Timber cladding issues

rajanm

Hi everyone

We've had a garden room built in the last few months with larch cladding. 

The cladding is showing signs of severe mould already and we believe it's because the cladding itself is in contact with the ground (i.e. there is no gap underneath it).

The garden room company say it's just something that affects timber cladding but we think it's to do with this lack of ground clearance.

Building control have verbally signed off the building but haven't formally issued a certificate. I have asked the officer to come round on Monday. We owe the garden room company a small amount of money but I'm hoping the building officer will say the cladding needs to be cut before the certificate can be issued. 

Does anyone know if there are any building regs rules on timber clearance from the ground?  I've heard it's a minimum of 150mm but I can't find that figure anywhere in the building regs.

ThisIsWeird

Photos?

There's a 'reg' - certainly a building recommendation/requirement - that the DPC layer in a solid wall should be at least 150mm above ground level, so that rain splashback doesn't constantly land above the DPC layer and potentially cause damp to penetrate through. 

If your builders have taken the cladding layer literally down to ground level, then that will almost certainly result in near-permanently damp bottom boards, and that is a design flaw imo.

And if there isn't a vent space underneath the room - presumably all a timber build - that is also asking for trouble; a permanently damp bottom.

A solution could be to reduce the ground height immediately around the room's perimeter, but it all just sounds 'not good'.

Photos!

stuart45

The lifespan of Larch cladding is said to be 50-60 years, apart from that in contact with the ground which is 10-15 years.

rajanm

ThisIsWeird said:

Photos?

There's a 'reg' - certainly a building recommendation/requirement - that the DPC layer in a solid wall should be at least 150mm above ground level, so that rain splashback doesn't constantly land above the DPC layer and potentially cause damp to penetrate through. 

If your builders have taken the cladding layer literally down to ground level, then that will almost certainly result in near-permanently damp bottom boards, and that is a design flaw imo.

And if there isn't a vent space underneath the room - presumably all a timber build - that is also asking for trouble; a permanently damp bottom.

A solution could be to reduce the ground height immediately around the room's perimeter, but it all just sounds 'not good'.

Photos!

No there is a space around the room. It sits on ground screws about 30cm up in the air 

rajanm

rajanm said:

ThisIsWeird said:

Photos?

There's a 'reg' - certainly a building recommendation/requirement - that the DPC layer in a solid wall should be at least 150mm above ground level, so that rain splashback doesn't constantly land above the DPC layer and potentially cause damp to penetrate through. 

If your builders have taken the cladding layer literally down to ground level, then that will almost certainly result in near-permanently damp bottom boards, and that is a design flaw imo.

And if there isn't a vent space underneath the room - presumably all a timber build - that is also asking for trouble; a permanently damp bottom.

A solution could be to reduce the ground height immediately around the room's perimeter, but it all just sounds 'not good'.

Photos!

No there is a space around the room. It sits on ground screws about 30cm up in the air 

Sorry also the dpc consists of a breathable membrane and vapour barrier that the building is wrapped up in.

I did see on building regs that cladding should 'resist penetration, not be damaged by precipitation or carry it to any part of a building that could be damaged by precipitation.'

I can't see how my cladding is resisting penetration if it's in contact with the ground.  It is already being damaged by precipitation as evidenced by the mould. And then I guess that mould could spread to the timber battens that it's fixed on to behind it?

That's what I'm hoping the building inspector will think too

Doozergirl

You just need the garden room company to fix it.   The cladding shouldn't be touching the ground, that is a no-brainer.  

It's nice if the inspector backs you up, which they no doubt will, but you don't need them and you're within your rights to withhold that small amount.  

Pictures would be helpful.  

rajanm

Doozergirl said:

You just need the garden room company to fix it.   The cladding shouldn't be touching the ground, that is a no-brainer.  

It's nice if the inspector backs you up, which they no doubt will, but you don't need them and you're within your rights to withhold that small amount.  

Pictures would be helpful.  

Yes here are a few that should show you the issue and also the mould developing. The cladding was already touching the ground when we put the patio in 

ThisIsWeird

Hmm.

Who put the patio in? It should not have been taken that close to the building, unless at a much lower height. I wouldn't start complaining to the GR builder until you sort that patio - most likely by cutting away a nice strip from around the wall. Currently, the patio is more at fault than the building.

Could we have a photo of the sides of the building, so we can see how close the ACTUAL building has been taken to the ACTUAL ground?

ThisIsWeird

(Oh, nice building, by the way. This needed Building Control oversight? Why - is it a habitable space?)

rajanm

ThisIsWeird said:

(Oh, nice building, by the way. This needed Building Control oversight? Why - is it a habitable space?)

It has a bathroom.  The patio sits just at the starting point of the building.  The building itself is up on ground screws 

Apodemus

I wonder if this is not simply splash-back from the rain hitting the patio?  The lower portion of the cladding is always going to be exposed to more water for longer as it runs down the walls, particularly during a damp, mild spell of weather. 

Also, while the timber looks "mouldy" at the moment, larch cladding will always look a bit off-colour during the initial stages of its weathering and again that weathering will be different at the lower edges of the wall than the top.  Eventually it will all even out to give a nice aged-timber effect, but it can be hard for some people to accept the intermediate stage.