Green Building Forum - Timber cladding with stone plinth

Timber cladding with stone plinth

fergoose — Tue, 05 Apr 2022 11:06:47 +0100

Hi I was wondering if anyone has any comments regarding this attached wall section detail? its going to be a timber clad building with stone plinth we want the timber and stone to be relitvely inline, due to cosntariants we cant have the stone sticking out.

Is the void behind the stone necessary? or can it be up aginst the insulation like an insulated cavity?

Thanks
Fergoose

Timber cladding with stone plinth

borpin — Tue, 05 Apr 2022 11:56:43 +0100

Timber and stone look in line to me?

My concern is the infill under the B&B being lower than ground level so inclined to fill with water unless the soil is very pourus.

I'd also be concerned the DPC is breached by the 25mm woodfibre insulation. If the bottom of the insulation gets wet, it will just wick upwards past the DPC. DPC should IMHO, come across the void to the outer blockwork/stone with weep vents just above it.

Think about inset screen between the stone and the cladding else you end up with wasps nests in the gaps and also allows a route for mice!

Timber cladding with stone plinth

philedge — Tue, 05 Apr 2022 13:15:56 +0100

Fairly sure you need the gap between the stone plinth and the breather membrane so the breather membrane has somewhere to breathe into.

Your 100mm block under the stone plinth is acting as a small retaining wall for the outside ground. Id be filling the space between the 100 and 140mm blocks to stop the 100mm block moving inwards over time.

Timber cladding with stone plinth

djh — Tue, 05 Apr 2022 17:17:45 +0100

Posted By: borpinTimber and stone look in line to me?

Yes, I'm not sure why you'd want to move the stone to fill the gap?

My concern is the infill under the B&B being lower than ground level so inclined to fill with water unless the soil is very pourus.

To me the gravel infill alongside the wall looks a bit narrow and would be better with a porous pipe to act as a French drain at the bottom of it.

What soil type is it? Is there blinding of some kind not shown on the soil under the floor?

I'd also be concerned the DPC is breached by the 25mm woodfibre insulation. If the bottom of the insulation gets wet, it will just wick upwards past the DPC. DPC should IMHO, come across the void to the outer blockwork/stone with weep vents just above it.

The woodfibre stops well above the DPC. It's XPS alongside the DPC, which is of itself a DPC and doesn't wick water.

Think about inset screen between the stone and the cladding else you end up with wasps nests in the gaps and also allows a route for mice!

Indeed.

Posted By: philedgeId be filling the space between the 100 and 140mm blocks to stop the 100mm block moving inwards over time.

That sounds like a good idea.

There's no board shown on the outside of the studs. Does the 40 mm woodfibre serve that function?

Timber cladding with stone plinth

fergoose — Tue, 05 Apr 2022 19:25:04 +0100

Hi thanks for the comments most concerns seam to be about the ground below block and beam. Most sections I have seen tend to have the exterior ground at 150mm below dpc (bottom of sole plate for timber construction) given the insulation required and the thickness of beam and then the void underneath results in this difference, I don't understand how it can be different unless you have a big step up to the house which is not really ideal. Some sections on attached of other typical examples I have found.

Insect screen is planned as well as the required ventilation under block and beam.

No blinding just the soil not sure eaxct type but we had to pile so I think it was sandy Clay.

I don't plan to move the stone I like it as drawn just wondered if was an odd detail, we plan to flash under the membrane where wood meets stone. To stop rain blowing in...

I suppose I was questioning if the void was a problem as I'm not quire sure of the detail at the bottom of it.

Timber cladding with stone plinth

fergoose — Tue, 05 Apr 2022 19:33:38 +0100

Section example for previous comment

Timber cladding with stone plinth

fergoose — Tue, 05 Apr 2022 20:15:54 +0100

Posted By: djhThere's no board shown on the outside of the studs. Does the 40 mm woodfibre serve that function?

no the OSB is on the inside, This is the structural racking board the woodfibre on the outsude is rigid insulation. this is the stahdard detail for this to have the osb and vcl on the warmside

Timber cladding with stone plinth

djh — Tue, 05 Apr 2022 20:56:58 +0100

Posted By: fergooseHi thanks for the comments most concerns seam to be about the ground below block and beam. Most sections I have seen tend to have the exterior ground at 150mm below dpc (bottom of sole plate for timber construction) given the insulation required and the thickness of beam and then the void underneath results in this difference, I don't understand how it can be different unless you have a big step up to the house which is not really ideal. Some sections on attached of other typical examples I have found.

Not really sure whose comment you're responding to here, or what point you're making?

150 mm is normal minimum for timber above ground, yes. (Incidentally, do you have level access anywhere?)

No blinding just the soil

I'm surprised building control are happy with that?

Timber cladding with stone plinth

richy — Wed, 06 Apr 2022 09:17:47 +0100

How about using a course of Kingspan insulation along the bottom and making it thicker to fill the void between the frame and the stone plinth. go higher than the stone and bevel the top so the membrane sits on it?