New Build - Weatherproof floorboards on upper floors and under-floor heating

[JamesN]

Hi, 

 

I'm installing wet underfloor heating on the upper floors, but the floorboards will be exposed to the elements for approximately 40 days before the roof is installed. I need a weatherproof solution. I had planned to use grooved floorboards, but the weatherproofing requirement changes things. I'm considering either using aluminum spreader plates beneath weatherproof boards, or adding grooved chipboard on top of the weatherproof layer after the roof is complete. What solutions have others used in similar situations?

[JohnMo]

New build well insulated with upstairs - do you actually need UFH upstairs or radiators?

 

Many have nothing other than the provision to add electric rads if needed. If you have a heat loss 3kW for downstairs and 2kW for upstairs, just size the UFH array downstairs to kick out 5kW. Upstairs heating provision added. Fully compliant with BR and MCS for heat pump install. Put electric heating mats in bathrooms upstairs.

 

Are you just making life difficult?

[nod]

48 minutes ago, JohnMo said:

New build well insulated with upstairs - do you actually need UFH upstairs or radiators?

 

Many have nothing other than the provision to add electric rads if needed. If you have a heat loss 3kW for downstairs and 2kW for upstairs, just size the UFH array downstairs to kick out 5kW. Upstairs heating provision added. Fully compliant with BR and MCS for heat pump install. Put electric heating mats in bathrooms upstairs.

 

Are you just making life difficult?

Need to stop agreeing with you John 

It does seem madness to be putting heating on the upper floors of a well insulated house 

[JamesN]

Thank you for the replies John and Nod. For more context the house has three stories with the third story having two rooms - one room with ensuite. That's really interesting you mention it will still be MCS compliant if only doing the downstairs.  This presumably means we would still be able to get the grant.!?

[Nickfromwales]

21 minutes ago, JamesN said:

Thank you for the replies John and Nod. For more context the house has three stories with the third story having two rooms - one room with ensuite. That's really interesting you mention it will still be MCS compliant if only doing the downstairs.  This presumably means we would still be able to get the grant.!?

If it's a 3 storey home then consider putting the money for the top floor into A2A (AC) for space heating, but more importantly cooling, as even the attic in my sack-o-crap house would be utterly unbearable in the peak of summer without 3kW of cooling power via the portable air con unit.

 

You will need access under the spreader plates to staple the plates up to the underside of the floorboards, as without surface to surface full contact of the heated plates to the sub-floor they'll just be a warm ornament. I've done plenty of these types of installs with great results, and I've been called out to trouble-shoot others where the flow temp is 65-70^oC and the rooms are 17^oC as the UFH is glowing in the dark but not contacting the sub floor.

 

If getting underneath is a no-go then you will need to install a cheap OSB tray and fill it with rockwool to belly the plates upwards, then the floorboards will compress this when being dropped on and screwed down. Ignore this at your peril!!

[JohnnyB]

Jumping in on this as I have the same question.  I want the floors warm in the bathrooms, and some heat, as we find the bathroom and one bedroom isn't warm enough during the coldest weeks in our existing build, built last year.

 

The plumbers have said we need to heat the whole house with the ASHP for the grant so need something upstairs and it needs to be powered by the heat pump

 

Do electric floor mats not count?

 

I was thinking of installing the usual chipboard flooring everywhere apart from the bathrooms and then installing a routed chipboard floor in those rooms once the house is watertight.

 

I have been told that the spreader plates expand and click as they warm up and cool down.  Anyone else have experience of that or is it an occasional thing if the plates aren't installed properly?

 

We are planning to fit radiators in the bedrooms as they will only be used during the coldest months of the year.

 

Edit to add that I have just read other posts about UFH with chipboard needing higher flow temps.  In the current build I've not had the LWT temperature above 35 degs and most of the time it is around 30.  Anyone have experience of routed chipboard or spreader plates and low flow temperatures

Edited March 22 by JohnnyB