I plan to build a sunroom along the long side of the house and I'm weighing the pros and cons of the foundation. The base already consists of gravel as a precaution after last year's drainage work.
Option 1 involves insulating with edge elements and cellular plastic at the bottom and covering with concrete. I don't know whether to install underfloor heating or not, but one might as well do it while in the process.
Option 2 is to cast pillars, build a frame, insulate, and screw on a wooden deck.
Option 2 I would do entirely myself and it seems like the cheaper option. However, I would be creating a crawl space that might not be completely desirable... It would also be manageable if there are problems in the future with the sewage, which lies in the gravel under the sunroom, and if later on someone decides to run something through the sunroom.
The advantage of casting is that you avoid the crawl space issue, otherwise, I only see disadvantages...
What is to be preferred? Is there a significant risk of moisture problems if building on pillars 10cm above gravel level?
Option 1 involves insulating with edge elements and cellular plastic at the bottom and covering with concrete. I don't know whether to install underfloor heating or not, but one might as well do it while in the process.
Option 2 is to cast pillars, build a frame, insulate, and screw on a wooden deck.
Option 2 I would do entirely myself and it seems like the cheaper option. However, I would be creating a crawl space that might not be completely desirable... It would also be manageable if there are problems in the future with the sewage, which lies in the gravel under the sunroom, and if later on someone decides to run something through the sunroom.
The advantage of casting is that you avoid the crawl space issue, otherwise, I only see disadvantages...
What is to be preferred? Is there a significant risk of moisture problems if building on pillars 10cm above gravel level?
Since you already have a macadam surface, you've already completed half the work of pouring a slab. So I would definitely choose that option.
Because I always tend to overdo things, I would of course have embedded underfloor heating and electricity in the slab and used properly insulated glass so that the room can be used year-round. Or at least I would have calculated the cost. A properly insulated sunroom works better in the summer (keeps heat out) and in the winter (keeps the room warm). Or at least prepared the slab so that it can be built in that way.
Because I always tend to overdo things, I would of course have embedded underfloor heating and electricity in the slab and used properly insulated glass so that the room can be used year-round. Or at least I would have calculated the cost. A properly insulated sunroom works better in the summer (keeps heat out) and in the winter (keeps the room warm). Or at least prepared the slab so that it can be built in that way.
Yep, that's definitely my plan to do it properly. But if we choose wood flooring, which is what we're leaning towards, then underfloor heating isn't that great, and a slab seems unnecessary in that case. If the choice were tiles, then the decision would be obvious.
The cost of the slab is also a bit higher. I've poured concrete in the basement myself and probably won't do it again on my own, so we'll have to hire someone in that case + concrete pump truck =>25k just for the pouring
If you choose to build up x cm over the crushed stone, what should you keep in mind to prevent moisture problems? The crushed stone is underneath, so I don't see what more I should do
Speaking of the price, it goes up significantly when you increase the insulation factor. I've checked Skånska Bygg and going from spring-summer-autumn to winter almost doubles the price. Maybe it's worth paying a bit extra for heating when you choose to use it in the winter.
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If you're going to use it in the winter, you should probably not have underfloor heating but rather a fan convector or a radiant heater. Underfloor heating makes it take about a day to heat up the slab, while the radiant heater and fan convector provide immediate effect.
It's also a bit of a question of what you actually want. A fully insulated glassed room is hardly a sunroom anymore. I've also thought about that but have settled for a patio so far.
It's also a bit of a question of what you actually want. A fully insulated glassed room is hardly a sunroom anymore. I've also thought about that but have settled for a patio so far.
I have a sunroom at the cabin. It has 16mm multiwall polycarbonate and "summer doors". The sunroom is on piers, the floor consists of asfaboard - 100mm insulation - windproof fabric in the floor framework, and decking on top. We use it in spring, summer, and fall. No problems with a 2kW infrared heater on cold (8-10 degrees outside) days. For the house, I want something a bit better and would like to use it year-round. Call it an extension or a sunroom 
It doesn't need to be heated on weekdays, but it's nice to be able to ramp up the heat on weekends, for example. If you're going to have tiles, it gets so darn cold without underfloor heating, but maybe it's better to install some comfort electric heating on the "surface" to take the edge off the cold, and then a fan convector for quick heat.
