Timber Frame Supply - Recommendations

[TonyT]

If it’s a build on a budget as per the first post, get a joiner to build it on site.

I did this for a 60m2 extension, worked out well, I also got to paint every end of  cut timber with green preservative which ticked another OCD box.

[TerryE]

I am another unashamed MBC evangelist.  6 days from hole in the ground to finished warm slab; 3 weeks for the slab to cure enough to erect the frame.  10 days from level slab to house with all the doors and windows fitted, and that  we could lock.  OK, it was another year to get the slate roof on, the external stone skin erected,  and the 1st + 2nd fit completed, so we could move in, but the house internally was weather-tight to do all this.

 

We did all the overall project management and detailed design so no architect or PM fees and after being in the house for 3½ years, I am still amazed how few niggles that we have.  Having only two major subs: MBC for the slab, TF, insulation and air-tightness; a local builder for the ground-works, stone skin plaster boarding out, and roof was a critical success factor IMO.  We did a lot of the internal 1st and 2nd fit ourselves. 

 

If you are going for a low U-value, high decrement delay spec wall profile then you will find it hard to do this with a wall profile shallower than 30 cm.  One thing that we did was to put 30° reveals on all our windows.  Everyone comments on how striking it is and how well it works.  Details in my blog.  

Edited February 13, 2021 by TerryE

[joe90]

9 minutes ago, TerryE said:

One thing that we did was to put 30° reveals on all our windows.  Everyone comments on how striking it is and how well it works. 

+1, I did this as well, looks really good ?(even with a brick and block build ?).

[TerryE]

We got the idea from our last house, which was a 1700s stone farmhouse which had similar reveals.

[Faz]

The thing is that working up quotes is time consuming and comes at a cost - if someone has gone out to 4 suppliers you (in theory) have a 25% chance of winning the job - if they have gone out to 20 then this becomes 5% - how much time and effort are you going to speculate on that one?

[TerryE]

@Faz, why this point? It's been raised before and most of us realise it, so it isn't relevant to the preceding discussion.

[dpmiller]

I'd say it's very pertinent. Another angle is that many of the TF suppliers will actively refuse to do a formal quote unless you've actually got planning permission, you mightn't even be able to get a guide price from some until that time.  They're *that* busy...

[TerryE]

Maybe I am just too sanguine after having lived through my own self-build, and it's not something that I would ever want to repeat despite it really being a 100% -- well certainly 99+% -- success.  When we started on this journey we naively thought that it might take a year from pre-planning to completion.  In the end it took us 3½ years, and that is a lot faster than many self-builders here have achieved.  Coming from a high-maintenance and pretty cold 1700s farmhouse, one of our goals was to have a truly low energy house that we going to be as near zero-maintenance as possible.  IMO, achieving decent low-energy performance with a tradition UK block / brick build is really hard.  @tonyshouse is one of the few members here that I know have achieved this and IIRC his wall profile is 10 block + 30 insulation + 10 brick, and he was intimately involved in the build process. IMO in practice you won't achieve any decent level of energy efficiency except by design both in concept and in detail.  The culture in the UK building industry is still anchored into processes that are decades out-of-date.   OK, there is a trade-off here in that you can use traditional approaches and accept the significantly higher running costs.

 

But to your specific points @dpmiller, we surveyed maybe 6 or 7 TF suppliers and shortlisted 3.  We were quite open with them about who we were shortlisting and why.  IMO, the planners interfere with your design to a degree that you'd be unwise to invest too much into TF design until after consent has been achieved, so we weren't able to down select until after we had obtained consent and have an overall approved concept to share with the two companies we eventually asked to quote.

 

Any form of price quote is meaningless without a clear definition of scope and responsibility.  A friend self-building in a nearby village discounted our supplier as too expensive and went for a cheaper quote, but in the end paid a more (and a lot more than he budgeted) because our scope was essentially a complete service: slab, frame, erection, insulation and air-tightness to contracted performance level, and he had to source many of the aspects as unbudgeted  extras.

