Crawl space heave gauge vapour barrier

[Daniel C]

As I mentioned in my first post, I will split the tasks which I need to work on.

 

I hope I am posting at the most relevant location, this post would be about the "insulation" of a granite house crawl space.

The crawl space is about 30 cm deep.

I have been advised to install/lay a heave gauge vapour barrier and put sand on it as an extra protection against vapour (joist wet root).

When I started to read up on it, I came across a few different solutions:

1. heave gauge vapour barrier (just on the ground) and put sand on it
   1. From my readings: it could create puddles, as water could leak from the side walls
2. heave gauge vapour barrier on the joists
   1. From my readings: bad idea could just collect water and pretty much continuously soak the joists in it
3. heave gauge vapour barrier on the walls as well
   1. From my readings: it might require a pump and/or guttering system
4. heave gauge vapour barrier on the walls, block the air vents, install dehumidifier and sensors
   1. I do not know how would that work with granite house and cavity walls, it might will depend on the wall insulation which I am still looking into it, but that's an other topic

 

What would be the best way top lay down the heavy gauge vapour barrier, do I even need one?

 

Please let me know if you need any other information and if I can answer, I will upgrade the original post.

[Tennentslager]

What are you trying to achieve?

What state are the floor joists?

Is there a vented underfloor?

You mentioned UFH ...is it to insulate the floor?

[Tennentslager]

Don't edit the original post, it will cause confusion

..just add a new post, makes it easier for others to follow the flow ???

[Daniel C]

9 minutes ago, Tennentslager said:

Don't edit the original post, it will cause confusion

..just add a new post, makes it easier for others to follow the flow ???

Thank you, good point.  I will just add the links, but I will not edit anything else on it.

And I guess I will create a post in my "main" post when I created a new topic

 

13 minutes ago, Tennentslager said:

What state are the floor joists?

Some of the floor joists, seem to suffer from wet rot and there are some signs of wood worm.

I would upload photos, but I did not take any when I went in last time and my official move in date is on the 03/07/2018. I am trying to be as prepared before hand as possible.

 

16 minutes ago, Tennentslager said:

Is there a vented underfloor?

There are vents, not sure how many and how big they are, should be able to update in a week. It even seemed that one of the vents is inside the living room, I assume it is for the wall cavitiy and/or crawl space

 

18 minutes ago, Tennentslager said:

You mentioned UFH ...is it to insulate the floor?

I will remove the radiators and want to have the under floor heating as the only source of heating (maybe fireplace, but I still would rather change those as they are gas ones).

I was going to go for Schlüter-BEKOTEC, I will create a post about that one as well, including all the other floor issues (or should I keep it in here as one?)

 

21 minutes ago, Tennentslager said:

What are you trying to achieve?

Well, I am trying to protect my floor joists, as I said I am not sure if I even need the barrier there, but as I will remove all the floor boards, it would be the best time to install.

[Ferdinand]

7 hours ago, Daniel C said:

hank you, good point.  I will just add the links, but I will not edit anything else on it.

And I guess I will create a post in my "main" post when I created a new topic

 

Add a unique project tag to your various threads and they will be able to be read together. Not many people will notice, but it will help you and anyone you are engaged withlosely.

 

Range of threads is good, but too many and it becomes disjointed, I have not got this right yet, so I cannot tell you how many threads works best ?‍♀️.

 

F

[Ferdinand]

I did a project last year on a small bungalow with a suspended underfloor.

 

I Put 100mm rockwool between the joists and a floating floor for more insulation for a u-value around 0.2. We took all the services out of the void, and left a 200mm service ‘duct’ within the floating floor running around the edge of or across some rooms to where sockets and rads would be. Next time I would use one of the ufh systems such as you mention.

 

There were significant benefits in savings on rewire and replumb, and in simplifying the floor construction, no cables in the insulation etc, and we got about £200 from weighing in the old copper pipes etc.

 

Your various options do not seem to consider insulation sufficiently, and that a vapour barrier needs to be on the warm side to avoid condensation. The layer of sand seems to be an attempt at buffering (?), and I question how well that would work in a ventilated void which is open to the outside.They also seem to me to be somewhat technically, rather than fabric, orientated.

