Suspended timber floor

[Stonehouse]

We had to replace some floor joists and replaced some of the slate the joists were put on.

We also isolated the end of the timber from the masonry walls using a piece of dpm. The end of the joist isn’t wrapped, just goes over.

However, with a lime plastered wall and lime outside the above wasn’t needed? Is that correct?

 

[Toby Newell]

No. Lime is more permeable, just means it expires faster and reaches equilibrium quicker. If it's exposed to excess moisture and the environment is cold and moist it will remain moist. It's not a magic material.

Timber absorbs moisture and above a certain level (12% for CFB wood worm and 20% for many molds iirc, I am sure Mr Green will correct me if I am wrong) it can become prone to pest and fungal (rot) attack. Also the ends of the joist are 'end grain' ie dense packets of straws that suck up moisture like, er, straws. Moisture can travel several cms in minutes this way.

You need to isolate the entire end, especially the end grain. I coat in Blackjack bitumen primer and wrap in Bitumen flashing tape.

In the past socket ends were left uncoated, with slates or sometimes bitumen paper, they all rot eventually. Sometimes this can take take decades, centuries or as little as within a couple of years, all depends on the conditions.

 

[Stonehouse]

No. Lime is more permeable, just means it expires faster and reaches equilibrium quicker. If it's exposed to excess moisture and the environment is cold and moist it will remain moist. It's not a magic material.

Timber absorbs moisture and above a certain level (12% for CFB wood worm and 20% for many molds iirc, I am sure Mr Green will correct me if I am wrong) it can become prone to pest and fungal (rot) attack. Also the ends of the joist are 'end grain' ie dense packets of straws that suck up moisture like, er, straws. Moisture can travel several cms in minutes this way.

You need to isolate the entire end, especially the end grain. I coat in Blackjack bitumen primer and wrap in Bitumen flashing tape.

In the past socket ends were left uncoated, with slates or sometimes bitumen paper, they all rot eventually. Sometimes this can take take decades, centuries or as little as within a couple of years, all depends on the conditions.

Thank you very much Toby - sound advice!