Problem with exterior render where plinth and wall meet (timber frame bungalow) causing condensation on interior skirting boards

[dpmiller]

Any chance the cavity is bridged at or above floor level?

[Iceverge]

Could you post some pictures of the skirting board please?
 

I too am suspicious if it is cold bridging leading to condensation rather than bulk water ingress. 

[Naoma]

1 hour ago, Iceverge said:

Could you post some pictures of the skirting board please?
 

I too am suspicious if it is cold bridging leading to condensation rather than bulk water ingress. 

 

This is a picture of the skirting board in an corner with two external walls (all furniture have been removed to allow enough ventilation to avoid mood)

 

We have carpet with underlay in some rooms which have the same issue on the external walls

[Radian]

18 hours ago, Naoma said:

This a picture of our front door, showing the floor level on the inside in relation to the gap on the outside, I hope this useful (sorry had to take the last two pic in the evening)

Is that concrete I can see underneath your inside door mat? If so how can there be any insulation between the concrete raft and floor tiles?

[Iceverge]

Ok, take this with a pinch of salt as we can't see inside your wall or behind the render. 

 

 

I think the timber frame and insulation was erected flush with the edge of the concrete foundation. This should have been overlapped with a step to allow rain water to drip clear of the wall and not risk running down into the rendered foundation. Now it has gotten behind the foundation render and damaged it, either just thought water ingress or frost damage. 

 

However I don't think that any water has made its way into the inside of the house, rather that the soleplate at the bottom of the wall has been sitting directly on the cold foundation and has caused condensation on the skirting boards. There should have been measures taken to keep the soleplate warm or a vapour barrier and insulation in board to prevent condensation. 

 

It may follow that the soleplate is suffering from decay having been cold and wet for so long but without seeing inside the wall I couldn't say. 

 

I would take off the the skirting boards in a good few locations, drill a large hole in the plasterboard and investigate the condition of the soleplate, and the back of the OSB as well as the insulation to see if any of it is damp or rotten. Hopefully it won't be but it's impossible to tell without looking. 

 

Hopefully this survey will give positive results but only time will tell. 

 

If it does then you're faced with trying to fix the problem. There's two issues here.

 

1. Water getting into the wall 

2. A cold soleplate collecting condensation. 

 

It depends how much money you have to spend but if it was my house I would reapply another entire layer of insulation (EWI) and render over the whole wall right down to the foundations and detail it properly with all bellcasts, drips and overhangs. This would solve both problems. 

 

If you're stuck for money you could endeavour to just do the bottom 600mm of the wall and right down to the foundations with EWI and detail it carefully to allow rainwater to be always directed down and out. 

 

I hope this helps. 

 

 

 

[Naoma]

17 hours ago, ProDave said:

I would want to strip some of the grey render off to understand firstly why it is so thick?  It is normally just 2 coats of sand / cement render and thinner than the roughcast coat.  and secondly to understand the logic of what they were trying to achieve with that gap?

We had a bit of a poke in an area where the render is quite cracked and behind the grey render is concrete.

 

So far we have not found anybody you could explain what the gap is for, nor anybody who has seen it before, we really wanted to know what it is for so we are not making a problem worse, but the original contractor is no longer in business.

[Naoma]

44 minutes ago, Iceverge said:

Ok, take this with a pinch of salt as we can't see inside your wall or behind the render. 

 

 

I think the timber frame and insulation was erected flush with the edge of the concrete foundation. This should have been overlapped with a step to allow rain water to drip clear of the wall and not risk running down into the rendered foundation. Now it has gotten behind the foundation render and damaged it, either just thought water ingress or frost damage. 

 

However I don't think that any water has made its way into the inside of the house, rather that the soleplate at the bottom of the wall has been sitting directly on the cold foundation and has caused condensation on the skirting boards. There should have been measures taken to keep the soleplate warm or a vapour barrier and insulation in board to prevent condensation. 

 

It may follow that the soleplate is suffering from decay having been cold and wet for so long but without seeing inside the wall I couldn't say. 

 

I would take off the the skirting boards in a good few locations, drill a large hole in the plasterboard and investigate the condition of the soleplate, and the back of the OSB as well as the insulation to see if any of it is damp or rotten. Hopefully it won't be but it's impossible to tell without looking. 

 

Hopefully this survey will give positive results but only time will tell. 

 

If it does then you're faced with trying to fix the problem. There's two issues here.