It doesn't need to be heated on weekdays, but it's nice to be able to ramp up the heat on weekends, for example. If you're going to have tiles, it gets so darn cold without underfloor heating, but maybe it's better to install some comfort electric heating on the "surface" to take the edge off the cold, and then a fan convector for quick heat.As I wrote earlier, I have the drain under the conservatory. If there were to be any issues with it in the future, it would be much easier to deal with a raised wooden floor than a reinforced cast insulated slab with underfloor heating....
How high above ground level should you have the finished floor?
If the floor level is close to the ground surface, a concrete slab is really preferable. But if it is a decent bit above ground level, I think the crawl space alternative feels the most sensible.
If the floor level is close to the ground surface, a concrete slab is really preferable. But if it is a decent bit above ground level, I think the crawl space alternative feels the most sensible.
One can build up a crawl space with leca blocks and frame up a floor on it, and if you later want to have an "inner room," you can fill it with foam plastic and cast a proper slab using the crawl space as an edge. It can be made inspectable via a floor hatch or through some inspection holes where a camera can be sent in.
You can even be clever enough to install some lights in there to make it easy to inspect.
You can even be clever enough to install some lights in there to make it easy to inspect.
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· Etelä Pohjanmaa
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Out of sheer curiosity, what do you mean by the crawl space problem? If you have issues with ground moisture, you have it regardless of whether you have a crawl space or a slab. The moisture doesn't disappear just because you hide it under the slab, except that it might feel psychologically better if you don't have to see the problem.
Well, if you pour a slab on the ground, you don't have air with different humidity and temperature variations in contact with a joist, so there is some difference after all. It's generally considered a risk construction with crawl space foundations, right?
I don't think there are any moisture problems under a potential slab. I filled it with 0.5-2 meters of mackadam! The 2 meters is because I dug down to the rock and drained the basement (whose wall stands on rock) last year and then filled it with mackadam.
Another thing that bothers me a bit about slabs... I hired a "knowledgeable" concrete slab worker a couple of years ago who poured a new slab in the kitchen and hall. It looked good until it was time for flooring... then we discovered it was quite uneven, and suddenly 10,000 SEK went to leveling compound as well... So a slab might be the best in an ideal world, but I do think that the price can increase quite a bit anyway.
I don't think there are any moisture problems under a potential slab. I filled it with 0.5-2 meters of mackadam! The 2 meters is because I dug down to the rock and drained the basement (whose wall stands on rock) last year and then filled it with mackadam.
Another thing that bothers me a bit about slabs... I hired a "knowledgeable" concrete slab worker a couple of years ago who poured a new slab in the kitchen and hall. It looked good until it was time for flooring... then we discovered it was quite uneven, and suddenly 10,000 SEK went to leveling compound as well... So a slab might be the best in an ideal world, but I do think that the price can increase quite a bit anyway.
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· Etelä Pohjanmaa
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The mantra that crawl spaces are a risky construction is probably unique to Sweden. A crawl space is more manageable because you're working with the medium of air, which is easier to control than concrete. A slab is practically the same as filling the crawl space with concrete.
ok... but if I have a slab that occasionally gets some moisture from the ground via foam plastic (however that should happen) what does it do?
On the other hand, if I have wood that cyclically gets condensation due to temperature changes in the air around the wood construction, it sounds to me like it could cause worse problems!?!? Maybe it's exaggerated, what do I know...
On the other hand, if I have wood that cyclically gets condensation due to temperature changes in the air around the wood construction, it sounds to me like it could cause worse problems!?!? Maybe it's exaggerated, what do I know...
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· Etelä Pohjanmaa
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The slab probably withstands the moisture, the problem is rather that the moisture travels up into what is above the slab. A crawl space can be dried up quickly and painlessly, a damp slab takes longer.