 

Our TF / warm-slab supplier's structural engineer and architect technician were crucial to our finalising our detailed design.  With a high energy performance house, the devil is in the detail.

Edited February 14, 2021 by TerryE

[Haku]

Did you look at Ipswich Timber Frame? They dont do in factory insulation - just design & erect the frame. I had a quote from them based on recommendation from others locally. They dont meet my needs as I want a high u-value factory insulated frame but could be good for what you need.

[Dominic]

On 10/02/2021 at 12:27, HerbJ said:

The most important element before windows are installed is to get the roof and guttering competed and get control of rainwater.  So, I ( and I believe @bitpipe) focussed all my early  efforts on the roof, facias and guttering being completed, with temporary downpipes before the window and door  installation

I would welcome advice on this. I have an MBC TF being erected later this month. Once the frame is up I am getting the roof (clay pantiles), in-roof solar and roof windows on immediately afterwards followed by windows and doors. But with the brick skin obviously taking a while longer, how did you (a) solve the problem of how to manage the lowest course of the roof which has to sit on the bricks (in my case) and (b) similarly, in the absence of the external skin, how did you rig up guttering?

[dpmiller]

if it's a TF how is the roof "sitting on" the bricks? And won't there be a fascia to hang the gutter from?

[Dominic]

3 hours ago, dpmiller said:

if it's a TF how is the roof "sitting on" the bricks? And won't there be a fascia to hang the gutter from?

A brick skin will be added to the construction with a 50mm cavity between the brick skin and the TF. Obviously most of the pantiles "sit" on the TF roof (or, rather, the battens) but the lowest course of tiles need to form a junction with and slightly overhang the bricks. No fascia board, gutter rise and fall brackets in brickwork.

[TerryE]

13 hours ago, Dominic said:

I would welcome advice on this. I have an MBC TF being erected later this month. Once the frame is up I am getting the roof (clay pantiles), in-roof solar and roof windows on immediately afterwards followed by windows and doors. But with the brick skin obviously taking a while longer, how did you (a) solve the problem of how to manage the lowest course of the roof which has to sit on the bricks (in my case) and (b) similarly, in the absence of the external skin, how did you rig up guttering?

 

I have an MBC frame and stone skin.  I'll post back later today with some hints, when I have more time.

[HerbJ]

I have a render/cladding external skin - rendered aquapanel  for the most part - but the same approach should work for your construction. 

I assume MBC's scope for the TF is the same a mine. MBC fiited fascia boards and noggins, as part of their scope. I then was able to fit my fascia and noggin board finish (UPVC) and  gutters (seamless aluminium) with temporary downpipes in eary November, immediatley before my windows were fiited, and several months before the aquapanel and render was completed in March/April.

 

Attached photos may help..

 

Your approach with a external brick skin should not be a lot different and you will have a gap between brick skin and installed soffit, to allow for the differential expanasion/setment of the brick skin and the timberframe holding the roff and fascias/soffits. @TerryE  will probably share his experience.

 

Trust this helps.

 

 

[Dominic]

2 hours ago, TerryE said:

I have an MBC frame and stone skin.  I'll post back later today with some hints, when I have more time.

Thanks Terry. Much appreciated. In the meantime, I have hit on the obvious solution of extending the counterbattens down the roof so they extend beyond the TF and the line of the eventual brickwork. This should permit my roofer to fix the bottom course of tiles in place and support them with a temporary dummy lat.  We should also be able to rig up some temporary guttering/downpipes pending the construction of the brickwork. The image below shows the solution.

[Dominic]

5 hours ago, HerbJ said:

I have a render/cladding external skin - rendered aquapanel  for the most part - but the same approach should work for your construction. 

I assume MBC's scope for the TF is the same a mine. MBC fiited fascia boards and noggins, as part of their scope. I then was able to fit my fascia and noggin board finish (UPVC) and  gutters (seamless aluminium) with temporary downpipes in eary November, immediatley before my windows were fiited, and several months before the aquapanel and render was completed in March/April.