 

AIUI two ways ventilated voids have traditionally been ‘greenly’ renovated in the last decade or two are

 

1 - Leave it ventilated, insulate under floor, vapour barrier over floor, then heating in room. And ufh requires a lot of insulation as it is low temp compared to rads and actually touching the floor. Ventilation under floor ie air bricks keeps joists dry.

 

2 - Seal the void to exclude moisture completely, fill it entirely with insulation such as polybeads or LECA in a water impermeable lining (ie poly sheet). Joists are kept dry because they are in a warm environment so water cannot condense on them. There are People who have got that approved by Building Control.

 

I went with 1 as my BCO raised his eyebrows about 2. Would have got it through at the cost of some time delay and a professional report. 

 

Your other option is to rip it out and insert an insulated slab, which in some ways is much simpler. 300mm ish is enough depth I think.. if you are gutting I would consider that. Do not underinsulate your floor if using ufh.

 

One more thing to watch is the height of your doors, and that there are sufficient trimming margins. This caught me out and I have a shed full of 50mm Celotex sheets that I had to replace with 25mm ones, to remind me of the non-existence of doors which can be trimmed by much more than 60mm.

 

It may be useful to have a conversation about the details over on the Green Buildig Forum and/or in our Boffin’s Corner. Mine is in Notts, and your local environment may vary.

 

Ferdinand

 

 

Edited June 25, 2018 by Ferdinand

[Daniel C]

3 hours ago, Ferdinand said:

Add a unique project tag to your various threads and they will be able to be read together. Not many people will notice, but it will help you and anyone you are engaged withlosely.

Hi Ferdinand

Thank you for the idea, now sure how to do that yet, but I will have a look around.

 

Thank you again for your detailed overview.

I think I might not be splitting up the topics right, so I should include info about the joists, floor replacement and the underfloor heating.

 

Current understanding and my plans:

1. I was planning to put the heavy gauge vapor barrier on the crawl space, which is in your description should not require.
2. I will replace or marry up the floor joists depending on their status
3. When replacing the joists at the external end, I will protect them with some foil for extra water resistance
4. My joists are about 50x130mm so I should be able to use 100mm celotex (or any brand) insulation boards. Drawing:
   
5. Replace floor boards with 18mm plywood
6. Install heave gauge vapor barrier on the plywood floor
7. Install UFH
8. Porcelain tiles and laminate floor on top of the UFH

If I understood correctly, you think this probably will not be enough for an efficient insulation for UFH.

I did not detail the materials yet, as I wanted to make sure I have the process right first.

Does it work looking into filling up the entire crawl space as your options 2? My crawl space is just soil, does it require any other preparation?

 

Good point about the doors, I have been warmed about that.

 

[Daniel C]

Not sure how much would it help but there could eb a possibility to install L brackets and use 150mm insulation boards like that:

 

What do you think? Not sure how beneficial it would be.

 

[Jeremy Harris]

100mm is really a bit marginal for UFH, where the floor will be a lot warmer than it would otherwise be and so lose more heat downwards.  If you can get spaced battens under the floor joists then that might be an option to support the insulation. Alternatively, you could try just bonding the insulation at the sides with low expansion foam.  Low expansion foam bonds very well to both PIR and timber, and may well be plenty strong enough to both hold the insulation in place and seal it at the sides.  It sets very quickly (five minutes or so) so with luck you should be able to work from one side, using temporary supports under the insulation to hold it up until the foam cures, with only the last bay being the slightly trick one where you only have access from above.  Making that bit a really tight fit, so you can squirt some foam along the joist and then tap it down into place should work OK.

 

I'd definitely go with 150mm PIR if you possibly can, you certainly won't regret adding more insulation.  We have 300mm of EPS under our floor, roughly the same as about 200mm of PIR.

[Daniel C]

OK, I will go for 150mm minimum, maybe even 200mm. Few questions:

• Do I need to do anything with my joists, should I put insulation on them from above?
• I assume I leave the vents open and clear the way they meant to be, should not I?
• Do you agree on replacing floor board with ply wood?
• Is my drawing above seems alright?

[Jeremy Harris]

Ideally insulate over them, but frankly the hassle of doing that, as it'll raise the floor etc, probably isn't worth it for the small improvement by reducing thermal bridging.  Tight fitting insulation to the sides of the joists, foamed in place, with significantly reduce the thermal bridging through the joists anyway, by reducing 3D heat flow to almost wholly 2D.

