20th March 2008, 05:01 PM
The last ones I built (the single ring ones) were based on excavtions at Glastonbury Lake Village where the bases of the posts actually did survive, as did multiple phases of fireplace and layers of charcoal and burnt reed suggesting the roof had burned.
The Butser ones are also based on excavated sites. Anyway, have you got any posts to show its palisaded - they might have just been holes in the ground or stubs of wood level with ground level so not really a palisade. Where abouts is the roundhouse that got the ?25 k (which sounds about right for a reasonable sized house unles you are employing slaves to gather the materials, which is the biggest element of the work, and how big is it?
Tip shedding drip problem - straw/reed bundles as used for thatch are not inherently waterproof - thatc hworks by shedding water off the outer layers faster than it can soak through the thatch so at 45-55 degrees water will run down the outer cm or so thickness of the thatch and not penetrate into the body of the material. The tip (and ridge of modern thatched houses) decays fairly fast as the water isn't shed from there so it rots faster and thatched houses need to be re-ridged every ten to 15 years, wher the main part of the roof can last for 50-60 years before needing redone (and even then often just needs a new layer added). A dome, by its very shape has a large area at the top which is well below the 45 degree angle and so water will run through the thatch at the top, so you will have a dripping roof every time it rains. Water in the thatch leads to it (and the fastenings which hold the thatch to the roof) rotting so in not many years your roof would disintegrate. Dome shaped buldings in climates similar to ours tend not to be thatched - the NE woods indians in N America covered their wigwams and longhouses with sheets of bark.
The Butser ones are also based on excavated sites. Anyway, have you got any posts to show its palisaded - they might have just been holes in the ground or stubs of wood level with ground level so not really a palisade. Where abouts is the roundhouse that got the ?25 k (which sounds about right for a reasonable sized house unles you are employing slaves to gather the materials, which is the biggest element of the work, and how big is it?
Tip shedding drip problem - straw/reed bundles as used for thatch are not inherently waterproof - thatc hworks by shedding water off the outer layers faster than it can soak through the thatch so at 45-55 degrees water will run down the outer cm or so thickness of the thatch and not penetrate into the body of the material. The tip (and ridge of modern thatched houses) decays fairly fast as the water isn't shed from there so it rots faster and thatched houses need to be re-ridged every ten to 15 years, wher the main part of the roof can last for 50-60 years before needing redone (and even then often just needs a new layer added). A dome, by its very shape has a large area at the top which is well below the 45 degree angle and so water will run through the thatch at the top, so you will have a dripping roof every time it rains. Water in the thatch leads to it (and the fastenings which hold the thatch to the roof) rotting so in not many years your roof would disintegrate. Dome shaped buldings in climates similar to ours tend not to be thatched - the NE woods indians in N America covered their wigwams and longhouses with sheets of bark.