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Author Topic:   Insulated and damp proof flooring
duncan
Senior Member
posted 05-17-2001 08:11 AM     Click Here to See the Profile for duncan   Click Here to Email duncan     Edit/Delete Message
I beleave this was a more common practice then realized. Several castles have signs of the use of this flooring but with age, fire, and the distruction of many, little is left to prove this theory.
Some flooring still exists as my first 'find' came about in a 12 C strong house and with the owners OK i was able to examine it. I also found several large areas still intact on the roof of a vault in Ireland. Else where in the UK several castles had peices of the flooring used as fill for a wall damaged in the 11 C. On other walls above where the corbel suported floor timbers would be are 'stains' or broken peices of flooring still embeded in the stones. I found in an area where a screen was used the same signs.
It's composition using reeds or straw layed in a bed over floor joists with several types of Lime mixes that were known would allow the use of lighter weight timbers and over a vault it must have added strength so the arch could be made thinner.
Since finding this little puzzle i have been researching and recreating many of the floor types with their mixes of lime as close to the originals as possible.

Erik Schmidt
Senior Member
posted 05-18-2001 08:14 PM     Click Here to See the Profile for Erik Schmidt   Click Here to Email Erik Schmidt     Edit/Delete Message
I certainly agree that the use of such a technique may have been extensive, and, unfortunately, prone to a short life. I can imagine it's use would be more widespread in the colder Nothern areas than the South if it was used as an insulation. My main travels have been in South and Central Europe, so it's not surprizing I don't recall seeing it.
Where you talk about the stains around the corbels, are you saying it was "plastered" underneath the floor, as a ceiling? If so, was this layer very thick?
I'm interested in knowing what percantage of straw it seems to have. If it's low, then it's used as a binder only, but if it's very high, then it would certainly confer insulative properties.
I have seen reeds plastered onto the wood ceiling of a celler at a relative's place in Denmark, no older than 150 years. The reeds were perfectly aligned paralell and adjacent to eachother in a single layer, using plaster to hold them in place. This must have been to insulate as it had little inherent strength.
This brings me to your comment about the strength of the straw/lime mixture. What have your experiments shown in this regard? As you probably know well, straw is used to add strength in mud brick making, but only really serves to hold the brick together under downward pressure. It is unsufficient to enable horizontal slabs of this mixture to bear any significant weight. Could this also be true if using lime?
Whereabouts in arched floors have you seen this material. I can imagine it would make a great insulation, placed between a cold cellar arch and the tile, brick or stone floor in the heated room above. Are there indications it was used as the floor surface?
I can certainly see an advantage to "pouring" a layer of this material over the floor once the arch and infill has been constructed, it's single stable mass helping to consolidate all the stones in the arched floor. Using it to consolidate an arched ceiling without infill, such as in the many vaulted churches, may also have been done.
That's enough raving for now. Look forward to reading your comments.

Erik

[This message has been edited by Erik Schmidt (edited 05-20-2001).]

Erik Schmidt
Senior Member
posted 05-19-2001 05:26 PM     Click Here to See the Profile for Erik Schmidt   Click Here to Email Erik Schmidt     Edit/Delete Message
I asked John Carignan for his input on this topic. He noted your reference to using the lime/straw mix as a damp proofing. The lime is in fact very porous, as you must well know, so it can't be used as a damp proofing. I didn't pick up on it either when you wrote it.
The porous nature of the lime would make it a good insulator on it's own, so maybe the straw was added simply as binding, the lime itself being the insulator.

Erik

duncan
Senior Member
posted 05-19-2001 09:19 PM     Click Here to See the Profile for duncan   Click Here to Email duncan     Edit/Delete Message
"I certainly agree that the use of such a technique may have been extensive, but prone to a short life." Short life? The first recorded use of this type of flooring was by the GREEKS and later by the Romans.

"Where you talk about the stains around the corbels, are you saying it was "plastered" underneath the floor, as a ceiling. If so, was this layer very thick?"
NO not plaster and the stains appear 6 inches to a foot ABOVE the corbels.