 

Attached photos may help..

 

Your approach with a external brick skin should not be a lot different and you will have a gap between brick skin and installed soffit, to allow for the differential expanasion/setment of the brick skin and the timberframe holding the roff and fascias/soffits. @TerryE  will probably share his experience.

 

Trust this helps.

Many thanks HerbJ.  I didn't see your very helpful post when I posted mine this afternoon so please don't think I was ignoring it. Useful to see your pics as well. In my case, I am planning not to have a fascia board as, with a chalet bungalow design, the overhang would bring the roofline just a little too low down so I don't have the option of forming the joinery for the fascia board/guttering. But your post is useful. I'm getting there. It might be that I could fix a temporary fascia and guttering in place. Views/ideas of others welcome. 

Edited March 15, 2021 by Dominic

[TerryE]

@Dominic, I assume that MBC are sharing the AutoCAD DRW files.  I assume that you have an AutoCAD vewing tool.  I used ViewCAD, but there are a few available, and I recommend using one to review and print drawings.

 

Is your roof racked? I can't remember whether this optional or required.  Our's was racked as we had a 3rd story in our warm loft space and the roof racking was a part of the shear strengthening design.  We also had our frame erected in early Nov and the slater couldn't start until Feb, so we had almost 4 months with the breathable membrane over racking as the whether tight roof.  No probs though.  But because of this the erection crew  just racked over the roof light holes, and I didn't actually cut the light holes in the racking until I agreed the timing and the exact vertical setting with my slater (to align the light positioning to the slate coursing).

 

The main drivers in all this are:

• Ventilation requirements, both for under slate and any behind the slips.  In our case the roof was counter battened and battened so we had under tile ventilation which employed a continuous ripple gap under the ridge tiles, and above soffit ventilation strips.  I am not sure that the approach with tiles is, but for slated roofs, you usually have a slight kick on the last course, so this strip doubled to act as the spacer for this kick.  We has a 50mm airgap beyond the cassette outer Panelvent, and then a stone course, but this is different for slips.  I believe that you uses some form of papered board over vertical battens and fix the slips to the board, so in this case the airgap is directly under the slip layer.
• Zero maintenance construction.  We used black powder-coated folded aluminum sections for our eaves, verges, slate edgings, etc.  Rot proof and won't need painting in our lifetimes.  Likewise all ties, ventilation strips, etc, where these were rust-proof andhad a min 25-year design life.
• Detailing.  Whatever the approach is, you will need detailed drawings of the cross sections including ventilation mechanisms at top and bottom including any coverings.  You need your SE, builder and BCO to OK all of this before you start the build.  The last thing that you want to happen is someone crying foul and stating "it's not going to work".   In our case we were not exactly sure what the final depth of the airgap and stone skin would work out at, so I got the MBC erection crew to leave the rafter overhand slightly long and boarded out the sarking about 10cm further than needed.  I later agreed the exact profile with my builder, and it was a quick job cut off the excess with circular saw -- a lot easier than adding a bit.  As well as tops and bases, you also need to detail window positioning and framing, cills, lintels, etc., remembering that you must achieve three goals (i) a decent thermal design with no material thermal breaks; (ii) airtightness; (iii) weather-proofing.

 

I am a little surprised that you don't have soffits or at least a decent overhang.  What about eave detailing on your gables?  You need to think about the ventilation and the risks of windward side rain ingress.

 

We used std mat back plastic guttering and downpipes but with metal gutter carriers that could be set both in depth and height. This allowed us to position the guttering pretty precisely for best run off. 

Edited March 16, 2021 by TerryE

[Dominic]

14 hours ago, TerryE said:

c, I assume that MBC are sharing the AutoCAD DRW files.  I assume that you have an AutoCAD vewing tool.  I used ViewCAD, but there are a few available, and I recommend using one to review and print drawings.

