I am planning the floor joist over the crawl space on an extension. I don't understand the purpose of the lower sill (marked in red) that I have marked from the principle solution from the wood guide?
Can't the floor joists rest directly on the edge beam instead? The span is reduced by ~15-20 cm (blue lines) if you let the floor joists lie directly on the edge beam.
I'm planning the floor joists over the crawl space for an extension. I don't understand the purpose of the lower sill (marked in red) that I highlighted from the principle solution from the wood guide.
Can't the floor joists rest directly on the edge beam instead? The span is reduced by ~15-20 cm (blue lines) if the floor joists lie directly on the edge beam.
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It distributes the pressure and anchors the house into the foundation. Choose a wider sill.
It distributes the pressure and anchors the house down into the foundation. Choose a wider sill.
Ok sounds reasonable. In the wood guide, it says that the bottom sill should be made of pressure-treated wood. I was under the impression that you couldn't build in pressure-treated wood?
Ok sounds reasonable. In the wood guide, it states that the lower sill should be made of pressure-treated wood. I was under the impression that you were not allowed to build with pressure-treated wood?
Opinions are divided on this. The sill lies outside the house construction and today's pressure-treated wood can't be compared to the old pressure-treated wood which had a very strong smell. Therefore, you can use a pressure-treated sill, but today they advise against using it. Some type of sill paper/insulation is always laid to prevent moisture from traveling from the footing and further up. Therefore, regular wood is used as a sill today. Best regards
I was under the impression that you were not allowed to use treated wood?
That is why it's positioned as it is. Outside the building envelope. The purpose otherwise, as mentioned, is to have something to attach the rest of the frame to that is affixed to the wall. Sure, you can solve it in other ways, but it's quite simple to attach a beam around before you start building the rest.
If you have sill paper in between and windproofing/vapor barrier on the outside covering the sill, it doesn't need to be impregnated.
Building without a sill takes much longer because each floor joist must then be attached to a masonry construction with lateral precision. It is an advantage if the sill has as large a cross-sectional area as possible. In the past, high-quality timber with a square cross-section was always chosen for sills. In properly executed wooden constructions in buildings, there should be no need for pressure-treated timber.
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