Green Building Forum - Foundations for a suspended timber floor Tue, 19 Dec 2023 06:47:56 +0000 http://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272302#Comment_272302 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272302#Comment_272302 Wed, 06 Feb 2019 23:44:09 +0000 bardo Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272304#Comment_272304 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272304#Comment_272304 Thu, 07 Feb 2019 00:25:02 +0000 djh Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272305#Comment_272305 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272305#Comment_272305 Thu, 07 Feb 2019 02:17:06 +0000 gyrogear
However, your building code is certainly different from mine, which demands 600mm height minimum, and 0.6 sq. metres of access.

If on the other hand it is a construction void, you will not have future access for checking your joists or adding extra insulation.

(without wanting to appear overtly intrusive, what is your floor insulation plan ?).

I inherited an 800mm unfinished concrete CS, that is twice the height of yours... When I discovered the actual heat-losses through the floor-above and decided to insulate it, I discovered it was a lot of work... even with years of caving (and cave-digging) experience not to mention a (once) slender frame... (?)
:shamed:

You might try running a Topic Search for "suspended timber floor"...

Otherwise, here is a good read:
https://www.sciencedirect.com/science/article/pii/S0378778817311350

Good luck

gg]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272306#Comment_272306 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272306#Comment_272306 Thu, 07 Feb 2019 07:17:15 +0000 tony
Dpc is neither here nor there under concrete obersite

What do sleeperbwalls sit on?]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272309#Comment_272309 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272309#Comment_272309 Thu, 07 Feb 2019 07:44:32 +0000 bardo Posted By: gyrogearFWIW, if this is going to be a crawlspace, then IMHO 400mm seems very minimal for future access, in which case you might consider digging access galleries or refuges or even a sump while there is still time...

However, your building code is certainly different from mine, which demands 600mm height minimum, and 0.6 sq. metres of access.

If on the other hand it is a construction void, you will not have future access for checking your joists or adding extra insulation.

(without wanting to appear overtly intrusive, what is your floor insulation plan ?).

I inherited an 800mm unfinished concrete CS, that is twice the height of yours... When I discovered the actual heat-losses through the floor-above and decided to insulate it, I discovered it was a lot of work... even with years of caving (and cave-digging) experience not to mention a (once) slender frame... (?)
:shamed:" alt=":shamed:" src="http:///newforum/extensions/Vanillacons/smilies/standard/shamed.gif" >

You might try running a Topic Search for "suspended timber floor"...

Otherwise, here is a good read:
https://www.sciencedirect.com/science/article/pii/S0378778817311350

Good luck

gg

The perimeter wall goes all the way round so no crawl space.]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272310#Comment_272310 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272310#Comment_272310 Thu, 07 Feb 2019 07:52:20 +0000 bardo Posted By: tonyHow much insulation will there be in the floor? And how will this join to insulation in the walls, will partition walls bridge your thermal envelope?

Dpc is neither here nor there under concrete obersite

What do sleeperbwalls sit on?

Trench is 900mm deep with 300 mm of concrete poured in base then twin skin blockwork on top.
300 mm of treated sheepswool insulation laid within steico i joists. These are fixed to a timber box beam which sits on top of the plinth wall (with DPC laid inbetween).

There is no concrete oversite.]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272311#Comment_272311 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272311#Comment_272311 Thu, 07 Feb 2019 07:53:09 +0000 bardo Posted By: bardo
Posted By: tonyHow much insulation will there be in the floor? And how will this join to insulation in the walls, will partition walls bridge your thermal envelope?

Dpc is neither here nor there under concrete obersite

What do sleeperbwalls sit on?




Trench is 900mm deep with 300 mm of concrete poured in base then twin skin blockwork on top.
300 mm of treated sheepswool insulation laid within steico i joists. These are fixed to an insulated timber box beam which sits on top of the plinth wall (DPC laid in between).

There is no concrete oversite.]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272312#Comment_272312 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272312#Comment_272312 Thu, 07 Feb 2019 08:36:59 +0000 bardo Posted By: djhLeave some weep holes between the blocks/bricks? Or drill some holes if it's already built. Maybe a sleeve pipe through the holes if required.

That's an interesting idea. Not built yet. Concern is providing access to rodents. I suppose if the holes are small enough then no problem.]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272314#Comment_272314 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272314#Comment_272314 Thu, 07 Feb 2019 10:11:14 +0000 djh Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272315#Comment_272315 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272315#Comment_272315 Thu, 07 Feb 2019 10:46:04 +0000 Peter_in_Hungary Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272317#Comment_272317 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272317#Comment_272317 Thu, 07 Feb 2019 11:49:14 +0000 gyrogear Posted By: Peter_in_Hungarygo for a well insulated solid floor, either concrete or limecrete

+1 for PIH !

Although OP *did* say "a low-impact home"...