 

1. Water getting into the wall 

2. A cold soleplate collecting condensation. 

 

It depends how much money you have to spend but if it was my house I would reapply another entire layer of insulation (EWI) and render over the whole wall right down to the foundations and detail it properly with all bellcasts, drips and overhangs. This would solve both problems. 

 

If you're stuck for money you could endeavour to just do the bottom 600mm of the wall and right down to the foundations with EWI and detail it carefully to allow rainwater to be always directed down and out. 

 

I hope this helps. 

 

 

 

Iceverge, thank you very much for your detailed feedback.

 

We were thinking of adding insulation to the exterior to reduce heating cost, but we're told it's 15 000 EUR, so we might have to go with just doing the bottom part.

 

How would the correct detailing look like, so that water would always drain away properly?

Are there any specific materials that need to be used?

 

Is there anything that could be done if there is damage inside the walls?

 

Can we be relatively certain that this gap has no purpose like breathing or expansion or anything else? As the proposed solution would mean that the gap will be closed off.

 

We really appreciate all the help

[Iceverge]

18 hours ago, Naoma said:

How would the correct detailing look like, so that water would always drain away properly?

 

Note the overhang of the top part over the bottom part and the layer of insulation outside the foundation rising walls. Most installers will try to fob you off and terminate the external wall insulation 150mm above the ground. It is very important in your case to keep the bottom of the timber frame warm to prevent condensation. 

 

18 hours ago, Naoma said:

Are there any specific materials that need to be used?

 

Below ground I would use EPS and then maybe XPS. 

 

Above ground EPS or Rockwool probably.

 

18 hours ago, Naoma said:

Is there anything that could be done if there is damage inside the walls?

 

Yikes, you'll be into structural engineering territory. Its hard to say but nothing is beyond rescue, for a price. 

18 hours ago, Naoma said:

Can we be relatively certain that this gap has no purpose like breathing or expansion or anything else?

Assumimg the wall buildup is as described I think it's a mess up first day. 

 

If it is a render board with a cavity then it would need a space for air to circulate but i don't think thats what is installed. 

 

18 hours ago, Naoma said:

We were thinking of adding insulation to the exterior to reduce heating cost, but we're told it's 15 000 EUR, so we might have to go with just doing the bottom part.

 

Are you planning on remaining in the house? As you're going to have to do something anyway it would be a missed opportunity to 1/2 do it, and it might look quite ugly. 

 

Do you have any wide shots of the house including a pic of your soffit overhang?

 

Get digging into the wall and analyse what you have also. You could cut a 20cm x20 cm hole out of the plasterboard (not below an electrical fixing or any pipes) in a discrete corner where there's damp and see whats there. Its not difficult to DIY patch up later. 

 

 

 

[Naoma]

9 hours ago, Iceverge said:

 

Note the overhang of the top part over the bottom part and the layer of insulation outside the foundation rising walls. Most installers will try to fob you off and terminate the external wall insulation 150mm above the ground. It is very important in your case to keep the bottom of the timber frame warm to prevent condensation. 

 

Iceverge, again thank you so much for your explanation.

 

As on the pictures, we have around most of the house a concrete path, would we need to break it to get the insulation below the ground or would it be sufficient to let it go down flush with the path?

 

Here are some pictures from back and front, I can get close up of the soffit if useful.

 

Yes, we have to remain in the house during all works. 

 

As a next step we will investigate the walls further, I will upload some pictures asap

[Naoma]

Here are some wider shots of the house from a few weeks ago

[Radian]

On 17/03/2022 at 14:23, Iceverge said:

However I don't think that any water has made its way into the inside of the house, rather that the soleplate at the bottom of the wall has been sitting directly on the cold foundation and has caused condensation on the skirting boards. There should have been measures taken to keep the soleplate warm or a vapour barrier and insulation in board to prevent condensation. 

That's what I've been trying to get across. But it's guesswork at a distance. A proper section needs to be taken to understand the build-up. A few small drill holes might just reveal the issue. I agree with you that a section of skirting could be removed and in addition to drilling horizontally, I would suggest a vertical hole to explore the floor layers. Once the skirting is replaced nothing will show.

[Iceverge]

20 hours ago, Naoma said:

would it be sufficient to let it go down flush with the path?

