Stones

Solid Oak on UFH

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We are planning to fit solid Oak flooring on our slab (wet UFH), bonded down with a polymer based flexible adhesive.

 

As houses have become better insulated and UFH flow temps have dropped, you can see manufacturers revising their advice that solid flooring isn't compatible with UFH (previous advice being you should only fit engineered boards), albeit from the research I've done 50% of suppliers say its okay, the others still advise against.

 

JSH has as we know bonded bamboo onto his slab.  Just wondering if anyone has yet bonded solid Oak down  onto their slab and how it has performed / reacted once the UFH was switched on?

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I went the semi solid route due to the advice I got about more chance of solid boards twisting more. I think it's a nicer feeing on the toes than the tiles I have when it's switched on.

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Last time around, everyone advised us against using Oak with UFH.

 

The one recommendation of a hardwood that was okay with UFH was Maple, and they would only warrant that in the narrow 90mm wide planks, no wider.  So that is what we used ad 13 years later it's as good as new, no warping, no cracks, very little shrinkage.
 

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What sort of flow temperatures does your UFH run at in winter?

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All wood moves with temperature and humidity changes. The wider the boards the more risk there is that solid boards will suffer from cupping or other movement. The problem is quantifying the risk. Each manufacturer has their own recommended maximum width but it's a lot narrower for solid than engineered wood. If you like narrow boards fine but I think wider boards look better. 

 

We opted for Engineered wood and have boards that are 200mm wide over UFH. Personally I think they look great and we've had lots of positive comments. People usually assume it's a solid wood floor unless I tell them. 

 

I went to several self build and DIY shows and picked up a lot of samples of ready treated engineered oak boards. I discovered many that looked ok at the show looked odd back home in natural light (one or two were positively orange and not like natural oak at all) so I strongly recommend you shop around before you buy. 

 

 

 

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Yes, we have found that with all the samples we have collected, some look positively dull while others are orange.  

 

The boards we are looking at are 130mm wide, so I think we would be okay there.  

 

All being well, we should be able to get the UFH going in the next couple of weeks to take the temp up and then back down in preparation for flooring and tiling, and .  From everything I've read, it's preparation that's key if using solid wood - getting the right level of RH (dehumdifier will be going in the house shortly to help progress any drying out that is required), getting flooring with a low moisture content and making sure the flooring acclimatizes in the house for a couple of weeks prior to laying.

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17 hours ago, ProDave said:

Last time around, everyone advised us against using Oak with UFH.

 

The one recommendation of a hardwood that was okay with UFH was Maple, and they would only warrant that in the narrow 90mm wide planks, no wider.  So that is what we used ad 13 years later it's as good as new, no warping, no cracks, very little shrinkage.
 

 

Interesting, just been reading info from one supplier saying maple is a species that reacts more dramatically to heat than others and shouldn't be used with UFH!

 

 

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3 minutes ago, Stones said:


 

Interesting, just been reading info from one supplier saying maple is a species that reacts more dramatically to heat than others and shouldn't be used with UFH!


 


 

It was probably a case of they had a surplus of Maple to get rid if, and they spun me a yarn then?  But it still seems fine.
 

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It does make you wonder.  You can understand the advice of 20+ years ago when UFH ran at much higher temps and could be quite uncomfortable underfoot.  Having 'developed' and marketed engineered wood products (where I'm guessing there may well be a greater mark up or ability to inflate the price as a specialist solution) why would they want to kill the golden goose?

 

Whilst there are still a few 'you cannot fit solid wood over UFH' bits of advice floating about online, there seem to be as many or more which say engineered wood is the preferred or more suited option (but do not specifically say you can't).

 

I've seen the effect of excessive concentrated heat on wood flooring - an upper floor room with wood flooring, halogen downlighters in the ceiling void beneath resulted in specific shrinkage and cracking to the timber around each spotlight.  

 

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I can't recall what temperature we run the UFH but it's not particularly high.  If you walk on the floor bare footed, you certainly don't think "gosh that's hot" but of course neither do you think it's cold.  In fact about the only time you really notice the UFH is if you lift the rug in the living room and then you can feel the warmth that's been trapped under the rug.  Likewise in the morning if you pick up a pile of clothes from the bedroom floor, the bottom of the pile feels warm.
 

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I was advised by several companies not to put rugs on wood over UFH but have done so without problem and ours does run quite hot.

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