houses with no foundations

[charlie-ia]

Around here the downhill wall quite often falls out of buildings( well after 300 years or so). Its particularily common when the ridge is running parrallel to the slope. Its is caused by the weight of the roof pushing the walls out as there is only one truss holding the front wall to the back wall. And of course by the rubbish foundations!
What the old timers did when they built my cottage (pre-1805) was to dig a trench over 24" deep, hurl in the biggest stones they could find, then build the walls on these. The problem is that they never filled the voids in and around these "foundation" stones, so over the years the action of water and the weight of the walls cause the soil to move into these voids and the building to settle. I discovered this when poking about to see if the building had a stepped foundation, and after about 6" of topsoil, my spike often dropped 2 feet into a void. if any one has a cure for this problem I too will be grateful.
I did french drains around my place working on the asumption that it is safe to dig down to 6" below the original floor level then if you want to go deeper, outwards at 45 degrees. As I reckon my foundation stones extend for 18" deeper then my drain level I think the building is secure.
Frank

 

[charlie-ia]

we spoke again with the surveyor. our house is built just like this too.

the roof pushing the walls out as there is only one truss holding the front wall to the back wall Frank

whats a truss? what does it does it look like? where is it, and what does it do?
you've made me nervous now!

thanks everyone for all the helpful advice so far!

 

[Penners]

whats a truss? what does it does it look like? where is it, and what does it do?
you've made me nervous now!

Trusses are beams that span your house from the bottom (usually) of a rafter on one side to the bottom of its opposing rafter on the other side. Its job is to tie (or truss) the two together, so the roof doesn't spread (and take the walls with it).

Think of a pair of rafters as an upside down V. When the weight of the tiles is placed on the V, the bottoms of the two sides (ie: the feet of the rafters) will tend to push apart. Now think of the upside down V as an A instead (but with the cross bar of the A at or near the bottom). You can see that this crossbar will prevent the feet from being pushed apart.

That's a truss.

 

[chuckey]

truss = triangular frame, the two sides are roof joists and the bottom one is running between the botom of the roof joists normally just above the ceiling. You can see them on any modern house being constructed, but modern ones have alot more pieces of wood in them to stiffen them up enough for the weight of the tiles.
Frank

 

[Penners]

Chuckey - yes, nowadays people use the word "truss" as a general word to describe the whole assembly of a roof 'A' frame. But isn't it true that, strictly, the assembly consists of two rafters and a truss across the bottom?

 

[charlie-ia]

then we've got a fairly normal roof. lots of trusses.

the surveyor tells us the foundations are just like Frank's. big pit, lots of boulders. Im very interested to hear more about them. How to stabilize them, problems people have met with them?

 

[Nemesis]

My house has been standing with those sort of foundations for over two centuries.

If it ain't broke don't fix.

 

[Penners]

Hear, hear to Nemesis. In fact it sounds as though you've got a lot more foundation than a great many period properties.

 

[Mark]

You can see them on any modern house being constructed, but modern ones have alot more pieces of wood in them to stiffen them up enough for the weight of the tiles.

The point being that in general the modern trusses are made out of very flimsy bits of wood when compared to the typical old house.

I was in my in-laws attic recently and the trusses are less than an inch thick. Although all have multiple braces and there are loads of them. Tends to mean that there is very little useful space in the attic compared to one based on purlins and rafters.

 

[chuckey]

r.e. Moderrn trusses, I was on an OU course where we had to make a bridge out of 50 gms weight of balsa wood. There was an architect on the course and he basicaly made a mini roofing truss. Most of the models collapsed at 1 to 3 kg, his one totally exploded at 15kgs. Why? because in his structure all the bits were carrying a load of 90% of their ultimate strength, so when one bit broke the others took the extra load, but not for long!
frank

 

[Penners]

By contrast, the chippie who's building our timberframe garage has just put up the roof structure - all cut and fitted by hand, on the spot. Compared with the kind of trussed rafters that are used on modern houses, this one (on a much smaller building) is massive.

If the bomb ever drops, I know where I want to be!