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Our SystemsWalls
Basement Insulation
Insulate basement and below-ground walls from the inside with breathable, non-combustible Multipor mineral boards, bonded and plastered directly to the wall. Built for walls where natural fibre insulation would sit in constant damp.
Overview
Below ground we don’t recommend natural fibre insulation. However well a wall is tanked, there is always a risk of moisture getting in, and constantly high moisture levels can cause natural fibres to decay. Instead, Multipor mineral insulation boards are bonded directly to the walls and plastered, giving a solid, breathable and non-combustible finish.
Where the walls are tanked, or only ever slightly damp with no water coming through, Multipor ExSal Therm boards are bonded with Multipor Fix X730 to a prepared, level surface. They are then plastered with Fix X730 and Baumit StarTex mesh, and finished with a lime plaster.
Where water comes in regularly and there is no waterproofing, a meshed drainage membrane such as Newtonite Lath is fixed to the walls first, draining to a perimeter drain or a drained sub-floor. Standard Multipor boards are then bonded to the membrane with Multipor Fix X710 – adhesive only, as mechanical fixings would puncture it.
Key benefits
- Mineral insulation that won’t rot or decay in damp below-ground walls
- Non-combustible boards and plasters
- Breathable, vapour-open build-up
- Bonded and plastered directly – no battens, and no fixings through any membrane
- Works on tanked walls or with a drained membrane system
- Joins neatly to wood fibre internal insulation on the walls above
Products used in this system
Related specifications
Ready-made build-ups using this system. Open one to see the full specification and 3D model.
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How it’s installed
Check how wet the walls are first. These steps are for walls that are tanked, or only ever slightly damp. If water comes through regularly, fix a meshed drainage membrane such as Newtonite Lath to the walls first, drain it to a perimeter drain or drained sub-floor, and bond standard Multipor boards to it with Multipor Fix X710.
Step 1
Prepare the walls
Brush or wash the walls down to remove loose mortar, plaster and salts, and any gypsum plaster. On bare masonry, apply a thin coat of Baumit SV61 spatterdash to create a key.
Step 2
Level the surface
The boards need a flat surface to bond to. If the walls are uneven, level them with a coat of Multipor Fix X730 adhesive mortar.
Step 3
Bond the Multipor boards
Comb Fix X730 across the back of each ExSal Therm board and slide it 5–10mm into place against the last one, in brick-bond rows from the base up. Butter the corner joints and lightly rub the surface flat with a float.
Step 4
Mesh and plaster
Comb on 5–6mm of Fix X730 and trowel Baumit StarTex mesh into it with 100mm overlaps. After 5–6 days, finish with 2–3mm of Baumit RK 70 N lime plaster, or Klima Glatte for a finer finish.
Not sure which system is right?
Our team can advise on the best build-up for your project. Call us on 01392 861763 or send us a message.