"I'm interested in knowing what percantage of straw it seems to have. If it's low, then it's used as a binder only, but if it's very high, then it would certainly confer insulative properties."
I'm very aware of straw being used as a binder in many items including plaster, but, i never implied other then a BED of material layed down then covered with a lime mix.

"I have seen reeds plastered onto the wood ceiling of a celler at a relative's place in Denmark, no older than 150 years. The reeds were perfectly aligned paralell and adjacent to each other in a single layer, using plaster to hold them in place. This must have been to insulate as it had little inherent strength."
I live in a house near 200 years old and even horse hair was used to increase strength in lime plaster just as other newer materials are used in concrete today. Your right that the straw was used as a insulater which was as i stated.

This brings me to your comment about the strength of the straw/lime mixture. What have your experiments shown in this regard? As you probably know well, straw is used to add strength in mud brick making, but only really serves to hold the brick together under downward pressure. It is unsufficient to enable horizontal slabs of this mixture to bear any significant weight. Could this also
be true if using lime."
No, lime is different then MUD becouse of the ingredients in the mix such as sand and pozzolans which when mixed together forms a chemical reaction with lime.

"Whereabouts in arched floors have you seen this material. I can imagine it would make a great insulation, placed between a cold cellar arch and the tile, brick or stone floor in the heated room above. Are there indications it was used as the floor surface."
Makeing up the floor above an arch so yes it was used in a few castles as a floor. I just heard that My familys castle in Ireland is one of them.

"I can certainly see an advantage to "pouring" a layer of this material over the floor once the arch and infill has been constructed, it's single stable mass helping to consolidate all the stones in the arched
floor. Using it to consolidate an arched ceiling without infill, such as in the many vaulted churches, may also have been done."
I agree that it would have a advantage being poured but what i saw was used over infill and i have not seen its use in a church but as i said in a very few castles.


"I asked John Carignan for his input on this topic. He noted your reference to using the lime/straw mix as a damp proofing. The lime is in fact very porous, as you must well know, so it can't be used as a damp proofing. I didn't pick up on it either when you wrote it. The porous nature of the lime would make it a good insulator on it's own, so maybe the straw was added simply as binding, the lime
itself being the insulator."
In one of John Carignan's favorite books that he quotes frequently
"Building with Lime" by Stafford Holmes and Michael Wingate
on page 174 under DAMP RESISTANT FLOORS They explain How to make a damp resistant floor. This also is not a new or unknown process.
Useing HYDRAULIC lime in EUROPE on BRIDGE FOUNDATIONS, PIERS BELOW WATER LEVEL, and even QUAY WALLs were made with LIME. In India lime concrete was used for CANAL LININGS and there are many other areas where lime was
used in wet conditions.
These uses suggest in them selfs that it can be made non porous.

------------------
Megan and Ralph
CASTLE DUNCAN

Vivo vivere vixi victum
simul Honorare

[This message has been edited by duncan (edited 05-21-2001).]

Erik Schmidt
Senior Member
posted 05-20-2001 11:47 PM     Click Here to See the Profile for Erik Schmidt   Click Here to Email Erik Schmidt     Edit/Delete Message
Ahh, now I see. I didn't realize the straw was laid down first, then having the lime poured over. I thought you had meant a it was evenly mixed. How thick a layer of straw?
Does the lime envelope the straw or just sit on top.
Lime is certainly stronger than mud and the Romans made use of it's strength, but I must say I can't see it adding strength to a wooden floor to the extent that the boards could be downsized. I guess it depends on the distance it had to span.

By "plastered" I meant applied like plaster, not actual plaster. But 6-12 inches above the corbels is probably something along the lines of the floors I saw in Swiss castles, where the wooden floor was overlaid with about that thichness of rubble and then covered in tiles or stone. The bit I saw looked like rubble, but it may have been consolidated somehow.
I meant the short life of the actual material(thus not many examples), not it's use through history. As a reference to the second sentence of your first post here.

