BUILDING AROUND TREES — 30

Make room for the roots.

Three foundations. A light frame. A tree at the heart of the house.

MaterialsClayLinework

Assembling the foundations and frame…

StyleView

CONSTRUCTION STUDY

From ground to canopy

Foundations & height

Bored pilesConcrete shafts into deeper groundScrew pilesSteel shafts with helical bearing platesConcrete padsShallow footings with wider excavation

Helical steel piles transfer load through their shaft and helices. Installation torque, corrosion, ground conditions and lateral capacity need verification; helices can still damage roots.

Floor above ground2.10 m

Low · 0.45 mRaised · 1.5 mHigh · 3 m

Finished floor level above flat ground. Raising it increases the sway and overturning demands for the same lateral load. Lowering it can leave too little room for useful diagonals; it does not remove the need for lateral resistance.

Braced load path shown. 4 across / 4 along bays. Open Beams, joints & stability for the load-path study.

Illustrative pile depth2.50 m

Cut away the soilReveal pile embedment, helices, shallow pads and schematic roots.

Beams, joints & stability

Timber frameSteel frame

Link foundation headsA continuous tie network follows both wings and the rear link. At low level, the floor grid doubles as the proposed head tie.

Automatic brace layoutPlace diagonals where geometry allows; flag missing directionsCross bracingStudy paired tension diagonals, including shallow baysKnee-braced frameRequires beam, post and joint stiffness analysisAlternative lateral systemOmit braces; pile fixity or another system must be designed

Braced load path shown

Brace rise available: 1.36 m
Across / along bays: 4 / 4
Head ties: Separate grid
Diagonal angle: 27–32°

Layout only. Strength, drift, connections and foundation resistance remain to be checked.

Ties restrain relative movement of foundation heads. Diagonals restrain sway above them. Automatic mode uses a 25–65° drawing preference, not a code limit; neither floor height nor frame material establishes structural adequacy.

Bolted saddleA bearing seat, side cheeks and through-boltsHead plateA bearing plate with holding-down fixings

Show connection hardwareReveal foundation caps, post bases, plates, anchors and beam fixings.

Use Beam joint to inspect the top of a post and Pile head for its base. Gussets show where brace forces enter the frame. Bearing seats and head plates do not imply moment restraint; tie anchors and hold-downs need force-based design.

Load direction arrowsOchre: gravity into the supports. Blue: lateral load on the house. Arrows show direction, not calculated forces.

Space for the tree

Open tree court3.00 m

Illustrative root-zone radius3.50 m

Root zone & schematic rootsShow the amber study zone and the supports whose foundation footprints overlap it.

Tree canopyHide foliage to inspect the frame. The retained trunk stays visible.

Widening the court moves its inner supports and shortens the wing spans. The court remains open through the floor and roof.

4 / 12 supports overlap the study zone

The circular zone is an illustration, not a calculated root protection area. Roots are not mapped. Foundations outside this circle are not automatically suitable. Protect soil, access routes, drainage and space for trunk growth as well as the roots.

Reveal the assembly

Floor deck / diaphragmCover the joists with the floor layer that would transfer horizontal loads through designed fixings.

Walls & courtyard glazingEnclose the two wings and connecting rear room.

RoofAdd a U-shaped roof with an open court around the tree.

Start with the exposed structure, then add each layer to read how the house is assembled.

Read this configuration

Paired steel diagonals provide a tension path for either load direction. Braced lines are separated across both wings and at front and rear; diaphragm stiffness and torsion still govern force sharing.

Automatic layout uses a 25–65° angle to the horizontal and at least 0.45 m rise as schematic detailing preferences. These are not engineering pass/fail limits. A direction with no remaining bays is unresolved; height alone never establishes the need for bracing.

Steel head ties connect the screw-pile caps in a continuous U-shaped network. Design ties and cap anchorage for axial tension/compression, bending and shear, including eccentricity. They tie the bases together; raised posts still need lateral restraint.

The floor deck is hidden to expose the joists. Diaphragm action is not represented in this view; the completed floor needs a designed horizontal load path.

4 of 12 foundation footprints overlap the illustrative root zone. This is a plan overlap, not a root survey or a suitability verdict.

Check compression, uplift, lateral pile–soil response, group effects and settlement. Embedment in this drawing is not a lateral fixity assumption; cap connections need to develop the specified forces.

Gravity: floor → joists → upper beams → posts → caps → piles or pads → ground.

Lateral load: roof and wall forces → floor diaphragm and collectors around the court → braced lines → cap connections and ties → foundation and soil resistance. The U-shaped floor needs designed chords and collectors at its internal corners; equal force sharing between bays is not assumed.

Before choosing sizes: establish wind loads, gravity loads, ground stiffness and strength, then check drift, post buckling, brace tension, joint slip, uplift, cap forces and differential settlement. Verify stability during erection before the diaphragm is connected.

Read a diagonal: for one braced bay with horizontal shear V and angle θ to the horizontal, a single active tension diagonal carries V / cos θ and adds a vertical reaction V tan θ. Steeper braces increase those forces; shallow braces have less rise for connections and can be long and flexible. These relations do not determine how the total building load is shared between bays.

Keep an air gap under spanning beams where required and determine any heave allowance from the soil investigation. Small piles can reduce excavation, but installation still needs a root-aware method and specialist review.

NHBC · Piled foundations and head connections ↗

Forest Research · Roots, excavation and compaction ↗