Airtight seal from footing to timber sole plate.

[saveasteading]

I am imagining the interface between the top of a block wall and the spiked down sole plate. I see in my mind a lot of gaps, equating to draught and heat loss.

 

Is there a recognised way to seal this?

I am thinking a strip of bituthene that might compress when the load is applied.

[Jenki]

I read on Viking House (Irish Passive Houses) that they use expanding foam. But that was onto an Insulated slab.  I'm thinking this will be my approach

[tonyshouse]

I would join the air barrier in the wall to the one in the floor on the warm side of the insulation hermetically. I like polythene as it also acts as a vapour barrier 

[saveasteading]

Expanding foam.  I see it as a last resort when a proper detail has not worked. The gap will realistically be 0  to 5mm , so I'm not sure it can be applied properly anyway.

 

Polythene, yes this will work as the airtight barrier, except where it doesn't at any horrible interface.

 

I now wonder whether a memory foam strip (basically draught strip), should be fixed under the plate, and squashed into place.

 

I wonder what the specialist timber frame people recommend/do.

 

[Jenki]

7 hours ago, saveasteading said:

Expanding foam.  I see it as a last resort when a proper detail has not worked. The gap will realistically be 0  to 5mm , so I'm not sure it can be applied properly anyway.

I Personally don't see this as a last resort.  My intention is to use J bolts cast into the insulated slab, the stick made panels will have the hold down holes drilled, then when lifting the panel into place, three beads of quality low expanding foam construction foam (ILLBRUCK FM310) applied to the slab, then the panel lowered down into place, lined up with chalk lines.   The adhesive will expand and fill any deviations in the surface and also stick the frame to the slab. Any movement will be accommodated by the foam.

I will be using radon barrier, so this will be lapped up the external Wood fibre insulation.

 

I think the problems of using a membrane is you introduce 2 joins.

 

Also the gap will be Plus and Minus X mm, so the membrane/ joint strip will have to take care of deviations both ways. 

[Russell griffiths]

I would use a pu adhesive, the problem with the illbruck stuff is it’s not designed to be left as a finished surface, as in it needs a covering to protect it from uv and other things like ants or anything else that might chew at it. 
so you would need to do two lines of pu adhesive with the expanding foam line down the middle. 
so you might as well just use the adhesive. 
will be expensive doing it with tubes, so the sausage type gun will be the cheapest method. 
If your buying it by the box you should get it for £5 a sausage. 

[saveasteading]

17 hours ago, Russell griffiths said:

pu adhesive,

Had a browse to see what pu adhesive really is. 

A lot of choice, and little indication ow what suits, although being suitable for outdoors has to be a  good sign.

 

Came across this one which is very cheap....any reason why?

It appears to be suitable even for sealing joints in concrete paving.

Soudaflex 40FC PU Sealant (310ml)

(12 Reviews)

£3.48 inc VAT

[saveasteading]

18 hours ago, Jenki said:

I Personally don't see this as a last resort.

It's personal:  have had m and e people squirt it into metal cladding voids and it came out of lap joints and ruined the cladding, and a replacement sheet of cladding is always a different shade.  It can be bridging gaps and causing dampness too.

 

I can imagine  it squirting everywhere as you place your panels,  but perhaps this make is more controllable.

 

 

18 hours ago, Jenki said:

J bolts cast into the insulated slab

A heavily reinforced slab I assume, or theoretically the bolts will pull lumps out of the slab in wind uplift.   I don't follow though, how you can slot a sole plate over pre-fixed bolts protruding from the slab , so i am probably misunderstanding.

 

Radon: Apologies if you know: it is very local, defined in big squares, and if you are on the cusp on the radon maps, £5 well spent on a certificate  if it turns out that you are in a nil radon spot. 

https://www.ukradon.org/radonmaps/

 

 

[Jenki]

On 29/03/2022 at 07:30, Russell griffiths said:

I would use a pu adhesive, the problem with the illbruck stuff is it’s not designed to be left as a finished surface, as in it needs a covering to protect it from uv and other things like ants or anything else that might chew at it. 
so you would need to do two lines of pu adhesive with the expanding foam line down the middle. 
so you might as well just use the adhesive. 
will be expensive doing it with tubes, so the sausage type gun will be the cheapest method. 
If your buying it by the box you should get it for £5 a sausage. 

Thanks for the info.  more research to be done.

 

8 hours ago, saveasteading said:

A heavily reinforced slab I assume, or theoretically the bolts will pull lumps out of the slab in wind uplift.   I don't follow though, how you can slot a sole plate over pre-fixed bolts protruding from the slab , so i am probably misunderstanding.

