Hello all knowledgeable helpful writers!
We bought a 1.5-story house about 1 year ago that was completely recently renovated on the inside, built in 1973 with a slab foundation. The facade consists of painted brick and wood. Original roof of asbestos cement.
The house was visually inspected by two surveyors before the purchase, the seller's and ours. The sills have been replaced by the previous owner we know, and the seller we bought the house from also tore up the ground floor's floor, cleared the slab of all organic material, and inspected the sills then. We were informed in writing when purchasing that the sills were thus replaced and that no bad smell occurs in the house. For it smells in the house, outside the house, and our clothes and other textiles have become odor impregnated. This smell was certainly not detectable during the viewings or inspections! We are horrified!
Our well-renowned surveyor informed us that a slab foundation with pressure-treated sills is a risk construction in these types of houses, but at the same time, we were assured that this was addressed in the best way. No other risk construction was pointed out. We therefore proceeded with the purchase happily and without worry.
We have now installed both air supply and mechanical exhaust according to the rules of the art without improvement.
In our search for the odor source, we have discovered that the facade's wood consists of pressure-treated timber!
We have now hired a new surveyor to track the odor source, but he seems divided. Are the sills still the ones that smell, not replaced sufficiently? Is it the facade? Maybe the roof sheathing? We just can't move forward.
Grateful for any advice and tips!
We bought a 1.5-story house about 1 year ago that was completely recently renovated on the inside, built in 1973 with a slab foundation. The facade consists of painted brick and wood. Original roof of asbestos cement.
The house was visually inspected by two surveyors before the purchase, the seller's and ours. The sills have been replaced by the previous owner we know, and the seller we bought the house from also tore up the ground floor's floor, cleared the slab of all organic material, and inspected the sills then. We were informed in writing when purchasing that the sills were thus replaced and that no bad smell occurs in the house. For it smells in the house, outside the house, and our clothes and other textiles have become odor impregnated. This smell was certainly not detectable during the viewings or inspections! We are horrified!
Our well-renowned surveyor informed us that a slab foundation with pressure-treated sills is a risk construction in these types of houses, but at the same time, we were assured that this was addressed in the best way. No other risk construction was pointed out. We therefore proceeded with the purchase happily and without worry.
We have now installed both air supply and mechanical exhaust according to the rules of the art without improvement.
In our search for the odor source, we have discovered that the facade's wood consists of pressure-treated timber!
We have now hired a new surveyor to track the odor source, but he seems divided. Are the sills still the ones that smell, not replaced sufficiently? Is it the facade? Maybe the roof sheathing? We just can't move forward.
Grateful for any advice and tips!
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If it smells like an old cottage and not chemical, it might be something other than the beams, or both. Was there no ventilation when you moved in? Did the realtor ensure that all surfaces were renovated? Walls, floors, and ceilings? I don't think the outer paneling is the culprit in the drama.
B boohoo said:
Thanks for the answer! From outside to inside, it's plastic paint, treated panel, air gap, asfaboard, exterior stud construction with insulation, vapor barrier, and then gypsum. It smells the most on the south side from outside and indoors in all rooms. Even upstairs.B boohoo said:
Gloomy.
The outer panel seems like an unlikely candidate. It’s a bit like a pressure-treated outdoor wooden deck giving off a smell indoors.
I interpret it as if the previous owner has done a speculative renovation? Always risky to buy. The risk is high that the renovation was done as cheaply as possible without regard for the outcome.
I would probably start by making inspection holes to check if the base plates have actually been replaced and how they have been replaced. The problem with base plates in 70s houses is actually two, or three.
In the early 70s (or late 60s), they started casting the base plates into the concrete slab. It was a rational way to anchor the house to the concrete slab. The problem was that IF the concrete slab gets damp (and concrete slabs with that construction from that time do, problem 1), then the embedded wood absorbs moisture. Wood in contact with a concrete foundation should always be protected from the concrete with, for example, tar paper in between. The embedded base plates are always just embedded without any protection.
This was then problem number two. The base plates become damp in most houses from this era. They rot, moisture migrates further up into the walls, and mold problems develop.
In the mid-70s, it was realized that this couldn’t continue, something had to be done. So they chose to use “modern materials” to solve the problem. They began embedding pressure-treated base plates. They are supposed to withstand getting damp. This solved part of the problem, but there was still a moisture migration up the walls (applies only to some houses with extra damp foundations). The mold problems persisted.
But over some years, a new problem emerged. Treated wood starts to smell bad if continuously exposed to moisture, due to a chemical reaction with the impregnating agent. This is problem number 3.
It's entirely possible that the house was mold-damaged at purchase, but temporarily addressed with an ozone treatment. But it is also possible that something (in good faith) was done during the renovation that somehow increased the moisture problem.
You will need moisture experts to assess the problem. Once you know what the problem is, you can consider investigating whether this may be a hidden defect, so you can claim compensation from the seller. It is quite an uphill battle, as this is a risky construction, which increases the requirement for due diligence.
The primary problem with virtually all houses built in the 70s is the construction with concrete slabs on the ground used at that time. It should not be confused with today’s slabs on the ground, which are cast on top of 30 cm of foam. The slabs from back then were uninsulated or incorrectly insulated on the underside, with the main insulation on top of the concrete. Therefore, the concrete is cold. And water vapor evaporating below ground will condense on the underside of the concrete and then be absorbed upwards into the concrete.