 

Leave the underfloor vents open so that the cold space under the insulation remains well-ventilated, to prevent damp build up.

 

Plywood is a good choice for a sub-floor, but you could equally well consider using T&G OSB3, which might be cheaper and would do as good a job if glued and screwed down well (our first floor is 18mm T&G OSB3 on 400mm centre joists and is fine).

 

The drawing looks fine, I just think you can do away with the L brackets and just fix the PIR in place with low expansion foam.  Others may care to comment on this, but it's what I'd do.

[Daniel C]

Perfect, thank you.

 

Yes I was going to go with your suggesting regarding the expanding foam as glue.

I think I should be able to get 18mm ply for relatively, cheap will update on the price and quality when I manage to get them.

[PeterW]

If your joists are 150mm then I would drop a few roofing battens down the gap and turn them across the joists to catch the insulation onto. Then as @JSHarris says, foam down the sides to hold it tight and stop and convection currents. 

 

Are you adding UFH to the mix too ..?

[Daniel C]

The joist are just around 130mm ( I will remeasure them next week with a caliper as I am not sure), although I still could put 20mm wood on them and then put some beams across to help pushing in the insulation boards, good idea @PeterW

 

2 hours ago, PeterW said:

Are you adding UFH to the mix too ..?

I will install UFH, it is on my drawing above. I am planning to use Scluther bekotec (water), any feedback on it?

[PeterW]

Sorry, missed that. 

 

Just put it under the OSB and use either a floating floor or use something like a spreader plate set into the PIR  as otherwise you’re building two floors. 

[Daniel C]

No worries.

I mean to have just every say 2m across the joists. You are right, I would not want to build a second floor under the insulation.

 

I am still trying to decide between running or dry screed for the UFH, I started to ask for quotes for a screed pump, and I may well end up cheaper to hire someone who can do the dry screed nicely, I do not think I would be able to do it nice and level.

[Ferdinand]

8 hours ago, Daniel C said:

Perfect, thank you.

 

Yes I was going to go with your suggesting regarding the expanding foam as glue.

I think I should be able to get 18mm ply for relatively, cheap will update on the price and quality when I manage to get them.

 

At this stage have a look at the savings threads in the General Discussion area. The first one is things you can put in place that are more like 'systems'. My favourite is a Trade Account plus Reloadable Cash Card at Wickes, which is another 20% off after the multibuys, but we all have our wrinkles.

 

 

and

 

 

Edited June 26, 2018 by Ferdinand

[Ferdinand]

11 hours ago, Daniel C said:

OK, I will go for 150mm minimum, maybe even 200mm. Few questions:

• Do I need to do anything with my joists, should I put insulation on them from above?
• I assume I leave the vents open and clear the way they meant to be, should not I?
• Do you agree on replacing floor board with ply wood?
• Is my drawing above seems alright?

 

With that setup - especially the celotex protruding beneath the joists imo you need to make sure your vents are very clear - if you need them you can use snorkels to get them below the level of the insulation. The reason aiui is that your joists become more enclosed than before and so if they do get damp (depends on climate) the setup has more resilience. That should not be a problem, but there is the Law of Murphy.

 

In the one I did we didn't take up the floor that thoroughly - just a couple of boards every .8m or, and used rockwool and a staple gun, plus celotex on top leaving the existing floor in place.

 

Ferdinand

 

Edited June 26, 2018 by Ferdinand

[Ferdinand]

19 hours ago, Daniel C said:

23 hours ago, Ferdinand said:

Add a unique project tag to your various threads and they will be able to be read together. Not many people will notice, but it will help you and anyone you are engaged withlosely.

Hi Ferdinand

Thank you for the idea, now sure how to do that yet, but I will have a look around.

 

Define a tag eg DanielFloor, and add it in to the tags by editing the first post of your thread(s).

 

Click on anywhere the tag appears to list all posts on that tag. Or search by tag.

 

For Ninja level forum reading you go into Browse > My Activity Streams > Custom and set up a stream on that tag. 

 

F

[Ferdinand]

Two Four we haven’t mentioned.

 

While the floor is up do all your joists with wood treatment as a matter of course. I Use one of the Five Star multitreatments. Last time was Cuprinol as they were 3 for 2 somewhere. It may feel expensive, but is one to do imo. 