Guess the "impact" bit is summarized by need to compare the grey-energy balance of cutting down trees to make joists, thus removing CO2-absorption possibilities, versus use of concrete that creates C02, versus the energy balance of the future heating system, modulated by the benefits of mass versus the grey-energy balance of plastic insulation etc. etc.

gg]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272320#Comment_272320 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272320#Comment_272320 Thu, 07 Feb 2019 16:07:55 +0000 djh
But I was not thinking as deeply about 'low-impact'. I don't think concrete is as bad as it is sometimes made out, especially given its expected lifetime, and I have an active aversion to sheeps wool in particular after reading and seeing some horror stories. So I was willing to put up with the sin of concrete, EPS and steel.]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272321#Comment_272321 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272321#Comment_272321 Thu, 07 Feb 2019 16:09:45 +0000 djh Posted By: gyrogearenergy balance of cutting down trees to make joists, thus removing CO2-absorption possibilities
Actually cutting down trees absorbs *more* CO2 rather than less, provided it is managed properly and replacements are planted.]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272559#Comment_272559 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272559#Comment_272559 Sun, 24 Feb 2019 08:22:19 +0000 bardo
If we didn't use underfloor heating would that leave us with a cold floor?]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272560#Comment_272560 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272560#Comment_272560 Sun, 24 Feb 2019 11:31:58 +0000 Peter_in_Hungary Posted By: bardoIf we didn't use underfloor heating would that leave us with a cold floor?
Not if you insulate the floor.
The floor will be warmer with UFH but the walls will be colder without radiators on them. In other words where you put the heating will always be warmer than an adjacent place that doesn't have a heating source. The escence is that if you have sufficent insulation the heating demands are low and it is easier to acheive an overall even temperature without cold spots either on the floors or the walls.

Other considerations - radiators respond quicker than UFH and some people find that their feet/ankles swell up with UFH, but this could be because a high(er) temperature is needed due to insufficient overall insulation.

Glapor vs. EPS - I would go with price and availability. Galpor is significantly worse at insulating than EPS so more will be needed.]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272564#Comment_272564 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272564#Comment_272564 Sun, 24 Feb 2019 20:39:09 +0000 bardo Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272565#Comment_272565 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272565#Comment_272565 Sun, 24 Feb 2019 21:43:36 +0000 bardo Posted By: Peter_in_Hungarybardo - Is it too late to go for a well insulated solid floor, either concrete or limecrete. Insulation is easy, no worries about ventilation or rot in the future and works better with UFH if you are going that way.

Peter, those who work with natural materials suggest using limecrete for a floor. It is apparently more responsive than concrete to heat and moisture buffering. Could limecrete be used with EPS or would that defeat the object of using a more open structured material? When I last looked at the cost of glapor it was relatively expensive.]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272567#Comment_272567 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272567#Comment_272567 Mon, 25 Feb 2019 00:31:36 +0000 djh
If it's well insulated then it makes more sense to keep it warm constantly, and if you do that then a heated floor slab would be a useful contribution as long as it is well controlled.

Lime is certainly better than concrete for moisture management. I'm not sure there's much difference as regards heat. There's no reason you couldn't put a limecrete slab on top of EPS that I know of. Perhaps worth reading http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5983 and other threads referenced.]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272571#Comment_272571 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272571#Comment_272571 Mon, 25 Feb 2019 04:56:28 +0000 bardo Posted By: djhTo some extent the relative merits of the various heating systems depend on how well insulated your building will be and how you plan to use it. You mentioned 300 mm of sheepswool in a timber floor, which is reasonably well insulated. What are you proposing for the walls and roof, and what standard of glazing and airtightness are you aiming for? Will you want to keep it warm pretty much constantly, or what?

If it's well insulated then it makes more sense to keep it warm constantly, and if you do that then a heated floor slab would be a useful contribution as long as it is well controlled.

Lime is certainly better than concrete for moisture management. I'm not sure there's much difference as regards heat. There's no reason you couldn't put a limecrete slab on top of EPS that I know of. Perhaps worth readinghttp://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5983" rel="nofollow" >http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5983and other threads referenced.

Walls are straw bale infil inside timber frame. Clay plaster inside, lime skin outside with larch cladding as rain screen. Triple glazing on all sides except south which is double. Wood fibre board insulation in roof. So well insulated with hygroscopic breathable walls. We are off grid and venting via extractors and trickle vents.]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272575#Comment_272575 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272575#Comment_272575 Mon, 25 Feb 2019 11:43:15 +0000 djh Posted By: bardoWalls are straw bale infil inside timber frame. Clay plaster inside, lime skin outside with larch cladding as rain screen. Triple glazing on all sides except south which is double. Wood fibre board insulation in roof. So well insulated with hygroscopic breathable walls. We are off grid and venting via extractors and trickle vents.
So you'll be close to passive but not quite, I suspect. If I were you I would upgrade to continuous ventilation - probably MVHR. I think it will make a big difference to air quality and comfort. Pay close attention to airtightness as well.