This is exacerbated by the fact that, in many cases, there was enormous cutting of corners during construction. When I was in high school in the 70s, 200 series-built villas were constructed nearby on farmland. They leveled the topsoil, laid about 5cm of gravel which was pressed into the soil, without a geotextile. And the concrete slab was cast on top of that. The ground was waterlogged. The previous year they had expanded the high school, and we saw when they were piling, a 6m concrete pile was just placed on the ground and sank under its own weight with a loud "plofff", the next pile didn’t sink until they put the piling hammer on it without hitting. Only when they were up to 5 or 6 piles did the machine start working a bit. The piling machine stood on a raft in the mud; otherwise, it sank. The villas were built about 200m from that spectacle.
The outer panel seems like an unlikely candidate. It’s a bit like a pressure-treated outdoor wooden deck giving off a smell indoors.
I interpret it as if the previous owner has done a speculative renovation? Always risky to buy. The risk is high that the renovation was done as cheaply as possible without regard for the outcome.
I would probably start by making inspection holes to check if the base plates have actually been replaced and how they have been replaced. The problem with base plates in 70s houses is actually two, or three.
In the early 70s (or late 60s), they started casting the base plates into the concrete slab. It was a rational way to anchor the house to the concrete slab. The problem was that IF the concrete slab gets damp (and concrete slabs with that construction from that time do, problem 1), then the embedded wood absorbs moisture. Wood in contact with a concrete foundation should always be protected from the concrete with, for example, tar paper in between. The embedded base plates are always just embedded without any protection.
This was then problem number two. The base plates become damp in most houses from this era. They rot, moisture migrates further up into the walls, and mold problems develop.
In the mid-70s, it was realized that this couldn’t continue, something had to be done. So they chose to use “modern materials” to solve the problem. They began embedding pressure-treated base plates. They are supposed to withstand getting damp. This solved part of the problem, but there was still a moisture migration up the walls (applies only to some houses with extra damp foundations). The mold problems persisted.
But over some years, a new problem emerged. Treated wood starts to smell bad if continuously exposed to moisture, due to a chemical reaction with the impregnating agent. This is problem number 3.
It's entirely possible that the house was mold-damaged at purchase, but temporarily addressed with an ozone treatment. But it is also possible that something (in good faith) was done during the renovation that somehow increased the moisture problem.
You will need moisture experts to assess the problem. Once you know what the problem is, you can consider investigating whether this may be a hidden defect, so you can claim compensation from the seller. It is quite an uphill battle, as this is a risky construction, which increases the requirement for due diligence.
The primary problem with virtually all houses built in the 70s is the construction with concrete slabs on the ground used at that time. It should not be confused with today’s slabs on the ground, which are cast on top of 30 cm of foam. The slabs from back then were uninsulated or incorrectly insulated on the underside, with the main insulation on top of the concrete. Therefore, the concrete is cold. And water vapor evaporating below ground will condense on the underside of the concrete and then be absorbed upwards into the concrete.
This is exacerbated by the fact that, in many cases, there was enormous cutting of corners during construction. When I was in high school in the 70s, 200 series-built villas were constructed nearby on farmland. They leveled the topsoil, laid about 5cm of gravel which was pressed into the soil, without a geotextile. And the concrete slab was cast on top of that. The ground was waterlogged. The previous year they had expanded the high school, and we saw when they were piling, a 6m concrete pile was just placed on the ground and sank under its own weight with a loud "plofff", the next pile didn’t sink until they put the piling hammer on it without hitting. Only when they were up to 5 or 6 piles did the machine start working a bit. The piling machine stood on a raft in the mud; otherwise, it sank. The villas were built about 200m from that spectacle.
What flooring solution do you have after the renovation, mechanically ventilated?
Hello again. Hm, do you mean insulation in the intermediate floor? Half of the ridge is an attic, in the attic there is no smell other than a faint smell of masonite. Nothing we react to at all. The rest of the house is open to the ridge.Jonatan79 said:
Thank you Hempularen for the detailed answer. The syllar should have been replaced by the previous owner in the early 2000s at the latest, and that family renovated for their own use and cared about the house. Therefore, we are confused, can it still smell from that part of the construction?
A passively ventilated floor risks pushing moisture towards the external walls. Do you have ventilated baseboards?
Are partition walls placed directly on the slab, or has sill insulation been used there as well?
I would look for any odor/moisture in the outer corners behind any baseboards. Especially if you have any wallpaper that goes down behind the baseboards.
Are partition walls placed directly on the slab, or has sill insulation been used there as well?
I would look for any odor/moisture in the outer corners behind any baseboards. Especially if you have any wallpaper that goes down behind the baseboards.
If the sill has been replaced and the slab is cleared of any embedded studs, my guess is that the asfaboard and insulation have been contaminated with odor. The main culprit is likely the asfaboard, and when you mention that the south wall is the worst, it should be because the heat releases the odor.
To be sure, one should open a part of the wall, take out a piece of board, put it in a plastic bag, then leave the home to reset the sense of smell, and then smell the board to see if it has an odor.
You have also switched to mechanical ventilation, how balanced is the flow? A large underpressure in the house will draw air from all different gaps in the house, so there is a risk that air with odor comes through gaps in the walls.
To be sure, one should open a part of the wall, take out a piece of board, put it in a plastic bag, then leave the home to reset the sense of smell, and then smell the board to see if it has an odor.
You have also switched to mechanical ventilation, how balanced is the flow? A large underpressure in the house will draw air from all different gaps in the house, so there is a risk that air with odor comes through gaps in the walls.