Thanks Terry.  All good points and I am reasonably comfortable I have this covered.  No racking in my case.  I will be crawling over the ventilation/weatherproofing with my roofer and builder and the BCO but, in general, with a warm roof, the counter battening and the clay pantile system, the tiles are sufficiently 'air open' to allow the transmission of water vapour from the batten cavity through the tiling without great need for extra ventilation. But I am not necessarily relying on that and I had planned on ventilation at the eaves and ridge with the exact configuration of this subject to the above BCO discussion. For the eaves, there will be a slight overhang of the tiles beyond the brickwork to the gutter. The brick will be corbelled at the eaves with the necessary eaves protection system/comb/vent sitting on top of the corbelled brickwork.  Out of interest, I was trying to look through your old posts and your blog to see if your MBC roof was pumped cellulose and vaulted insulated roof (which is the case with mine) or whether the thermal envelope in your build is lower down below a cold roof void? Going back to my original question about starting the lowest course of clay roof tiles in the absence of the brick skin, my current plan is to extend the counterbattens 250m or 300mm out from the TF and support them with a temporary propped boards underneath to take the weight of the bottom row of tiles plus temporary guttering (it is a chalet bungalow design so the eaves are only 2.4m or so high, enabling us to prop them easily from the ground). This will be removed gradually when the brick work gets up to eaves level and the bottom course of tiles can then be lifted and refitted allowing the final eaves system to be put in place between the corbelled brickwork and the tiles. 

[TerryE]

5 hours ago, Dominic said:

Out of interest, I was trying to look through your old posts and your blog to see if your MBC roof was pumped cellulose and vaulted insulated roof (which is the case with mine) or whether the thermal envelope in your build is lower down below a cold roof void?

 

It was pumped cellulose.  It was amazing watching the guys do this.  The same crew were also responsible for signing off air-tightness.  They first boarded out the inner surfaces of the cassettes with a special OSB that includes an air-tightness surface.  They taped all of the joints, including redoing the Internorm seals; their logic is that they want to pass the test first time, so don't trust anyone else's seals.  They also battened out the walls for the service cavities.  They filled ½ the kitchen and ½ the living room with bales of filler and started at the first floor working up into the roof.  In each vertical between the battens, they cut a circular hole at the top for filling access and pumped filler until full, then taped up the hole.  

 

As I said we have a warm roof because the under-roof space is a third living floor (that my son effectively uses as his own apartment).  Because the rafters were lined with a semi-transparent membrane you could see the filling in action.  Amazing.  The cellulose was packed in really solid.

 

The independent air-tightness test was done one the last day.  The guy was gobsmacked when the house comfortably passed the 0.6 ACH target first time without any tweaks or leak searching; he said that was the first time he'd seen this done.

 

We added most of the through-cassette access channels (e.g. for power for external lights, etc.) afterwards at our leisure.  The trick was that I used a 60cm × 15mm masonry bit (because I already had one, but any 60cm drill would do) to drill through inside to out then used the appropriate hole cutter on both sides using the 15mm pilot as centre; and then twisted a PVC pipe through and cut it to length leaving ~ 1cm proud enough to Sikaflex and tape to ensure a good seal.  (We then foamed and taped the tubes after the wires or whatever were run.)  A good trick here is to use a mutlitool to cut a couple of saw teeth in the end of the pipe that you twisting in, and this way it will cut its way through the filler; it's too solid just to push through.

 

BTW, you do need to think about wind lifting tiles.  IMO, it's just too easy to loose chunk of tiles along unsupported eaves and verges in a severe storm.  Google Kytun dry verge; they also do eaves systems.  Also search the forum.  I used Kytun for our eaves, verges, and verge trims; we were extremely pleased with the products.  They also do systems for tiles as well as slate and fold custom profiles on request -- which is what we did.  I am sure that there other vendors offering similar products if your want to shop around.  You might also consider notching the bottoms of your rafters so that you can run a 150mm plank flush along the base of the rafter line to support your tile eaves properly.  Again this can be painted as needed or  aluminium-wrapped for zero-maintenance.