 

I am not sure whether you plan ply or OSB. I think both should be OK, though personally I would go OSB3 as it usually the same price as the other OSB. Others may differ on that.

 

Screw or nail the floor? Personally I prefer screwing to nailiing to future proof, and I use a collated screwer bought off eBay. But I renovate properties mainly to keep for a decade or two. Others may differ.

 

And think about tools. If you plan future projects it may be a good point to buy something powerful and shiny. Seriously, having an impact or collated driver is a big benefit.

 

Ferdinand

 

Edited June 26, 2018 by Ferdinand

[Daniel C]

Thank you for all your replies @Ferdinand

1. Discounts:
   1. I will look into the discount threads, I am sure they will be more then beneficial
2. Venting:
   1. I will make sure to clear the vents, of course as soon as I start doing that I will post photos, and hopefully videos.
3. Tagging:
   1. Tagging is done, thank you for explaining
4. Wood and joists treatment:
   1. I was looking into treatment against wood worm, wet and dry root. I assume wood worm not even important if I keep the joist dry, but well. I guess I newer know.
   2. I assume I do not need to apply any treatment if I fully replace the joists, or at least on the replaced bits if I use C16 graded ones, or do I? I know I should threat them if I cut them.
   3. Do I need to threat the ply wood as well?
   4. I am planning to make a separate thread for the floor joists/treating, but maybe there is no point, just expand this one to make it easier to search for other users in the future.
5. Floor:
   1. I will go for Ply not OSB
   2. I was gonna go for nails, I was looking to get these ones: TurboGold PZ Double Self-Countersunk Woodscrews 5 x 60mm 100 Pack for 18mm pl
6. Tools:
   1. I was going to get a nail gun and a plunge saw, depending on if I use any other support for the insulation boards than the expanding foam. If I do not,  I might won't need the nail gun just now.
   2. I got already some tools like reciprocating saw, jigsaw, corded and cordless drill from different brands and so on.
   3. Do you know anything about VanHouse brand, their tools seems quite cheap and they do not have bad reviews? 

[Daniel C]

Just remembered that there is a timber report which have been made before the property went on market. Regarding the heavy gauge vapor barrier:

"Solum

From the existing ground floor hatches, a visual inspection of the sub-floor area revealed the solum to be unsealed and significantly damp with one or two localised areas of ponding water caused by deeper sump pits having been formed for access points for services. This sub-floor dampness together with limited sub-floor ventilation creates conditions suitable for the germination and growth of wood rotting fungi and insect attacks such as are present. In view of these findings we would recommend that the solum be overlaid with our heavy gauge vapour barrier in order to prevent sub-floor evaporation and condensation further affecting ground floor timbers and with works being carried out as detailed in our attached schedule headed “Solum Schedule”.

Note:

Please note that our heavy gauge vapour barrier is designed to prevent sub-floor evaporation and condensation affecting flooring timbers, it is not designed to prevent flooding of the sub-floor area caused by any significant water ingress. Our vapour barrier will be finished with a layer of sand in order to hold this in position."

 

I was going the leave the crawls space the way it is after your comments. Is the report section above changes that?

Edited June 27, 2018 by Daniel C

[ProDave]

If you are going to lay a vapour barrier to stop moisture from the ground making the sub floor void damp, I would think some form of gravel would be better to weigh it down, rather than sand, which would probably just end up being permanently damp and not solve the issue.

[Daniel C]

@ProDave From the discussions from above, I pretty much draw the conclusion that there is essentially no point to put down vapour barrier if I insulate the floor and install UFH. What do you think?

 

Correction: I am going to install the vapour barrier between the Ply wood and UFH.

Edited June 27, 2018 by Daniel C

[Ferdinand]

34 minutes ago, Daniel C said:

@ProDave From the discussions from above, I pretty much draw the conclusion that there is essentially no point to put down vapour barrier if I insulate the floor and install UFH. What do you think?

 

Correction: I am going to install the vapour barrier between the Ply wood and UFH.

 

You need the vapour barrier to prevent the wet warm air from eg your breathing condensing in your floor structure where there is a cold surface.

 

Given your ground conditions you could consider an insulated concrete slab floor instead.

Edited June 27, 2018 by Ferdinand