roofs.
• The ridge has a typical life expectancy of circa 15 years.
• The decision to strip off all the old thatch, or simply re-coat it, is typically based on how deep the thatch is overall and whether simply adding a new coat may compromise any fire safety guidance associated with the relative heights of any chimneys and the top of the thatch.

In your case then you can expect to have to have the house re-thatched completely in about 10 to 15 years. Whilst, again depending on the depth of the extant thatch, it may not be necessary to completely strip all the thatch back to the rafters - some thatched houses have been found in which the inner coat is believed to be 400-500 years old - you may find that you are exposed building regulations with which your insurers insist you comply.

At present, many insurers require that thatched roofs are equipped with 60 minute fire resistant barriers. This consists of semi-flexible foil like material that is pinned to the outer face of the rafters and the thatch is laid over this. Some may think that quite attractive but bluntly its not. Other fire resistant products consist of rigid boards that again are pinned to the upper face of the rafters. Given that yours are 'Crook' timbers these are unlikely to be suitable.

Another consideration for you planning is that thatch plays host to considerable wildlife populations. For the most part these are insects of one sort or another but its not unusual to find that it hosts mice and other rodents such as squirrels and even rats. As a consequence its not unusual when investigating the loft spaces of thatched houses to find traps and poison dishes used by previous owners.

With the above in mind, and should you decide to proceed with the idea of vaulting this roof space I would strongly recommend that you follow Ivors advice and plaster the inner face of the thatch between the rafters and consider including some fire resistant material while doing so.

Anyone sleeping below will have a better night knowing that some incontinent rodent cannot bomb them.

 

[Zebra]

I found the link to the thread from years ago where I thought about doing the same thing, it's not quite relevant actually, because I was thinking about putting the ceiling just above the beams, but in any case here it is.....the images don't seem to have pulled through so it might not make a lot of sense https://www.periodproperty.co.uk/forum/threads/does-this-look-stupid.12868/page-2

 

[Cubist]

You're right, it does not.

That reminds me, I need to put carrots on the shopping list.

 

[88v8]

Zebra is right about the cold bridging. One reason I was working on that room is the extent of mould that had taken root in the lower rafters and the wall plate. This had been exacerbated by the use of plastic paint - vinyl - by the PO - which conduces to condensation.

Due to the extreme fragility of the plaster it was not possible to strip the paint from the ceiling, but I did manage to strip the wall panels so there is now a small degree of breathability in the room, and I repainted with a somewhat breathable paint incorporating a lot of fungicide, and I have two small fans running on timers to create a periodic degree of air movement so fingers crossed...

The point which I forgot to mention where your roof is concerned is that it is essential if you went the plastering route, essential that you use lime plaster and breathable paint, otherwise the health of the thatch will be impaired and the room will grow mould. Limewash, distemper, would be suitable.

On the whole though, given that you are not listed, I would sidestep the notion of underceiling the thatch... what I would do if you wish to see the roof is to introduce a couple of full-length glass panels into the new ceiling, and put some LED uplights in the roof space above them.

That way you will be able to admire the roofspace without creating potential damp problems and future maintenance liabilities.
Also, you will not have to heat the roof space!!

The rest of the ceiling can be re-beautified by lathing it with split wood lathe, and having it replastered with a single lime coat, laid on so as to show the lathe.
Like this... sorry about the poor pic



As regards the animalcules, this was a particular problem with wheat reed as rats & mice used to tunnel the thatch seeking the ears. Nowadays, netting has largely eliminated the problem, provided that eaves spaces have been assiduously netted.
Oddly enough, we get mice in the 'new' attic - created in the 60s - despite my efforts at blocking ingress, but none in the old attic above the original room of the house that you see to the right of my avatar. That space was originally vaulted, but was ceiled under perhaps 200 years ago when the cottage was elaborated by the Georgians. There is ample scope there for animals to get in, but for some reason they do not.

Ivor