If it were me, I would use a slab with low-temperature UFH since I think the time constant of the building will be long enough to make continuous heating the best policy. I believe a UFH system can also usefully even out the effects of solar gain throughout the building.]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272810#Comment_272810 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272810#Comment_272810 Thu, 07 Mar 2019 10:26:20 +0000 bardo Posted By: djh
Posted By: bardoWalls are straw bale infil inside timber frame. Clay plaster inside, lime skin outside with larch cladding as rain screen. Triple glazing on all sides except south which is double. Wood fibre board insulation in roof. So well insulated with hygroscopic breathable walls. We are off grid and venting via extractors and trickle vents.

So you'll be close to passive but not quite, I suspect. If I were you I would upgrade to continuous ventilation - probably MVHR. I think it will make a big difference to air quality and comfort. Pay close attention to airtightness as well.

If it were me, I would use a slab with low-temperature UFH since I think the time constant of the building will be long enough to make continuous heating the best policy. I believe a UFH system can also usefully even out the effects of solar gain throughout the building.

Hi DJH, in the end we opted for a suspended timber floor to sit on the perimiter plinth wall. We are off grid with a sustainable supply of woodfuel so will use this for our cooking hot water and heating when the solar system low. On another note, I saw that you also used straw bale walls. Did you use a machine to render the walls? We intend to put a coat of lime on and clad for extra rain screening in our wet part of Wales.]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272816#Comment_272816 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272816#Comment_272816 Thu, 07 Mar 2019 15:33:05 +0000 djh Posted By: bardoOn another note, I saw that you also used straw bale walls. Did you use a machine to render the walls? We intend to put a coat of lime on and clad for extra rain screening in our wet part of Wales.
Yes, we employed a chap called Arthur Philip to do all the lime plastering on the bales. He's an expert plasterer who's extremely enthusiastic about bales. He uses a Putzmeister SP11 to spray most of the material on, plus loads of elbow grease to compact it and get a result. I expect you'll need an initial scratch coat to cover most of the bales and perhaps to fill out hollows and then probably a second coat just to get enough thickness. I think you can skip the third, finish coat if you're cladding over the top.

A pump needs good quality lime to avoid blockages; Arthur used to collect every stone and take them back to the supplier! The mix is everything to avoid cracking. Lots of fibres and some secret additives. One lime plasterer I know says that traditional mixes sometimes have up to 30% hair in them.]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272833#Comment_272833 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272833#Comment_272833 Thu, 07 Mar 2019 21:25:38 +0000 bardo Posted By: djh
Posted By: bardoOn another note, I saw that you also used straw bale walls. Did you use a machine to render the walls? We intend to put a coat of lime on and clad for extra rain screening in our wet part of Wales.

Yes, we employed a chap called Arthur Philip to do all the lime plastering on the bales. He's an expert plasterer who's extremely enthusiastic about bales. He uses a Putzmeister SP11 to spray most of the material on, plus loads of elbow grease to compact it and get a result. I expect you'll need an initial scratch coat to cover most of the bales and perhaps to fill out hollows and then probably a second coat just to get enough thickness. I think you can skip the third, finish coat if you're cladding over the top.

A pump needs good quality lime to avoid blockages; Arthur used to collect every stone and take them back to the supplier! The mix is everything to avoid cracking. Lots of fibres and some secret additives. One lime plasterer I know says that traditional mixes sometimes have up to 30% hair in them.

Thank you. Where is Arthur based and how long did he take to complete the job? Did you also clay plaster the interior?]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272836#Comment_272836 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272836#Comment_272836 Thu, 07 Mar 2019 22:49:09 +0000 djh Posted By: bardoWhere is Arthur based and how long did he take to complete the job? Did you also clay plaster the interior?
I'll PM you contact details - I don't like posting emails in public.

I don't have notes as to exactly when he started but my best estimate is that the whole process took six five months. There were idle periods in there waiting for the lime to go off et al.

I had originally planned to use clay plaster on the inside but in the end I decided it was simpler and better to use lime inside too. So the six five months covers both outside and inside. Just the bale walls that is; we used gypsum on the internal partitions.]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272849#Comment_272849 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272849#Comment_272849 Fri, 08 Mar 2019 11:43:41 +0000 djh Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272852#Comment_272852 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272852#Comment_272852 Fri, 08 Mar 2019 14:46:33 +0000 bardo Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272853#Comment_272853 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=272853#Comment_272853 Fri, 08 Mar 2019 14:46:58 +0000 bardo Posted By: djhWe like the lime finish both inside and outside. Inside is a pretty smooth finish; outside has a slightly rough surface texture. Both the lime and the gypsum inside are painted with clay paint so they look similar. One of the main reasons for using lime inside was that I had already found a tradesman I trusted to do it. Clay would have meant finding another team and there are even less clay plasterers than there are lime plasterers. Lime is also stronger and I trusted it (and Arthur) to have fewer problems with cracks, which matters since it is our airtightness barrier. There are only a few cracks, all in areas where there is a change of materials and geometrical stress but fortunately also a membrane behind all those places.

I hear your reasoning. Thanks for sharing that DJH.]]> Foundations for a suspended timber floor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=274443#Comment_274443 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16015&Focus=274443#Comment_274443 Tue, 02 Jul 2019 15:43:18 +0100 Petlyn