 

It would help but ultimatly not be the best solution. EWI suppliers will tell you it'll be fine but thats because of the generally terrible understanding of how thermal bridging works, and they don't want the hassle of digging and replacing footpaths etc. Have a look at the below post to see the difference with and without taking insulation down to the foundations.

 

 

You're better off tackling this once and properly, treat it as not only remedial actions but a comprehensive thermal upgrade. Remember if it's left your house will gradually rot away and if done well you will have a much warmer and really cheap to run house.

 

The wide soffit is good news. you should be able to do another layer of ewi without going near the roof. 

 

Assuming the wall structure is ok inside I would proceed as follows. 

 

1. Dig out the footpaths.

2. remove the soffit

3.Apply another layer of EPS EWI outside the current one, the thicker the better .

( you may need to remove the current layer, you may not)

Take it from as high up behind the soffit as possible to ensure it meets the roof insulation right down to the foundations. It may be 300-900mm below the floor level. This will have the benefit of defacto insulating your floor too. 

4. Move the windows and doors out into the insulation layer if they're not there already. 

5. make sure the insulation goes around all sides of the doors too including below You currently have some bad thermal bridging here.

6. Render the New EWI, replace the soffit.

7. Install a comprehensive french drain and gravel boundary around the house. 

8. Replace the footpaths if you wish.

 

If you could find the budget for new triple glazing and a MVHR unit you would have an extremely comfortable house that required almost no heating.

 

That is of course at one side of the budget spectrum. At the other, keeping the air fresh and damp free through the use of constant mechanical ventilation will help avoid too much condensation. 

 

Something like this

 

https://www.bpcventilation.com/pozidry-compact-479188

 

 

or better still this 

 

https://www.bpcventilation.com/vent-axia-mvdc-ms

 

 

or best of all

 

 

https://www.bpcventilation.com/vent-axia-mvdc-ms

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[Naoma]

Iceverge, great feedback, thank you. I understand your point.

 

We will be getting quotes for the works and will see how far the budget will stretch.

 

We were busy on the weekend having a closer look at the structure of the house, by breaking the interior plasterboard in one of the bedrooms and in the kitchen.

 

The wall in the bedroom is completely dry not a sign of damage of damp!

 

In the kitchen we had some damage to the plasterboard from a small old leak in the plumbing, no damage to the frame), but it gives a really good look on the foundation of the frame, I will upload some pictures asap 

[Naoma]

This the kitchen, where frame meets floor and where the pipes of the kitchen sink go out

 

The outside gab is on the level where that small timber is (underneath the DPC and the big timber with the number 5 written on it)

[Naoma]

Here a wider shot of the same area

[Naoma]

Here a close up of the layer underneath the big timber 

[Iceverge]

That's really good news. Those timbers look sound.  It suggests that your wall is pretty vapour permeable allowing it to dry out easily. 

 

The thermal bridging will really be sucking heat out if you do nothing and there is a high chance of bulk water damage (our wonderful Irish rain!) with the render as it is. 

 

If you want a stop gap solution make sure that the bottom of the internal walls have plenty of free airflow and you keep a close eye on the internal Relative Humidity. A RH meter is very cheap online. You need to aim for below 60% RH through ventilation and heating (it can be tricky without mechanial ventilation). Also patch up the cracks in the external render as is. 

 

 

 

 

[ProDave]

So the unusual "feature" in this build is the DPC and start of the timber frame is above the finished floor level, so the bit of wall the skirting is fixed to is the block wall below the DPC with little or no insulation.

 

I would be looking to take a bit of skirting off in one of the rooms and see how it is fixed.  The block wall seems set back a bit so there might be scope to get some thin PIR insulation in before putting the skirting back.

[Naoma]

3 hours ago, ProDave said:

So the unusual "feature" in this build is the DPC and start of the timber frame is above the finished floor level, so the bit of wall the skirting is fixed to is the block wall below the DPC with little or no insulation.

 

I would be looking to take a bit of skirting off in one of the rooms and see how it is fixed.  The block wall seems set back a bit so there might be scope to get some thin PIR insulation in before putting the skirting back.

On the pic below a view of a corner where on one side the skirting board has been removed,

Unfortunately not really space to add anything there.

[Naoma]

Thank you all so much everyone for the feedback and helpful advice, we have learned a lot about our new house.

 

Time will tell what our budget will allow and there is definitely a lot we need to understand and learn about mechanical ventilation and what might be the best option for our house in that area too, but one step at the time 😉