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Let The Cladding Commence

Posted by ProDave , 28 April 2016 · 5,060 views

Time to start fitting the wood fibre board cladding to the outside of the house.

This is 100mm thick Pavatex wood fibre board. It gets screwwd to the outside of the timber frame all around the outside of the house.

I am fitting the frame insulation as we go. That's a big change from the original plan where we had intended to use blown in insulation that would have been filled after the wood cladding was on. Instead I am using Earthwool Frametherm 35 that comes on a roll. It has the same insulation value as the blown in stuff, but is less than half the price.

So the insulation goes in from the outside immediately before the wood fibre board goes on. The reason being I don't want the insulation getting wet, so I am only fitting the insulation in as much wall as I can get properly clad that day.

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It's been a case of dodging the weather this week. It's nearly May, but we have had strong northerly, cold winds, hail sleet and snow in the last few days. But eventually I got there, finishing the cladding of the front today.

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The observant amongst you will notice I still have a number of screws to fit. These are long screws to go through the wood fibre board and into the timber frame, with plastic caps to spread the load and stop them pulling through the wood fibre board. There will be about 400 screws holding the cladding on the front elevation once it's finished.

The next stage is rendering the front elevation, that of course is now waiting for a weather window, the requirement being above 5 degrees for at least 3 days, and dry.


In response to a few questions, here are some more details.

This photo shows how the bottom rail that screws to the wall of the building supports the wood fibre board, and the drip bead profile that slots into it. It also shows how the boards are tongue and grooved to interlock together.

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This is the primer coat material

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This is the main coat of render

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Anf this is the top coat material

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Another update:

The last bit of cladding (for this session) has been done, The little strip of the gable end alongside the garage and around the small window. Also the strip up and down the gable wall between the house and the garage has been uncovered. That was done last year and has been under wraps all winter.

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All being well the guys turn up tomorrow to start the rendering of the front, and the gable wall between the house and the garage.

Is it ever above 5 degrees dry for 3 consecutive days up there?
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Doesn't feel like it! So glad I got my concreting done during one of the good spells. Froze again overnight here so will likely be even colder where Dave is.
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29 Apr 2016 09:07 AM
Looks good Dave,
Nice colour...maybe just leave it like that :)
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29 Apr 2016 11:45 AM
Dave - have you detailed your floor build up (inc the floor/wall junction) anywhere? Just looked back in your blog and didn't spot anything in the relevant section.
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You are right I don't think I have detailed that, so here goes.

The foundations are simplified strip founndations. By that I mean the strip fouinds only go around the perimiter of the house, and under the two load bearing internal walls that help support the roof ridge beam and first floor joists. I deliberately didn't want to complicate the foundations with the usual practice of sleeper walls to support the mid point of ground floor joists. (if the first floor joists can span that distance, then so can the ground floor joists)

Ground floor joists are 300mm deep I engineered timber I beams sitting on the sole plate on top of the founds. These will be filled with 300mm of insulation. A timber ring beam surrounds the joists and is the main support (plus the joists) for the timber frame. So the floor insulation will fill right up to the ring beam, so partly under the timber frame.

On top of the joists will be OSB, then a 25mm battened cavity for UFH pipes then the final floor material.

The Wood fibre external wall insulation cladding extends down over the outer ring beam and sole plate, terminating where the blockwork walls start.
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How long are you able to leave the wood fibre board before the rain and the sun start to damage it, as in are you now on the clock to get it plastered up. Never seen it before and it looks a very easy system to use. How heavy is a board???
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The boards are an easy lift for one person, I have done all that cladding on my own.

The outer surface of the boards has a water resistant coating and they claim it can be left exposed for up to 3 months before the render goes on. I don't expect it to be that long. The rain we have had in the last few days does indeed just seem to run off the face.

The first stage of the render system is a paint on waterproofer / primer, once that is on it's even more secure.

I think I am the first on ebuild using this particular system, but definitely not the first in the UK.
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29 Apr 2016 05:25 PM
Thanks for the info, Dave. Should I ever build a house (unlikely) I'd like a suspended floor, albeit for no real reason. I think you've said you've had a condensation risk analysis so I guess the sole plate came out of that OK. Will the underside of the wood fiber be protected in some way and is there any risk of splashback on to the sole plate?
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The wood fibre board rests at the bottom on an L shaped plastic strip (I'll take a picture of the next bit and update the blog). this strip screws to the wall and the wood fibre board rests upon it at the bottom.

The long outward part of the L is in fact 2 layers of plastic and in between them the drip bead profile slides. That again has a solid strip of plastic that slides between the two on the wall bracket, and a mesh on the part that's against the wood fibre (I can see that will only become clear with a photo)

So the bottom of the wood fibre board is protected by the platic profiles and the render comes down to a drip bead so any water running down drips off and doesn't get underneath.

So I am 100% sure the sole plate (wich is covered anyway) won't ever get wet.

When I do the next bit, I will take a close up picture of the bottom detail
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Looks far easier a system than cement boards and plaster on to these. Lighter to lift and improve your overall uvalue so its a winner for me.
Is the waterproofer a special product designed for use in this application or can you use a PVA type sealant.
I take it you still need to use a mesh in the first coat of plaster.
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The water proofer is all part of the "system" That's a liquid you paint on. the main coat of render is mixed from poweder, and when that is applied you roll in fibreglass mesh into that base coat. the top coat comes reay mixed in tubs. i have about 2 ton of this lot in the house waiting right now.

Another advantage that has been mentioned before, is that there is no cavity between the timber frame and the wood fibre board. So no inspect mesh to fiddle with and as you say it adds a further layer of insulation all around the outside of the building.

The wood fibre boards are tongue and grooved so interlock together, so that, plus the render coat should add to the air tighness of the building (though that is not being rergarded as the air tightness layer)

And lastly no cavity means no need to fit those horrible ventilation slits you have to fit to a blockwork and render outer skin, so you get a clean rendered finish with no "warts". Also aparently no need for expansion breaks to the renderr either.
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I have just added some more pictures showing the bottom channel profile, and the materials that will be used for the render.
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Just another bump to say I have added another photo.
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Really like the simplicity of this product, being one that any competent person could do themselves, with of course the added bonus that it is an insulating layer. I know the render system is more expensive than a sand/cement based one (as is the render that will finish my ICF). The big saving of course is in labour as you are doing it yourself. It would be interesting to know the number of man hours it takes you to cover all of your build, and the render completed render costs as a comparison against other forms of construction.

We had a quote for our last house based on a similar system by a company which was at the time building commercially with it on the road to Oban. I had hoped for a good price given they were selling houses for less than traditional builds but alas no, their quote was almost double that I eventually paid. Made me discount this form of construction for our current build.
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It's very hard for me to compare the total cost of the external wall system, as all the wood fibre came included in the price I paid for the timber frame and it's erection. The builders fitted the wood fibre to the roof and bought enough for the walls at the same time, even though it is now me fitting it, so I don't have an itemised price of how much the wood fibre board cost.

I do know in round figures, the materials and labour for the render is £10K give or take a little.

It's an easy job to fit so a definite saving in labour cost, though I am employing somebody to do the render as I want a good finish.
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Wish we had been able to do this on our self build. Next time.............

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