I realize now what you mean by damp proofing, not the modern form where it pertains more to stopping water, rather than not being degraded by it.(What would we do without the dictionary? ) I know lime can handle water, but what about the straw. It would rot in these conditions. No?

Misunderstandings can go both ways.

Erik

duncan
Senior Member
posted 05-21-2001 06:44 AM     Click Here to See the Profile for duncan   Click Here to Email duncan     Edit/Delete Message
I see what you meant, my mistake!!
The little i have found was layered 6 inches to a foot above the infill and about the same for the floor joists.
What i have been able to find out the lime seemed to envelope the top layers and not go any deeper.
I can understand if the straw was placed 90% to the joists it could have added some strenght if the timbers were close enough together.{I'm trying to find the R value and tensil strength of straw and will post as soon is do} I'm sure your aware certain reeds are also very strong.
I wonder if what you saw in the Swiss castles were examples of a lime ash flooing. Was the "rubble" small aggregate sized?
About the short life of the flooring. For an example, i was told that the flooring in the famlies castle is over several hundred years old.
If a mix of moist lime and ash laid over the straw then somewhat compacted as in a 'grip floor' would extend the life of the bedding material and even the use of gypsum as a guick setting agent if hyd. lime was not used.
Was their a layer of what we would now call 'underlayment' of some kind i wonder?


duncan
Senior Member
posted 05-21-2001 05:21 PM     Click Here to See the Profile for duncan   Click Here to Email duncan     Edit/Delete Message
Well John, You might go back and re read the topic before posting.
For your infomation i did not quote any one and of course as all ways your opinion has been noted.....

Erik Schmidt
Senior Member
posted 05-22-2001 02:31 AM     Click Here to See the Profile for Erik Schmidt   Click Here to Email Erik Schmidt     Edit/Delete Message
With such a thick layer of straw, capped with lime, it makes me think that it may have been used as a sound dampner. I'm sure you have experiences with wooden floors, even substancial ones can amplify the sound of footsteps and dropped objects in the level below. A thick layer of straw would not carry this sound.
Maybe not important over arches though?

The tensile strength of some grasses is very high, but when used in a floor this strength is not put to use, as the stress is from the side(ie downward pressure).
I can certainly see that a floor may not even need floor boards if the joists are close enough together, but the straw is not adding to the strenth of the floor in itself, but simply replacing the boards.

The floor infill, in Thun Castle, Switzerland, as far as I remember had various sizes of stone, some up to fist size.
Maybe also soundproofing?

What's a grip floor?

Must go.

Erik

duncan
Senior Member
posted 05-22-2001 06:31 AM     Click Here to See the Profile for duncan   Click Here to Email duncan     Edit/Delete Message
You see thats a part of what i'm not sure of, the mark was above the corbels and much of the straw was for the most part missing or should i say decompossed. What if any thing is missing? There is a reference in the above book, but not really what i'm looking for.
Here is an excert from what it says about the use of straw to make light weight slabs on page 175 under suspended floors "Two of the most common methods of constructing suspended floors, i.e. upper floors, are with gypsum and 'lime-ash' laid on timber joists in colder climates, or with coral laid on boriti poles in warmer climates. Both methods take advantage of lightweight aggregates combined with the binder to give a light, low cost floor slab with an integral finish. Becouse the floor construction is lightweight, the floor slab may be supported by timber joists of minimum section. This allows greater spans to be achieved, providing larger rooms." {Now that is a quote} It gives a nice picture of the lime ash flooring, straw, lath nailed to the joists {to hold the straw}, and then the ceiling below.
In the Swiss castles i'm not at all sure about the large and small stones being other then as you said infill.
Grip flooring, as far as i can find out the name came about in Gloucestershire around the 19 C but the method had been in use for much longer. "composed of lime and ashes laid moist to a thickness of 100mm to 125mm on a compacted sub-base and rammed down hard with a heavy timber tamper until a hard and smooth surface was obtained." Page 174 of the same book under damp resistant floors. {minus the typos of course}

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