Bolts are 200mm With a hook at the end, they will be buried hook end first, around 120mm into the wet foundation and left to cure. If these pull out I've got big problems with the slab.

All you are left with is a threaded section sticking out of the slab.  You lower the sole plate over the 'stud' then use washers and nuts to bolt down.  As I m stick building on site, I will uses the studs to mark the sole plate and drill before I make the panels.

 

 

[Russell griffiths]

The good thing with the stud sticking out of the slab @Jenkiis that if you are in a high wind area you can extend the stud to go all the way through the wall up to the top plates. 

I built in a sub tropical area known for high wind and had multiple studs that did this. 

Holds the entire structure down, not just relying on the sole plate being held in position. 

[Jenki]

4 hours ago, Russell griffiths said:

The good thing with the stud sticking out of the slab @Jenkiis that if you are in a high wind area you can extend the stud to go all the way through the wall up to the top plates. 

I built in a sub tropical area known for high wind and had multiple studs that did this. 

Holds the entire structure down, not just relying on the sole plate being held in position. 

I suppose I could just use connector joining nut and then add screwed rod after. ill look into this.👍

[saveasteading]

8 hours ago, Jenki said:

120mm into the wet foundation

No problem then:  in the foundation rather than the slab.

 

How do you get the bolts in exactly the right position for holes in the sole plates? I ask this with much experience of bolting steel plates to foundations to precise dimensions, but with theodolite (or string-line)  and templates essential.

Most contractors work to 50mm tolerance on the bolts, such is their uncertainty of lining up properly.

 

Nice idea I would like to explore, if there is a technique to share.

 

Our current plan is to build the footings with hollow blocks and J shaped bars from the concrete footing through the blocks and infilled with concrete. Then it needs straps screwed to timber studs, and bolted to the slab/footing.

 

Your small bolts could be cast precisely into the concrete infill of the wall IF the holes could be  precise enough in the sole plates.   Drilling holes to fit over the bolts sounds tricky though. Oversize holes and big washers paerhaps.

 

 

3 hours ago, Jenki said:

you can extend the stud to go all the way through the wall up to the top plates.

Interesting, but seems over the top here, as there will be studs at 600cc and a lot of nails, plus the external board for stiffness. If you tried to lift the completed wall by crane, the failure would be the bolts at the concrete interface I am sure. ie the bolts would pull out of the concrete with little cones of concrete attached.

 

3 hours ago, Jenki said:

use connector joining nut and then add screwed rod after.

This rod will be passing through noggins and insulation, so will be tricky. I would also want to revisit the nuts after the structure has had time to settle and shrink.

Rods and connectors are readily available online at much better rates than  the usual suppliers. I use a supplier to the M and E industry who use the rods to hang cable trays.

[MikeSharp01]

My idea to make our seal is to use a bead of Orcon F or simlar to seal the airtight membrane to the floor nail a batten onto the soleplate about 10mm above the floor and put an Illbrook expanding seal along in the gap to force the membrane down onto the orcon F and close any gaps.

[Russell griffiths]

@saveasteadingyou are overthinking the bolt placement. 
it’s actually very simple. 
you basically have a plan of a run of wall showing where the stud spacing is, if you have a 600 centre on the studs then you have a 550mm gap in which to place the bolt. 
you start at the corner and mark on the shuttering stud placement, you then measure 600 for next stud, this gives you 550mm to place your bolt, all you need then is the measurement in from the edge, so a 150mm sole plate will be 75mm in from the edge of slab to centre of sole plate. 
 

push your bolts into the wet concrete at the approximate rough locations. 
when dry you lay your sole plate all around the perimeter of your build and using a square mark a line from the bolt to the timber. Drill a 20mm hole for a 12mm bolt and you will have no alignment problems. 
the threaded stud that goes up to the top plate only goes in strategic points, normally on the racking corners, so the first bolt closest the corner then 1200mm away, then your first sheet of racking board is added and it’s all turned into one big braced corner. 
probably very OTT for most of England, but could be handy for some coastal areas. 
we also used to add cyclone straps to our trusses, these wrapped over a truss and underneath the two top plates instead of just nailed on the top. 
not had one of my houses blow away yet 🤣🤣

[saveasteading]

2 hours ago, Russell griffiths said:

a 20mm hole for a 12mm bolt

Yes that works, but it isn't normally a great idea to have such a big tolerance. The washers need to be very big and sturdy.

I was assuming that the sole plate will be in long timbers, to minimise joints, so more chance of error.

Doing this myself it wouldn't be a concern, but I can't see our contractor being thrilled with this.

 

I like the idea in principle, better than shot-firing down which I think is the norm, and will give it more thought.

 

Had more thought.

Let the chippy fix it any which way, then drill through the plate, into the concrete and fix studs with epoxy.