Collecting the materials for finishing my roof

[dnb]

I am aware of the requirements of BS5534 for roof battens. As it turns out these battens are produced in huge numbers so seem to be really cheap, so happy days. But I am concerned that I can't find a similar requirement for the counterbattens that hold the roof battens and are required for ventillation on my SIPS roof, and I am struggling to find wood of the right size at a price and quality I like. Surely there must be some requirement on these counter battens to catch out the unwary?

 

The build up is:

SIPS

membrane

counter battens (architect says 38x38mm at 600mm ctrs on the approved plans)

slate battens (25x50mm spaced for 80mm headlap - since it's a 40 degree roof pitch in SE England)

slates (250x500 because I can't justify the expense of 300x600 slates)

 

I am wondering if I should replace the 38x38 battens with more 25x50 roofing battens since these are at least a defined grade and I can get them locally, but it reduces the ventillation space by about 20%. I am not sure if this is a problem or not - I suspect not because the over facia vents are only 25mm high, and air isn't getting in from anywhere else.

 

I am about to ask my building inspector the question by email, but although he's very helpful, he is very busy so will take a while to answer a detailed question, but asking a yes/no type question is usually quick.

[LA3222]

I used JB Reds at 25x50 for both the batten/counter batten on my SIP roof. L

[Chablais]

I am not an expert, however, just fitted the roof on our build, and slated the whole roof. We used 25 x 50mm treated slate battens and counter battens, when speccing the roof, nobody was advising anything other than 25 x 50 battens. On your slate size, if you are laying yourself, then the larger slates will go on faster and have more sidelap. They may cost more but surely you will need fewer of them

 

[Russell griffiths]

There is no standard for the counter batten. 

The standard for the tile batten is its strength in allowing a man to stand on it at 600mm centres without it breaking. They are coloured to show they have been graded without you having to look on each batten for a bs mark. 

 

Roof battens are cheap just buy whatever brand your merchant stocks. 

I would think with slate a 25mm gap is plenty as they are draughty roofs compared with say a metal sheet. 

[dnb]

20 minutes ago, Chablais said:

They may cost more but surely you will need fewer of them

Yes, but the cost increases faster than the coverage. Hence it's more expensive overall.

 

8 minutes ago, Russell griffiths said:

There is no standard for the counter batten. 

Good to know. Thank you!

25 minutes ago, LA3222 said:

I used JB Reds at 25x50 for both the batten/counter batten on my SIP roof.

Thanks. I suspect I will be doing similar with whatever the local Jewsons will sell me. I will redraft the drawing slightly to work out some new measurements for positioning the facia and all should be good. Not a clue why I have the 38mm counterbatten specified but it seems it isn't particularly important. Might save a few £ and be able to afford to eat next week...

[dnb]

Thinking about it, the BS5534 document for roofing seems to demand 65mm round headed nails. These are supposed to penetrate 40mm into the rafters I don't have - the counterbattens take their place. So I expect my architect has asked for 38mm because it is as close as possible to 40mm so that the nails are all in wood and don't penetrate the SIPS OSB top by more than 2mm. Otherwise if I use 25mm counterbattens the roof batten nails will penetrate the totality of the OSB plus 2mm of the insulation which I suspect he would have considered to be less than optimal.

 

Now wondering what the best fastening technique for the counterbatten is going to be, and what centres to use for the fixings.

Edited July 8, 2020 by dnb

[SuperJohnG]

Following this with interest especially the last part about punching through into the insulation 

[LA3222]

5 hours ago, dnb said:

Thinking about it, the BS5534 document for roofing seems to demand 65mm round headed nails. These are supposed to penetrate 40mm into the rafters I don't have - the counterbattens take their place. So I expect my architect has asked for 38mm because it is as close as possible to 40mm so that the nails are all in wood and don't penetrate the SIPS OSB top by more than 2mm. Otherwise if I use 25mm counterbattens the roof batten nails will penetrate the totality of the OSB plus 2mm of the insulation which I suspect he would have considered to be less than optimal.

 

Now wondering what the best fastening technique for the counterbatten is going to be, and what centres to use for the fixings.

The counterbattens have to be screwed in - if you go to the Kingspan Tek site there are a raft of standard details available including the roof and what fixings to use.

