Rotten ground floor joists...

[leedjc]

Hi all

I'm in the midst of renovating our front room in our 1850s house.

It's stone wall, so no DPC, have noticed that the end of the floor joists are rotten.

It seems that the floor is laid by way of red brick in soil, the joists laid over the brick, and floorboards laid on joists.

Around the edges of the room it seems that the soil level has risen (insect activity?), the joists have damp soil next to them, and have of course rotted over the years.

In order to sort this, I'll need to rip up the floor and lay new including joists.

The question is, should I lay it the same as the original floor? Or should a different approach be taken?

As a side note, I am trying to be sympathetic to the original building during restoration, using lime etc instead of gypsum, if that makes any difference.

Thanks

 

[AronSearle]

Lasted 150 years, and would have lasted another 150 years if the ventilation and soil levels had remained adequate.

Copy the original (with new insulation).

using lime etc instead of gypsum, if that makes any difference.

Generally you want to use materials of the same breathability as the original materials, IIRC those materials are fairly similar in that regards.

The difference is plasterboard tends to be dot and dabbed, leaving gaps behind the plasterboard, which may or may not matter (sometimes an airtightness issue).

 

[leedjc]

Lasted 150 years, and would have lasted another 150 years if the ventilation and soil levels had remained adequate.

Copy the original (with new insulation).

using lime etc instead of gypsum, if that makes any difference.

Generally you want to use materials of the same breathability as the original materials, IIRC those materials are fairly similar in that regards.

The difference is plasterboard tends to be dot and dabbed, leaving gaps behind the plasterboard, which may or may not matter (sometimes an airtightness issue).

Thanks, thought that was probably best.

As for plasterboard...I've just finished ripping a ton of it out and stripped back to bare stone for a nice fresh coat of lime plaster

 

[KenGMac]

leedjc, Hi

One thing that you can do to increase the life span of the new joists is that when you install them you wrap the joist ends in the old masonry walls with a suitable DPM. And that this wrapping is done so that the wrapping is taken as far back along the joist as is possible, suggest not less than about 300.MM?

Ken.

 

[AronSearle]

NO!

Just wrap them where they are in contact with the masonry.

Wrapping the timber more along it's length may allow condensation to form internally or any trapped moisture to sweat.