 

It states Ejot screws. I had a discussion with their technical department to see what they recommend and it seems they have conducted tests on the pull out strength of fixings into SIP. I was informed that fixings need to be long enough to penetrate 20mm into the actual insulation. I believe I gave the roofers a load of 70mm TKE stainless steel fixings from Ejot.

 

I would not recommend those though. Having used them they are a PITA as the bits chew the head up if you aren't careful which happened a lot. I would suggest using an equivalent Spax type fixing - no doubt more costly but easier to use.

 

@SuperJohnG - for your info aswell as I know you're going the SIP route too?

[dnb]

Thanks.  I knew it had to be screwed but I had no clue what the best type of screws were. Looking at those you suggest I don't use indicates course parallel threads are the thing. I assume the 20mm penetration is to guarantee to get to the parallel (non tapered) section. Screwfix do seem to have a few suitable alternatives. 

 

It looks like the centres need to be 100mm which sounds a little extreme but no doubt the maths has been done.

[Onoff]

I don't know if you have the time to investigate but my mate bought Spax (decking) screws from here in bulk. Even with shipping they were miles cheaper than he could have bought them in the UK. Not sure how / if the whole Brexit thing will have affected things as it was pre this:

 

https://www.klokow-gmbh.de/

[LA3222]

3 hours ago, dnb said:

Thanks.  I knew it had to be screwed but I had no clue what the best type of screws were. Looking at those you suggest I don't use indicates course parallel threads are the thing. I assume the 20mm penetration is to guarantee to get to the parallel (non tapered) section. Screwfix do seem to have a few suitable alternatives. 

 

It looks like the centres need to be 100mm which sounds a little extreme but no doubt the maths has been done.

Not sure about the 100 centres - off the top of my head I seem to recall it being 300 centres?

[dnb]

1 hour ago, LA3222 said:

Not sure about the 100 centres

Neither am I.  300 sounds much more sensible but I am not that sort of engineer...

[LA3222]

4 hours ago, dnb said:

Neither am I.  300 sounds much more sensible but I am not that sort of engineer...

 

Its 300, just checked.

Edited July 9, 2020 by LA3222

[Dan F]

On 08/07/2020 at 22:01, Russell griffiths said:

There is no standard for the counter batten. 

 

Do you have a reference for this?  NHBC/Permier warranties specifiy BS5534 as a requirement for counter-battens, so I suspect this may have been introduced in the last revision of BS5534.

[Russell griffiths]

@Dan F just use the same batten quality that you will use to hold the roof covering on. 

[ToughButterCup]

On 09/07/2020 at 08:50, Onoff said:

I don't know if you have the time to investigate but my mate bought Spax (decking) screws from here in bulk. ....

 

They  (Klokow) are probably the cheapest, @Onoff .  I needed 4000+ stainless steel screws for our cladding. Less than half the Screwfix price - including the shipping. 2 full days order lead time.

@dnb, you'll need to be really unlucky to have a BCO who goes through your roof construction in quite so much detail.

 

Quote

7.9.5.2 Timber battens
Timber species
Tiling battens and counter battens should be selected from the timber species set out in BS 5534, and their characteristics and defects should not exceed the permissible limits given in Annex C of
BS 5534

(LABC Technical Manual Version 8,  downloaded summer 2020)

 

... or in other words @Russell griffiths is right. As usual. ?

[epsilonGreedy]

On 08/07/2020 at 21:31, dnb said:

slates (250x500 because I can't justify the expense of 300x600 slates)

 

 

Larger slates make a roof look more commercial. If 200 x 400 slates were mainstream I would select these for my roof as they give more of a heritage look, if this is the objective.

 

One reason I have not confirmed an order for Nu-lok is because the system's reduced lap gives a roof a different look.

[Ferdinand]

2 hours ago, epsilonGreedy said:

 

Larger slates make a roof look more commercial. If 200 x 400 slates were mainstream I would select these for my roof as they give more of a heritage look, if this is the objective.

 

One reason I have not confirmed an order for Nu-lok is because the system's reduced lap gives a roof a different look.

 

if you are concerned I would suggest sketching the requisite number of rows of tiles onto your elevation or 3D view if you have one. Should give something of a sanity check.

 

The small cottage I used to live in had been done with inappropriately large pantiles , and there were only SEVEN rows on each side of the roof.

 

Made it look like a dolls house.

 

Ferdinand

Edited September 23, 2020 by Ferdinand

[Dan F]

22 hours ago, Dan F said:

 

Do you have a reference for this?  NHBC/Permier warranties specifiy BS5534 as a requirement for counter-battens, so I suspect this may have been introduced in the last revision of BS5534.

 

You would if it's the same person doing counter-battens and battens.   In our case the roofer will be using BS5534 rooding battens, but the timber-frame supplier has used non-BS5534 for the counter-battens.

 

This isn't a major issue in my view, but apparently the latest revision of BS5534 as well as the most warranty providers now require BS5534 battens for coutner-battens too.

 

 

 

 

[dnb]

17 hours ago, ToughButterCup said:

you'll need to be really unlucky to have a BCO who goes through your roof construction in quite so much detail.

 

That wasn't my main concern, but I'm often that lucky! It's one of the first full SIPS builds on this little island to my knowledge so I'm expecting scrutiny and a few interesting questions from the BCO since he may have very limited experience of this sort of build.

 

That's a very useful document you referenced too. It interprets of many horrible documents in a much clearer form - and has pictures! Just what I needed while recovering from the 'flu. (Proper 'flu, not Covid19 or man flu! )

Edited September 24, 2020 by dnb

[Russell griffiths]

Surely @dnb it’s not the quality of the batten that needs clarification, but the fixing down method onto the sips panels. 

 

You could use the highest spec batten you can buy but if the fixings pull out of the sips then that’s where problems start. 

[dnb]

@Russell griffiths I am not particularly concerned with the counterbattens on the SIPS other than what my BCO and warranty provider will accept. They don't span anything when all said and done.

 

The fixings and spacing are indeed a large concern as discussed (and concluded from my viewpoint) earlier in the thread. I don't expect the counterbattens to be pulled out by anything the weather can do because they are more secure than the battens.

[junglejim]

Just about to build our timber frame house with cassette panels and looking for information about fixing counter battens etc. does anyone have any further information/advice. I was trying to find a the document mentioned but can’t see a link… any help/advice greatly appreciated. 
many thanks

[Dave Jones]

On 08/07/2020 at 21:31, dnb said:

I am aware of the requirements of BS5534 for roof battens. As it turns out these battens are produced in huge numbers so seem to be really cheap, so happy days. But I am concerned that I can't find a similar requirement for the counterbattens that hold the roof battens and are required for ventillation on my SIPS roof, and I am struggling to find wood of the right size at a price and quality I like. Surely there must be some requirement on these counter battens to catch out the unwary?

 

The build up is:

SIPS

membrane

counter battens (architect says 38x38mm at 600mm ctrs on the approved plans)

slate battens (25x50mm spaced for 80mm headlap - since it's a 40 degree roof pitch in SE England)

slates (250x500 because I can't justify the expense of 300x600 slates)

 

I am wondering if I should replace the 38x38 battens with more 25x50 roofing battens since these are at least a defined grade and I can get them locally, but it reduces the ventillation space by about 20%. I am not sure if this is a problem or not - I suspect not because the over facia vents are only 25mm high, and air isn't getting in from anywhere else.

 

I am about to ask my building inspector the question by email, but although he's very helpful, he is very busy so will take a while to answer a detailed question, but asking a yes/no type question is usually quick.

 

 

may be cheaper to jsut double counter batten with 2x1 than 1.5x1.5 as your architect has suggested (they are clueless on wasting your money with pointless expensive options). graded (red, green, blue coloured) is pretty cheap although our local BCO was fine with the cheaper bog standard 2x1

[dnb]

2 hours ago, Dave Jones said:

may be cheaper to jsut double counter batten with 2x1 than 1.5x1.5 as your architect has suggested (they are clueless on wasting your money with pointless expensive options).

The second bit I know... But this very sensivlke advice comes about 4 years late. I'm not changing anything now!! For the record the BCO and warranty folk were happy with the C24 graded 2x1.5 I sourced for reasonable cost, and happy with all of the fixing plans.

 

My understanding is that the documentation has moved on a stage now so perhaps I wouldn't get away with it so easily now, but if that's the case then a product would have become available.

 

@junglejim The BS document isn't freely available. The BSI like you to buy it from them! But you can usually find the useful sections from it in places like a LABC technical guide or NHBC documents.